Archive for the 'DSLR' Category

Are you smarter than your camera? 5 ways to prove it

Friday, December 28th, 2007

Modern dSLRs are technological wonders. They are crammed with components, sensors, LCDs and advanced circuitry. They do everything but talk — and a few are working on that.

Despite all this technical wizardry, the average dSLR is fairly dumb. It can’t think. It knows nothing about art, composition or lighting effects. It doesn’t care if you are photographing a beautiful sunset or the local garbage dump. It doesn’t see the difference and wouldn’t care if it did.

Yet, far too many dSLR owners allow this non-thinking, non-appreciative hunk of electronics to rule over their photographic endeavors. “The camera knows best,” is their motto and the more automatic controlled features their cameras have the better the like it.

True photographers know better. They can appreciate the wonderful features camera designers have incorporated into their hardware, but they remain the master of the thing. They aren’t afraid to use manual modes, and more importantly, they know when they should. They are smarter than their camera and their work shows it.

Under perfect conditions — bright, overcast day with no shadows and lots of reflected diffuse light — any camera can capture wonderful images. The problem is those perfect conditions don’t come along very often and they don’t exist indoors. Or in a shady forest. Or at night. Or…well you get the idea. Most of the time, you and your camera have to work together to get the best images. You have to be a team –and in any team there has to be a leader. You have to step up, overrule your camera and force it to capture the images you want.

The more I use my digital cameras, the more I find myself reverting to some sort of manual control. That doesn’t mean I never shoot in a fully automatic mode — it’s just that more and more often I find that my knowledge and experience lets me make better decisions than my camera. Sometimes I’m wrong and the camera actually knows best. Much of the time, however, my images show a marked improvement when I take control.

How do you develop this knowledge? It can start gradually, by occasionally experimenting with manual settings. If you always shoot fully automatic, in the program mode, try a few of these suggestions next time you are shooting.

Turn off auto focus.

Auto focus is useful and can be a lifesaver many situations. However, if you always let your dSLR select the focus you may be missing out on some great images. You might prefer part of your subject be out of focus. Its an artistic decision and your camera can’t make that decision for you. In addition, no matter how fast camera makers make their AF systems, pre-focusing will always be faster. So try using manual focus when it is appropriate.

Switch out of the program mode

I am finding less and less use for the program mode when I shoot. Since I understand what type of image I am trying to capture and the camera can’t read my mind — I find I am far better at selecting the best combination of aperture and shutter speed to get what I want. Camera makers have gone to great lengths to add program modes like sports, night, portraiture and the like. The idea is you can set your camera to the appropriate mode and forget about it. Sometimes this works, but I find I get better results when I determine the optimal settings. lately, I have been shooting almost exclusively in aperture priority. I set the F-Stop and the camera selects an appropriate shutter speed. Occasionally I will use shutter priority — especially if the light is shifty and I want to make sure I don’t fall below a certain speed. Sometimes I will use full manual — when I want to ignore the camera’s meter in order to get exactly the shot I have in mind.

Of course you don’t have to use any single mode for an entire shoot — many times I will find myself shifting between all four modes during a busy session. The thing is, you have to learn which modes work best for which situations. So next time you are out, switch out of program mode for at least part of the time. Once you learn how to make decisions your dSLR could never make on it’s own, you may find the program setting will become your least used mode.

Play around with exposure compensation

Most dSLRs offer some form of exposure adjustment, which will allow you to override the actual meter reading by a set number of stops. Much of the time, the default setting will be very close, but if you are attempting a special effect or the light is tricky, exposure compensation can be your best friend. Learn how to use it to your advantage.

Experiment with contrast

If your camera offers contrast adjustment, learn how this can improve your images in varying lighting conditions. If you are shooting outdoors at noon on a bright, cloudless day, normal contrast may make your images appear awful. See if toning down the contrast will soften the shadows and eliminate hot spots. If the light is weak and dull, can you improve the image by cranking in some additional contrast?

Vary your flash settings

It’s true. camera makers have created some wonderfully intelligent flash units. Even the built in flashes can produce stunning results under the right conditions. But there are plenty of times when the flash should be overruled. Start with flash compensation. Try more or less compensation to see how the light changes. Experiment with different shutter speeds to see how that affects the background. If you have a separate flash unit, get a cord and try shooting with the flash off the camera. Experiment, You’ll get some duds, but you will also get some wonderful images. And you will never allow your camera to dictate how your flash should be used in the future.

I urge you to try all of these techniques when you get the chance. You might not use every one every time, but make it a point to try at least one of these each time you head out with your dSLR. If you do, and you ware willing to learn from your successes and your failures, you will quickly se your photographic IQ surpassing your cameras. When you are smarter than your camera, you will be well on the way to capturing some outstanding images.

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Alpha A700 firmware upgraded to version 3,
upgrade appears Windows only

Thursday, December 27th, 2007

Sony has released another firmware update for the Sony Alpha A700, which will update the camera’s firmware to Version 3.

Sony says the new firmware will fix several issues with the A700. Sony discovered that occasionally an Alpha A700 SLR would stop responding with the Access lamp lit after capturing several images in quick succession. It was also discovered that turning the A700 off in the “MR” mode could cause some settings to carry over to other modes.

The new firmware resolves both of these issues, as well as

  • Sharper images for pictures taken under low contrast conditions
  • Reduced noise for pictures taken at ISO 3200
  • Improved flash control for objects closer than 1 meter with non ADI controlled lenses

Sony suggests all Alpha A700 camera owners upgrade their camera if the firmware version is less than 3.

