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Archive 2015 · Problem with ZM 35 f/1.4 on A7 Series?

  
 
rsolti13
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p.1 #1 · p.1 #1 · Problem with ZM 35 f/1.4 on A7 Series?


I put together the post here showing the Zeiss ZM 35 f/1.4 vs the FE 35 f/1.4 on the A7II. I have been playing around with the two lenses a lot since, and am starting to wonder if my Zeiss ZM is defective or if this is how the lens renders. See below, picture 1 taken with the ZM 35 f/1.4 and picture 2 taken with the FE. Both taken straight out of camera, no editing. Both at f/1.4. Look at the top right corner, the ZM is almost in focus (real jaggedy look to it when zoomed) and the FE is blown out. Look at the bottom of the photo, the ZM has a blur to it where the FE is pretty sharp.











Edited on Apr 07, 2015 at 01:38 PM · View previous versions



Apr 07, 2015 at 01:18 PM
rsolti13
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p.1 #2 · p.1 #2 · Problem with ZM 35 f/1.4 on A7 Series?


Additionally, take a look at these. Both at f/1.4. Dead center the ZM is sharper, as soon as you go outside the center it loses its sharpness quick. Look at the ground/corners/sign on the right of the ZM (pic 1) vs the FE. I'm curious how this would look on a rangefinder. I would assume if anything this is a problem with the thicker sensor glass on the A7 series

http://www.soltiphotography.com/Other/Zeiss-vs-zeiss/i-hfbqLj8/0/X3/DSC01060-X3.jpg

http://www.soltiphotography.com/Other/Zeiss-vs-zeiss/i-9rKZPVp/0/X3/DSC01064-X3.jpg



Apr 07, 2015 at 01:23 PM
Tariq Gibran
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p.1 #3 · p.1 #3 · Problem with ZM 35 f/1.4 on A7 Series?


It's due to the thicker sensor glass covering incompatibility with the ZM as you suspected. The ZM MTF shows that lens to be amazingly good across the frame even wide open when used on a digital Leica with thin cover glass. The theoretical MTF for the FE looks good as well but you can see the dips it takes. One also must take into account that since the FE MTF is calculated (unlike the ZM MTF which is actually measured from a lens), the FE should be dropped probably around 10-20 pts or so to even start to compare with what an actual MTF might look like for that lens.

https://dl.dropboxusercontent.com/u/5540407/ZM3514.jpg
https://dl.dropboxusercontent.com/u/5540407/IMG_471676.jpg



Edited on Apr 07, 2015 at 02:15 PM · View previous versions



Apr 07, 2015 at 02:11 PM
rsolti13
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p.1 #4 · p.1 #4 · Problem with ZM 35 f/1.4 on A7 Series?


Thanks for that. Never seen a lens impacted so much like that, what a shame.

About the FE dropping 10-20, that may be true for most lenses when calculated but I don't see how that is possible with the FE 35 after examining hundreds of images I've taken. It is sharp, even wide open across the frame



Apr 07, 2015 at 02:15 PM
Tariq Gibran
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p.1 #5 · p.1 #5 · Problem with ZM 35 f/1.4 on A7 Series?


rsolti13 wrote:
Thanks for that. Never seen a lens impacted so much like that, what a shame.

About the FE dropping 10-20, that may be true for most lenses when calculated but I don't see how that is possible with the FE 35 after examining hundreds of images I've taken. It is sharp, even wide open across the frame


We know it's true just by looking at the F8 graph as it's impossible to make a perfect lens that has 100% contrast in the center (note how the 10 and 20 lines start at 100, that's impossible). Even if you optimistically drop things by 10 points, that's a very best case scenario I would think.

None of this is to say the lens is not sharp but it would be interesting to see some more posted distant shots taken at F8 that show detail mid frame and in the corners. Previously, such images have shown some mid frame drop (notice that huge dip in the F8 MTF chart). The DPreview aperture series of the distant buildings show it here:
http://www.dpreview.com/galleries/reviewsamples/albums/sony-zeiss-distagon-t-fe-35mm-f1-4-za-samples#page=2

What's so nice about this lens imo (based on what you and others have posted) is what it does wide open and at F2 with closer subjects. The rendering is gorgeous.




Apr 07, 2015 at 02:29 PM
Jonas B
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p.1 #6 · p.1 #6 · Problem with ZM 35 f/1.4 on A7 Series?


I think you need to use a tripod and focus carefully at the exact same thing in the image (a small test chart in the sofa for example) to be able to compare. Bigger images also makes it easier.
Maybe the result will be that the thick sensor glass stack on the Sony results in a bent focus plane when using the ZM lens? Probably a focus plane going away from the camera at the borders and corners?



Apr 07, 2015 at 03:26 PM
philip_pj
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p.1 #7 · p.1 #7 · Problem with ZM 35 f/1.4 on A7 Series?


