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Sony A7 and RF wides: a possible solution.
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PostPosted: Mon Jan 19, 2015 3:11 pm    Post subject: Reply with quote
All distortionless lenses produce the same perspective, which is the rectilinear perspective by a pinhole. No difference here between symmetrical and a retrofocus lenses.


PostPosted: Mon Jan 19, 2015 3:37 pm    Post subject: Reply with quote
Gerald wrote:
All distortionless lenses produce the same perspective, which is the rectilinear perspective by a pinhole. No difference here between symmetrical and a retrofocus lenses.

A shame these don't exist.


PostPosted: Mon Jan 19, 2015 3:53 pm    Post subject: Reply with quote
araucaria wrote:
Gerald wrote:
All distortionless lenses produce the same perspective, which is the rectilinear perspective by a pinhole. No difference here between symmetrical and a retrofocus lenses.

A shame these don't exist.

What? There are many lenses with negligible distortion. Excuse me to ask, aren't you confusing "distortion" with "aberration"?


PostPosted: Mon Jan 19, 2015 4:36 pm    Post subject: Reply with quote
No I'm not confusing them.


PostPosted: Mon Jan 19, 2015 8:07 pm    Post subject: Reply with quote
Perhaps some examples will better illustrate.


PostPosted: Mon Jan 19, 2015 10:57 pm    Post subject: Reply with quote
Lightshow wrote:
Perhaps some examples will better illustrate.

OK. See the photo of a tiled wall taken with an ultra wide angle lens, the Flektogon 20mm F2.8. The Flektogon mustache-type distortion is small (about 2%), but it is readily apparent due to the presence of so many straight lines of the tiling pattern. Nonetheless, the distortion would pass unnoticed for most photographic subject without straight lines.

Original picture:



See now the picture below, which is the result of the correction of distortion through the PTLens program. Note that the distortion was virtually eliminated, what is proven by the fact that the lines lose the slight bend that they had before; now they are much straighter.

Distortion corrected picture:


Note: I believe PTLens correction is optimized for infinity focus. Since the focus distance for the picture above was only 1m, maybe some residual distortion still remains, but I believe the result is already good enough for serious architectural photography, for example.
You may also notice some small keystone effect, but this has nothing to do with lens distortion. The cause is a small error of parallelism between the wall and the plane of camera's sensor. The alignment error was photographer's fault.


PostPosted: Tue Jan 20, 2015 1:13 am    Post subject: Reply with quote
I'll quote a new post from Charles K, at FM, who is pretty meticulous with his observations, usually, and also very nice:

"Lloyd has further detailed his results diglloyd - Blog , comparing with the stock A7r and modified A7r, comparing with actual examples with the 18 SEM and 24 Elmar, at f/3.8, 5.6, 8 and 11. The results are very compelling in the difference between the stock and modified version of the A7r. There is no difference in the effect of vignetting or magenta cast. But this is very easily corrected in PP'ing with a simple step in LR, by taking WB disc shots with the lens at difference f stops, and keeping this shots on file. This is no different than with M9 prior to the later firmware corrections.

I must admit I had to subscribe to see the results but it was well worthwhile. I am very glad now that I have sent my A7r to Kolari Vision I really did not expect to see such an improvement, but the 18 SEM and 24 Elmar are definitive options with the A7r MOD. I am sorry I just sold my 21 SEM "

A thinner sensor stack may be possible after all! - FM Forums

Of course this is not definitive. We never know till we actually have the cameras in our hand and take many shots. But it seems hopeful for some of us with A7 camera lying around and RF wides who really want to play Smile

Colorshift I will expect, but with A7 it is not crazy: even M240 will shift on some glass like ZM35/2, and this can be dealt with to a pretty fair degree. Smearing, on the other hand: nothing you can do. Embarassed


PostPosted: Wed Jan 21, 2015 1:43 pm    Post subject: Reply with quote
I suspect that replacing the sensor filter by a thinner one is not enough to solve the problems of adapting M and ZM lenses on Sony A7. The microlenses on photo sites do not work well when the rays are very inclined. Besides, a photosite is not a flat structure. In due proportion, the photodiode is like a square surrounded by many buildings. In the early morning when sun is low, the buildings project many shadows on the square. This is more or less what happens when the photodiodes in the corners are illuminated by a wide-angle M lens.