The serial numbers of the applicable A700 dSLR models follows:

  • DSLR-A700 (body) with serial numbers 0500001 - 0508500
  • DSLR-A700P (body bundled with 16-105 lens) with serial numbers 800001 - 800200
  • DSLR-A700K (body bundled with 18-70 lens) with serial numbers 1100001 - 1105600

Unfortunately, Mac and Linux users need not apply. The upgrade utility is supplied as a Windows .EXE file, so you will need a Windows box (or an Intel Mac running Bootcamp) to prepare the upgrade.

I’m rather disappointed in this, as it appears the only thing the EXE file does is extract the upgrade application. I could be wrong, possibly it needs some system resources. But it seems you run the EXE file and it extracts a file called DSCA700.APP, which you then copy to a Memory Card. The actual upgrade occurs when you insert the Memory Card into the camera and follow a sequence of steps to upgrade the camera from the card. (There is also a provision to upgrade through a USB cable if you simply can’t afford a $7.99 card reader to upgrade your $1500 camera.)

Since the camera doesn’t need to be connected to a computer during the upgrade, I don’t understand why Sony needed to use an EXE file for this — couldn’t they simply have used WinZip or something similar? That way any computer capable of unzipping the file (which would include Mac and Linux boxes) could transfer the application to a Compact Flash card or Memory Stick and proceed to upgrade their camera. As long as you can extract DSCA700.APP, you’re in business. Why select an extraction model that will only run under Windows?

Hopefully, Sony will realize that a large number of professional photographers use a strictly Mac workflow. They aren’t going to be happy if they are forced to scrounge up a Windows machine every time they have to upgrade their camera’s firmware. Just put all the resources in the upgrade app, zip it up and provide it to the users.

You can find the Alpha A700 version 3 update at the Sony support site.






Full frame sensor with image stabilization revisted

Friday, December 14th, 2007

There is intense interest in the yet unnamed and unannounced full frame Sony Alpha (possibly to be called the A900?) among Alphatracks readers. I recently received another e-mail suggesting further ideas regarding the full frame sensor with in-camera image stabilization problem. Or non-problem, depending on which theory you wish to follow.

This time around, Marek Kaszycki weighs in with his analysis of the situation.

I’m not an engineer, yet I’d like to provide another perspective on the possibilities of SSS working with a full frame sensor.

Looking at tests of stabilization systems, I can’t help but wonder about two things:

1. Effectiveness of stabilization overall.

2. Effect of lack of stabilization.

Starting with the latter, it’s fairly obvious that if you take a 3600×2400 image (ca 8.6 megapixels) and have a shake that causes smearing of fine detail across two pixels, you’re losing 50% of the linear resolution in that direction. Since losing 50% of resolution in one direction leads to the perception of losing half of the resolution overall (extra resolution in the other direction is redundant), this means losing 75% of the pixel count, reducing the perceived resolution down to 1800×1200, ie. ca. 2 megapixels. Worse shake leads to further image degradation with even further loss of resolution, down to unacceptable levels.

I used the images from some dpreview reviews for Minolta cameras:

http://www.dpreview.com/reviews/KonicaMinoltaA200/page7.asp

http://www.dpreview.com/reviews/KonicaMinolta7D/page19.asp

http://www.dpreview.com/reviews/KonicaMinoltaZ5/page6.asp

They have different sensor sizes and pixel counts, so I will use relative numbers.

The Z5 is 5 megapixels, 2560×1920, Dynax 7D is 6 megapixels, 3008×2000, and Dimage A200 is 8 megapixels, 3264×2448.

The Z5, at 420 mm equivalent focal length, produces a blur about 30 pixels long, the D7D, at 75 mm equivalent, about 15 pixels (at 1/4th, with AS on, curiously), and the A200 about 35 pixels. Relative number of pixels per frame height is: 1.5%, 0.75% and 1.4%.

Since D7D handily corrected blur at 1/8th of a second, which is almost ten times longer than ‘handholdable without stabilization’ 1/focal length rule, with about 0.5 pixel shift, it’s perfectly reasonable that the system has a three stop effectiveness with 0.75% frame height shift (0.12 mm movement of a 16 mm high sensor!).

Let’s say the system would correct for even more, and would move the frame within 4% around the sensor boundaries. This would correct about 5.5 stops slower than at the reciprocal of the focal length rule, while moving the sensor only about 0.96 mm up and down, and 1.44 mm left and right. Amazingly simple, let’s simplify that further and allow for 1.5 mm movement in both axes in both directions, which is a bit extreme.

Taking a full frame film gate, and a full frame shutter (both of which have sligthly larger clearance than 36×24 mm), as well as a full frame sensor, we lose 3 mm of the sensor to allow SSS to work. It boils down to 33×21 mm available area, or 31.5×21 mm to allow 3:2 aspect ratio. This means a “crop factor” of only 1.14x, making a 24 mm lens into a 27 mm one. Still a loss, but I think it’s an acceptable one.

What could Sony do to make us happy? In this rather extreme example (3 mm movement), three things:

1. Setting SSS effectiveness in the menu. Restrict movement to 0.25 0.5, 0.75, 1, 1.5, 2, 2.5 and 3 mm, independently for horizontal and vertical axes (e.g. 2 mm for vertical axis and 3 mm for horizontal, making image area equal to 33×22 mm, or less than 1.1x crop).

