50L a.k.a. Zeiss C-Sonnar T* 1,5/50 ZM?

So I'm thinking, this long-standing "50mm f/1.2L issue" with the "focus shift..." It's obviously tied to Canon's decision not to include a floating rear element. Some have ventured a guess as to why; relating to using SA to improve bokeh.

This sounds very similar to the principle behind the design of the Zeiss C-Sonnar T* 1,5/50 ZM lens. To wit, the following explanation from Zeiss regarding their lens:

"Information about special features for dealers and users

The C-SONNAR T* 1.5/50 ZM is a very special lens; based on a classical lens design concept from the 1930´s. The additional letter “C” in the name of the lens expresses this designation.

This lens design helps to achieve pictures with a special artistic touch. This lens ‘draws’ your subject in a fine, flattering manner and is therefore ideally suited for portraiture. It renders a sharpness that is slightly rounded, being less aggressive than in contemporary lens designs, but at the same time not soft in its rendition.

Many famous portraits of glamorous and prominent people during the 1930´s used this technique to great effect. These images are characterized by portraying the person in a shining, nearly celestial way. This effect is very well balanced and not exaggerated; therefore many viewers see it in a subconscious way. The trained observer, however, understands the underlining technique and enjoys the results.

This lens design exhibits some additional effects, which should be understood to achieve the maximum benefit from the C-Sonnar T* 1.5/50 ZM:

Because of the above mentioned classical characteristic of the lens the best focus position in the object space can not be kept exactly constant for all f-stop settings.
The passionate photographer might notice a slightly closer best focus in his pictures than expected. When stopping down the lens to f/2.8 or smaller this effect is minimized, so the focus position will be as expected.
In order to balance the performance at full speed and other f-stop settings the lens is adjusted with above described characteristic.

The special features of the C-SONNAR T* 1.5/50 ZM are best used in emotional, artistic, narrative images, portraits or atmospheric landscapes. For documentation or technical subjects CARL ZEISS recommends to stop down the lens at least to f/5.6 or to use the PLANAR T* 2/50 ZM lens."

Interesting, possibly related - and if nothing else, shows that there just might not be anything "wrong" with the 50L. I know I love mine and don't see what all the hubub is about - and am regularly rewarded with some amazing shots; both in sharpness and bokeh, as well as the usual lens parameters used in describing a "good lens."

Hi DN,

Yes, the Zeiss 50 F/1.5 also makes use of residual spherical aberrations to create very good bokeh. However, it is possible to make such a lens focus well enough, both in AF and MF modes to work well at all apertures and distances, as peopel do report perfectly working 50Ls.

Essentially, I reckon the 50L is too short FL-wise, in a Gaussian design at such a large aperture and optimized for excellent bokeh, to have a floating rear element, where the 85L is long enough. Unfortunately it is also a little too short to make it into a telecentric design, and too long for a WA design. One could argue Canon could have created a 40 or 45 mm F/1.2L, or a 60 or 70 mm F/1.2L, to get around the issue, but those are rather close in focal length to existing fast Ls ., athough I would have loved a 60L or 65L F/1.2 .

And yes, it is an amazing lens, with excellent, even incredible bokeh, very sharp, essentially totally flare-proof, and with great IQ when you get a sharp pic. Heck, even when the pic is not sharp, just that it is less usable in that case .

BTW, only resized after straight jpeg conversion; 40D + 50L at F/2, 1/3200, 800 iso.

Kind regards, Wim

P.S.: you still need a 24L in your line-up .

HOSTED PHOTO
please log in to view hosted photos in full size.

That's a great example, Wim... Definitely shows off the nice drawing of the 50L, which I really like. Canon is making some great strides in this regard with various lenses having rounded, eight aperture blades, etc. Interesting point, about Canon making "off" focal length lenses in order to be able to apply different designs to their lenses. Indeed, a 40mm or 60mm lens would be interesting. I think Canon is too focused on "standard 35mm SLR" focal lengths, avoiding the more "unusual" ones from the RF world.

