APO-Digitar 35mm f/5.6 L-88° is a bad old version of the 35xl! I verified it at the cost of money.Compared with the XL-102° version, it produces huge dispersion and purple fringing, and the clarity is significantly lower. From the appearance, the diameter of the XL-88° rear group is larger than that of the XL-102°, and the diameter of the XL-102° rear group is 43mm.If you peel off the casing of the rear group there will be further discoveries!
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Schneider-Kreuznach APO-Digitar 35mm f/5.6 L-88° on GFX
- Thread starter rdeloe
- Start date
Doppler9000
Active member
Could your conclusions reflect issues with the “L” sample(s) ypu tested?
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rdeloe
Well-known member
That's very interesting. I don't know what lens you had, but it doesn't sound like the same one as the L-88 I have.
The one time I encountered a similar situation, someone had purchased a lens where a rear lens cell from a different lens was attached. That would explain the different size, the poor image quality, and the purple fringing.
The diameter of the rear group on my L-88 is exactly 43mm, same as the XL.
This is as much peeling as I'm going to do, but there's nothing unexpected under that cover. It keeps dust out, and adds a bit of height to protect the front of the glass.
I'm not sure what you mean by "dispersion", but I looked for purple fringing. Zooming to 400%, I found a tiny bit on the edge of this building against the sky at the top of an image that was shifted 8mm. It's the one called Hagey in the full resolution sample collection (link in original post in the thread). It cleaned up nicely with one click in Lightroom.
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rdeloe
Well-known member
Whoa. Mine looks like neither of those!
I have questions though...
First, where are the Copal 0 29.5mm thread on those two rear cells in your picture? The one on the left seems to have threading on the surface at far left, just before the bump for the glass. The one on the right may be in the same place. In both cases, that doesn't look like Copal 0, or if is Copal 0, the elements are not 43mm in diameter (which is the diameter of the rear cell on an XL-102. I've held one in my hand. The picture below is the rear end of an XL-102 in a Copal 0 shutter.
Second, where's the cover plate with the three screws in the cells in your picture? Every picture I've seen of the XL-102 -- and the XL-102 I had in my hand -- shows that cover plate. It's definitely not on the cell on the right in your picture, and it doesn't seem to be on the one on the left.
And third, why does the rear cell of the XL-102 I briefly had look like the rear cell in my L-88? I can't put them side-by-side, because I don't have the XL-102 anymore, but check out this picture. The shape of this XL-102 rear cell looks like my L-88 rear cell. It doesn't look anything like either of the cells in your picture.
So... I'm wondering, how do you know that those two cells in that picture are actually cells from S-K APO-Digitar 35mm lenses? To me, they look like cells from a completely different lens.
I have questions though...
First, where are the Copal 0 29.5mm thread on those two rear cells in your picture? The one on the left seems to have threading on the surface at far left, just before the bump for the glass. The one on the right may be in the same place. In both cases, that doesn't look like Copal 0, or if is Copal 0, the elements are not 43mm in diameter (which is the diameter of the rear cell on an XL-102. I've held one in my hand. The picture below is the rear end of an XL-102 in a Copal 0 shutter.
Second, where's the cover plate with the three screws in the cells in your picture? Every picture I've seen of the XL-102 -- and the XL-102 I had in my hand -- shows that cover plate. It's definitely not on the cell on the right in your picture, and it doesn't seem to be on the one on the left.
And third, why does the rear cell of the XL-102 I briefly had look like the rear cell in my L-88? I can't put them side-by-side, because I don't have the XL-102 anymore, but check out this picture. The shape of this XL-102 rear cell looks like my L-88 rear cell. It doesn't look anything like either of the cells in your picture.
So... I'm wondering, how do you know that those two cells in that picture are actually cells from S-K APO-Digitar 35mm lenses? To me, they look like cells from a completely different lens.
That two rear cells was inside rear group when you remove three screws and bring it out.I had an arca f-line and gfx100s before.I was researching how to slim down the rear of the 35xl to get more shift inside the gfx bayonet. The rear group core in my picture can be taken out by removing 3 screws. It was installed on the copal shutter through a shell with a 29.5mm thread.
There are differences in appearance between L-88, L-102 and 24XL rear groups.
It seems that the size differences between Schneider products are not uncommon. I have two Schneider filters of the same model, and their sizes differ by 2mm!This caused the cap of one of the filters to keep falling off. I'm guessing Schneider modified the housing diameter on your L-88 35XL rear group to fit some room of helical.
rdeloe
Well-known member
@kinglang, thanks for explaining what you're seeing.
Schneider was constantly fiddling with the design of its products, and was not the best at documenting the changes. They also did a lot of custom work. Your evidence demonstrates differences in the rear group housing. These may be custom to the Plaubel digital view camera system for which the lens was made. It would take more equipment and skill than I possess to determine if there are subtle optical differences between my L-88 and later XL-102 lenses. Having said that, the evidence is clear that image circle size is not one of the things that is different.