2. Letting users choose whether to always crop the image to preset restricted movement, leave it as it is, to crop it in software, or crop it automagically (the camera would crop based on restricted movement and detected underexposure).

3. When SSS is off, no crop occurs, unless preset in the menu (automatic mask in the viewfinder).

Back to the 3600×2400 sensor (8.64 megapixels), a 31.5×21 mm available area is 3150×2100 pixels, 6.61 megapixels. Not a huge loss in resolution, either (linear: 14%, planar: 23%).

All of these options are possible, no extra gain, or exposure increase is necessary, the sensor is full frame when doing critical work, and slightly smaller when not.

Regards, Marek Kaszycki

Past posts in this series:

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Sony Alpha grip sensor for US market, not Europe

Wednesday, November 28th, 2007

So how do you tell the US version of the Sony Alpha A700 apart from it’s European cousin? The US version includes Sony’s version of the Minolta Grip Sensor, while the European models don’t.

This isn’t a case of Sony short changing European customers. Although the details are rather murky, it appears that the Grip Switch is made of a nickel alloy, and the European Union recommends that nickel not be used in proximity to human skin for lengthy periods. So apparently Sony decided to follow along with the recommendations and simply eliminated the grip sensor from the Alpha A700 models bound for Europe. This also applies to the add on vertical grip, the European models of both the camera and the accessory grip are sans the Minolta style grip sensor.

Here’s where everything gets sort of fuzzy. Apparently the recommendation is just that: a recommendation, not a law. So Sony probably wouldn’t have broken any regulations by including the grip sensor in European Alphas. No one seems to know whether Sony simply chose to voluntarily remove the sensor for the Alpha models sold on the European continent, or whether the European Union used some political muscle to force their hand.

No more phantom Eye-Start problems

Sony A700 grip sensor

Grip sensor on the Sony Alpha A700 helps prevent unwanted Eye-Start trigger, but don’t look for it in Europe.

Photo: Sony Corp, used with permission

Basically, the grip sensor is a useful addition to the Eye-Start system available in the Alpha A100 and many Minolta cameras. Eye-Start allows the camera to be in a low power standby mode until you raise the camera to your eye. When the camera senses your eye near the view finder, the camera changes to full operation, including metering, auto focusing, image stabilization, etc. When you move the camera away from your face, it returns to standby — a feature that can greatly extend battery life.

The problem with the eye-start system is that it can’t always tell your eye from your shirt sleeve or your pant’s pocket. Dangle an A100 on a neck strap while you wander about and the camera may turn on and off constantly as the camera falls against your clothing. It thinks it senses your eye, so it powers up the LCD, and attempts to meter and focus, even though you have no intention of shooting anything.

You can turn the camera off, but then if something really interesting turns up, you have to hope you don’t miss the shot while the camera goes through it’s start up sequence. Neither choice is very appealing, and many people have criticized the eye-start system because of the phantom power up cycles.

Sony listens to Alpha users

As I’ve said before, it appears that Sony listens to it’s customers, because they have corrected a number of issues that people had with the A100. One of the things they did was reach back into Minolta film SLR technology to bring back the grip sensor. If you have the grip sensor mode turned on, the A700 will remain in standby, even if it thinks you are looking through the viewfinder. Only when your hand is covering the sensor and your eye is at the viewfinder does the camera become fully operational. Or least that’s the way US versions of the A700 operate.

Grip sensor is not a pressure switch

If you are wondering why the switch has to be made of nickel, instead of some other material, the grip sensor is not pressure sensitive. Instead it actually uses a small electrical field across your skin to sense that your hand is there. So the sensor has to be made of a conductive material and Sony apparently couldn’t find an adequate substitute for nickel.

Many have pointed out the European Union recommendation are aimed primarily at things like ear rings and other body piercing jewelry. Simply touching nickel probably doesn’t present much danger for most users. Some people apparently have or are prone to develop allergic reactions to nickel. Let’s not forget the electrical current involved in the switch. It’s very small, but perhaps it could aggravate an allergy in someone using the Sony A700.

So no grip sensor for the Europeans, at least until Sony finds another material for the sensor. Does this mean that US cameras will cause allergies? I rather doubt it. There might be some people with a severe skin sensitivity that could be adversely affected by the nickel in the sensor. On the other hand, you find nickel in all sorts of products, from automotive controls to fountain pens to silverware. Most people aren’t bothered by these items — I sort of doubt that a camera control will have a much greater effect. Of course, I am not a doctor, so if you have a nickel allergy, you might want to discuss this with your medical adviser.

Remember that Minolta has made long use of a similar nickel grip sensor in the Maxxum/Dynax 7 and 9 as well as the A2 and A200. I haven’t heard of a rash (no pun intended) of photographers developing skin allergies from using these older Minoltas.

Why choose a electrical sensor over a switch?

Which leads to my next question, why exactly did Minolta choose to use the nickel sensor in the first place? A simple pressure switch would be cheaper, could be made of any hard materiel and could even be used with gloves on — something that can’t be said of the nickel sensor.

About the only reason I can think of for choosing the nickel sensor is that if you left the camera on when you put in a camera bag, padding or other equipment might possibly trigger both a pressure switch and the eye start system — running down the battery. Because the grip sensor actually measures current through your skin, it can tell the difference between a hunk of foam rubber and the fingers of your hand.

The Senswitch — forgotten Minolta technology

Yet Minolta long ago developed technology that could eliminate false triggers and didn’t require any electrical skin contact. Im refereeing to the Senswitch that appeared on the Minolta XK cameras in the mid seventies.

