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Slrgear tests Sonnar T* FE 35mm f/2.8
  
 
Tariq Gibran
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p.2 #1 · Slrgear tests Sonnar T* FE 35mm f/2.8


Toothwalker wrote:
I don't know what causes it. Automatic correction of vignetting may play a role, but can't this be switched off?

What about the offset microlenses? Perhaps the rings correspond to regions with variations in the offset of these lenses.

I would be surprised if the FE 35 is to blame.




Yes, the auto correction can be turned off. According to Tim's testing above, even at F5.6 and F8, the shading/ vignetting is still quite strong so if correction is being applied, It is likely to have an effect with subtle tonal transitions. There is also some color cast correction occurring which might compound the issue. I'm less inclined to believe it's the microlenses but someone more knowledgeable about the sensor design would know more.



Feb 21, 2014 at 05:47 PM
theSuede
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p.2 #2 · Slrgear tests Sonnar T* FE 35mm f/2.8


An offset ML layer does not have integer "steps" in correction. What you do is linear scaling and then placement offset.

Like: The APS width is 23.766mm split over 6080px line widths. Then you make a mask for the ML deposit/erosion that has 6080 "bumps" over 23.760mm (6.00Ám smaller) and place it centered on the substrate.
The offset will then be a gradual increase in px(cc)>ML(cc) starting at zero at the optical axis (sensor center) and 3.00Ám at the short edge. At half this image height (23.766/4=5.941mm) the offset will be 1.50Ám, at 90% image height it will be 0.90*3.00=2.70Ám. A smooth increase with image height from center.

carstenw wrote:
My hunch is that it is related to the lossy compression. If you throw a couple of bits of information away, there are bound to be places where you can see that, and very gradually changing sky-colours would fit that scenario.


In a flat surface, the lossy compression has almost exactly zero impact on the tone resolution of ARW2. Posterization in surfaces like skies and other colored flats is almost always a combination of applying color transforms to 8-bit converted data (and it's present in monitor presentations of 16 bit data to, even float32 is affected!).

Raw data > noise variance is way stronger (3x at base ISO and the worst ARW compression) than the value step. But apply even the slightest amount of noise reduction to this - and in this case, even the raw Bayer interpolation counts as "slight NR" since it's a blurring transform! - and then your base data is stairstepped. But WAY below the threshold of visibility.

What makes this smooth surface (with solid patch tones) break up into "bands" of differing brighness/hue is the steps in converting the base data to a presentation format like sRGB or ARGB. Especially if you do in in an 8-bit limited presentation. This is especially noticeable in blue and purple, where the luminance-bearing channels (R,G) are very coarse.
So even a mathematically "perfect" conversion may include (presentation) banding if the base data was close to a perfectly even gradation.

First the data conversion raw color > standard RGB space, and you get a banding that's bordering on visible. After that push the converted, slightly banded data through a monitor profile - which will have another set of threshold levels for the gradation.

Doing this will almost inevitably create round-off errors so that you may get real banding, a gradation where the surface that originally was perfectly even going from dark to bright in stead has distinct brighter-darker-brighter-darker bands that doesn't coincide with the chroma band cutoffs.

Since the image chain in bad executions of CM (like Apples colorsync, and of course also several versions of implementations of the choices you have in Windows) are often limited to 8-bit even if the base data is 16-bit or even floats, you get banding on screen, even with high tone-res material.



Feb 22, 2014 at 01:46 AM
wfrank
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p.2 #3 · Slrgear tests Sonnar T* FE 35mm f/2.8


Thank you Tariq and theSuede. From this I conclude that if you turn any in-camera correction OFF problem is gone.


Feb 22, 2014 at 08:47 AM
edwardkaraa
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p.2 #4 · Slrgear tests Sonnar T* FE 35mm f/2.8


wfrank wrote:
Thank you Tariq and theSuede. From this I conclude that if you turn any in-camera correction OFF problem is gone.


Nope, I keep all corrections off and still got the problem.



Feb 22, 2014 at 09:06 AM
wfrank
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p.2 #5 · Slrgear tests Sonnar T* FE 35mm f/2.8


Thanks Edward. Too bad, still a mystery then


Feb 22, 2014 at 09:24 AM
Toothwalker
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p.2 #6 · Slrgear tests Sonnar T* FE 35mm f/2.8


theSuede wrote:
An offset ML layer does not have integer "steps" in correction. What you do is linear scaling and then placement offset.

