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G21mm Biogon vs CY 21mm Distagon %a1V Which one better


If purely based on optical quality at f5.6 -f8 (no need to take into account for lens size, weight, cost, distortion,) Would 21mm Biogon better than C/Y 21mm Distagon. It is noted from the Zeiss description that all of possibilities of correcting residual chromatic aberration were utilized to full for C/Y 21mm Distagon while not applied for 21mm Biogon. Any member has both for side by side comparison. Thanks for advice.


Hi Edmond

about the 21 Biogon for the Contax. Some owners call it "the little brother of the Hasselblad SWC". I thinks this say enough about this lens. I think it's obsolete to discuss about the quality of this two lenses. If you have a SLR you need a Distagon, if you have a Contax RF, you need a Biogon. On the strenghth of construction, a SLR needs a retrofucs based lens (Distagon) and a RF allows a symetric construction like the Biogon. Regarding on the high quality of both lenses - that's all.

Hans Villars, Switzerland


The only advantage I know of that the Distagon has over the Biogon is in light falloff towards the edges, which is inherent to the Biogons. The Biogons are well corrected in all regards, and the 21 for the G is my favorite of all my Contax lenses, G or SLR.



G21 has less complicated lens design and means less internal reflection. I vote on it. Or you can get a G1 for this lens only.


I would opt for the G Biogon personally. The Y/C Distagon is a comparatively big and heavy lens with a 82mm filter size. It is a rather complex design with 15 elements in 13 groups. The Biogon is small, light, simple and has a 55mm filter size.


I've also been pondering this question, mainly because the only ultra-wide I own is the Canon EF 20mm f/2.8, which isn't an outstanding performer (especially not at f/2.8 or f/4). Judging by test shots posted on, the Biogon seems like a contender for the title of world's sharpest ultra-wide lens. It (literally ;o) edges out the 21mm f/2.8 for Leica M, a lens which costs so much more that it would be cheaper for me to buy a used G2 specifically for the Biogon.

But what about the Distagon? Comparing the MTF charts on the Zeiss site, it does seem to give a bit of ground to the Biogon. The distortion reaches a peak of 2.5% towards the edge of the field, compared with just 0.5% for the Biogon. At f/5.6 it holds its own until the corners, where there is a pronounced drop-off in the sagital curves. This only happens around 19mm from the centre, which is in the far reaches of the corners (the frame ends at 21.6mm).

At full aperture, the Biogon is a clear winner in terms of contrast at the edges, holding 0.8 or better for the 10lpmm curves right to the edge of the frame. The sagittal curve for the Distagon crosses the 0.8 barrier 17mm out from the centre and finishes up almost exactly on 0.6. That amounts to an observable difference in the corners at full whack, but it is still good performance. Interestingly, the recording of fine detail (indicated by the 40lpmm curves) is actually slightly better with the Distagon at f/2.8.

In conclusion it would be hard to be disappointed by the performance of either of these lenses. According to the charts, the Biogon "wins" marginally while the lower number of elements and the compactness also weigh in its favour. However, one important factor that nobody has yet mentioned is the closest focusing distance: 0.5m for the Biogon plays 0.25m for the Distagon, and that advantage could open the door to some interesting shots that would not be possible with the Biogon. Finally, the matter of bokeh is something that can't be assessed from charts, so we can only hope that some lucky user of both lenses passes by here and posts some comparative test shots. Meanwhile I'm planning to pick up the Distagon when I see one for the right price, and see how I get along with it.

Regards all,

-= mike =-


Well-Known Member
Is there really that much difference between any of the top rated lenses? What is the obsession with having the absolute best if there isn't much difference? Finally, if there is a reason, what are you photographing where the difference would be seen? Sincerely, Scott


On one level at least, a good lens is a good lens, no matter who's name is etched into it. Once you've achieved a certain level of quality the dominant variable becomes the eye behind the camera.

But on another level, ergonomic differences aside (and there are huge handling differences between a G+21 and an SLR+21), there are nuances to each lens' performance that should not be ignored.

