edwardkaraa wrote:
Ok, I received a reply from them saying they can remove the AA filter from the A7 but they have to replace it with glass of the same thickness otherwise the camera will become nearsighted. Now I need to convince him that it's ok to make the camera nearsighted as I will only use it with RF glass. Now I think this is an important aspect to consider, that a thinner glass cover will change the focal distance and focusing on lenses designed for the unmodified camera. Your thoughts?
So, if the surgery makes it nearsighted, would that not still pose an issue with adapted rangefinder lenses if you needed to reach infinity even with manual focus? It would seem you would need an adapter that normally allowed focusing past infinity somewhat(slightly thinner to adjust for the missing thickness)...or is my reasoning off?
Tariq Gibran wrote:
So, if the surgery makes it nearsighted, would that not still pose an issue with adapted rangefinder lenses if you needed to reach infinity even with manual focus? It would seem you would need an adapter that normally allowed focusing past infinity somewhat(slightly thinner to adjust for the missing thickness)...or is my reasoning off?
That's a good point, but my understanding is that the opposite will happen, the lens will focus beyond infinity with the same adapter, so a thicker adapter would be required.
edwardkaraa wrote:
That's a good point, but my understanding is that the opposite will happen, the lens will focus beyond infinity with the same adapter, so a thicker adapter would be required.
Hmm. The focal point of the sensor is essentially moving back by removing the AA filter so I would think the adapter would have to become thinner to compensate since at infinity focus the rear element is at it's shortest physical distance to the sensor. For the lens to focus past infinity as you suggest, the focal point of the sensor would have to move forward not backward I think.
So I've been shooting a ton with the Voigt 15/4.5 II the past two days since picking it up.
SOOC jpgs are just fine (for me), with minimal color shift wide open. The corners are pretty dark, but they clean up quite a bit when stopped down some. The lens handles amazingly well on the camera, thanks to the focusing tab and nice, big aperture ring.
I'll do some more shooting and testing vs my 17/4 FD, but I think i'll stick with the heliar.
Tariq Gibran wrote:
Hmm. The focal point of the sensor is essentially moving back by removing the AA filter so I would think the adapter would have to become thinner to compensate since at infinity focus the rear element is at it's shortest physical distance to the sensor. For the lens to focus past infinity as you suggest, the focal point of the sensor would have to move forward not backward I think.
To be honest, I'm not really sure, so you might be right about this. My thinking is that the glass cover makes the optical distance longer due to refraction, so by making it thinner, it's like you're bringing the sensor forward. Where are you Joachim?
Anyhow I believe even though the difference might be important enough to screw up AF it must be negligible for manual focusing.
Tested a zeiss 18mm f/4 on my a7r today. Lots of color shift and minimal corner smearing. Not usable for me but maybe folks with more patience using corner fix would be okay.
edwardkaraa wrote:
To be honest, I'm not really sure, so you might be right about this. My thinking is that the glass cover makes the optical distance longer due to refraction, so by making it thinner, it's like you're bringing the sensor forward. Where are you Joachim?
Anyhow I believe even though the difference might be important enough to screw up AF it must be negligible for manual focusing.
Yeah, I don't know. If somehow removing the AA filter actually brought the point of focus forward... With the cheaper adapters which allow focusing past infinity anyway, it might not matter but it might be hit or miss. The better/ more exact adapters will have a problem at one of the extremes even with manual focus. Depending on which condition exists, you will either loose infinity focus or minimum focus distance will be much greater.
Tariq Gibran wrote:
Yeah, I don't know. If somehow removing the AA filter actually brought the point of focus forward... With the cheaper adapters which allow focusing past infinity anyway, it might not matter but it might be hit or miss. The better/ more exact adapters will have a problem at one of the extremes even with manual focus. Depending on which condition exists, you will either loose infinity focus or minimum focus distance will be much greater.