Like: The APS width is 23.766mm split over 6080px line widths. Then you make a mask for the ML deposit/erosion that has 6080 "bumps" over 23.760mm (6.00Ám smaller) and place it centered on the substrate.
The offset will then be a gradual increase in px(cc)>ML(cc) starting at zero at the optical axis (sensor center) and 3.00Ám at the short edge. At half this image height (23.766/4=5.941mm) the offset will be 1.50Ám, at 90% image height it will be 0.90*3.00=2.70Ám. A smooth
...Show more

Thanks. This makes perfect sense.



What makes this smooth surface (with solid patch tones) break up into "bands" of differing brighness/hue is the steps in converting the base data to a presentation format like sRGB or ARGB. Especially if you do in in an 8-bit limited presentation. This is especially noticeable in blue and purple, where the luminance-bearing channels (R,G) are very coarse.
So even a mathematically "perfect" conversion may include (presentation) banding if the base data was close to a perfectly even gradation.

First the data conversion raw color > standard RGB space, and you get a banding that's bordering on visible. After that push the converted,
...Show more

Hmm. Is there a part of the explanation that is specific to the A7(R) + FE 35?





Feb 22, 2014 at 11:23 AM
edwardkaraa
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p.2 #7 · Slrgear tests Sonnar T* FE 35mm f/2.8


By the way, the FE 55 does it too. Less often due to the FL, but it can easily be reproduced.

I just aimed my camera at the white ceiling without EC and took a shot, and the effect is very clear and visible even on the camera LCD.



Feb 22, 2014 at 11:29 AM
Toothwalker
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p.2 #8 · Slrgear tests Sonnar T* FE 35mm f/2.8


edwardkaraa wrote:
By the way, the FE 55 does it too. Less often due to the FL, but it can easily be reproduced.

I just aimed my camera at the white ceiling without EC and took a shot, and the effect is very clear and visible even on the camera LCD.


Ok then :-)

Is there a part of the explanation that is specific to the A7(R)?



Feb 22, 2014 at 11:39 AM
edwardkaraa
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p.2 #9 · Slrgear tests Sonnar T* FE 35mm f/2.8


Toothwalker wrote:
Ok then :-)

Is there a part of the explanation that is specific to the A7(R)?


I really don't know, I'm not a technical guy. Waiting for explanations from you and Joachim

But I could swear the concentric circles look like badly polished aspherical surfaces.



Feb 22, 2014 at 11:42 AM
Tariq Gibran
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p.2 #10 · Slrgear tests Sonnar T* FE 35mm f/2.8


edwardkaraa wrote:
I really don't know, I'm not a technical guy. Waiting for explanations from you and Joachim

But I could swear the concentric circles look like badly polished aspherical surfaces.


Hmm, that's very strange Edward. You get this effect with directly converted raws to a wide color gamut profile (Pro Photo RGB or AdobeRGB) at 16bit before re-sizing and/or changing to 8bit SRGB for web viewing? Have you shot side by side tests with another camera that does not give the same result (to maybe eliminate hardware/ software variables beyond the camera)?

If you can send me a link to download the raw, I would love to see what is going on.



Feb 22, 2014 at 12:57 PM
 

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Tariq Gibran
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p.2 #11 · Slrgear tests Sonnar T* FE 35mm f/2.8


edwardkaraa wrote:
By the way, the FE 55 does it too. Less often due to the FL, but it can easily be reproduced.

I just aimed my camera at the white ceiling without EC and took a shot, and the effect is very clear and visible even on the camera LCD.


If you zoom in with Live View before taking the shot, is it there or only in the reviewed shot that is taken?



Feb 22, 2014 at 01:03 PM
edwardkaraa
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p.2 #12 · Slrgear tests Sonnar T* FE 35mm f/2.8


Tariq Gibran wrote:
If you zoom in with Live View before taking the shot, is it there or only in the reviewed shot that is taken?


Sorry Tariq, false alarm, the effect is visible in LV and on screen shot, but not in the raw file.

However, I have an FE 35 file where the effect is very visible (posted it 2-3 days ago in the picture thread). I can email you this one if you like.