I've been debating a 24L for a while, kind of on hold right now...

I'm thinking about returning to my RF roots and picking up a Zeiss Ikon and shooting some film again! Not sure about a lens yet... As much as I like the notion of a Voigtländer 1,2/35 Nokton (with it's TWELVE aperture blades) I find the size kind of defeats the purpose of a RF... So I may stick with the tried-and-true Zeiss Biogon 2/35 ZM - or even smaller with something like a Voigtländer 1,4/35 Nokton (though I'm not keen on the plastic bits and tabs). The Skopars are nice size-wise, but too dark for my tastes. Ahh, decisions, decisions.

I picked up my 1v-HS, ripped off the grip and threw on the 50L thinking I'd shoot some film the other day. There is nothing "small" about that rig, no matter how you slice it. The A-1 w/50mm f/1.2L is better, but it's still bulky. LOL.

Double Negative wrote in post #6059276
That's a great example, Wim...

Thanks, and yes, I think so too, and the only reason why I haven't thrown this pic out yet .

Yes, not to mention flare resistancy. Note that I focused on the circle of the setting sun here... Try that with any other lens .

Well, Canon wants to make money I guess, and primes are not their hottest selling items, I think, especially not the L primes, so it si understandable. They do have an interesting trio with the TS-Es, of course, with 24-45-90 (doubling each step). BTW, bokeh with the TS-Es is incredible as well, and actually, even with the 24, at any aperture...

Ah, but you don't know what you're missing in that case .

I'm thinking about returning to my RF roots and picking up a Zeiss Ikon and shooting some film again! Not sure about a lens yet... As much as I like the notion of a Voigtländer 1,2/35 Nokton (with it's TWELVE aperture blades) I find the size kind of defeats the purpose of a RF... So I may stick with the tried-and-true Zeiss Biogon 2/35 ZM - or even smaller with something like a Voigtländer 1,4/35 Nokton (though I'm not keen on the plastic bits and tabs). The Skopars are nice size-wise, but too dark for my tastes. Ahh, decisions, decisions.

I picked up my 1v-HS, ripped off the grip and threw on the 50L thinking I'd shoot some film the other day. There is nothing "small" about that rig, no matter how you slice it. The A-1 w/50mm f/1.2L is better, but it's still bulky. LOL.

I considered buying my old Pentax MX with 40 F/2.8 and 20 F/4 back from the person I sold it to 7 or 8 years ago, but I just can't see myself shooting film anymore... . For me, it is only a hobby, and it would just cost too much time .

I have been thinking of picking up a used Contax G2 as well, with 21, 45 and 90, but didn't, for the same reason .

Kind regards, Wim

I have to agree, the 50L and even some of the other L primes - are quite flare resistant. I've been looking at the 24L quite closely and some day I'll probably snatch one up. But for now I have the FL covered with the 16-35mm, 24-70mm and a close second by the 35L.

I've had a real itch for a high quality camera and shooting film again; I really miss the whole experience of souping my own.

The Leica MP is nice, followed by the M7/M6 - but the cost is just... Stupid. It's nice stuff but WAY overpriced. As for the M4s, they're nice too - but c'mon, no meter? I'm not going THAT retro... I thought about a Voigtländer Bessa R2A thinking it's relatively inexpensive and decent and I get to use all the world reknowned M lenses. But somehow I wanted a little more quality. The Zeiss Ikon is right in between with the nice features of the Bessas without the nasty pricetag of the Leicas.

I ordered my Zeiss Ikon today from Japan! w00t!

Now, if I can only decide once and for all on a lens. So far I'm still tossing around either the Voigtländer 1,2/35 Nokton or the Zeiss Biogon 2/35. I like the size of the latter better, but not the speed. So I'm sort've leaning towards the former. I've ruled the 1,5/35 Nokton out despite being a great size due to the plastic aperture/focus rings (I want metal damnit and it's a little too small) and the 1,7/35 Ultron because it's so-so optically. So almost there...

