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21mm comparison: Zeiss ZM f/4.5 Biogon - CV VM f/1.4 Nokton - E-mount f/3.5

  
 
Andrew CD
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p.1 #1 · p.1 #1 · 21mm comparison: Zeiss ZM f/4.5 Biogon - CV VM f/1.4 Nokton - E-mount f/3.5


For some time, I have wanted a small 21mm lens for my M11, and was interested to try the Zeiss ZM 21mm f/4.5 Biogon. Having finally tracked down a nice copy, I was keen to compare it with my other two 21mm lenses, the CV f/1.4 Nokton and ó on our Sony A7R mk IV ó the f/3.5 Color-Skopar.

I never use my Leica cameras on tripods, but the first set of comparisons (with a tree in the centre of the frame and a green bush in the bottom left corner) were down with my elbows resting on a fence. All f/5.6 (ignore the cameras aperture estimates), shutter speeds chosen to just avoid any over-exposure. The second image (with the sun near the centre of the frame and big tree to the left) were both f/8, hand-held. No adjustments made in Lightroom other than to make the exposure in the centre roughly equal.

The images Iíve attached here are screenshots from Lightroom with the screen at its native resolution (to avoid the strange behaviour that LR exhibits when the display is using a scaled resolution) with 100% or, in one case, 200% crops. The screenshots are scaled down by 50% to make them a reasonable width to post here. In all cases, the Zeiss is on the right. CV f/1.4 Nokton and ZM f/4.5 Biogon on the M11, CV f/3.5 Color-Skopar on the Sony A7R iv. All 100% crops unless otherwise stated.

A few observations:

1. The ZMís centre resolution seems to me pretty good (although the tree in the centre of the frame is, admittedly, some distance away). Given how impressive the Nokton f/1.4 is, I was surprised not to see more of a difference, given the size and greater complexity of the Nokton.

2. It is, however, appreciably less sharp in the corner (green bush) and the edge (tree in deep shade). The f/3.5 Color-Skopar seems to me surprisingly good ó but bear in mind that it is on the Sony, not the Lecia.

3. Vignetting is also much greater with the ZM.

4. Although this is entirely subjective, I like the ZMís colour rendering best of all (but, again, bear in mind that, in the case of the f/3.5 C-S, there is also the Sony / Leica difference).

5. It is interesting to see (in the final screenshot, showing the middle of the left edge of the frame) that, with the sun near the centre of the frame, the CV Nokton appears to show appreciably more chromatic aberration. The Zeiss does have a reputation for very low distortion, though. (I boosted exposure to offset the vignetting here.)

I hope that this is of interest. Incidentally, Iíd welcome any advice or suggestions about the approach Iíve taken in making these comparisons (I would not claim to be anything other than an enthusiastic amateur when it comes to this sort of thing ).

Andrew





CV f/1.4 -- ZM f/4.5, both f/5.6, centre of frame






CV f/3.5 (Sony) -- ZM f/4.5, both f/5.6, centre of frame





© Andrew CD 2024

CV f/1.4 -- ZM f/4.5, both f/5.6, bottom left corner of frame






CV f/3.5 (Sony) -- ZM f/4.5, both f/5.6, bottom left corner of frame






CV f/1.4 -- ZM f/4.5, both f/8.0, near centre of frame






CV f/1.4 -- ZM f/4.5, both f/8.0, near centre of frame, 200% crop






CV f/1.4 -- ZM f/4.5, both f/8.0, centre left of frame, 200% crop, ZM exposure boosted




Apr 16, 2024 at 01:57 AM
hanay78
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p.1 #2 · p.1 #2 · 21mm comparison: Zeiss ZM f/4.5 Biogon - CV VM f/1.4 Nokton - E-mount f/3.5


Thank you very very much for your comparison!

The Color-Skopar is Sony version, is not it?

Thank you again for the fantastic comparison. For what I understand the Biogon should be worse in the Sony than in the Leica camera?

Jorge

Andrew CD wrote:
For some time, I have wanted a small 21mm lens for my M11, and was interested to try the Zeiss ZM 21mm f/4.5 Biogon. Having finally tracked down a nice copy, I was keen to compare it with my other two 21mm lenses, the CV f/1.4 Nokton and ó on our Sony A7R mk IV ó the f/3.5 Color-Skopar.

I never use my Leica cameras on tripods, but the first set of comparisons (with a tree in the centre of the frame and a green bush in the bottom left corner) were down with my elbows resting on a fence.
...Show more




Apr 16, 2024 at 07:46 AM
Fred Miranda
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p.1 #3 · p.1 #3 · 21mm comparison: Zeiss ZM f/4.5 Biogon - CV VM f/1.4 Nokton - E-mount f/3.5


Thanks for putting this together Andrew!
The CV 21/1.4 at f/5.6 is softer than the CV 21/3.5 at the same aperture?? Have you checked if your CV 21/1.4 is well centered?