Somebody could rightly say that there's no effective difference between a Bordeaux and a Napa Valley cabernet, but to a wine aficonado the statement would border on heresey.

You get the idea.



Well-Known Member
Rick, I had to jump back into the conversation since you mentioned wine! ;) You write, "Somebody could rightly say that there's no effective difference between a Bordeaux and a Napa Valley cabernet, but to a wine aficonado the statement would border on heresey." I agree. However, I guess when one tries to compare wines or lenses, one must limit the comparison to what is important. I.e., what is the very specific reason for distinguishing them? Otherwise, I would enjoy drinking either of them (in the case of wines), neither of which may be better, worse. In the case of lenses, I might enjoy using either of them and would need specific reasons why they should be distinguished or in what applications they should be distinguished. My 2 cents, Scott


>>> Somebody could rightly say that there's no effective difference between a Bordeaux and a Napa Valley cabernet, but to a wine aficonado the statement would border on heresey. >>>

Absolutely right, Rick. I can't agree more!

Cheers, Ludwig Argüelles


Hi Scott,

I think you're overestimating the ability of even the premium manufacturers to produce lenses that perform well at wide apertures, especially wide angle lenses, and especially at the edge of the field. The difference between 0.8 (80% contrast) and 0.6 that we have in the corner performance of the two lenses is clearly observable even in a small print. I find that much of the time with an ultra-wide lens, I have the subject off-centre and near the camera, because this uses the exaggerated perspective to best effect. For that reason, edge performance is a key concern, and although the Distagon gives something away in the far corners, the sides of the frame are still within its sweet spot. This is definitely relevant information when it comes to lens purchasing and usage.

You ask "Is there really that much difference between any of the top rated lenses?" to which I can reply "yes there is". I've been slowly going through my lenses taking simple real-world comparison shots to get a feel for the optimum results I can expect of each of them, and I'm surprised how much variation there is among different top-quality lenses at full or wide apertures. The fact that a lens says "Planar", "Distagon", "L", "Summicron" (or whatever) on the barrel doesn't guarantee anything, so it's important to match your own requirements to the characteristics of a lens before splashing out all that cash.

One thing that has consistently amazed me in my assessment of the comparison shots is the very low magnifications at which differences are clearly visible. As an extreme ex&le, I can reliably distinguish shots from my 85/1.4 at 1.4 vs 2.8 on the file browser thumbnails in PS, never mind any kind of print! More relevantly, there is an observable difference in crispness between my Planar 50/1.4 @ f/2 and a Summicron 50/2 at 12.5% magnification on the screen. So yes, these are very practical considerations for shooters like me who are into available-light work.

Best regards,

-= mike =-


Well-Known Member
I suspected Zeiss has made an enormous effort to make sure 21 Distagon as successful as it is,and indeed it amazes me all the time. To correct one previous sentence,the minimal focal distance for this lens is actually 0.22m.
There are two sites which I trust to tell the differences between the lens.
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. 21 Distagon scores very high in ilprode site and is above 50 1.7 planar and 85 1.4 planar. Photodo does not give a score for 21 Distagon but with the help from ilprode site the score should be above 4.6 which is the score for 50 and 85. I suspect it scores either 4.7 or 4.8. 21 Biogon scores 4.3 in photodo.
Although one person suggested the 21 Biogon is better based on Zeiss MTF data,when I looked at these curves the difference is not that great.
Zeiss MTF curves is sometimes not useful. For ex&le,judging from these curves,100 Makro Planar should be better than 100 2 Planar. From my own experience of using these lens, 100 2 is definitely better than 100 MP. In fact, 100 2 at f=2 is better than 100 MP at f=2.8. In this case,ilprode is more able to provide useful informations than Zeiss curve.
In conclusion,I believe 21 D is significantly better than 21 B.
Is there anyone who have direct experience in using both lens?
Based on my conclusion,I don't bother to purchase the 21 Biogon when I have 21 Distagon,despite the fact that I have a G2.