sebboh wrote:
i believe you correct about the purpose of the rear element (i haven't looked at the diagram recently, but that is common with mirrorless), but that means it will be harder not easier to work on cameras with a longer register distance i would think.
I have no actual knowledge, so take this with a rock of salt, but I imagine that the real rear element is spreading the light as wide as possible, projecting onto that rear collector, and then combined for more perpendicular projection, to work with the thick sensor glass. If this is the case, then the complete removal of the rear collector and the relaxation of the rear element would still yield a proper lens, which might then fit with a mirror box. I can't measure anything, so who knows if I am right. Anyway, I think that this design *might* work on larger cameras.
edwardkaraa wrote:
I can guarantee you Zeiss had nothing to do with the design of the ZA 50, 24, 55, 35, 24-70/4. Any Zeissness you may see is caused by the T* coatings.
Sony is also reputed to be enamoured with Zeiss designs and the Zeiss look, and have designed these "Zeiss" lenses accordingly, so there is probably also plenty of Zeiss DNA in the designs.
carstenw wrote:
Sony is also reputed to be enamoured with Zeiss designs and the Zeiss look, and have designed these "Zeiss" lenses accordingly, so there is probably also plenty of Zeiss DNA in the designs.
No doubt, they even borrowed the design of the Contax 85/2.8 Sonnar for a non ZA lens. However, Sony designers seem to use aspherical elements liberally, while Zeiss mostly avoids them.
carstenw wrote:
I have no actual knowledge, so take this with a rock of salt, but I imagine that the real rear element is spreading the light as wide as possible, projecting onto that rear collector, and then combined for more perpendicular projection, to work with the thick sensor glass. If this is the case, then the complete removal of the rear collector and the relaxation of the rear element would still yield a proper lens, which might then fit with a mirror box. I can't measure anything, so who knows if I am right. Anyway, I think that this design *might* work on larger cameras....Show more →
removal of the rear collector would necessitate making the other lens groups closer to the sensor and make the design very untelecentric i would think.
Tariq Gibran wrote:
Zeiss is of course free to call a Distagon a Biogon and a Double Gauss designed lens a Sonnar, as they seem to do with some of the more recent "Sonnar" lenses. It's confusing and just marketing at this point I guess. A bit sad really.
Well, not really... They're defined by their groups.
Planar = ++--++ (pos,pos,neg-neg,pos,pos) ; with the corrective elements in a specific RI and PD order.
You can of course then split individual elements into two or even more sub-groups, but the original overall correction schemes stay the same. You often split elements to get further correction possibilities, and when you do you can also use different glasses for the split element - increasing your possibilities to get chromatic correction.
Since you can't see the refractive indices and the partial dispersion data for most lenses, it can be impossible to tell the differences between a planar and a sonnar (from just looking at a lens diagram sans glass specification). The element curvatures can be close to identical, but the base construction idea - and chromatic correction scheme - totally different.
The defining characteristic of the sonnar is IMO the lower order correction of SA.
Do remember that the order of correction is NOT equal to the sum or result of the correction!
Think of it as trying to graph a function having a certain degree n (y=x^n) so that it corrects an unknown other function back to the y==0 line of your graph as closely as possible. The higher order of "n" you can use, the faster the curve can be corrected for any given distance "x".
Given higher order corrections, you can maybe get closer to the y=0 line where x approaches maximum (the rays that go through the lens right at the edge of the aperture opening) - this can improve maximum aperture sharpness with relatively cheap constructions - but that y=0 at x=max tells you nothing about what happens between x=0 and x=max.
Sonnar constructions take more effort to get critically sharp at very large apertures (f/1.8 and lower), but if you get that sharpness you're guaranteed a very smooth and uniform rendering.
It's like comparing the sharpness combined with uniformity you get from a Sony ZA135/1.8 to the sharpness/rendering uniformity you get from a fast normal planar - like the ZA85/1.4. The 135 has no abrupt changes in rendering or behavior as you stop the lens down. It just gets even sharper, even smoother in OOF rendering. The Planar can change personality completely going from wide open to half a stop down. The Sonnar does therefore also give MUCH better contrast at large apertures... The contrast is destroyed by the undulations of the SA line that a Planar inherently gets.
Unfortunately the Sonnar construction does not lend itself to angles wider than FL~1.5 x image diagonal. The corners are destroyed by the inherent length you need from rear to front of the lens package. The ZM50 is really at the edge of what you can achieve, and that's probably (again IMO) why it's an f/1.5 - not an f/1.4.
theSuede wrote:
Well, not really... They're defined by their groups.
Planar = ++--++ (pos,pos,neg-neg,pos,pos) ; with the corrective elements in a specific RI and PD order.
You can of course then split individual elements into two or even more sub-groups, but the original overall correction schemes stay the same. You often split elements to get further correction possibilities, and when you do you can also use different glasses for the split element - increasing your possibilities to get chromatic correction.