Minolta XK Senswitch

Minolta Senswitch is neatly hidden inside the grip on the XK Motor

The Senswitch was just simple pressure switch that turned the camera meter on when you touched it. It saved battery power, because the camera could be left in standby until the user pressed the switch.

I’ve heard that a lot of XK owners didn’t like the Senswitch on the basic XK model. It was just a long strip on the front of the camera, and apparently many photographers had trouble engaging the switch consistently. And it would also be vulnerable to pressure from other sources like the foam padding that could press upon it and drain the battery.

Minolta, however, followed up the plain vanilla XK with the incredible XK-Motor. This wonderful camera was my main shooting machine for many years, I loved the Senswitch on the XK-M, because Minolta moved it from the front of the camera to the inside of the built in grip. You would have to work awfully hard to miss engaging the Senswitch on the XK-M. If you were holding the camera by the grip, your middle-finger just naturally fell upon the switch. You almost couldn’t miss it.

Located deep inside the recess of the grip, the XK-Motor’s Senswitch was also fairly invulnerable to being pressed accidently by something other then your finger tip. I’m not saying it would be impossible for a hunk of padding or gear to engage it…but it would be a very rare occurrence. I never saw it happen in all the years I shot with my XK, Then again, I usually switched the camera off when it put in the bag.

One final thing. The XK-Motor’s switch was made of some sort of hard plastic , so you could use it with gloves.

It seems to me that Minolta had almost fool proof system with the XK-Motor’s Senswitch. Too bad Sony didn’t study the XK-M grip before opting for the nickel grip switch on the A700. It works even with gloves, it is fairly safe from accidental triggering and it won’t cause skin allergies. Oh yeah, they could sell the Senswitch in Europe as well.

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Sony A700 battery life analyzed by engineer

Friday, November 23rd, 2007

Bart Pasquale, who last appeared on these pages with his insightful comments on the Sony Alpha Full Fame - Antishake question, is back with a detailed analysis of the Sony battery for the A700 Alpha and it’s lack of compatibility with the A100 batteries.

The complete text of Bert’s email follows:

Hello Tom!

Here’s some info regarding the new Alpha A700 battery, the NP-FM500H. As you may know, there is a grove in the new battery, and a ridge in the A700 battery compartment, which prevents interchangeability with the A100 battery. I contacted my usual 3rd-party battery suppler from eBay, and he said Sony has blocked the manufacturing of NP-FM500H compatibles. It was not clear weather this is legal/political maneuvering, or simply an issue being able to reproduce the circuitry required for A700 to display the % charge remaining, but he expected something out of Taiwan by January. What he did know is that one person reported to him filing out the ridge inside their A700, and the A100 batteries did NOT power the A700.

A700 Battery

A700 battery shown being loaded into new vertical grip. Notice the groove that allows battery to fit the A700 compartment.

Photo: Sony Corp, used with permission

Being the anti pay-for- proprietary-items consumer that I am, I find myself waiting it out to avoid buying a $80 Sony battery, understanding the implications of battery consumption suddenly became very important. So, I spent the past day and a half draining a fully-charged battery under controlled conditions. My goal was simple: take bursts of pictures throughout the day at various intervals, review the pictures, delete a few, and record the image count and battery charge remaining. Many batteries fall off very quickly once they indicate “half charged”, but SONY claims the new battery’s reported % is “accurate”, and the battery is good for 650 shots. Curiously, the second day I had the camera, I cranked off 900 pictures on a photo shoot, but the battery indicator still showed being more than half-charged. Let’s examine…

I began with a fully charged battery two days ago, At various intervals (a few hours to a few minutes) I would fire off 50-100 images, and review them, at a medium pace, deleting every few images as I went. I was shooting compressed RAW, anti-shake on, DRO standard. This simulates my camera use in the studio or shooting on location. After the first 50%, I continued to review the imagers quickly, but did not delete many images, as I might do to conserve battery power while on a shoot. The results are summarized in the following table:

Shots % Charge Charge Drain Rate
Day One: 0 100%  
  550 75% 1% = 22 frames
  1200 50% 1% = 26 frames
Day Two: 1800 25% 1% = 24 frames
  2600 1% 1% = 32 frames
  3080 Dead 1% = 400 frames

Over 3,000 shots from a single charge! I’ve never worked so hard to drain a battery. That was the battery’s third charge, so we’ll see how that changes after a couple dozen cycles, and how the generic versions hold up to that when they finally do come out. A few other statistics:

  • Reviewing 150 images uses 1% of battery charge
  • Leaving the display on for about 5 minutes uses 1% of battery charge
  • Overnight, the battery looses about 2%-3% of it’s charge
  • Straight shooting without reviewing images can achieve 30+ frames per percent at any phase in the charge cycle.
  • Once the battery indicates zero charge, you can still quickly eek out a few hundred shots!
  • This is about an extra 12% of charge not indicated in the charge level.

During recharge, the first 15 minutes were spent to achieve 1% charge status back. After that, it was pretty linear, adding about 12% every 15 minutes achieving 86% after 2 hours of charging. The battery indicated “100%” about 35 minutes later, but continued to take a charge for an additional 15 minutes to top it off. So, one could theoretically shoot 400 frames, recharge for 15 minutes while the model changes, and never run out of charge. Of course, YMMV; I don’t know how consistent one battery will be to the next. Happy shooting all!

