What is Flange Focal Distance? The simple textbook answer is FFD represents the distance from the lens mount (the flange) to the film plane. (The vertical plane of the sensor.)

If your eyes are starting to glass over, don’t worry. It is nowhere as complex as it sounds.

The Film Plane

Inside every interchangeable lens you will find elements designed to project the view from the lens onto a fixed vertical plane. This vertical surface is known as the film plane. The lens expects the film plane to be a precise distance from the rear element, although this distance varies by manufacturer and lens line.

Photographic lenses consist of a complex collection of elements that gather light rays and focus them at a specific location. The sharpness of the lens is dependent on how well it is able to concentrate a focused image on the film plane.

If you examine the top of any camera, you will most likely find a symbol consisting of a circle with a line intersecting it. The line indicates the exact location of the film plane. This symbol is a useful aid for those creating extreme close-up photographs, but most photographers will never require this information. Still, it is worth understanding where the film plane lies.

A digital camera’s sensor is located on the film plane. In the same way, the film in an analog camera is arranged so it lies on the film plane. The measurement between the lens mount and film plane is called the Flange Focal Distance, which can vary for each camera manufacturer.

dSLR Cameras require a wide Flange Focal Distance

On a dSLR the Flange Focal Distance must be large enough to include the mirror box.

With no need for a mirror box, evil (mirrorless) cameras can be designed with a much smaller Flange Focal Distance.

A dSLR camera will require a large FFD because the mirror and ground glass occupies the space between the lens mount and the film plane. The film plane can be placed much closer to a mirrorless camera’s lens mount, but even mirrorless cameras need some separation between the lens and the sensor. So E-Mount cameras have an FFD, although it is considerably smaller than that of a dSLR.

dSLR and SLR cameras require a large FFD to allow room for the mirror box

Mirrorless Cameras have a small Flange Focal Distance

Are you with me so far? A sharp photo can only be obtained if the light rays from the lens merge directly on the film plane. If the light rays converge on a location other than the film plane, the images cannot be sharp at infinity.

Every manufacturer settles on an FFD for their lenses. In the case of Minolta, the original Rokkor (SM Mount) lenses are designed to focus correctly at an FFD of 43.50 mm. All SM Mount lenses were created to have a point of convergence at that distance.

SR mount cameras require a FFD of 43.5 to allow for the mirror box.

E-Mount and NEX cameras only require an 18mm FFD.

When Minolta introduced the A-Mount cameras, the auto-focus mechanism required additional space. Thus, the FFD of the A-Mount lenses was increased to 44.50 mm. When Sony acquired Minolta in 2006, they retained the A-Mount, which meant the Sony dSLRs also maintained the 44.50 mm FFD.

The 18mm FFD of the Sony E-Mount Simplifies Adapting SLR Lenses

Since the NEX and subsequent E-Mount Sony cameras do not use a mirror and ground glass, the engineers were free to reduce the FFD to a mere 18mm. In addition to making the cameras lighter and more compact, the smaller FFD made it ridiculously simple to adapt a variety of dSLR lenses to the new evil cameras.

Because dSLR lenses were created with a much larger FFD, they can be easily fitted to E-Mount cameras. As long as the adapter holds the lens at the expected FFD, the lens will deliver quality photos.

A Rokkor adapter needs to be exactly 25.5 mm thick. This distance added to the ‘s built-in 18mm will suspend the lens at exactly at 43.50. This will allow the lens to focus perfectly at infinity.

Obviously, an A-Mount adapter will need to be 26.5 mm thick, in order to hold the lens at the required 44.5 mm distance from the film plane.

You can perceive why E-Mount lens adapters for vintage dSLR lenses have proliferated. Because of the mirror box, all vintage dSLR lenses have a large FFD. Older manual-focus Canon FD (42 mm), Nikon F (46.5 mm), and Pentax K (45.46 mm) lenses only need a simple adapter to attach the lens to the E-Mount at the proper distance.

You Cannot have a Negative Flange Focalplane Distance

Things get trickier when you attempt adapting lenses designed for a smaller FFD to a camera with a thicker FFD. You can’t very well design an adapter to have a negative FFD. The lens would have to move inside the lens mount.