I've tested these lenses and could never achieve results like this. The CV 21/1.4 is one of the sharpest 21mm lenses available at f/5.6, even compared to the 21/3.4 SEM.







Apr 16, 2024 at 11:43 AM
Andrew CD
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p.1 #4 · p.1 #4 · 21mm comparison: Zeiss ZM f/4.5 Biogon - CV VM f/1.4 Nokton - E-mount f/3.5


hanay78 wrote:
Thank you very very much for your comparison!

The Color-Skopar is Sony version, is not it?

Thank you again for the fantastic comparison. For what I understand the Biogon should be worse in the Sony than in the Leica camera?

Jorge



Thanks.

Without having seen any evidence, I would have blithely assumed that the ZM f/4.5 Biogon would work less well adapted on the Sony than natively on the Leica. But itís always worth checking. Here are a couple of comparisons, using it with the Novoflex NEX adapter on the A7R iv and natively on the M11 You can judge for yourself Ö. All f/5.6, ISO 200, exposure chosen to just avoid highlight clipping, lens correction profile applied to reduce vignetting, IBIS turned off on Sony. In all cases, the Sony (adapted) is on the left, the Leica on the right.

However, perhaps unsurprisingly, on the Sony, the Biogon does seem to exhibit colour smearing (as I understand it does on earlier digital M cameras). Iím not sure how well it will show at this resolution, but you can probably see some colouring down the left side of the final image ó which I can assure you isnít there in real life. On this image too, I applied the lens correction profile to reduce vignetting.

Andrew





1. Sony A7R iv - Leica M11, CV ZM f/4.5 Biogon, centre 200% crop






2. Sony A7R iv - Leica M11, CV ZM f/4.5 Biogon, centre 200% crop






3. Sony A7R iv - Leica M11, CV ZM f/4.5 Biogon, centre 200% crop






4. Sony A7R iv - Leica M11, CV ZM f/4.5 Biogon, top right 200% crop






5. Sony A7R iv - Leica M11, CV ZM f/4.5 Biogon, right edge middle 200% crop






6. Sony A7R iv - Leica M11, CV ZM f/4.5 Biogon, bottom left 200% crop






  ILCE-7RM4    Zeiss C Biogon T* 4.5/21 ZM lens    21mm    1/1000s    200 ISO    0.0 EV  




Apr 17, 2024 at 12:47 PM
 


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Andrew CD
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p.1 #5 · p.1 #5 · 21mm comparison: Zeiss ZM f/4.5 Biogon - CV VM f/1.4 Nokton - E-mount f/3.5


Fred Miranda wrote:
Thanks for putting this together Andrew!
The CV 21/1.4 at f/5.6 is softer than the CV 21/3.5 at the same aperture?? Have you checked if your CV 21/1.4 is well centered?

I've tested these lenses and could never achieve results like this. The CV 21/1.4 is one of the sharpest 21mm lenses available at f/5.6, even compared to the 21/3.4 SEM.


Thanks for taking the trouble to reply. I find making this sort of comparison quite interesting ó it gives me a better understanding of how the lenses behave.

As for the CV Nokton / Color-Skopar comparion: quite! I was baffled by this. It doesnít seem credible that the C-S should be sharper at f/5.6. Were you looking primarily at the left hand sides of the third and fourth screenshots (the redcurrant bush next to the corner of the greenhouse)? These were the bottom left corner of the frame.

Two things that may be worth mentioning: the C-S had an appreciably shorter exposure, 1/640 vs. 1/250 for the Nokton, although I should have thought that 1/250 would be fine for 21mm; and the Sony has IBIS (which I had neglected to turn off). I rather doubt that either of these would have made a huge difference, though, so have made some more comparisons. For these, I was as careful as I could be ó sitting down, with my elbows resting on the arms of the chair.

In all cases, Color-Skopar f/3.5 (A7R iv) on the left, Nokton f/1.4 (M11) on the right. ISO 200 on both, all f/5.6 unless otherwise stated. The blossom and the brick wall with door were taken from c.2m, the big oak tree was about 100m away. Minor adjustments made in LR to roughly equalise exposure only, no other changes, default sharpening. All 200% crops, screenshots made using the displayís native resolution (to avoid LR resizing).

The blossom, the hinges on the stable door and the big oak tree are at the centre of the frame. The four areas of brick are middle of left edge, middle of right edge, top right and bottom left. Iím pretty sure that the Nokton looks noticeably better in the two mid-edges and top right but less good in the bottom left. If thatís the case, it seems clear that itís not working perfectly. Any further thoughts would be appreciated!