- Bert Pasquale

BTW, I have a couple well-cared-for A100’s for sale! (With several extra batteries…)

Wow, that is a pretty exhaustive (no pun intended) sample of the battery life of the NP-FM500H when used in the A700.

I found it interesting that someone would actually go as far as removing the locking ridge from a new A700 to try to use the older battery. The fact that the NP-FM55H (used in the A100) would not power the A700 indicates to me that the ridge serves a purpose beyond an attempt to sell more batteries. It’s easy to point to an incompatibility like this and suggest it is being done to sell more batteries. I’ve found that manufacturers rarely make components less compatible just to move additional product. They have to stock additional components, manufacture additional components and distribute two lines of batteries instead of one. Usually is in the company’s best interest to stock and sell as many common items as they can, because that drives manufacturing and stocking cost down.

That said, several printer manufactures have taken great pains to make sure only their own cartridges work with their hardware. So who knows? This could be Sony’s attempt to eliminate after-market battery competition, but I doubt it. Usually when an electronic product carries a lock out ridge like the one described above, it is to prevent using a non-compatible item that might cause damage to the devise. The upshot is A100 batteries are NOT compatible with the A700 — don’t try to reengineer the camera or battery in attempt to make them work.

It Bert’s tests are indicative of how long a typical NP-FM500H will last, it seems like for most shooters a single battery will cover most assignments. A second battery, either used as a spare or inserted in the A700 Vertical grip should be more then sufficient power for most A700 shooters.

Thanks again Bert, this is a great report. If anyone is interested in Bert’s A100 gear, email me and I will get you in touch.

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What exactly is a Single Lens Reflex anyway?

Sunday, November 11th, 2007

Alphatracks has always been aimed at Sony and Minolta SLR users. Not that there is anything wrong with non-SLR gear, There have been numerous great non-SLR cameras sold under the Sony/Minolta brands. You have to draw the line somewhere, however, and since I have primarily used SLRs, I like to stick to what I know.

I’ve noticed that many readers are somewhat unclear as to which cameras are actually SLRs. Some appear to think it means any camera that uses interchangeable lenses. (Which is not the case.) Others mistakenly apply the term to so-called “bridge” or pro-summer cameras. These cameras typically rely on an electronic view finder (EVF) , which disqualifies them as a dSLR. So what exactly makes a camera SLR?

Shouldn’t that be a MLR?

Mirror box of Maxxum 7000

It’s the instant return mirror (and supporting system) that puts the reflex into a SLR.

Most people know that SLR stands for “single lens reflex,” which in itself is fairly confusing. After all, nearly 100 percent of the SLRs ever produced are designed with an interchangeable lens mount. Shouldn’t these cameras be called Multiple Lens Reflex cameras?

To understand just why we refer to these cameras as single lens units we need to examine a bit of camera history, The early cameras, such as those used by Matthew Bradey during the American Civil War, recorded a single image at a time. The photographer looked through the lens, focused, composed and then inserted the film plate behind the lens to make an image. While the entire process was crude by today’s standards, the photographer enjoyed great control, since he looked directly through the actual imaging lens to compose the shot.

While this was satisfactory for still life, portraits and landscapes, this process did not lend itself to rapid photography. These early cameras could only record one image at a time. Which is why you have never seen a motor-driven view camera.

Realizing the need to offer sequences of exposures, camera makers begin to experiment with various roll-film designs, With a roll of film in the camera, the photographer could fire off continuous images without reloading. While this improved throughput dramatically, it caused another problem. The roll of film had to pass closely behind the camera’s optics, which meant that the photographer could no longer look through the camera lens to design the shot.

Rangefinder cameras appear to keep things in focus

There was no problem with the lower-end consumer roll-film cameras, because these generally used an inexpensive “fixed-focus” lens. Better quality optics require the lens to be focused, however, and as we’ve seen, the photographer couldn’t look through the lens with a roll-film camera. One of the first solutions to this problem was the Rangefinder — a type of camera that offered a distance measuring scale in the viewfinder. By determining the range from the viewfinder, the photographer could then adjust the focus to match — usually with very good results.

Twin Lens Reflex cameras offer another solution

Typical Twin Lens reflex.

Twin lens reflex used upper lens to focus, lower lens actually took the photo.

While the rangefinder type cameras worked well, the camera industry is always evolving. A second method of allowing the photographer to focus and compose appeared in the “Twin-Lens Reflex” cameras. These cameras used two identical lenses, arranged one on top of the other in the manner of an over-and-under shotgun. The film winds past the lower lens, while the photographer can focus through the upper lens. Since most of the twin-lens cameras were fairly bulky, designers added a mirror and ground glass to the top of the camera, hence the term “reflex.

Now the user could hold the camera at waist level and look down at the ground glass which previewed the image via the mirror behind the upper lens. As the user adjusted the focus on the upper lens, a gear mechanism moved the lower “taking lens” to match.

While both rangefinders and twin-lens cameras offered a credible way to focus and preview a shot, neither allowed the photographer to look directly through the imaging lens. This made exact composition difficult in certain situations.

SLRs take cameras another step forward.

Light path through a single lens reflex camera.

Cut-away view shows the light path through a typical SLR. Light enters through the lens, hitting the lower mirror, where it is reflected upwards. It then strikes the top of the prism, where it is reflected again to strike the front of the prism. It is reflected yet a third time to pass through the viewfinder.

