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Archive 2015 · A thinner sensor stack may be possible after all!
  
 
Lee Saxon
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p.1 #1 · p.1 #1 · A thinner sensor stack may be possible after all!


Did everybody see Roger's article today testing an A7r with a modified sensor stack? (http://www.lensrentals.com/blog/2015/01/a-thinner-sensor-stack)

Little performance degradation with the native FE lenses. Which means Sony could reduce the stack without shooting themselves in the foot. I doubt this is news to be hopeful that they will, but it's still interesting to know that they can.

Edit: A few people have commented that the improvements we see on M wides isn't enormous, making me realize I left an important disclaimer out of this post. These lenses experience peformance degradation mostly at/near infinity - we're not seeing much "correction" of degradation at the shorter focus distances Imatest uses because there isn't as much degradation to "correct."

Edited on Jan 14, 2015 at 05:10 AM · View previous versions



Jan 08, 2015 at 05:35 AM
johnctharp
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p.1 #2 · p.1 #2 · A thinner sensor stack may be possible after all!


Would like to have seen a test on the 24-70/4 at 24mm, but it's good to know that the problem- as it were- may be addressed.

Wonder how much it would cost to have the cover glass changed, and whether people would go for the service?



Jan 08, 2015 at 06:00 AM
philip_pj
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p.1 #3 · p.1 #3 · A thinner sensor stack may be possible after all!


Could be a business model emerging? Might make resale an interesting exercise. Why doesn't Leica simply buy Sony sensors? They're the best, and will only open more of a gap on everyone else over time.

Everyone lives a fantasy life on the net, so I now petition (petitions being big around Sony) Roger to check out the Super-Elmar 24/3.8, one of the few WA M lenses to not have significant curvature and/or poor corners. Get the corners up to MTF chart standard (about 80% of on-axis MTF in the very corners) and that will impress me like Stevie Wonder taking the wheel. These two picked are technically not the best, might be why they were chosen. The 35/1.4 40lpmm has more ups and downs than a president's poll figures.

But I ain't giving up my pristine FE55 corners for no stinking M lenses, however. Not one smidgen, I say. And what will it do to the host of alt lenses out there, one wonders? Well, I do anyway, having quite a few that work bloody brilliantly on the a7r.



Jan 08, 2015 at 06:07 AM
philip_pj
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p.1 #4 · p.1 #4 · A thinner sensor stack may be possible after all!


Thinking more about it, seeing the small (as tested) drop in FE corners, I wonder if Sony went the way they did to get the best corners on the a7r and future higher Mp sensors with 'normal' beam angle lenses?

Axial performance is almost child's play if you are prepared to surrender performance elsewhere, but corners present a savage challenge to lens designers, and Sony (and Zeiss in modern times) seem to really care about midfield CoF as well (the two FE primes and the RX1 Sonnar are all very tidy in these respects).

Not to mention how will the thin stack go with all the 'must have' 15-18mm lenses users crave these days? M and otherwise? You might need to end up with something very different.



Jan 08, 2015 at 06:22 AM
Beni
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p.1 #5 · p.1 #5 · A thinner sensor stack may be possible after all!


I think more data is needed to form a conclusion?


Jan 08, 2015 at 09:33 AM
gyoung143
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p.1 #6 · p.1 #6 · A thinner sensor stack may be possible after all!


It didn't seem to be that much pf an improvement with the M lenses, considering the probable cost.
And look whats happened to the M9 sensor with thin cover glass, who's to say this smaller company (than Sony or Leica) has got it right.

Gerry



Jan 08, 2015 at 09:43 AM
philber
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p.1 #7 · p.1 #7 · A thinner sensor stack may be possible after all!


What I pick up from Roger's tests is that the theory that Sony are just a bunch of clowns and penny-pinching bean-counters because it would have been soooo easy to get rid of the problem with something as obvious as a thin sensor stack (I am exaggerating just a bit) may have been overoptimistic. It ain't that simple. An improvement? Yes, some. An end to the issue/problem? No way.


Jan 08, 2015 at 10:18 AM
RCicala
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p.1 #8 · p.1 #8 · A thinner sensor stack may be possible after all!


Beni wrote:
I think more data is needed to form a conclusion?


Absolutely. This was just a kind of feasibility study. Remember with Imatest we're shooting close up (about 9 feet for the 24mm) so we'll have to see what happens at infinity and with wider lenses.

But there's some promise here. It won't be a panacea, there's a lot more going on than just stack thickness. But it's interesting and worth exploring more.

Roger



Jan 08, 2015 at 11:53 AM
retrofocus
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p.1 #9 · p.1 #9 · A thinner sensor stack may be possible after all!


Good test, indeed - I just suggest to add some photos which might show the differences seen in the tables. I found this remark very interesting in reference to the tested Leica 24/1.4 ASPH lens: "The absolute corners, however, hadn't changed a great deal. Whether this is because the sensor-stack change isn't helping enough at extreme angles, or because of other factors (micro-lens alignment on the sensors for one, perhaps raw data manipulation in-camera, or stuff I haven't even thought of), I can't say."