Feb 22, 2014 at 03:39 PM
AhamB
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p.2 #13 · Slrgear tests Sonnar T* FE 35mm f/2.8


edwardkaraa wrote:
But I could swear the concentric circles look like badly polished aspherical surfaces.


Whether it has something to do with asphericals should be easy to determine: is the banding perfectly circular (following the circular grooves/ridges that are present in the mold into which the aspherical element was pressed), or does it follow the vignetting/luminance falloff? If it's not circular I think you can rule out that it's an artifact caused by aspericals.



Feb 22, 2014 at 03:51 PM
edwardkaraa
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p.2 #14 · Slrgear tests Sonnar T* FE 35mm f/2.8


AhamB wrote:
Whether it has something to do with asphericals should be easy to determine: is the banding perfectly circular (following the circular grooves/ridges that are present in the mold into which the aspherical element was pressed), or does it follow the vignetting/luminance falloff? If it's not circular I think you can rule out that it's an artifact caused by aspericals.


A picture is worth a thousand words


A7 - FE 35/2.8 ZA by edward karaa, on Flickr



Feb 22, 2014 at 03:55 PM
carstenw
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p.2 #15 · Slrgear tests Sonnar T* FE 35mm f/2.8


Do you have another 35mm lens to try?


Feb 22, 2014 at 04:06 PM
edwardkaraa
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p.2 #16 · Slrgear tests Sonnar T* FE 35mm f/2.8


carstenw wrote:
Do you have another 35mm lens to try?


Yep, I have the ZM 35/2. Will try tomorrow if the weather allows.



Feb 22, 2014 at 04:08 PM
theSuede
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p.2 #17 · Slrgear tests Sonnar T* FE 35mm f/2.8


In the preview, it's certainly the 8-bit transform for the LCD (and OLED) screen.

But in the PP steps in camera ("lens correction") preparing jpgs it might be insufficient bit depth in the calculations. It's no use having good tone resolution base data if you apply low-precision maths to it...

I've actually never inspected in-camera jpg's from the A7/A7r that closely for that error. I just found them generally better than the previous generation of cameras, and set them back to raw only.
Is the banding there (in the in-camera jpgs) too?

If it is, then I'd turn OFF lens correction, then turn OFF any NR, and then turn OFF any monitor profile (color management on the computer) and look again.
If it's still there then, you have a problem. But I've actually never had that happen in a Sony, even with compressed 12-bits (11 bit precision).

That the problem is more noticeable with the 35 might actually just be that the vignette gives blue skies a certain gradation "slope" speed that makes the effect worse.



Feb 22, 2014 at 04:08 PM
edwardkaraa
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p.2 #18 · Slrgear tests Sonnar T* FE 35mm f/2.8


carstenw wrote:
Do you have another 35mm lens to try?


I just remembered I already did a comparison when I first received the FE 35. Sorry about the extreme PP, but it is meant to make the issue more visible.

Both files have been PPed similarly.



a7 - fe 35/2.8 za by edward karaa, on Flickr


a7 - zm 35/2 by edward karaa, on Flickr



Feb 22, 2014 at 04:27 PM
wfrank
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p.2 #19 · Slrgear tests Sonnar T* FE 35mm f/2.8


Thanks for the examples Edward. So these are with in-camera lens compensation settings OFF (both chromatic and vignetting)?

And no lens compensation profiling by lightroom/PS either?

(I assume RAW)

BTW, got myself the FE35 today. Shot some blue skies and will look for posterization and post if I find it. Mine settings were ON.





Feb 22, 2014 at 04:38 PM
edwardkaraa
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p.2 #20 · Slrgear tests Sonnar T* FE 35mm f/2.8


wfrank wrote:
Thanks for the examples Edward. So these are with in-camera lens compensation settings OFF (both chromatic and vignetting)?

And no lens compensation profiling by lightroom/PS either?

(I assume RAW)

BTW, got myself the FE35 today. Shot some blue skies and will look for posterization and post if I find it. Mine settings were ON.



Correct, all corrections off, no profiles applied to the raw files.

Congrats for your lens! It is really wonderfully sharp with a nice drawing style.



Feb 22, 2014 at 04:51 PM
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