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| p.3 #3 · p.3 #3 · A7 or A7R with Vintage MF glass? Poll Inside! |
i shot the same scene with the rokkor 24/2.8, rokkor 28/2, 58/1.2, contax g 28/2.8, contax g 45/2, and leica m 40/2 summicron-c on both the a7r and the a7 (but on different days). only the contax g 28/2.8 looked worse on the a7r when downsized to 24mp, all the rest looked sharper (even in the corners) on the a7r. i will try to normalize white balance etc and make crops when i have time to post the comparisons.
Well it would not be the first time I was wrong about something
Obviously a good test would be something like:
Infinity past 30 meters. 35mm 28mm 20ish mm SLR glass.
wide open f/4 5.6 8 11 and 16.
At any of those FLs superior corners wide open with A7r would really surprise me.
I've been having a email corespondence with Dan at Maxmax which I don't think he will mind if I share:
Have you had a chance to work on a Sony A7 sensor?
Are you ready to do so?
We need to update our website, but, yes, we can converted quite a few A7 and A7R cameras. We plan to do a monochrome conversion at some point, but do have a lot of other work to get done first.
Would be very interested to talk with someone who has a maxmax HR conversion on the Sony A7 (not R).
Thick sensor toppings seem to limit the A7 with Leica M wide angles, .i.e soft edges. Does the HR conversion reduce this problem?
Does the HR conversion effect auto-focus?
What would be the downside of a HR conversion on a Sony A7.
cost would be 450USD?
TY so much for you time and info.
I have gotten some questions about this from others as well.
The Sony A7 ICF/AA stack is 1.75mm thick which is relatively thick. The lens flange to sensor distance is also short. If you think about the path of light exiting the lens as it goes to the sensor, it has to pass through the ICF/AA. If the light is going through the center, then the path is the shortest. As you move toward the sensor edges, the light has to travel at greater distance because the light is going through the ICF/AA at an angle. The effect is the same as if the ICF/AA stack changes thickness getting thicker towards the edges. The lens design and aperture also will affect this. A wide aperture longer lens will have less of a problem than a small aperture wide angle lens.
When we do an HR conversion, we remove the stock ICF/AA and replace it with a new ICF-Only having the exact same thickness. If you don't use the correct thickness, then you change the focal plane of the camera. So, our HR conversion AF will work correctly. Biggest downside on HR, and this changes depending on the camera ICF/AA design, is that the AA part of the stack is clear while the ICF has a teal tint. The new ICF-Only has a thicker ICF which shifts WB toward the cyan. Most just set a custom WB if it is an issue, but some don't like it. The thinner the ICF/AA stack, the less of a color shift.
To fix the A7, you would need to go with a thinner ICF. A thinner ICF is going to move the focal plane towards the lens. To get correct focus, you would need to move the sensor closer to the lens which is hard to do on the A7. You would have to either mill the sensor mounting points and modify the camera body sensor mounting points. Neither is an attractive option. Possible, but it would be a lot of work and easy to spend a lot of time trying to get it just right.
The Sony conversions are $550 because their bodies are all really hard to take apart.
Can't thank you enough for the detailed reply.
I'm hearing that it would be 1.75mm before and after HR conversion, hence edge performance with short flange wide angle lenses is unlikely to improve. Moving the sensor would only cause the same issue.
Here's the thing: many of us are using the A7 for manual focus lenses only. Hence auto focus is not an issue.
On special request, would maxmax apply a thin ICF stack, and how thin could it be?
Is there some special reason the HR ICF has a teal tint, and could that be avoided, since Sony auto WB is actually very good?
TY so much,
I will get this information out to many interested Sony owners at FM and RFF forums.
If I could put and a thin ICF and move the sensor closer to the lens, then the camera would focus. If put in a thinner ICF, then the camera will become near-sited. You would need to focus past infinity for focus or use one of those adapters that moves the lens back and forth. The thickness of the ICF/AA stack is the problem - you would still have the issue with a thinner ICF, but not as bad.
A quick check shows I have a 0.58mm ICF that I can cut to fit.
Most camera ICF/AA stack have a teal tint to the ICF layer. On a DLSR, typically, there is something like BG38 IR absorbing glass which has a teal tint and then vapor deposition coatings to help block IR as well. Since I put in a new ICF only that has the same thickness as the stock ICF/AA, the WB gets more teal. If I used 0.59mm, I don't think you would see much WB shift. There would be some shift somewhere because the stack is changing. Also, not sure if the Sony auto WB is off the sensor anyhow rather than a separate sensor like a typical DLSR.
end of conversation
So I think what jumps at me right away, is that we could go to .58 and maybe have some great performance with RF wides, but our adapter infinity would be 1.17mm off. We would need to shave this amount.
My new Hawks has an adjustable infinity, but I'm not sure it's that much.
I bet he would make a custom one...what a fun experiment that would be