(I took the same three shots using the ZM f/4.5 Biogon, too, Iíll post those comparisons later.)

Andrew





1. CV 21mm f/3.5 (A7R iv) - CV 21mm f/1.4 (M11), centre 200% crop






2. CV 21mm f/3.5 (A7R iv) - CV 21mm f/1.4 (M11), f/4.0, centre 200% crop






3. CV 21mm f/3.5 (A7R iv) - CV 21mm f/1.4 (M11), centre 200% crop






4. CV 21mm f/3.5 (A7R iv) - CV 21mm f/1.4 (M11), centre 200% crop






5. CV 21mm f/3.5 (A7R iv) - CV 21mm f/1.4 (M11), left edge (middle) 200% crop






6. CV 21mm f/3.5 (A7R iv) - CV 21mm f/1.4 (M11), right edge (middle) 200% crop






7. CV 21mm f/3.5 (A7R iv) - CV 21mm f/1.4 (M11), top right 200% crop






8. CV 21mm f/3.5 (A7R iv) - CV 21mm f/1.4 (M11), bottom left 200% crop




Apr 17, 2024 at 01:02 PM
rscheffler
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p.1 #6 · p.1 #6 · 21mm comparison: Zeiss ZM f/4.5 Biogon - CV VM f/1.4 Nokton - E-mount f/3.5



Andrew CD wrote:
However, perhaps unsurprisingly, on the Sony, the Biogon does seem to exhibit colour smearing (as I understand it does on earlier digital M cameras). Iím not sure how well it will show at this resolution, but you can probably see some colouring down the left side of the final image ó which I can assure you isnít there in real life. On this image too, I applied the lens correction profile to reduce vignetting.

Andrew


I briefly tried the ZM 21/4.5 on an M9 ~13 years ago and it indeed resulted in very strong peripheral color shift, which IIRC was red/magenta. At the time I could have tried Corner Fix to correct it, but given the color shift severity, combined with heavy vignetting and the amount of image noise that would result, I didn't bother. I got the ZM 21/2.8 instead (which still required Corner Fix correction on the M9).

Your example above on the Sony suggests to me that the color shift is actually caused by uneven IR absorption across the image by the stack above the sensor, and isn't caused by suboptimal microlens design and/or the sensor itself, as was likely the case in my situation with the M9.

Due to the ZM 21/4.5's design, light ray angles towards the image periphery are far from passing perpendicularly through the sensor stack as compared to on-axis light rays. As a result, the distance peripheral light rays travel through the stack is greater, which means the stack's IR absorption is also greater for these rays compared to on-axis light rays, which results in the blue/cyan color shift.

The a7RIV and M11 share basically the same sensor with the biggest difference likely being the thicker stack used by Sony (CFA differences would affect overall color response but not necessarily edge color shift, if my understanding is correct). Leica's thinner stack therefore affects the ZM's peripheral rays less, in respect to uneven IR absorption/blocking, resulting in less or no noticeable edge color shift.



Apr 17, 2024 at 01:15 PM
Andrew CD
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p.1 #7 · p.1 #7 · 21mm comparison: Zeiss ZM f/4.5 Biogon - CV VM f/1.4 Nokton - E-mount f/3.5


rscheffler wrote:
I briefly tried the ZM 21/4.5 on an M9 ~13 years ago and it indeed resulted in very strong peripheral color shift, which IIRC was red/magenta. At the time I could have tried Corner Fix to correct it, but given the color shift severity, combined with heavy vignetting and the amount of image noise that would result, I didn't bother. I got the ZM 21/2.8 instead (which still required Corner Fix correction on the M9).

Your example above on the Sony suggests to me that the color shift is actually caused by uneven IR absorption across the image by the stack
...Show more

Thanks, Ron. That's fascinating.

I was familiar with the ray angle problem which arose when using this lens on the earlier M-digital models. My understanding was that the reason the problem doesn't occur with the M11 (and M10-R?) is that it has a thinner stack, whereas with a thicker stack, the angle at which light hits micro lenses to the side of the frame can cause it to be misdirected, correct? (Film cameras don't need a CFA with micro lenses, of course.) So it seems entirely plausible that, if the Sony has a thicker stack, a similar problem will occur.




Apr 21, 2024 at 11:42 AM
Fred Miranda
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p.1 #8 · p.1 #8 · 21mm comparison: Zeiss ZM f/4.5 Biogon - CV VM f/1.4 Nokton - E-mount f/3.5


Just for curiosity here are the Zeiss 21/4.5 ZM and CV 21/4 Color-Skopar lens cut-outs:




Zeiss 21/4.5 ZM






CV 21/4 Color-Skopar




Apr 21, 2024 at 12:07 PM







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