Tariq, the discussion and images relate purely to f1.4.
If you look at the f1.4 MTF for each you will notice the greater fall-off of imaging quality in the ZM...by 20mm out, just inside the corner, we see - on Zeiss's own optical bench - just ~30% contrast. Center is ~82%, these are for detail readings off the 40 lpmm line pairs, but echoes are seen in more broad detail lps from around 12mm - the short edges. This is a very large drop and it is a valid result. I would not expect great corners on any Leica camera for this lens at this aperture. But, see the stuff hanging off the trees? Not so good on the ZM, is it? A confusing picture..not much that is off center in the ZM image looks very good to my eyes, when it should be very good.

The FE at same aperture, but with 'optimistic' calculated MTF results, show data going from high 60s at center to an average of around 45% at 20mm out. With a much less severe hit for the 10 and 20 lpmm pairs of lines as well. It's very likely the *shape* of Sony's measurements are faithful and accurate across the frame, if not the level.

My view is that - at f1.4 - the Sony has better (more 'Zeiss-like') shaping and can be expected to show greater consistency from axis to corner, based purely on MTF data. As your eye moves across the frame, the reference point is the sharpest point - the center. It's our visual system at work and it may contribute to the appearance of the images posted. [As an aside, such a flat profile occurs very often in lenses with outstanding bokeh - 50AA, Otuses, all good teles).]

I don't say it is the only factor at play; it's hard to find exit pupil distances from Zeiss's latest charts and we don't even know its max beam angle; it was not a lens intended for the Sony system; nor have I seen any comparable f8 MTF data. CZ only publish 'best overall' aperture data in their charts (f4 here), it may be that the ZM tanks early, it can and does happen. [Sony publish f8, come what may.] Maybe LC has covered some of this, I don't subscribe. It's doubtful either of these are great shakes at f8, it's far from their intended purpose.

These are unpopular messages, I realise that, we all want the ZM lenses to work well. If the center is very sharp on the ZM, a tripod is not needed for 'same image' analysis, deterioration will affect all of the image. If it shows up in successive images the case is strengthened. But yes, a pod eliminates more grey area, when digging deeper.



Apr 07, 2015 at 09:56 PM
philip_pj
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p.1 #8 · p.1 #8 · Problem with ZM 35 f/1.4 on A7 Series?


Posted on the ZM 35/1.4 thread by _serhan_, a very interesting set of findings with the lens on the Monochrom and the a7r - excuse the Spanglish:

http://www.dslrmagazine.com/pruebas/pruebas-tecnicas/zeiss-distagon-t-35-mm-f-1-4-zm-rendimiento.html

"What can we tell the difference in resolution between 36 Mpx system. Sony A7R and 18 Mpx. pure black and white, Bayer pattern Leica-M Monochrom? We think the graphics are crisp regard: 36 Megapixel sensor. the A7R to boot up to 8% more resolution maximum for some isolated diaphragm aperture value, but only in the center while in the corners is quite clearly below, except for f / 8, f / 11 and f / 16."

"the Zeiss has been optimized with a retro focus almost telecentric design for cameras like the Sony A7R"

Interesting claim. Good MTF bar charts too, with caveat of only 'centre / corner'. Note much better results at f5.6 and f8 than Zeiss's f4 choice to chart.



Apr 07, 2015 at 10:37 PM
Tariq Gibran
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p.1 #9 · p.1 #9 · Problem with ZM 35 f/1.4 on A7 Series?


Philip, my view is that even if we apply the optimistic figure of dropping the theoretical FE 35/1.4 MTF by 10 points wide open, you would end up at best with performance equal to the measured MTF of the ZM outside of the center (and worse than the ZM in the center, which as been observed). It's possible the extreme corner of the FE might be better wide open but I expect it would be much, much closer than the posted examples show (when used on either a Leica or modified A7). The performance we are seeing on the unmodified Sony does not reflect the MTF outside of the center in my opinion due to the cover glass issue. The general shape of the MTF with the FE stopped down with the dip reminds me more of classic Leica (though not nearly as exaggerated). Just for kicks, here is the Leica R 35 1.4 measured MTF at 5.6.

https://dl.dropboxusercontent.com/u/5540407/R3514.jpg

Ultimately, I think both the ZM 35/1.4 and the FE 35/1.4 are great. There is an interesting comparison of how the ZM 35/1.4 behaves on the A7r vs M Monochrome in the lab below. I'm sure it will not be long before we see back to back real world critical comparisons between the FE 35/1.4 and ZM 35/14 shot on various bodies (FE on Sony, ZM on perhaps modified and unmodified Sony.)

http://www.dslrmagazine.com/pruebas/pruebas-tecnicas/zeiss-distagon-t-35-mm-f-1-4-zm-rendimiento.html


Edited on Apr 07, 2015 at 11:35 PM · View previous versions



Apr 07, 2015 at 11:20 PM
Tariq Gibran
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p.1 #10 · p.1 #10 · Problem with ZM 35 f/1.4 on A7 Series?


Funny, I posted the same link after I also saw serhan's post!