In their quest to allow users to see through the actual “taking” lens, camera makers turned to the periscope — a simple device using two mirrors placed at opposite angles to bend the light path. Periscopes are easy to understand — any kid can construct one from a couple of mirrors and some scrap wood. In a camera, the lower mirror is placed at a 45 degree angle directly behind the lens. Light striking the mirror is projected upwards to a ground glass. A pentaprism, which contains two additional mirrors, is located behind the viewfinder. The prism is used to flip the image so it can be viewed “right-side up”

There is just one hitch. If you’ve been paying attention, you no-doubt realized that the lower mirror blocks the light path to the film (or digital sensor as the case may be.) Now the photographer can look though the lens, but the image can’t be projected on to the film plane.

So the camera designers had to add another wrinkle. They had to move that mirror. Just long enough to make an exposure, since when the mirror moved, the photographer couldn’t see anything through the lens. So they designed the “instant-return” mirror.

At the instant of exposure, the mirror flies upward, the shutter opens, closes and the mirror snaps back down. It is a incredible feat, when you consider that instant return mirrors have to flip up and back in a heartbeat, over and over for the life of the camera.

Once the instant return mirror was perfected, photographers could once again design their images by looking through the lens. Unlike the twin lens reflex, this new breed of camera needed only one lens to focus and shoot with. So they became known as… you guessed it…. Single-Lens Reflex cameras.

Digital SLRs work exactly the same way — the same reflex system of mirrors and prism is used in front of a a digital sensor instead of film.

For further reading:

Wikipedia SLR page>

How Stuff Works - Single Lens Reflex

Images on this page published under the GNU Free Documentation License.

SLR Cutaway derived from image provided by:
Juhanson

Rolleiflex Twin Lens Reflex provided by
Jean-Jacques MILAN/Photographie - 40

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Sony Alpha dSLR no longer “vertically challenged”

Wednesday, November 7th, 2007

Sony’s first dSLR. the Alpha A100, was a great effort, but it did fall short in a few areas. From the e-mail and comments i get at Alphatracks, the biggest complaint about the A100 is that it didn’t offer a vertical grip option.

As I’ve pointed out before, this wasn’t Sony’s oversight. The A100 was based to a large degree on the very successful Konica-Minolta Maxxum 5D. For some unexplained reason, Minolta and friends crippled the 5D by not designing it to use a vertical grip. The 5D’s big sibling, the Maxxum 7D, did offer an optional battery grip, but the 5D was a different design and couldn’t use the 7D grip.

Grip installed on A700

New grip adds 3.5 inches and a pound of weight to the A700

When Sony built the A100 on the chassis of the 5D, there was no provision for a grip. Sony would have had to heavily massage the 5D components to add grip connections and controls, making the camera more expense and most likely delaying the launch. So Sony wisely brought the A100 to market without an accessory battery grip.

Aftermarket vertical grips for the A100 selling briskly

This hasn’t stopped some aftermarket accessory makers from developing grip fro the A100. We’ve discussed the DeCain and Ownuser accessory grips on these pages in the past.

Many photographers have had good experience with the aftermarket units, but since there are no internal contacts to allow a grip to communicate withe the camera, users have to put up with external cables to get the job done While it’s mice to have an aftermarket alternative, it’s obvious that a factory designed grip with internal connections would be a preferable solution..

When the Sony started to design the Alpha A700 dSLR, they started from scratch. Sony went to a lot of effort to make sure the Alpha A700 corrected any weaknesses inherent in the A100. One of the first things they did was add internal connections for a battery grip. The grip, known as the VG-C70AM is due to start shipping this month.

The two biggest demands for a vertical grip center around better handling when shooting in a vertical mode and the addition of extra battery power. Sony nailed both of these objectives with the VG-C70AM grip.

Grip installed on A700

Vertical grip enhances the Alpha A700’s ability to shoot in the portrait orientation.

Everything the horizontal grip can do, the vertical grip can do as well

The new A700 vertical grip looks like someone took an A700, cut the standard grip off and glued it to a battery container. Every control and button that appears on the camera’s built-in grip is mirrored on the accessory grip — in virtually the same location. Anything you can do with the standard grip you can accomplish with the accessory grip as well. Since the A700 automatically rotates the menus on the camera’s big LCD screen, this results in an excellent vertical image making machine.

Two batteries are better than one

As far as extra power goes, the grip has provision for two NP-FM500H batteries, which Sony claims will produce twice the battery life. (Well, duh!) . You have to remove the camera’s standard battery to attach the grip, so you only have two batteries available — but that is still a major improvement.

Grip is powered by two rechargeable batteries

Two batteries power the removable grip.

The question of weight naturally arises. The VG-C70AM weighs in at 10.1 ounces without batteries. Add two NP-FM500H power cells at 2.75 ounces each and the whole works is still slightly under 1 pound. The grip also adds about 3.5 inches (87.2mm) to the height of the A700 — a nice bonus if you have large hands.

Like he A700 itself, the VG-C70AM battery grip is constructed with an internal Magnesium-Alloy. Sony also says the unit has rubber gaskets to seal out dust and moisture.

Vertical grip should be forward compatible

Now there is good news and bad news. The bad news is that the VG-C70AM cannot be retrofitted to the A100, The A100 and A700 have completely different camera bodies and as we’ve already discussed, there are no internal provisions for a grip on the Alpha 100. So if you were hoping to bolt one of these bad boys to your A100, you’ll have to be content with on of the aftermarket solutions.