Since you can't see the refractive indices and the partial dispersion data for most lenses, it can be impossible to tell the differences between a planar and a sonnar (from just looking at a lens diagram sans glass specification). The element curvatures can be close to identical, but the base construction idea - and chromatic correction scheme - totally different.
The defining characteristic of the sonnar is IMO the lower order correction of SA.
Do remember that the order of correction is NOT equal to the sum or result of the correction!
Think of it as trying to graph a function having a certain degree n (y=x^n) so that it corrects an unknown other function back to the y==0 line of your graph as closely as possible. The higher order of "n" you can use, the faster the curve can be corrected for any given distance "x".
Given higher order corrections, you can maybe get closer to the y=0 line where x approaches maximum (the rays that go through the lens right at the edge of the aperture opening) - this can improve maximum aperture sharpness with relatively cheap constructions - but that y=0 at x=max tells you nothing about what happens between x=0 and x=max.
Sonnar constructions take more effort to get critically sharp at very large apertures (f/1.8 and lower), but if you get that sharpness you're guaranteed a very smooth and uniform rendering.
It's like comparing the sharpness combined with uniformity you get from a Sony ZA135/1.8 to the sharpness/rendering uniformity you get from a fast normal planar - like the ZA85/1.4. The 135 has no abrupt changes in rendering or behavior as you stop the lens down. It just gets even sharper, even smoother in OOF rendering. The Planar can change personality completely going from wide open to half a stop down. The Sonnar does therefore also give MUCH better contrast at large apertures... The contrast is destroyed by the undulations of the SA line that a Planar inherently gets.
Unfortunately the Sonnar construction does not lend itself to angles wider than FL~1.5 x image diagonal. The corners are destroyed by the inherent length you need from rear to front of the lens package. The ZM50 is really at the edge of what you can achieve, and that's probably (again IMO) why it's an f/1.5 - not an f/1.4....Show more →
Thanks. Great info! The block diagrams are what I was going on and you cleared that up nicely.
theSuede wrote:
Unfortunately the Sonnar construction does not lend itself to angles wider than FL~1.5 x image diagonal. The corners are destroyed by the inherent length you need from rear to front of the lens package. The ZM50 is really at the edge of what you can achieve, and that's probably (again IMO) why it's an f/1.5 - not an f/1.4.
I guess except for fixed lens solutons such as the RX1's 35mm Sonnar?
theSuede wrote:
I don't like the edgyness you get from constructions with abrupt aberration line modulations, even though it can give superbly sharp renditions of what is actually IN focus when stopped down a bit. Some find it "interesting", I find it "distracting" and "ugly".
Have you ever considered writing a book? I'd love to know more about abrupt aberration line modulations! (I assume you mean if you graph the magnitude of the aberration you would see spikes or step changes).
Aug 29, 2014 at 05:45 PM
Steve Spencer Offline • • • • • • • Upload & Sell: On
theSuede wrote:
Unfortunately the Sonnar construction does not lend itself to angles wider than FL~1.5 x image diagonal. The corners are destroyed by the inherent length you need from rear to front of the lens package. The ZM50 is really at the edge of what you can achieve, and that's probably (again IMO) why it's an f/1.5 - not an f/1.4.
That is very interesting. I always learn a lot from your posts, but with that as a given, hopefully they can make a little longer sonnar something like a 58 that is f/1.4 and has fewer compromises. Personally, I would love to see that sort of lens and with a 50 f/2 already, it might even be nice to have an f/1.4 that is a little longer.
Aug 30, 2014 at 09:42 AM
Steve Spencer Offline • • • • • • • Upload & Sell: On
Now that we have strong rumours of the two lenses that will be available at Photokina, and it seems that they will announce 3 more lenses I want to hazard a guess about what will be announced and then talk about what I hope they build.
What I think they will announce:
A 18 f/4 distagon - it shouldn't be that hard to modify the ZM version and they build an equivalent fov lens with the 12 touit early on, and it would make a nice almost 28mm on a crop camera (a focal length needed there). I still think this lens will be announced.
A 85 f/2 sonnar - I think this will come eventually but maybe not in this first announcement. They may make an 85 f/4 tessar instead
A 25 f/2.8 biogon - I don't know how easy the modification of the ZM would be, but this is a great ZM lens and did no worse on the A7 cameras than the 35 f/2 biogon. The narrower aperture might well help, but there will probably need to be some distagon like features added to get it to work.
What I would like to see:
A 21 f/3.5 distagaon - Let it be a little bigger than even the 18, but keep it to 70mm in length or less. Letting the aperture be narrower should allow the lens to be quite a bit smaller than the DSLR f/2.8 lens. If they could keep this to no bigger diameter than 67mm and no longer than 70mm, it would be great.
A 35 f/1.4 biogon - It would need some distagon design elements to make it work, but even if it was 75mm long and 65mm in diameter I would be thrilled.