So other factors seem to play a crucial role here, too. Again, photos taken with this lens on a regular A7R and on one with modified sensor stack might help here.



Jan 08, 2015 at 12:35 PM
Tariq Gibran
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p.1 #10 · p.1 #10 · A thinner sensor stack may be possible after all!


I'm curious how things would look with the lenses tested stopped down a bit. I believe Roger mentioned all the tests were performed with the lenses shot wide open and we know the performance improves off axis, particularly with the Leica 1.4's, when stopped down (and stopping down also helps mitigate some of the poor interaction between the lens/sensor "incompatibility"). Particularly if infinity tests are performed, this would be great to see.


Jan 08, 2015 at 01:23 PM
 

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mikedefieslife
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p.1 #11 · p.1 #11 · A thinner sensor stack may be possible after all!


To be fair to Sony, the sensor stack isn't a weakness of the camera. Afterall it's not designed for people to be using RF lenses with, and there isn't a reason why Sony should pander to this community. That being said they don't do themselves any favours with their limited lens range at the moment.

Lens rentals have compiled a chart of sensor stacks with the both the A7 and A7r at 1.85 (similar to many other models measured). I thought the A7r stack would be a bit thinner (I don't why)



Jan 08, 2015 at 02:49 PM
Steve Spencer
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p.1 #12 · p.1 #12 · A thinner sensor stack may be possible after all!


retrofocus wrote:
Good test, indeed - I just suggest to add some photos which might show the differences seen in the tables. I found this remark very interesting in reference to the tested Leica 24/1.4 ASPH lens: "The absolute corners, however, hadn't changed a great deal. Whether this is because the sensor-stack change isn't helping enough at extreme angles, or because of other factors (micro-lens alignment on the sensors for one, perhaps raw data manipulation in-camera, or stuff I haven't even thought of), I can't say."

So other factors seem to play a crucial role here, too. Again, photos taken with this lens
...Show more

One very plausible, IMO, explanation for the midfield and not corner improvement on the 24 Lux ASPH is that if the lens has pretty poor corners wide open even on the Leica cameras, there may be a limit on how much reducing the sensor glass can improve performance if the lens just can't perform well in that zone. Especially if this reduced corner performance is due to curvature of field, then thicker cover glass might exacerbate the curvature and affect mid zone performance primarily, and reducing the thickness of the sensor glass would then increase mid zone primarily, but the normal curvature of field would still be affecting the corners.

One way to examine this that I would like to see (I hate asking Roger to do more, because it is great he does so much already) is how the lens does in the same set up on a Leica camera. If a lens has weak corners on a Leica M, we can't expect reducing the cover glass on the Sony cameras to somehow make sharp corners.



Jan 08, 2015 at 03:09 PM
RCicala
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p.1 #13 · p.1 #13 · A thinner sensor stack may be possible after all!


Tariq Gibran wrote:
I'm curious how things would look with the lenses tested stopped down a bit. I believe Roger mentioned all the tests were performed with the lenses shot wide open and we know the performance improves off axis, particularly with the Leica 1.4's, when stopped down (and stopping down also helps mitigate some of the poor interaction between the lens/sensor "incompatibility"). Particularly if infinity tests are performed, this would be great to see.


Tariq, that is true, but the sensor stack thickness effect is most pronounced at wider apertures. So whatever difference we see should lessen as we stop down.

Steve, I've been out sick most of December so I'm a bit too far behind to do anymore testing in the next few weeks, but hopefully by early February I'll be caught up.



Jan 08, 2015 at 03:25 PM
Steve Spencer
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p.1 #14 · p.1 #14 · A thinner sensor stack may be possible after all!


RCicala wrote:
Absolutely. This was just a kind of feasibility study. Remember with Imatest we're shooting close up (about 9 feet for the 24mm) so we'll have to see what happens at infinity and with wider lenses.

But there's some promise here. It won't be a panacea, there's a lot more going on than just stack thickness. But it's interesting and worth exploring more.

Roger


Thanks for doing this test and for all your work on these issues. It has been a great help in understanding what is going on. It will be interesting to see how much reducing the cover glass improves performance. These tests may actually be underestimating the improvement. One thing to keep in mind is that the 35 lux ASPH and 24 lux ASPH are two of the better performing lenses on the Sony A7 series cameras. It will be interesting to see how more problematic lenses like the 28 cron ASPH and the 35 cron ASPH and the 18, 21, and 24 SEMs do with the new cover glass. There is a lot more room for improvement with those lenses. I would also, selfishly, to see testing with the 50 lux ASPH both at shorter distances and infinity. Significant improvement with that lens is what would probably get me to think about changing the cover glass.



Jan 08, 2015 at 03:40 PM
Steve Spencer
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p.1 #15 · p.1 #15 · A thinner sensor stack may be possible after all!


RCicala wrote:
Tariq, that is true, but the sensor stack thickness effect is most pronounced at wider apertures. So whatever difference we see should lessen as we stop down.

Steve, I've been out sick most of December so I'm a bit too far behind to do anymore testing in the next few weeks, but hopefully by early February I'll be caught up.


I hope you are feeling better. Certainly take care of yourself and don't worry about this sort of stuff.