Naturally, I'll wrap it in a handmade leather half-case by Luigi (leicatime.com) to finish it off. Heh.

So tonight I'm digging out my ol' developing reels and tanks, beakers, thermometer and changing bag... I think I still have an old bottle of Rodinol handy!

wimg wrote in post #6059204
Hi DN,

Yes, the Zeiss 50 F/1.5 also makes use of residual spherical aberrations to create very good bokeh. However, it is possible to make such a lens focus well enough, both in AF and MF modes to work well at all apertures and distances, as peopel do report perfectly working 50Ls.

Essentially, I reckon the 50L is too short FL-wise, in a Gaussian design at such a large aperture and optimized for excellent bokeh, to have a floating rear element, where the 85L is long enough. Unfortunately it is also a little too short to make it into a telecentric design, and too long for a WA design. One could argue Canon could have created a 40 or 45 mm F/1.2L, or a 60 or 70 mm F/1.2L, to get around the issue, but those are rather close in focal length to existing fast Ls ., athough I would have loved a 60L or 65L F/1.2 .

And yes, it is an amazing lens, with excellent, even incredible bokeh, very sharp, essentially totally flare-proof, and with great IQ when you get a sharp pic. Heck, even when the pic is not sharp, just that it is less usable in that case .

BTW, only resized after straight jpeg conversion; 40D + 50L at F/2, 1/3200, 800 iso.

Kind regards, Wim

P.S.: you still need a 24L in your line-up .

The old chrome mount 551.2 aspherical FD version has a floating rear element. Surprised they didn't put on on the L.

airfrogusmc wrote in post #6065560
The old chrome mount 551.2 aspherical FD version has a floating rear element. Supprised they didn't put on on the L.

I reckon that is because it is 55 mm, and therefore could just fit one in ...

The back nodal plane has to be 50 mm away from the sensor, with an FL of 50 mm, and with a (symmetrical) Gaussian design with the rather large bulges of glass required for F/1.2, and a lens mount at 42 mm or thereabouts, that may just be not enough, not even taking the thickness of the lens mount into consideration. Maybe they should have stopped near focus at 60 cm or 90 cm i.s.o. 45 cm ... .

Kind regards, Wim

Double Negative wrote in post #6065547
I have to agree, the 50L and even some of the other L primes - are quite flare resistant. I've been looking at the 24L quite closely and some day I'll probably snatch one up. But for now I have the FL covered with the 16-35mm, 24-70mm and a close second by the 35L.

I've had a real itch for a high quality camera and shooting film again; I really miss the whole experience of souping my own.

The Leica MP is nice, followed by the M7/M6 - but the cost is just... Stupid. It's nice stuff but WAY overpriced. As for the M4s, they're nice too - but c'mon, no meter? I'm not going THAT retro... I thought about a Voigtländer Bessa R2A thinking it's relatively inexpensive and decent and I get to use all the world reknowned M lenses. But somehow I wanted a little more quality. The Zeiss Ikon is right in between with the nice features of the Bessas without the nasty pricetag of the Leicas.

I ordered my Zeiss Ikon today from Japan! w00t!

Now, if I can only decide once and for all on a lens. So far I'm still tossing around either the Voigtländer 1,2/35 Nokton or the Zeiss Biogon 2/35. I like the size of the latter better, but not the speed. So I'm sort've leaning towards the former. I've ruled the 1,5/35 Nokton out despite being a great size due to the plastic aperture/focus rings (I want metal damnit and it's a little too small) and the 1,7/35 Ultron because it's so-so optically. So almost there...

Naturally, I'll wrap it in a handmade leather half-case by Luigi (leicatime.com) to finish it off. Heh.