A 58 f/1.4 sonnar - see my post above.
These three plus the three I think they will announce would be just what I am looking for.
New images and more details of the first two lenses have been posted on SAR. It seems the blue ring is a "special gasket at the mount" which "protects the connection between camera and lens" (and provides weather sealing?)
Apparently the aperture ring can be made clickless. I'm a little worried by this line:
• High quality images thanks to proven optical design.
Would that be the optical design proven to work badly with digital sensors with thick filter stacks?
Aug 31, 2014 at 08:15 AM
Steve Spencer Offline • • • • • • • Upload & Sell: On
Interesting that they give the physical dimension as well, which confirms what others have thought from the pictures--these lenses are not going to be any longer (well maybe .2mm) than the ZM versions plus an M to E mount adapter. They are a bit bigger in diameter at about the size of the E-mount.
Interestingly the do say, "The functionality of the Loxia lenses is perfectly matched with the camera functions of the Sony α7-series." Let's hope that extends to well tuned to deal with the thick cover glass of these cameras.
Hopefully they will also tell us in the next day or two what the other three lenses are as well.
"Proven optical design," same number of groups and elements, and similar size as ZM lenses + adapter is not a good sign, IMO. These could actually just be rehoused ZM lenses.
The size of these lenses and the fact that they are duplicate focal lengths of the AF Zeiss lenses already available leaves me with little interest in them.
I'm lucky enough to already own Leica lenses, and given that the 50mm Summicron is already proven to work well, and the 35mm Summilux asph. is also good, I think I'll stay with these smaller and lighter lenses.
I would have been far more interested in an improved for this sensor 25mm f2.8, since that is where the gap is and exactly where the problems seem to be when trying to use what is already available. Zeiss seems to have missed an opportunity there.
douglasf13 wrote:
"Proven optical design," same number of groups and elements, and similar size as ZM lenses + adapter is not a good sign, IMO. These could actually just be rehoused ZM lenses.
It doesn't sound good but I think it will only be until one of us on the forum takes the plunge that we know if Zeiss tweaked the designs sufficiently. Hard to believe they would not have done so, particularly with the 35.
I think you guys are being paranoid. You have to get used to Zeiss marketing language. A proven optical design means the planar, the biogon, in general, not necessarily a specific ZM or other design. It's really crazy to think that Zeiss will release the ZM lenses with a built in adapter. Come on! Have some faith!
edwardkaraa wrote:
I think you guys are being paranoid. You have to get used to Zeiss marketing language. A proven optical design means the planar, the biogon, in general, not necessarily a specific ZM or other design. It's really crazy to think that Zeiss will release the ZM lenses with a built in adapter. Come on! Have some faith!
I know this all just rumor at this point, so we're just having fun with it, but I really think that these could be re-housed ZMs. Zeiss would certainly be touting an "all-new" design of some kind, even if a minor change was made to the ZM design. In fact, when they announced the Touit 32, they said, "instead of six lens elements, which is common for the Planar, the Touit 1.8/32 is equipped with eight lens elements and therefore offers an even higher imaging performance when used with digital sensors." Seems odd to me that now they're simply going with a 6 element Planar "proven designs," and, judging by the size and number of groups/elements, I think re-housed ZMs with "proven designs" is the simplest answer.
These new lenses are coming so quickly that I initially thought we'd see a full line of re-housed (and oversized) ZFs, but now I think I see what they're doing. Get the 35 and 50 quickly to market without a major optical redesign, and then spend time on getting the wider lenses with new designs onto the market in the next year or two. Why else would Zeiss start with the only two prime focal lengths already offered on FE mount?
douglasf13 wrote:
I know this all just rumor at this point, so we're just having fun with it, but I really think that these could be re-housed ZMs. Zeiss would certainly be touting an "all-new" design of some kind, even if a minor change was made to the ZM design. In fact, when they announced the Touit 32, they said, "instead of six lens elements, which is common for the Planar, the Touit 1.8/32 is equipped with eight lens elements and therefore offers an even higher imaging performance when used with digital sensors." Seems odd to me that now they're simply going with a 6 element Planar "proven designs," and, judging by the size and number of groups/elements, I think re-housed ZMs with "proven designs" is the simplest answer.
These new lenses are coming so quickly that I initially thought we'd see a full line of re-housed (and oversized) ZFs, but now I think I see what they're doing. Get the 35 and 50 quickly to market without a major optical redesign, and then spend time on getting the wider lenses with new designs onto the market in the next year or two. Why else would Zeiss start with the only two prime focal lengths already offered on FE mount? ...Show more →
I really doubt it, because both the ZM 50 and 35 were very crappy on the A7, the 35 being much worse. There is absolutely no point for Zeiss to introduce the ZM without modification. I suspect Zeiss might have come up with a quick fix, modifying the rear element in a way to cope with the sensor cover. In this case, I don't really mind. All what I want is lenses that perform well. I don't care how they do it.