PostPosted: Wed Jan 21, 2015 9:22 pm    Post subject: Reply with quote
Gerald wrote:
I suspect that replacing the sensor filter by a thinner one is not enough to solve the problems of adapting M and ZM lenses on Sony A7. The microlenses on photo sites do not work well when the rays are very inclined. Besides, a photosite is not a flat structure. In due proportion, the photodiode is like a square surrounded by many buildings. In the early morning when sun is low, the buildings project many shadows on the square. This is more or less what happens when the photodiodes in the corners are illuminated by a wide-angle M lens.


I suspect you see a target, then look for arguments. Troll-think. LOL

It's not a question of "solving" anything. It's a matter of reducing the problem enough to make the great compact wide lenses sing a bit. If the conversion can do that, it is well worth it to me and quite a few others.

Here is the wonderful guy who got Kolari to proceed on this issue at FM recently:
Quote:
mdemeyer wrote:
I understand from KolariVision that the IR characteristics of the new filter are (essentially) the same as the stock filters. Regarding humidity resistance, Leica used S8612 in the M9, etc. which is more prone to humidity damage (according to the Schott technical information, although they are not as transparent on the subject as one might wish) than the BG39 used here.


It's a tricky balance - IR rejection, matching the visible band transmission curve to minimize white balance changes, availability of glass in small quantities in the needed thickness, adjusting sensor position to maintain proper optical path length (focus), etc. Having been involved in the project since last fall (I'm the Michael mentioned on the KolariVision web site. I initiated the project - although I have no commercial interest in the project or KolariVision) I have seen personally how difficult it is to come up with a modification like this that actually works and can be implemented at a reasonable cost IMHO for what it delivers.

Perfect? I'm sure not. Could it be done better by a manufacturer in volume? Almost certainly. But so far none but Leica seem to have taken on the challenge and I can't justify putting that much into a rapidly depreciating digital asset. I love my RF and other glass acquired over the years and was frustrated by years of people talking about the problem and not solving it. I'm delighted that Ilija at KolariVision was willing to take it on and develop something that, for many of us, will breath life into the glass we treasure for whatever reason. For those who think it's an imperfect or un-needed solution, that's fine. We each have our priorities and values and can choose to participate or not.

At least we have another option now. I, for one, am happy to have that choice and to share it with others of like mind.

Michael


@Nordento, would you mind reducing the size of that image at the top of this page? Such a large imbed throws all the posts into weird wide view so one need to scroll laterally in safari. Much apreciated, link to full would be fine Smile


PostPosted: Wed Jan 21, 2015 9:45 pm    Post subject: Reply with quote
uhoh7 wrote:

@Nordento, would you mind reducing the size of that image at the top of this page? Such a large imbed throws all the posts into weird wide view so one need to scroll laterally in safari. Much appreciated, link to full would be fine Smile

I agree, the posts are extending off the screen and over the desk to the far wall.This is a very informative thread as it stands. Whatever the differences I am benefiting from both uhoh7 and Gerald's input here, most informative. Gents, hat doffed to the pair of you for your information.


PostPosted: Wed Jan 21, 2015 9:52 pm    Post subject: Reply with quote
Guys, you need higher res. screens Wink
Removed...


PostPosted: Thu Jan 22, 2015 1:45 am    Post subject: Reply with quote
There seems to be a lot of people living the dream that a thin IR filter is everything you need for a proper adaptation of M lenses on Sony A7. See, for instance, what Roger Cicala of Lens Rental commented in his blog in June 2014:

So in theory, the 135mm f / 4 lens SLR is not going to care much about the stack thickness sensor. The 24mm f / 1.4 lens rangefinder can be hugely affected.

http://www.lensrentals.com/blog/2014/06/sensor-stack-thickness-when-does-it-matter

Hugely affected? Hmmm...
Few weeks ago, Cicala tested a Summilux 24mm F1.4 on a stock Sony A7 and on a modified Sony with a thin 1-mm-thick AA filter. Result of Cicala's measurements? Virtually no difference in performance!



http://www.lensrentals.com/blog/2015/01/a-thinner-sensor-stack

If the old Oskar Barnack were alive, he would certainly agree that the Leica world is more complicated than it seems.


PostPosted: Thu Jan 22, 2015 3:00 am    Post subject: Reply with quote
The change to a thinner filter should be more noticeable on a lens with short exit pupil distance to sensor when focus to infinity. I would like to see a test with a Jupiter 12.