So tonight I'm digging out my ol' developing reels and tanks, beakers, thermometer and changing bag... I think I still have an old bottle of Rodinol handy!

Congratulations!

I think I know why you can't decide between those two lenses . I reckon it is because you really want both; the 35 F/2 for a light, easy to carry around camera, and the F/1.4 for low light shooting. So get both, problem solved .

BTW, just got my 50L (and 40D) back. I will test both extensively over the next few days, and report back.

Kind regards, Wim

^ That's exactly why I'm torn... I want f/1.2 but not the relatively huge size penalty (I've got that aplenty with a sack of Ls). What I find very attractive also is the insane bokeh both wide open at f/1.2 and stopped down with 12 aperture blades keeping things nice and round. I can live with f/1.4 - but I'm not convinced on the 1,4/35 Nokton "Classic" and I'm not paying for a Summicron.

So that leaves the 1,7/35 Ultron and Biogon 2/35.

I could get both... Or compromise at one FL or another and get a 50 of some sort instead...

Definitely looking forward to your 50L experiments - and findings.

wimg wrote in post #6066460
I reckon that is because it is 55 mm, and therefore could just fit one in ...

The back nodal plane has to be 50 mm away from the sensor, with an FL of 50 mm, and with a (symmetrical) Gaussian design with the rather large bulges of glass required for F/1.2, and a lens mount at 42 mm or thereabouts, that may just be not enough, not even taking the thickness of the lens mount into consideration. Maybe they should have stopped near focus at 60 cm or 90 cm i.s.o. 45 cm ... .

Kind regards, Wim

Makes sense. Maybe they should have made a 55 1.2L instead of a 50?

airfrogusmc wrote in post #6068121
Makes sense. Maybe they should have made a 55 1.2L instead of a 50?

I do think so . Or even better, a 60L .

5 mm extra should be enough to cater for a floating element and still have an MFD of approximately 45 cm, I think.

There is an alternative, I think, and that is to introduce a different AF processing unit and more complicated AF lookup tables, but that would require quite some extra processing power, and potentially a new interface for the EF-mount.

One thing's for sure with the 50L, though: when this lens hits the mark, it does it in an awesome way, very much like the 24L and 85L.

Kind regards, Wim

Hi DN,

Double Negative wrote in post #6067813
^ That's exactly why I'm torn... I want f/1.2 but not the relatively huge size penalty (I've got that aplenty with a sack of Ls). What I find very attractive also is the insane bokeh both wide open at f/1.2 and stopped down with 12 aperture blades keeping things nice and round. I can live with f/1.4 - but I'm not convinced on the 1,4/35 Nokton "Classic" and I'm not paying for a Summicron.

. I can understand, I saw the prices on those.

Hmmm. Biogon I would say.

I could get both... Or compromise at one FL or another and get a 50 of some sort instead...

That's another option indeed, but heavier again (50). What about a 28 or 24, in combination with a 45? Of course I do not have any experience with these lenses whatsoever, so I wouldn't know how they compare, other than what I occasionally see on the 'net.

I can give you some preliminary results after two hours of testing yesterday, both on the 5D and on the 40D, done immediately after receiving the lens back. This is not conclusive, though, because all testing was done handheld.

Anyway, in short, after studying the pictures, it looks like there is focus shift now which wasn't there before, but only under artificial light, at focusing distances in the danger zone. Do note that this lens originally had slight and consistent "normal" backfocus under all conditions.

So, fine at F/1.2, and then from F/1.4 shifting further and further out, until about 1 -1.5 inches (2 - 4 cm) at F/4, where it stays constant. The exact moment where at longer distance it is fine again, I haven't been able to determine yet (no time), but at 5 or 6 metres, it is fine.