Ah, but there is a very good chance that the VG-C70AM will be fully compatible with Sony’s next dSLR; the famous Sony Alpha flagship. Based on the mockups shown last March, the A700 and the flagship share a common body. Thus the flagship (which many observers are calling the A900, although Sony hasn’t confirmed the name) will most likely be able to use the VG-C70AM. It makes sense, as it will save tooling and design costs if Sony can create a single grip for both models.

controls on the new Sony Alpha vertical grip

Rear side of the grip shows the thoughtful control layout.

Of course the standard disclaimers apply. Sony has only revealed a mockup of the flagship, so there is no guarantee that the A700 grip will be compatible. Don’t base your buying decisions on the mockup, as things could very well change. If I was a betting man, however, I would give you pretty good odds that the VG-C70AM will fit the flagship when it appears..








Sony updates Alpha A700 firmware and software

Thursday, November 1st, 2007

Sony is offering a free firmware update for the A700. According to the release, the new firmware update

“improves image sharpness and reduces noise under certain circumstances and improves flash control at very short distances with non-ADI control lenses.”

Sony says the update offers:

  • Sharper images for pictures taken under low contrast conditions
  • Reduced noise for pictures taken at ISO 3200
  • Improved flash control for objects closer than 1 meter with non ADI controlled lenses

In addition to the updated firmware, Sony is also updating the Image Data Converter SR and Image Data Lightbox SR applications included with the camera.

You can download the Windows and Macintosh versions of the firmware and software updates at the Sony Support site.




Sony full frame sensor with anti-shake discussion continues

Wednesday, October 31st, 2007

This will be the final post on the Sony Alpha full-frame sensor / anti-shake quandary. The first in the series outlined the full frame with anti-shake problem, while the second consisted principally of remarks by Bert Pasquale, a well-respected optical engineer.

Since several readers are sill somewhat confused, I have created some illustrations to help explain the situation.

Figure one shows the relative sizes of various sensors, They are drawn to the exact size, but since monitors and screen resolutions vary, the sizes may not be correct on your screen. The size of each sensor in relation to each other, however, is accurate.

size comparison digital sensor

Figure 1: Sensor sizes compared

The red rectangle represents a “full-frame” 24×36mm sensor. The green rectangle is a 17×2mm APSC sensor. The blue rectangle is 90% of a full frame.

Figure 2 shows the APS-C sensor overlaid on a circle that represents the minimum coverage of a 35mm full-frame lens. As you can see, there is plenty of “wasted coverage” as only the area inside the green rectangle will be captured. It is obvious that the sensor can move freely in any direction and still be covered by the lens.

size comparison digital sensor

Figure 2: Coverage of a APS-C sensor by a full-frame lens

Figure 3 is a full frame sensor contained inside the exact same coverage circle. There is no established size for the coverage area, as lenses will vary slightly. The designers only have to create a lens that will offer adequate coverage and sharpness of the 24×36mm film area, and still fit within the lens mount. Of course, the greater the lens coverage, the larger and heavier it will need to be. It will probably be more costly as well, so typically lens designers try to keep near the minimum dimension.

As Mr. Pasquale mentioned, the circle of coverage doesn’t immediately fall off to nothing. Rather, the edge of the circle gradually starts to provide lens light and become less sharp.The fall-off increases slowly until the image eventually fades away.

As you can see from Figure 3, there is little room for the sensor to move without clipping at least one of the corners. Again this will vary from lens to lens, as well as with different focal lengths of a zoom lens.

size comparison digital sensor

Figure 3: Coverage of a full-frame sensor by a full-frame lens

Figure 4 is an arbitrary 90% sensor. You can see that such a sensor is much larger than the APS-C size, yet still has room to float inside the coverage area. I chose this because several people “in the know” have suggested they believe this will be Sony’s answer to the problem. However, some other authorities have suggested that Sony may opt for a 1.25 crop sensor.

size comparison digital sensor

Figure 4: Coverage of a 1.1 crop sensor by a full-frame lens

On the other hand, Mr. Pasquale has suggested that the sensor may not actually move sufficiently enough to require a “crop” lens of any sort. That would be ideal, but until Sony announces the sensor, we really won’t know.

The final figure is one suggested by Alphatracks readers Warren Massey and LEdgars. In their comments, they suggest Sony could simply build an oversize sensor. As you can see by the rectangular outline in figure 5, such a sensor can move some distance in any direction without clipping. The idea is that the big sensor can move around and the camera can crop to a 24X36mm dimension at exposure. it’s a novel idea — but I not sure we will see it in the near future.

size comparison digital sensor

Figure 5: Coverage of a oversize sensor by a full-frame lens

First off, it would be expensive. As sensors increase in physical size, the manufacturing yield is less because typically there are more rejects. Even more significant however, is that an oversize sensor would most likely be confined to the Sony flagship. A full-frame sensor would be attractive to many other dSLR makers and in the past, Sony’s sensor division has profited by selling sensors to a wide range of camera makers. Would Nikon have any interest in an oversize sensor? It’s rather doubtful. Nikon uses a lens based image stabilization method, so there wouldn’t be a need for an oversize sensor.

So if Sony does produce an oversize sensor, their principal customer would be Sony — and for the time being only for the top-of-the -line, limited-production flagship. Would that justify designing and manufacturing an oversize sensor? Or would Sony prefer to invest their resources in a sensor they could sell by the truckload to other camera makers as well as their own dSLR division?

Time will tell, but I’m guessing Sony has a plan up their sleeves. It should be quite interesting!