Apr 07, 2015 at 11:24 PM
Tariq Gibran
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p.1 #11 · p.1 #11 · Problem with ZM 35 f/1.4 on A7 Series?


philip_pj wrote:
Posted on the ZM 35/1.4 thread by _serhan_, a very interesting set of findings with the lens on the Monochrom and the a7r - excuse the Spanglish:

http://www.dslrmagazine.com/pruebas/pruebas-tecnicas/zeiss-distagon-t-35-mm-f-1-4-zm-rendimiento.html

"What can we tell the difference in resolution between 36 Mpx system. Sony A7R and 18 Mpx. pure black and white, Bayer pattern Leica-M Monochrom? We think the graphics are crisp regard: 36 Megapixel sensor. the A7R to boot up to 8% more resolution maximum for some isolated diaphragm aperture value, but only in the center while in the corners is quite clearly below, except for f / 8, f / 11 and f
...Show more

Their "optimization" claim seems to be in direct conflict with their finding ("corners is quite clearly below, except for f 8, f 11, f 16"). I would have really liked to see some real world comparative images taken at distance.



Apr 07, 2015 at 11:31 PM
serhan_
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p.1 #12 · p.1 #12 · Problem with ZM 35 f/1.4 on A7 Series?


I saw this thread after I posted over there. Viktor has a very nice comparison of A7R, A7 and ME in his ZM 35 1.4 review. Per his comparison shots, ZM is designed for M performance. To max on Sony, A7's need a mod for this lens. His comparison:
http://www.verybiglobo.com/zeiss-distagon-35mm-f1-4-zm-review/2/

DSLR magazine also have an interesting comparison for Otus 55mm on D800 vs 5DIII vs Medium format. Corners suffer more compared to center when we go to higher MP sensors, eg rate of return diminishes at the edges. So we'll see how these lenses will perform with 50MP sensors and maybe we'll see more big lenses. Here is Otus review:
http://www.dslrmagazine.com/pruebas/pruebas-tecnicas/zeiss-otus-apo-distagon-55-mm-f-1-4-zf2-t-enorme-potencial.html



Apr 07, 2015 at 11:57 PM
kape06111
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p.1 #13 · p.1 #13 · Problem with ZM 35 f/1.4 on A7 Series?


What a strange results of this ZM. Really confusing in the first images with the trees.


Apr 08, 2015 at 07:55 AM
rsolti13
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p.1 #14 · p.1 #14 · Problem with ZM 35 f/1.4 on A7 Series?


Look at these two, the first picture looks like it sharpens up in the building on the right, the second picture has the building sharpening up at the top. Its like an opposite of a mid zone drop

http://www.soltiphotography.com/Other/Zeiss-vs-zeiss/i-SPsbZ8x/0/XL/DSC01079-XL.jpg

http://www.soltiphotography.com/Other/Zeiss-vs-zeiss/i-B5zXTmZ/0/XL/DSC01081-XL.jpg



Apr 08, 2015 at 09:03 AM
Jonas B
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p.1 #15 · p.1 #15 · Problem with ZM 35 f/1.4 on A7 Series?


Strange look indeed. I _think_ my post above explain this.Here the phenomen is accentuated as you hade focused up close at something at the borders rather than the center - if my theory holds.


Apr 08, 2015 at 10:24 AM
Jochenb
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p.1 #16 · p.1 #16 · Problem with ZM 35 f/1.4 on A7 Series?


That looks like a bad adapter or lens to me. The focus plane is tilted, not parallel to the sensor. If it's because of the A7 sensor stack, both the background left and right should look the same.


Apr 08, 2015 at 12:22 PM
Jonas B
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p.1 #17 · p.1 #17 · Problem with ZM 35 f/1.4 on A7 Series?


Jochenb wrote:
That looks like a bad adapter or lens to me. The focus plane is tilted, not parallel to the sensor. If it's because of the A7 sensor stack, both the background left and right should look the same.


I understand what you mean. But, the two first images - how do you identify a tilted focus plane in the ZM image there? Of course, any good idea here may be obscured by a bad adapter or a misaligned lens element, there are unknown factors at play.

Edited on Apr 08, 2015 at 12:42 PM · View previous versions



Apr 08, 2015 at 12:37 PM
Mescalamba
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p.1 #18 · p.1 #18 · Problem with ZM 35 f/1.4 on A7 Series?


Looks like tilt effect, that last sample. Adapter probably not in line with sensor.


Apr 08, 2015 at 12:42 PM
Jochenb
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p.1 #19 · p.1 #19 · Problem with ZM 35 f/1.4 on A7 Series?


Jonas B wrote:
I understand what you mean. But, the two first images - how do you identify a tilted focus plane in them? Of course, any good idea here may be obscured by a bad adapter or a misaligned lens element, there are unknown factors at play.


It's hard to tell because of the small images, but if the left background doesn't have the same weird sharpness as the right background... it's always a bad lens, adapter or mount (the mount isn't the problem here). A lens should always show the exact same behavior on the left and the right side of it's center.




Apr 08, 2015 at 12:43 PM
Jonas B
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p.1 #20 · p.1 #20 · Problem with ZM 35 f/1.4 on A7 Series?


Well, whatever it is (the last image) it doesn't look pretty...


Apr 08, 2015 at 12:44 PM
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