A classic example would be adapting a Rokkor lens to an A-Mount camera. No matter how you configure it, there is no way the Rokkor SR Mount can project a sharp image onto the A-Mount’s film plane. Even if you could design an adapter with zero thickness, the Rokkor lens would project a sharp image at 43.5mm, but the A-Mount’s film plane is located at 44.5. The result would be soft images when focusing at infinity.

The only practical solution is to add an additional lens element inside the adapter. This extra lens refocuses the light path from the Rokkor lens so it projects the image correctly at exactly 44.50 mm.

Naturally, adding a new lens element could affect image quality. Although the additional element does not have the same lens coating as the original Minolta lens, I have not encountered any serious quality issues with the MD to A-Mount adapters that I have used.

Most adapters are built and sold by small third-party manufacturers. These firms may or may not have the ability to design an internal lens that measures up to the quality of the lens you are attempting to adapt.

One final note about Rokkor to A-Mount adapters. The internal lens is only required when you need to focus at infinity. You can encounter adapters without the internal lens; often these are marketed as “glassless” adapters. These will most likely give you soft images at infinity, but they will allow you to do excellent macro and close-up work.

Just to be clear, the preceding several paragraphs only apply to Rokkor to A-Mount adapters. Adapting 35mm lenses to E-Mount cameras does not require any added lens elements.

Because of the large FFD of various dSLR lens lines, you should be able to find an E-Mount adapter for almost any vintage 35mm lens. These lenses cover a full 35 mm film area, so they can be used on both the full-frame A7 series as well as the APS-C A6000 and NEX cameras.

The thrust of this post is aimed at explaining Flange Focal Distance and how it impacts adapting lenses from one camera to another. This article does not explore autofocus adapters or focal reducers that will modify a lens’ effective focal length. I will discuss those advanced adapters in a future post.

Wikipedia Chart of Standard Flange Focal Lengths

M42 Lens Specifications

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TIPA members selected gear, software, and services in forty photographic categories for 2022. The awards for cameras and lenses are likely to be of most interest to Alphatracks readers

Sony captured four of the twenty-three combined camera and lens awards.

BEST FULL FRAME EXPERT CAMERA

The Sony Alpha 7 IV was selected as The BEST FULL FRAME EXPERT CAMERA. The judges praised the A7 IV’s backlit 33MB sensor, the 15 stops of dynamic range, and low light performance. They were equally struck by the camera’s ability to record one hour of continuous video.

BEST VLOGGER CAMERA

The Sony ZV-E10 scored another gold star for Sony, as it was judged the BEST VLOGGER CAMERA. This wasn’t a huge surprise, as there isn’t much competition in the Vlogging space.

The judges were enamored by the 3-inch flip-around touch screen, the directional mic, and the variety of shooting modes. The judges also highlighted the E-10s array of ports and external connections. Additionally, they cited the E-10’s compatibility with the full complement of E-mount lenses as a major benefit.

BEST FULL FRAME STANDARD ZOOM LENS

Speaking of lenses, the Sony FE 24-70mm F2.8 GM II was judged the BEST FULL FRAME STANDARD ZOOM LENS. The panel highlighted the myriad ways the GM II outperforms the original FE 24-70mm. The judges liked the fact the GMII is smaller and lighter and features quicker focus tracking.

BEST FULL FRAME TELEPHOTO ZOOM LENS

Another second-generation lens, the Sony FE 70-200mm F2.8 GM OSS II, received the nod for BEST FULL FRAME TELEPHOTO ZOOM LENS. The panel recognized this 70-200mm focal range is most likely the most popular tele zoom across the board.

Choosing the Sony 70-200 as the “Best” is a testament to how this lens stands out in this crowded focal range. Sony has built this lens with 4X quicker AF speeds while at the same time making it almost 30% lighter than the previous model. The jury also lauded the quiet AF and reduced focus breathing.

Third-Party Lenses also scored Awards

Canon and Nikon optics did receive awards for other focal lengths. Of course, Sony E-mount photographers cannot make use of these lenses directly. Of more interest were third-party optics from Tokina, Sigma, Voigtlander, Laowa, and Tamron. Each of these manufacturers scored a Best award for a particular focal length. Tamron and Sigma were ranked Best in multiple focal lengths.

You can see the entire list of 2022 TIPA awards winners on the association’s website.

There was a time Sony wasn’t considered in the same league as Canon and Nikon. Sony’s ability to excel in the TIPA awards proved those days are long past.