PostPosted: Thu Jan 22, 2015 5:40 am    Post subject: Reply with quote
Gerald wrote:

The 24mm f / 1.4 lens rangefinder can be hugely affected.[/i]

http://www.lensrentals.com/blog/2014/06/sensor-stack-thickness-when-does-it-matter

Hugely affected? Hmmm...
Few weeks ago, Cicala tested a Summilux 24mm F1.4 on a stock Sony A7 and on a modified Sony with a thin 1-mm-thick AA filter. Result of Cicala's measurements? Virtually no difference in performance!
.


Always racing to be the expert, as usual you have no clue. Smile

You act as if a preliminary test on a lens that was one of the least effected of 24 and wider in conditions which don't even show the real issues (they were short range tests), and expressly stated as not to regarded as in any way conclusive, on the A7R, which is a totally different sensor with acute smearing, somehow comes to your aid in attacking this thread.

If you really want to learn something before you spout "the truth" to all of us mortals, subscribe to DigiLloyd, who actually has real test images before and after, at landscape distance with critical lenses like the 18SEM. But I'm sure reality is too expensive for you. Smile

Since the A7 has been better behaved than the A7r, because bigger pixels allow lower ray angles, I hope it may become usable for lenses like the ZM18, SEM21 and 28cron, which are fantastic state of the art M lenses unrivaled in there respective FLs by any Canikon, or legacy SLR lens. I am pretty sure it's going to improve quite a bit with all lenses designed for film, the wider the more obvious.

But I won't know for a week or so when I have the camera back. Then I'll post real images, as opposed to malicious guesses, and let those interested decide if there are improvements which might make this conversion worthwhile to them. My goal is not to prove how brilliant I am, but simply to share an experience with those who may be interested.

As a person who does not own any A7 or any RF glass, why do you choose to make this thread a platform for your "opinion", over and over?

And why the rush to judge?

The truth will out soon enough Smile

Nordentro wrote:
Guys, you need higher res. screens Wink
Removed...

TY sir Smile

calvin83 wrote:
The change to a thinner filter should be more noticeable on a lens with short exit pupil distance to sensor when focus to infinity. I would like to see a test with a Jupiter 12.

hi Calvin,
I was going to remark that the jupi 12 was too deep for the Sony, but I see that was only the Nex, so your post already informs me! TY
I agree with your thoughts, although the Jupiter 12 may be like the Biogon 21/4.5 and to a lesser extent the CV 21/4, where the exit pupil is really really close, so though better, still not close to film quality.


PostPosted: Thu Jan 22, 2015 10:04 am    Post subject: Reply with quote
...so 5 pages later. if you want to shoot wide angle buy a M9, or a Pentax SLR with it's DA15mm Razz


PostPosted: Thu Jan 22, 2015 11:32 am    Post subject: Reply with quote
It's fun to see how a half Leica man get nervous with any opinion different of him. A real Leica man does not buy obsolete Leica cameras and then get frustrated when reality imposes on his dream. The real Leica man buys a Leica M240, which is also a outdated camera but, at least, has liveview and lets you focus accurately with an electronic viewfinder.

The Leica fanboys have not yet realized that the problem is not only the thickness of the stack filter.

Last edited by Gerald on Thu Jan 22, 2015 12:19 pm; edited 1 time in total


PostPosted: Thu Jan 22, 2015 11:44 am    Post subject: Reply with quote
tromboads wrote:
...so 5 pages later. if you want to shoot wide angle buy a M9, or a Pentax SLR with it's DA15mm Razz


Or hang onto your lenses until the real McCoy gets developed and built. Laughing


PostPosted: Thu Jan 22, 2015 5:33 pm    Post subject: Reply with quote
Quite sharp discussions here, close to what can be accepted, but still enjoyable. It is ok to have different views and opinions as long as we behave as gentlemen Wink

I am tempted ro shoot a few rolls of film with my wide rangefinder lenses just to see how they performs as intended...


PostPosted: Thu Jan 22, 2015 6:28 pm    Post subject: Reply with quote
The J-12 and the postwar Opton Biogon 2.8/35 are both superb on film. the J12 needs to be closed one stop to be really sharp and at f4 it has a nice 3d pop with Soonnar-like rendering and bokeh. The post-war Opton revision of the Biogon is better, sharp wide open, and out performs just about every other 35mm lens I've tried such as the Hexanon 2.8/35, Skoparex 3.4/35, Flektogon 2.4/35, Primagon 4.5/35, Curtagon 2.8/35, Canon FL 2.5/35 and a few others.