I shot it on the a7 and thought it was one of the better performers. Wide open at ~infinity it's going to be a bit low in contrast and relatively soft, but it only needs to be stopped down a little to improve. By f/5.6 it looks to be equal to the FE35 across the frame. In less technical applications I doubt you're going to find much fault with it on the a7/R, even at wider apertures.
p.126 #10 · A7/A7r - performance with WA RF lenses
waterden wrote:
There's been a lot of chat about the VM 21/1.8 here, and it seems to be a runner with the a7, but nothing I've found about the VM21/4. I remember using the old M39 version on my Leica M6 and MP and it was fine. I imagine if the 1.8 21 works this should too unless the pancake design causes problems. Anyone here tried one yet?
I tried it and i am not that happy about it.
I am prepared to live with magenta cast as its easy to fix but i also saw smear when focused at infinity. Granted i only took it once with me to shoot and it was a cloudy rainy day with haze so it wasn't ideal. I dont want to give up on the lens just yet, so more testing is due...
I shot it on the a7 and thought it was one of the better performers. Wide open at ~infinity it's going to be a bit low in contrast and relatively soft, but it only needs to be stopped down a little to improve. By f/5.6 it looks to be equal to the FE35 across the frame. In less technical applications I doubt you're going to find much fault with it on the a7/R, even at wider apertures.
Yes, and thank you -- got some info in the other thread, it's looking very promising -- in fact, I'm now feeling I should be able to cool my Lux 50 jets by switching my attention to the CV 35 1.2 (that might not seem logical to most folks here, but there is a logic for me -- I could then start off with the CV 35 1.2 on an NEX-7, for 50mm FOV, and later switch to a FF Sony body).
One last unresolved question: anybody happen to know if the CV 35 1.2 performs equally well on the A7r as it does A7? Or does the color cast creep in on the A7r?
p.126 #12 · A7/A7r - performance with WA RF lenses
I did a test today of my Leica M 24 Elmar and Zeiss ZM 25 Biogon and shot them with both the A7r and my Leica M9.
In short, the M9 produced the best images across the frame but when stopped down to f/8 and f/f11 the Elmar wasn't to far behind on A7r. The ZE 25 Biogon performed a little worse than the Elmar on all apertures.
p.126 #13 · A7/A7r - performance with WA RF lenses
joakim wrote:
I did a test today of my Leica M 24 Elmar and Zeiss ZM 25 Biogon and shot them with both the A7r and my Leica M9.
In short, the M9 produced the best images across the frame but when stopped down to f/8 and f/f11 the Elmar wasn't to far behind on A7r.
Joakim, in what way was the M9 superior? Just in corner sharpness or in other ways as well?
p.126 #14 · A7/A7r - performance with WA RF lenses
Corner and edge sharpness was what I looked most at but SOCC the M9 delivers better colors without any color cast. I posted 2 photos in another thread and apart from what I said there in the defense of the A7r it should be said that I am much more used to work with the M9 files.
p.126 #15 · A7/A7r - performance with WA RF lenses
Thanks Joakim! Actually, there is color shift on the left side of the Sony shot, but I notice how it handles highlights differently from the M9. To my eye, it looks like much better DR on the lit part of the building and on the crane. If I can clean up the colour shift with CornerFix, it will even improve some more. That is really super good news, I had pretty much given up on the Elmar 24. Thanks again!
p.126 #16 · A7/A7r - performance with WA RF lenses
edwardkaraa wrote:
To be honest, I'm not really sure, so you might be right about this. My thinking is that the glass cover makes the optical distance longer due to refraction, so by making it thinner, it's like you're bringing the sensor forward. Where are you Joachim?
Anyhow I believe even though the difference might be important enough to screw up AF it must be negligible for manual focusing.
When you remove parts of the filter stack, then the sensor moves forward - from the lens' point of view. I.e focuses further away (than if the filter plates were still there). You can then focus past infinity - if the lens was "correct" from the beginning. And if the lens contains floating elements, they'll be slightly off - they'll compensate for "infinity" at the new, shorter, focal distance.