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Photographers who shoot with the Sony NEX-3 and NEX-5 mirrorless cameras as well as videographers using the NEX-VG10 camcorder have something to be excited about. Sony has announced that they will provide full specifications of the brand new E-Mount lens mount to third party lens makers. As a result, aftermarket lens makes will be able to  produce E-mount lenses without paying a licensing fee.

Sony is even encouraging lens adapter makers to produce adapters to fit various non-Sony lens to the NEX cameras.

Obviously, this will be welcome news to NEX shooters. When the brand new NEX models shipped last year, the only available lenses were the 16mm prime and the 18-55mmm zoom.  The 18-200 zoom was announced but didn’t ship until a couple of months afterward.

Sony has promised more E-mount lenses, and showed several prototypes at Photokina.  Still the E-mount lens line is fairly sparse, although Sony does offer an adapter to allow Sony Alpha A-mount lenses to be used on the cameras.

Offering the specifications to third party lens makers should ensure that the E-mount will thrive n the coming years. We should see many new lenses and adapters appear in the E-mount. In addition there is a chance there will be more inexpensive lenses offered as well.

The Sony press release carries endorsements by Carl Zeiss, Cosina, Sigma and Tamron. Of course endorsement doesn’t necessarily mean these companies will produce E-mount optics, but it is an indication they are considering it.

The specification will not be released until April, so it is doubtful any of these manufactures have even seen the specification. It will probably take months before aftermarket E-mount glass starts to trickle in to dealers. But Christmas is the big selling season for digital cameras, so I think some  of these manufactures will do their best to provide new optics in time for the holidays.,

I find it interesting to see Carl Zeiss endorsement on the press release. Zeiss, of course, licenses some of their optical designs to Sony for the A-mount dSLR cameras. Some of Sony’s top-of-the-line A-mount lenses carry Zeiss optics but are sold under the Sony Alpha brand. Will Zeiss create their own line of E-mount lenses independent of Sony?

There are already several aftermarket lens adapters designed to attach various brands of lenses to the E-Mount cameras. Once the specification is released, adapter makers will have full reign to attach all manner of older  film lenses to the NEX cameras. With only an 18mm flange to sensor offset, almost any lens will be able to focus at infinity when adapted to the NEX.

Provide the E-mount specifications without licensing fees. Smart move Sony!

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One of the most intriguing things about the Sony Alpha NEX-5 and NEX-3 cameras is that you can use your existing A-mount lenses on the new models. Well, sort of. You need the Sony LA-EA1 adapter to mount an A-mount lens on the NEX system, and that involves some minor sacrifices. Overall, however, your current lenses should deliver great images on the NEX system.

The LA-EA1 is a far cry from the simple adapters used to mount non A-mount lenses on the Sony Alpha. It differs from the typical simple machined ring found in  MC to A-mount adapters or M-42 lens conversion mounts. The A-mount to NEX adapter is a sophisticated piece of electronics.

Unlike Minolta Rokkor or M-42 lenses, A-mount lenses from Sony and Minolta do not have an aperture adjusting ring, Older style lenses have a mechanical ring that allows the user to change the aperture opening manually. When Minolta introduced the Maxxum cameras in 1985, however, they did away with the aperture ring and used electronics inside the camera to regulate the aperture. If desired, the photographer could still manipulate the aperture manually, but it had to be done through a menu on the camera body.

This makes a conversion adapter for A-mount lenses more challenging to design. Conventional adapters rely on the user manually setting the aperture. Since there is no external method for changing the aperture on an A-mount lens, any useful adapter needs to provide a way for the camera to actually control the lens electronically.

Admittedly, it isn’t difficult to pass electrical information through an adapter. but the adapter needs to be designed so the camera’s aperture control can control the lens.

The LA-EA1 can do just that, providing automatic — and presumably manual — control of the lens from the camera’s  controls. Since the auto-diaphragm on the A-mount lenses is also controlled electronically, the new adapter will provide auto-diaphragm capability as well.

What the adapter will not provide, however is auto-focusing. The overwhelming majority of A-mount lenses do not have internal focusing motors, so the adapter is not designed to offer auto-focus.

The other limitation is image stabilization. Sony Alpha dSLRs are famous for having image stabilization built into the body. In order to make the NEX bodies as small as possible, however, Sony engineered the small cameras to use in-lens stabilization. As a result, A-mount lenses mounted to the NEX series cameras will not have stabilization.