PostPosted: Thu Jan 22, 2015 8:35 pm    Post subject: Reply with quote
The arrival of Sony A7 captured people's imagination, in particular, the Leica fanboys who are desperate to find a modern and affordable camera that could replace the M9 and M240. Sony A7 would be that camera, but unfortunately, the symmetrical wide-angle lenses with short back focal length do not combine friendly with digital sensors.

I dare to say that with the arrival of digital sensors, the time of symmetrical wide-angle lenses has passed. But isn't the Loxia line a revival of those venerable old lenses? No, it's just a kind of swan song. The Loxia lenses are old designs that have been re-cooked for the FE mount. Zeiss is simply trying to earn some money from its old ZM line. Leica, in turn, will continue manufacturing M lenses while it can. But Leica has surely realized that the future of the M-system is uncertain. Many famous photographers who liked to use Leica migrated to other types of cameras. The most famous is perhaps Sebastiao Salgado who left Leica and switched to Canon. Leica knows better than anyone the limitations of the M-system. This explains why Leica has put tremendous effort to develop in recent years the S and T system. For the best of my knowledge, no symmetrical wide-angle lens was designed so far for these systems.

This Ken Rockwell's article is verys interesting. He compares the sharpness of several Nikon lenses and a Voigtlander retrofocus 20mm lenses:

http://kenrockwell.com/tech/comparisons/2010-09-22-20mm/index.htm

The tests show that many good retrofocus lenses are small, focus to very short distance, are affordable, and are very sharp. What more is needed? Who needs a very expensive symmetrical wide angle lens?


PostPosted: Thu Jan 22, 2015 8:44 pm    Post subject: Reply with quote
Gerald wrote:
...This explains why Leica has put tremendous effort to develop in recent years the S and T system. For the best of my knowledge, no symmetrical wide-angle lens was designed so far for these systems.
..


To design a symmetrical wideangle for the SLR S system would be very out of fashion - as discussed earlier.
For sure they know their M system and its limitations.


PostPosted: Thu Jan 22, 2015 10:00 pm    Post subject: Reply with quote
tromboads wrote:
...so 5 pages later. if you want to shoot wide angle buy a M9, or a Pentax SLR with it's DA15mm Razz

Unfortunately there is considerable misinformation and pre-judgement in the 5 pages.

There may very soon be a serious M9/240 alternative with key RF wides in a number of hands, including my own.

Lloyd Chambers, who has forgotten more than Gerald will ever guess, claims this is the case after extensive testing with exactly the mod which is the subject of this thread, on the A7r, which has the problem worse than the A7.

But maybe you don't care to entertain the possibility, but prefer do dismiss the idea before it's really put to the test, as do several people, for apparently psychological reasons Smile


PostPosted: Thu Jan 22, 2015 11:43 pm    Post subject: Reply with quote
I confess I'm confused as to what possibility we are dismissing now. Embarassed Change the Glass on the A7* to make it Super Dooper?


PostPosted: Fri Jan 23, 2015 1:00 am    Post subject: Reply with quote
uhoh7 wrote:
tromboads wrote:
...so 5 pages later. if you want to shoot wide angle buy a M9, or a Pentax SLR with it's DA15mm Razz

Unfortunately there is considerable misinformation and pre-judgement in the 5 pages.

There may very soon be a serious M9/240 alternative with key RF wides in a number of hands, including my own.

Lloyd Chambers, who has forgotten more than Gerald will ever guess, claims this is the case after extensive testing with exactly the mod which is the subject of this thread, on the A7r, which has the problem worse than the A7.

But maybe you don't care to entertain the possibility, but prefer do dismiss the idea before it's really put to the test, as do several people, for apparently psychological reasons Smile


If it works, I'll be delighted because the Biogon 2.8/35 is perhaps my favourite lens and with the rapidly falling prices of the A7 secondhand....


PostPosted: Fri Jan 23, 2015 2:57 am    Post subject: Reply with quote
Nordentro wrote:
Quite sharp discussions here, close to what can be accepted, but still enjoyable. It is ok to have different views and opinions as long as we behave as gentlemen Wink

I am tempted ro shoot a few rolls of film with my wide rangefinder lenses just to see how they performs as intended...

You are right the discussions are sharp. But the content is blurred.
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