p.12 #3 · Zeiss Distagon 2.8/15 ZE official, release in May 2012
FYI I got this response from Zeiss. We´ll have to wait and see.
Dear Mr. Isaksson,
Thank you for your hint.
We will correct the wrong MTF charts of the Distagon T* 2,8/15 as soon as possible.
I´m sure you already know our CLN articles from our Dr. Nasse about "how to read MTF charts" which explain in detail especially what cannot be read out of them:
Standard filter threads, primarily intended for lens protection (since digital photography usually does not require filtration). Support for filters resulted in a lens face significantly larger than the front element in order to cope with off-axis rays when using filters.
Avoidance of a bulbous front end which is subject to damage, and would have precluded filters. The front element is relatively well protected, since it is recessed significantly deeper than the lens shade. This is helpful in rainy conditions also. [diglloyd: as I found when shooting for several hours of rain!]
Digital sensor friendly with a very low ray angle of 11° (full frame), which is superior to the ZEISS 100/2 at 13.6°, or the 19° of the 18/3.5 Distagon.
p.12 #6 · Zeiss Distagon 2.8/15 ZE official, release in May 2012
S. Dilworth was correct in guessing that the 15 has an aspherical element for the 2nd element after the front element just like the 14-24G and that is how they corrected the distortion so well. Nasse said that they wanted to make the front element aspherical for even better correction but it would be too expensive because of size.
Looks like they really have the color correction process of lens design, via using different glass types with different diffraction and Abbe numbers, down very well.
Too bad LC didn't ask Nasse why they didn't and have not designed a super wide angle lens with shift.
p.12 #11 · Zeiss Distagon 2.8/15 ZE official, release in May 2012
wayne seltzer wrote:
Ok, 2nd tough question for Dr Nasse:
After seeing what Zeiss did for the design of the new 15, what was their excuse for their 18 design?
p.12 #12 · Zeiss Distagon 2.8/15 ZE official, release in May 2012
I think that Zeiss, whether through accident or design were very clever in how they have brought these lenses to market. The initial batch were clearly based on the old Contax designs, simply brought up to date with the allowed modern glass types (18mm F3.5, 25mm F2.8, 50mm F1.4 and 85mm F1.4). Using the 85mm was like going back to 1980 in a time machine for me after my time spent with modern Canon AF lenses. I'm sure that this was both easier to design and bring to market in a short amount of time and also allowed them to tap into the nostalgia surrounding the old designs.
Since then they have started branching out and producing state of the art new lenses (35mm F1.4, 25mm F2 and now 15mm F2.8) as their 21st Century legacy.
It is very exciting (but also very expensive). However my pre-order is in. I also have the Canon 14mm L Mark II so it will be interesting to see if Zeiss have come up with something better than their Canon and Nikon counterparts.
p.12 #13 · Zeiss Distagon 2.8/15 ZE official, release in May 2012
I am among the folks who throwed 1500€ towards Zeiss for that 18mm, which was definitely too much for this design. Since Zeiss made it available for 1200 and you can get it (from time to time) for under 800 on you-know-where, it's not so bad. Now when the 15mm is that good, Zeiss should consider to stop production of the 18mm (like they did with the 25) and go "high-end only" with the 21 and the 15
p.12 #15 · Zeiss Distagon 2.8/15 ZE official, release in May 2012
Z250SA wrote:
The f/5.6 graph is a copy of the Distagon 25/2 f/4 graph. My quick search did not locate any other source for the f/2.8 MTF graph. Quite sloppy!
Just e-mailed Zeiss and asked them to look into the problem.
(However, the datasheet for the 50 mm f/1.4 Planar still has wrongly-labelled MTF charts (they're labelled f/2 and f/4 but should be f/1.4 and f/5.6). I emailed them about that error a while ago, and got a thank-you note, but they didn't fix it. Your emails seem to work better. Hint hint!)
Lotusm50 wrote:
Well, it seems my estimate of $2995 was pretty much on target.
You were $1 closer to the launch price than my guess of $2900. Good work [he says grudgingly].
philip_pj wrote:
Dr Nasse is quite an asset, the gift that keeps on giving.
Indeed. His description of how anomalous partial dispersion glass helps lens designers correct chromatic aberration is unusually clear and accessible. But I suppose that's why he does what he does.
Simon's story of how Zeiss has approached the Z-series lenses sounds plausible to me, though I have a soft spot for the lenses that some denigrate. The 18 mm Distagon, for example, is much smaller than the 15 mm or 21 mm Distagons. (It also has a much longer focus throw, for better zone focusing.) It already uses loads of special glass, but it doesn't have any aspherical elements. As we've been told by Dr Nasse, aspherical surfaces are extremely useful in controlling the aberrations found in wide-angle retrofocus lenses.