Best wishes,

Steve



Jan 08, 2015 at 03:42 PM
rscheffler
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p.1 #16 · p.1 #16 · A thinner sensor stack may be possible after all!


Steve Spencer wrote:
One way to examine this that I would like to see (I hate asking Roger to do more, because it is great he does so much already) is how the lens does in the same set up on a Leica camera. If a lens has weak corners on a Leica M, we can't expect reducing the cover glass on the Sony cameras to somehow make sharp corners.


I don't have the 24 Lux at my disposal, but do have the 21 Lux, which has fairly similar MTF characteristics, and is also one of the M lenses that many seem to think performs better on the a7 cameras. I tested the 21 on both the a7S (actually on all the a7 cameras) and the M240. High-rez files are posted here (go to the 21 Lux link to access the files).

The 21 Lux MTF values would lead one to believe it's a relatively poor performer wide open, away from center. But it's surprisingly very usable, on a digital Leica M body. On the a7S, the edges are quite smeared. As Roger notes, the 24 Lux being tested at 9 feet is a substantially different distance than infinity where the edge smearing problem is the worst, so we'll have to wait until he has the chance to test this further... Unless he's willing to send one of these modified cameras to me here in Canada for me to repeat the shootout against the M240... ?



Jan 09, 2015 at 09:58 AM
Steve Spencer
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p.1 #17 · p.1 #17 · A thinner sensor stack may be possible after all!


rscheffler wrote:
I don't have the 24 Lux at my disposal, but do have the 21 Lux, which has fairly similar MTF characteristics, and is also one of the M lenses that many seem to think performs better on the a7 cameras. I tested the 21 on both the a7S (actually on all the a7 cameras) and the M240. High-rez files are posted here (go to the 21 Lux link to access the files).

The 21 Lux MTF values would lead one to believe it's a relatively poor performer wide open, away from center. But it's surprisingly very usable, on a digital Leica
...Show more

If he does, I would be happy to drive down to Hamiltion and provide my unmodified A7 II as a comparison I would love to see how one of those things work. On a more serious note, thank you too Ron for all the work you put into testing M lenses on the Sony A7 cameras. That too has been immensely helpful.



Jan 09, 2015 at 02:40 PM
mdemeyer
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p.1 #18 · p.1 #18 · A thinner sensor stack may be possible after all!


I have a modified A7 on the way back to me and will post some before-and-after photos in a week or two as time and weather permit. WA lenses on-hand include Leica Elmar 24mm 3.8, Summicron 35mm (v4), and a Voigtlander 21mm Skopar (particularly bad on the unmodified Sony and really improves a lot with the mod). I'll also test other longer RF lenses but expecting less improvement there.

If someone in the San Francisco area with an unmodified A7 and/or other lenses wants to collaborate to broaden the testing set, PM me.

FYI, I was involved in the project (initiated it) but don't have any commercial interest in Kolari Vision, who is offering the modification.

Michael



Jan 10, 2015 at 07:38 PM
sebboh
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p.1 #19 · p.1 #19 · A thinner sensor stack may be possible after all!


rscheffler wrote:
I don't have the 24 Lux at my disposal, but do have the 21 Lux, which has fairly similar MTF characteristics, and is also one of the M lenses that many seem to think performs better on the a7 cameras. I tested the 21 on both the a7S (actually on all the a7 cameras) and the M240. High-rez files are posted here (go to the 21 Lux link to access the files).


ron from the samples i've seen the 24 lux performs better than the 21 lux on the a7 and is one of the best performing m wides on the a7 series. i'm not surprised the improvement seen is relatively small given that it already performs pretty well and the test is at imatest chart distances. i'd be much more interested to see how really troublesome lenses perform on this modified sensor stack like 18 SE, zm 18/4, cv 21/4, cv 25/4, and 28 elmarit asph.

mdemeyer wrote:
I have a modified A7 on the way back to me and will post some before-and-after photos in a week or two as time and weather permit. WA lenses on-hand include Leica Elmar 24mm 3.8, Summicron 35mm (v4), and a Voigtlander 21mm Skopar (particularly bad on the unmodified Sony and really improves a lot with the mod). I'll also test other longer RF lenses but expecting less improvement there.

If someone in the San Francisco area with an unmodified A7 and/or other lenses wants to collaborate to broaden the testing set, PM me.

FYI, I was involved in the project
...Show more

i live in SF and have an unmodified a7 along with a few rangefinder lenses. will pm you.

i'd particularly like to test out my contax g 28/2.8 to see how much improvement there is.




Jan 11, 2015 at 12:06 AM
rscheffler
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p.1 #20 · p.1 #20 · A thinner sensor stack may be possible after all!


Derek - thanks for the additional info. It would be interesting to see how close the 24 Lux's performance on the a7 and a digital M to get a better feel for how close (or far) the a7 is. But I agree with you, I'm more interested in the typically more problematic RF wides.

Michael - are you able to comment on the cost of the conversion? (Edit: disregard, I found the price at the Kolari Vision website: $400 US).

Looking forward to your test results!

Edited on Jan 12, 2015 at 10:33 PM · View previous versions



Jan 11, 2015 at 08:16 AM
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