Optical expert addresses the Sony full-frame SLR question

Tuesday, October 23rd, 2007

Last week, I posted about the alleged difficulty of using a full-frame sensor with the Sony/Minolta anti-shake system. See the post: Can Sony build a true full frame dSLR? I made critical error in my post, when I suggested that the sensor had room to move up and down but not side to side. This is incorrect. The typical 35mm image circle only needs to cover the full-frame sensor from corner to corner, so there would be no room to move the sensor in either direction.

So I was mistaken, but sometimes mistakes can be a positive thing. My error encouraged Bert Pasquale, an optical engineer (and Sony/Minolta SLR user) to write me with his assessment of the full-frame, anti-shake situation. In addition to pointing out my little misconception, he has several innovative ideas on how Sony could deal with the problem.

I asked Mr. Pasquale for permission to reprint his comments and he readily agreed. His remarks follow:

Hey Tom,

Bert Pasquale here, nicetameetcha! 7D & A100 owner… but not for long — the A700 is in stock in my local store since last week, and all the online dealers have them. (Sidebar: Beware ANY low-ball online dealer! - Be sure to Google any potential dealer for reviews before purchasing.)

About full-frame & sensor anti-shake: Note that you get clipping moving either vertical or horizontal; the image circle intersects the corner of 3:2 image rectangle. (Which does make the vertical less sensitive, and luckily that’s the typical hand-held motion.)

But how much movement does a sensor typically need during an exposure? Let’s say a “full-frame” image needed to be stabilized +/-1mm outside the 43.26 mm circle (the diameter of the image circle surrounding a 24×36mm film rectangle) That’s a +/-2.3% shake allowance. (Note: I don’t know how much the current mechanism even allows.)

Let’s think about how much image movement is typically introduced in an exposure? Assuming equal shake, it’s proportional to the focal length. (Of course for short exposures, it’s also proportional to the time.) Taking a few test shots at 1 second at 200mm, I am not shaking more than 1% total of the measured frame. That translates to only 0.42 mm of shift. Even if this was drift in just one direction, I’m still within a reasonable clearance, and if it’s vertical, even less of the image is potentially affected. So, fear not for your ultra-wide angles not working with full-frame sensor-based AS — You would have <<1% shake.

So, what are the implications if you DO move the sensor out of this circle? SLR lenses do not just fall off to zero throughput at Image Radius = 21.63 mm. Though each lens has it’s own characteristics, vignetting often begins before then, and continues out a few mm beyond before reaching zero throughput. (This is especially true when using a near wide-open aperture.) So the final implication of sensor-based AS is this: Some portion of some corners could be somewhat more vignetted than w/o AS. If we were talking about film, this might be an issue, but this is digital imaging, Baby!

What are the solutions digital imaging offers? Here a few:

  • Option 1: The camera could, hypothetically, apply an appropriate amount of gain to the corners that went out of the circle to try to make up for lost luminance. It could very intelligently combine general knowledge (Lens ID, focal length and f/# info) and individual frame measurements to compensate. Or, a manual in-camera or computer software user interface could be given. (If the camera embedded the shift info for each corner, and the user could apply the supplied or manual falloff curve correction. (You can already do this in Photoshop manually, as you do for existing “symmetric” vignetting correction.) It would be great to have lens correction built into the capture, anyway (a-la-DxO or the sort.)
  • Option 2: The camera could “warn” that possible excessive vignetting occurred, and give the user the option to crop the file right in the camera (manually or automatically), or in software on the computer. Before you even pull the trigger, the camera could observe your stability and let you know the frame is going to be clipped or not so you could frame appropriately, or become more stable. (This would be sweet!)
  • Option 3: Limit the AS movement. A user option for given situations could beep, flash or just not move beyond a certain amount, unless willing to crop.

These could be combined to make the AS sensor vignetting issue almost a non-issue. The competition would continue to point out the “superiority of lens AS” (while failing to mention the cost) and Sony will get beat up on discussion boards by people who don’t even have a portfolio. However, the majority of images would be fine — most AS movement would be a fraction of a mm and the corners would show minimal additional falloff. Notice that no one is complaining that the APS-C lenses made by Sigma and Tamron are hopelessly useless on a sensor-stabilized A100. I hope this discussion is helpful.

As an aside: If the “full-frame” sensor used the same pixel size as the A700 (5.3 micron), it would be about a 28.8 effective Mpixel sensor. If it had a 1.1 crop factor (32.7×21.8mm), it would only be 23.8 Mpixels. (If it used the A100’s 6 micron pixels, well, it would only be 23.5 full / 19.5 cropped Mpixels…) (If it used the Canon EOS-1Ds Mark III’s 6.4 micron pixels, it would be 21.0 full / 17.3 cropped Mpixels.)

Bert Pasquale
Optical Engineer

Thanks for sharing your knowledge, Bert. This is exciting stuff! In camera, computer controlled gain? Falloff curve corrections. Sensor based warning that the stability could cause vignetting! Wonder how much of this Sony has considered — and more importantly how much they will actually implement in the Alpha flagship camera. Stick around. it looks like things are going to get really interesting. It looks like its a great time to be a Sony A-mount user!


Who is that guy?


Web designer and photographer Tom Bonner has three decades of experience with Minolta camera equipment

Hi. I'm Tom Bonner and I've been shooting with Minolta SLRs for over three decades.

Alphatracks is my attempt to follow Sony's maneuvers in the dSLR market, and at the same time provide a resource for Minolta film and digital SLR users. A-mount shooters have to watch each other's backs, because there aren't as many of us. At least not for now....

You can view my design portfolio at http://adventuresindesign.com.


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