Nonetheless, considering the large size difference between the 15 mm and 18 mm Distagons, I think the old lens still has a place:
p.12 #16 · Zeiss Distagon 2.8/15 ZE official, release in May 2012
Thanks for the insight, Simon, very interesting to see it that way, and it does make good sense..but I would add the word 'character' to your first para's last sentence. And can you add the enigmatic 50MP to the 21st century lens list, maybe? There is no Contax antecedent, the older 60MP is very different.
Both Nasse and Puts make a large issue of glass type matching, and it was interesting to read that the first batch will be MTF tested, *for each individual lens*.
If we look at sagittal lines only (and Nasse accounts for the drop in the tangential data occurring in the outer frame as due to 'residual CA') the 15mm is as strong at f11 as the much-vaunted 100MP is at f4 - in the extreme corners as much as the image centre.
In other words, the 15mm is so strong that even diffraction merely brings the overall performance back to that level, as well as evening out the contrast across the frame, thereby delivering very high image evenness. The f8 performance is very special, for those who need distant planar performance into the corners.
The revised DOF charts - and how novel/refreshing to read of a modern digital adjusted COC measure, down from 0.03mm to a mere 0.005mm - give a good indication why landscape users should have a good reason to stray far from the infinity focal distance. Thank you for the very informative diagram also.
On undue denigration of old lenses (true of all of us probably) I got so enamoured of MTF data that I was shocked to see how good the low cost allrounder 80-200/4 zoom actually delivered on modern cameras. It should not do so, going by its modest data sheet numbers, and even Zeiss describe it merely as having 'very good image quality'...but what a fine lens that one is proving to be in the modern era.
p.12 #17 · Zeiss Distagon 2.8/15 ZE official, release in May 2012
This thread (and the previous 'What would you like to see Zeiss making next?') has piqued my interest in the beginnings of the original C/Y Zeiss lenses. I had a little dig around using Google and came across a link to an old brochure from 1975 for the original line-up of Zeiss lenses:
I think I can actually remember my dad having a brochure of a similar vintage and being entranced by the double page spread of all the lenses together.
I have to say that I'm amazed at the number of lenses that were available from the very beginning and seems like a huge undertaking to have around 17 designs ready for the original RTS system.
I wonder how many of these were unique to the C/Y mount and how many were adaptations of earlier designs?
Comparing to where we currently stand with the ZE/ZF line we are still missing the fisheye and medium telephoto offerings.
Now all Zeiss have to do is buy in a few of the new Sony 36MP sensors and shove them into an RTS style body and I would be eternally happy.
p.12 #18 · Zeiss Distagon 2.8/15 ZE official, release in May 2012
A fine brochure, Simon. (I like the "tight, not touching" letterspacing treatment on the front cover. Straight from the seventies!)
It's interesting to see how proud Zeiss was of the Distagon T* f/3.5 15 mm, despite performance that seems so modest today. Wide-angle lenses have come a long way.
It's also interesting to compare the focus scales of the 15 mm and 18 mm Distagons. They closely match today's equivalent Z-series lenses: the 18 mm has a much more generous focus throw than the 15 mm.
(By the way, the 1975 brochure shows an incorrect depth-of-field scale for the 15 mm Distagon, in the photo of that lens on page 10. A prototype or mockup lens, perhaps? The production lens must have had a much more cramped scale, similar to our new 2012 model.)
simonw wrote:
I wonder how many of these were unique to the C/Y mount and how many were adaptations of earlier designs?
I can't answer that, but I know the Distagon T* f/4 18 mm was optically identical to the earlier Contarex lens, which I think dates to around 1967. The Contax version was mechanically different, and – as the brochure explains – gained floating elements for better close-up performance.
The Contarex lenses were stunning things in their day, just before the collapse of the German camera industry. To me they represent the apogee of the old German design philosophy. Zeiss put a massive effort into developing them, and the result was optically magnificent. They focused closer, had unprecedented MTF characteristics, less field curvature, less vignetting, and superior build quality. The Contarex mount is probably still the best ever designed. But the lenses were fabulously expensive and shockingly large. The cameras were engineered to ludicrous precision but usability was never closely considered. We all know what happened in the end.
p.12 #20 · Zeiss Distagon 2.8/15 ZE official, release in May 2012
That is interesting information about the 18mm lens. I guess the 50mm is also a standard configuration too being a 'Planar'. I'll have to have a closer look at the Contarex lenses.
One curious thing I have noticed from the brochure is that the profile shots of the lenses on page 42/43 show the bayonets being almost identical and flat, i.e. none of the lenses have the shark fin (even on the short telephoto 135mm and 200mm) and the 18mm does not have the protruding cowl around the last element.
Are these perhaps prototypes that were changed for actual production of do some of these very earliest lenses have a more adaptable mount?
I have always been interested in trying out the C/Y telephoto lenses as they are still not available in an equivalent ZE/ZF version but I can't bring myself to shave off the shark fin to avoid fouling the interior of my camera (I would rather keep them as is). However this brochure does imply there may be some non-shark fin versions around...