Getting upset by this, I also did some tests in daylight, at distances of approx. 50 cm, 60-70 cm, 90 -100 cm, 150 cm, 180 cm, a little further, and some general distance shots, at apertures F/1.2, F/1.4, F/2, F/2.8, F/4, F/5.6 and F/8, and guess what? Spot on! Amazing! There seemed to be a little variation in AF at F/2 and F/2.8, compared to shots at other apertures, but all within DoF, although I must note that this was all handheld, so not entirely conclusive. BTW, IQ, sharpness, colour, contrast also was just plain amazing.

I did notice with the 50 F/1.4, to a lesser degree with the 50 F/1.8, and with some other lenses that there seems to be a difference in AF under artificial light vs daylight, so I have started wondering now whether that isn't an AF-system problem under different types of lighting, which just gets compounded by lens complexity or design, large apertures and maybe low light. The artificial light shots were at about EV 4-5, and I can remember reading somewhere that the AF-system is only guaranteed to EV 6, although that may just have been the old 350D. Also, the AF sensors are rather large compared to the AF indicator squares in the VF, so I also have started wondering whether the AF sensor sees more than lies within DoF of the lens (at F/1.2).

Anyway, so far for some thoughts and preliminary, not-yet-conclusive results after a first cycle of calibration hoopla.

I'll do some proper tests later, and report back once the results are in .

Kind regards, Wim

Well, FWIW - I picked up a new 2/35 Biogon and a mint used 2/50 Planar w/hood (which works on both lenses). Almost identical in size, shape and weight as well as filter size. Each are represented by bright lines only for their focal length in the VF which is a nice, uncluttered view - there's one more set but it's a shared 28/85. Should be a fun week next week!

Interesting findings about the 50L regarding different lighting. I've mostly shot my 50L outdoors and I have to say, I don't see any problem. Indoors I mostly use it in the studio at deep apertures (f/11 even f/16) so it won't show up there. The images I get are just excellent in every measure, so I'm happy with it.

Hi DN,

Double Negative wrote in post #6074128
Well, FWIW - I picked up a new 2/35 Biogon and a mint used 2/50 Planar w/hood (which works on both lenses). Almost identical in size, shape and weight as well as filter size. Each are represented by bright lines only for their focal length in the VF which is a nice, uncluttered view - there's one more set but it's a shared 28/85. Should be a fun week next week!

Congratulations! So I guess the 28/85 is next, then.
Wouldn't you want a 21 rather than a 28, since you now have the 35 already?

Well, IQ is awesome, I agree. Just that focusing with this lens is such a pain.

BTW, did a quick test with the 85L in fluorescent lighting, and it seems to have a problem as well with that, just to a much smaller degree. I reckon it is very likely a problem with the AF system and focusing algorithms. I am planning to do some formal tests with all of my AF lenses now .

Will take a lot of time, we'll see.

Kind regards, Wim

wimg wrote in post #6077429
Congratulations! So I guess the 28/85 is next, then.
Wouldn't you want a 21 rather than a 28, since you now have the 35 already?

Thanks, Wim! 28/85 would be the logical next choice since that's what the brightlines would show. I kind of agree though, a 21 or even 25 would probably be nicer... But I don't want to get into external VFs. I'm not even sure I'll get any more lenses (ya, where have I heard that before, LOL). I might just go for the 2,8/28 and call it a day. I've got more than enough in the Canon stable and don't want to go down another rabbit hole.

wimg wrote in post #6077429
Well, IQ is awesome, I agree. Just that focusing with this lens is such a pain.

BTW, did a quick test with the 85L in fluorescent lighting, and it seems to have a problem as well with that, just to a much smaller degree. I reckon it is very likely a problem with the AF system and focusing algorithms. I am planning to do some formal tests with all of my AF lenses now .

Will take a lot of time, we'll see.

That's so strange. I don't do anything out of the ordinary with mine; but I do use AF points very selectively, rarely the center one.

I wonder if the frequency (blinking) of the fluorescent lights might be causing that? Have you tried standard tungsten lighting? What body is it on?