June 18, 2021

Alphatracks

Sony and Minolta SLR Weblog

Can Sony really make a full-frame dSLR? Not will Sony…but CAN Sony really do it?

Some months back, I wrote that I expected the so-called “flagship” Sony Alpha (possibly named the A900?) to carry a full-frame sensor. I still believe that to be true, however I’m hedging my bets a little. It will be “almost” full-frame or “close” to full-frame. It may not be the actual size of a 35mm negative, however, which is the definition of a full-frame dSLR to most photographers.

It isn’t that Sony lacks the technology to build an actual full-frame sensor. Sony has the ability to build just about any sensor they could wish.

Super Steady Shot doesn’t play well with a full frame sensor

The problem is the Super Steady Shot (anti-shake) system. Not that there is anything wrong with SSS itself, the in-body image stabilization is one of the Sony Alpha dSLR’s major advantages. However, one of the Alpha’s other major advantages is that it can use the extensive line of Minolta A-mount autofocus lenses. And thereby hangs a tale.

Twenty-some years ago, when Minolta engineers were designing the original A mount glass, there were no digital SLRs and no anti-shake systems. Thus, there was no reason to design a lens to cover anything other than the standard 35mm film image.

Thus the AF A mount lenses were designed to project a circle that would encompass a 24 X 36mm area at the camera’s film plane. There was no need to cover a larger film plane, because no Minolta SLR offered a larger negative size.

Maxxum 7D and Antishake: no worries

When Konica Minolta engineers developed the Maxxum 7D, they designed an in-body anti-shake system. The system works by moving the camera’s sensor in relation to camera movement. In essence, if there is camera vibration, the sensor stays in one place, despite the lens and body movement. The same system is used in the Maxxum 5D, the Sony Alpha A100 and the Alpha A700. All of these dSLRs use a 17 X 23mm APS-C sensor.

See the problem? If Sony develops a 24 X 36mm full frame sensor, any lens will need to cover an area larger than 36mm — at least when SSS is turned on. If vibration occurs in an up and down motion, there is room for the sensor to move in relation. If, however, the sensor moves to the left or right, it could move outside of the area covered by the lens. Update: I was in error about room for up and down motion. See these remarks by an optical engineer to understand why the image would be clipped in any direction the sensor moves.

This isn’t an issue with the current Sony/Minolta dSLRs, since the smaller APS-C sensor has plenty of room to move in any direction without moving outside of the lens coverage. When you move up to a full frame sensor, however, there isn’t nearly as much breathing room.

Lens coverage varies

Of course lenses vary. Some of the existing Sony/Minolta lenses may offer enough coverage to allow the SSS system to move — but others would probably exhibit some vignetting if the sensor moves too far to the left or right. Who wants to drop a ton of cash on a professional dSLR when many (most?) of the available lenses might display some vignetting?

How will Sony handle the full frame design?

Sony can tackle this problem in a number of ways. The first could be to drop SSS for the flagship model. That makes little sense, since Sony would then have to develop a line of image stabilized lenses. If they are going to develop an entirely new lens line, they might as well design larger coverage lenses and retain the in-body image stabilization.

Neither of these options are very credible, however. As I said, one of the Sony Alpha’s major selling points is that you can use those millions of Minolta A-mount lenses. Start redesigning the lenses and there is far less reason to choose the Alpha over the competition.

The rumor sites are suggesting that Sony could eliminate any vignetting problem by reducing the sensor size. The sensor could still be much larger than the current 1.5 crop sensor, but not exactly the size of a 35mm film negative. The figure bandied about is 1.1 crop. That would indicate a sensor of something like 21.6 X 32.4mm.

I want my super wide angle lens back!

Loosing 3mm on the width and 2.5mm on the height doesn’t seem like a lot — but it will affect the camera’s ability to display the widest angle of view with current lenses. One of the biggest problems with the APS-C sensor is that most of the original A-mount wide angle lenses aren’t very wide any longer. Cropping a 35mm lens to APS-C size yields something equivalent to the “standard” 50mm lens on a full frame camera. A 24mm lens is now closer to a 35mm. Even a 16mm fisheye is will only show what you would see with a 24mm lens on a full frame camera.

So one of the prime reasons for choosing a full frame camera is to make all those Minolta wide angles truly wide again. A 1.1 crop would be much better than a 1.5 crop in this regard — but is it enough? That 16mm would now be equivalent to 17.6. A 35mm would look like a 38.5 lens.

Those differences seem fairly insignificant, but there are times when you need the widest angle of view you can get. I hate to give up even a millimeter when I am working with an extreme wide angle.

There is one other option that Sony could adopt. Create a full frame 24mm X 36mm sensor and allow the camera to use the full sensor only when SSS is turned off. Turning on the image stabilization would automatically turn off the outer ten percent of the sensor. This would give the best of both worlds. When SSS is engaged, the sensor size is reduced so there is no chance of movement causing vignetting. Turn the image stabilization off and you get the entire full frame area and the ability to shoot at your lenses widest field of view.

Taking a page from Nikon’s book?

This isn’t as far fetched as it seems. Until recently, Nikon didn’t have any full frame cameras in it’s line up, and they sold a ton of APS-C type lenses to go with their 1.5 crop dSLRs. With their all new full-frame D3, Nikon users who owned a bag full of 1.5 crop lenses faced a big problem. “Big N” sidestepped the issue of the APS-C lenses not covering the FF sensor with a switch that reduces the sensor to APS-C size when shooting with a 1.5 crop lens.

Sony could do the exact same thing with their offering, simply reducing the sensor to 90% when SSS is turned on. Of course to be truly useful, there would need to be some way of indicating the crop area in the view finder. This would probably be in the form of engraved lines on the ground-glass to show the crop area.

Would this be worth it? I’m not sure it would be worth the trouble and cost — but it would sure be slick.

If you were on the Sony design team, how would you handle this issue?