Adding material to an airspace changes the ray-path "length" from point to point by +(material thickness*refractive index). Remove 1mm of RI 1.5 glass (both the crown glass used for most UVIR filters and quartz is ~1.50-1.55, air is very close to 1.0) and you have to shim the sensor by about:
before: (1.0mm * 1.5) - after: (1.0mm * 1.0) = 0.5mm
0.5mm isn't much, but since I haven't bombed an A7 yet I can't say if there's room behind the main board to shim the sensor mount plate by that amount.
I'd recommend you (they) use the thinnest normal multicoated AR glass they can find, laminate the color filter plate to it, and use at least the cage/sensor mount plate shim they find possible. If that isn't possible, shim the lens mount ring in stead. Be aware that shimming the lens mount on the camera must be done with metal shims, while keeping the contact area as large between shim and cage as large as possible. This area is what gives all of the lens>mount>camera mechanical stability.
Should they refuse, I could do it if I ever get some spare time in the workshop... I've already done a few NEX'es and a few Nikons.
p.126 #17 · A7/A7r - performance with WA RF lenses
theSuede wrote:
When you remove parts of the filter stack, then the sensor moves forward - from the lens' point of view. I.e focuses further away (than if the filter plates were still there). You can then focus past infinity - if the lens was "correct" from the beginning. And if the lens contains floating elements, they'll be slightly off - they'll compensate for "infinity" at the new, shorter, focal distance.
Adding material to an airspace changes the ray-path "length" from point to point by +(material thickness*refractive index). Remove 1mm of RI 1.5 glass (both the crown glass used for most UVIR filters and quartz is ~1.50-1.55, air is very close to 1.0) and you have to shim the sensor by about:
before: (1.0mm * 1.5) - after: (1.0mm * 1.0) = 0.5mm
0.5mm isn't much, but since I haven't bombed an A7 yet I can't say if there's room behind the main board to shim the sensor mount plate by that amount.
I'd recommend you (they) use the thinnest normal multicoated AR glass they can find, laminate the color filter plate to it, and use at least the cage/sensor mount plate shim they find possible. If that isn't possible, shim the lens mount ring in stead. Be aware that shimming the lens mount on the camera must be done with metal shims, while keeping the contact area as large between shim and cage as large as possible. This area is what gives all of the lens>mount>camera mechanical stability.
Should they refuse, I could do it if I ever get some spare time in the workshop... I've already done a few NEX'es and a few Nikons....Show more →
Wow, thank you so much for your detailed answer Joachim! Much appreciated! My assumption was based on previous posts of yours, but I wasn't entirely sure I remembered correctly.
And I might take you up on your offer if they won't do it
p.126 #18 · A7/A7r - performance with WA RF lenses
I'm not too sure about searching for lenses either. If I am too specific I get no results and a search term like CV 35 1.4 for message body, whole phrase just finds 35, etc. So can anyone point me to any threads for this lens on the a7 - it's a much more manageable size than the CV 35/1.2 II and only half a stop slower?
p.126 #19 · A7/A7r - performance with WA RF lenses
Keep at em Edward!!!
Why not an RF edition? Smaller and lighter, like the Leica one, would be a plus also.
RIght now we have a camera near identical in size and weight to the M6, but I can live with it
TY very much for highly informative post, Joachim.
Vern Dewit wrote:
Tested a zeiss 18mm f/4 on my a7r today. Lots of color shift and minimal corner smearing. Not usable for me but maybe folks with more patience using corner fix would be okay.
Corner Fix is not attractive to me but LR flat field seems easy---I need to try it.
zm 18 @ f/11 shot raw in camera and exported from LR w/o change: DSC00097-2 by unoh7, on Flickr
I'd be shocked if the M9 can match this sharpness at f/11 but it doesn't need to
at f/4 corners edges are smeared but I like the lens character, if I can get the CS out.
p.126 #20 · A7/A7r - performance with WA RF lenses
Vern Dewit wrote:
Tested a zeiss 18mm f/4 on my a7r today. Lots of color shift and minimal corner smearing. Not usable for me but maybe folks with more patience using corner fix would be okay.
Try the 10-18mm sony lens, in full frame mode. Works much better than I expected, with the added flexibility of a few extra millimetres and image stabilization.