One other interesting feature of the adapter is the built-in tripod collar. The NEX series cameras are so small that there might be problems using a heavy lens on the camera while it is on a tripod. Sony eliminated the problem by incorporating a standard tripod mount within the adapter. You merely hang the camera body on the adapter, while all the weight of the lens is borne by the adapter.

The LA-EA1 is available for pre-order at Sony Style for $199.00.

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May 17, 2010 Sony has introduced a brand new lens mount for the NEX series, which will be known as the E-Mount. Older A-mount lenses from Sony and Minolta can be used through the LA-EA1 NEX Alpha Camera Mount Adapter, but if you want Auto-Focus and Image Stabilization, you will need E-mount lenses,

Sony is introducing the NEX cameras with catalog of three lenses. Undoubtedly the E-mount lens line will grow, but for the time being the available lenses include:

16mm f/2.8 Pancake lens

The smallest and lightest E-mount lens is the 16mm f/2.8 pancake prime lens. The term pancake referrers to the narrow appearance when attached to the camera. This is one of the two “kit” lenses offered for the NEX series.

Like all cameras with APS-C sensors, the 16mm focal length doesn’t provide as wide a view as a 16mm lens on a 35mm, full-frame camera. The crop factor is 1.5, which means that the 16mm lens will provide the view of a 24mm lens on a 35mm camera.

Besides being the widest lens in the E-Mount series, the 16mm lens is also the fastest at f/2.8. This is suitable for shooting in poor light, but you will need to increase the ISO to match the low-light capabilities of the f/1.8 or f/1/4 A-Mount dSLR lenses.

Unlike the Sony Alpha dSLRs, which have in-body image-stabilization, the NEX cameras require in-lens stabilization. Sony has built stabilization into all of the initial E-Mount lenses, including the 16mm f/2.8

You should consider this lens if you want to shoot with available light, shoot wide-angle views (real-estate interiors, scenic vistas) or want to carry your NEX camera in a (large) pocket.

The SEL16F28 will list for $250.

Sony has announced two auxiliary converters for the NEX 16mm f/2.8. One converts the lens to a fisheye, while the other creates a much wider view. I’ll discuss the converters in another post

18-55mm f/F3.5-F5.6 zoom lens

The other available kit lens is the 18-55mm f/3.5-5/6 zoom lens. Although not as wide or as fast as the 16mm pancake, the 18-55mm lens offers a convienent wide-angle to short-telephoto zoom range. At the wide end, the 18mm setting will yield roughly the same field of view as a 27mm lens on a 35mm camera. At the other side of the scale, the 55mm length will be equivalent to 82.5mm on a full frame SLR.

The lens isn’t a speed demon, as the maximum aperture at the wide end is f/3.5, while at the telephoto side the aperture drops to f/5.6. Still, with the built image stabilization, the lens should be fast enough for most photography situations.

The minimum focusing distance is a respectable 9.8″ (0.25m). The filter ring diameter is 49mm.

Chose this lens for portrait or all around shooting in good light. It is isn’t as pocketable as the 16mm pancake, but it offers more versatility.

List price for the SEL1855 lenses will be $300.

18-200mm f/3.5-6.3 zoom lens

If you want or need longer telephoto capabilities, Sony will be adding a 18-200mm f/3.5-6.3 zoom to the E-mount line up in the fall of 2010. This will not be offered in a kit package, at least initially. Since Sony currently doesn’t market the NEX models in a body-only package, buyers will need to buy a camera with a lens, then purchase the 18-200mm zoom as an accessory.

Since the big zoom completely overlaps the 18-55mm lens, it makes little sense to buy the 18-55mm kit lens, then buy the 18-200 zoom. To my mind, it would make much more sense to buy the kit with the 16mm prime lens if you plan to buy the 18-200mm zoom.

The crop factor on this lens makes it equivalent to 27-300mm lens on a 35mm camera. This lens also features the Active Mode image stabilization that Sony claims makes it possible to shoot movies while walking.

Of course all lenses are compromise and the big zoom has a slow maximum aperture of f/6.3 at the 200mm focal length. That is fine for outdoor shooting in bright sunlight, but don’t expect to shoot indoor basketball action at f/6.3.

The SEL18200 zoom lens should be available this fall for about $800.

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