Another example of Schneider's approach that stand out for me is the APO-Componon 90mm f/4.5 Makro-Iris lenses, which come in several different variants. Some of these are documented, and some (like mine) are not. When a colleague of mine asked his contact in Schneider about my Type -024 APO-Componon HM 90/4.5, the Schneider person said it was a typo that only affected a few copies! My lens is actually a type -025, this person reported. That didn't make sense to me because every copy for sale from Asia on eBay at the time I bought mine was a Type -024.
Another interesting case I've seen is the Schneider-Kreuznach Super-Angulon 40mm f/3.5 for the Rollei 6000 system. The vendor who sold me my L-88 in the Plaubel board also sold a Super-Angulon 40/3.5 in a Plaubel board, minus the focus helicoid. This is the same design they did with the Digitar 28/2.8, which was also sold as the Leica PC Super-Angulon, and the Schneider-Kreuznach PC Super-Angulon (for all kinds of 35mm mounts).
Schneider was constantly fiddling with the design of its products, and was not the best at documenting the changes. They also did a lot of custom work. Your evidence demonstrates differences in the rear group housing. These may be custom to the Plaubel digital view camera system for which the lens was made. It would take more equipment and skill than I possess to determine if there are subtle optical differences between my L-88 and later XL-102 lenses. Having said that, the evidence is clear that image circle size is not one of the things that is different.
Another example of Schneider's approach that stand out for me is the APO-Componon 90mm f/4.5 Makro-Iris lenses, which come in several different variants. Some of these are documented, and some (like mine) are not. When a colleague of mine asked his contact in Schneider about my Type -024 APO-Componon HM 90/4.5, the Schneider person said it was a typo that only affected a few copies! My lens is actually a type -025, this person reported. That didn't make sense to me because every copy for sale from Asia on eBay at the time I bought mine was a Type -024.
Another interesting case I've seen is the Schneider-Kreuznach Super-Angulon 40mm f/3.5 for the Rollei 6000 system. The vendor who sold me my L-88 in the Plaubel board also sold a Super-Angulon 40/3.5 in a Plaubel board, minus the focus helicoid. This is the same design they did with the Digitar 28/2.8, which was also sold as the Leica PC Super-Angulon, and the Schneider-Kreuznach PC Super-Angulon (for all kinds of 35mm mounts).
rdeloe
Well-known member
I just checked mine. It's definitely the one on the right. So there's one physical difference between the L-88 and the XL-102 confirmed. Nice work figuring that out.
How to summarize all this for posterity?
I'd offer the following with certainty:- The L-88 and the XL-102 have a different physical shape in the rear element.
- The physical shape looks different enough to support the optical design being different.
- The L-88 has the same image circle as the XL-102.
Where there's less certainty is in comparison of overall image quality. I'm less certain because I can't compare them head-to-head. I do have files from each, so have some thoughts.
- When I look at images I made when i briefly had an XL-102, they don't seem sharper in centre on the same scene (shot at different times) than the L-88 in the centre. I don't have any complaints about the sharpness of the L-88 I'm using. It's right up there with the 35mm end of my GF 35-70mm lens, which is no slouch.
- I'm happy with shift performance on the L-88 within the 8mm I can shift on my GFX 100S and F-Universalis setup. The XL-102 copy I had did not let me evaluate shift performance.
- After shooting a lot more images with the L-88 recently, I am seeing some purple fringing in very specific situations (e.g., branches against sky at the edge of an image, in out of focus areas). It's not a lot worse than other lenses I use all the time, and it cleans up perfectly well. Importantly, it's a bit worse than the purple fringing I'm seeing in comparable scenes that I shot using the XL-102 copy I briefly had, but not enough to be a problem.
When I fall into the rabbit hole like this, I pull myself out by asking, "Is the difference I am seeing in images photographically significant?" In the images I made with both lenses, I'm not seeing differences that are photographically significant to me. I appreciate the savings; those I see.
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It might be correctable by shimming in front of the shutter. I'm not sure but I have seen CA when there's wrong shim and purple fringing is probably caused by longitudal CA.
I think you could try installing shims with different thickness.
rdeloe
Well-known member
Thanks for the suggestion Tim. However, I've confirmed that the correct spacing on my donor Compur 0 shutter is one 0.09mm spacer. It's currently under the front cell. Increasing or decreasing the spacing has negative impacts on image quality at the sides and corners of the images.
Lest anyone conclude the fringing is a big deal, this is the worst I've seen. These branches are on the sides of an 8mm shift, and well outside the plane of sharpest focus. On the left is the purple fringing, and on the right is the correction. I've seen some ugly correction of fringing that leaves something almost as bad behind. I consider this a best case scenario for correction and very easy to fix. I don't have an XL-102 to try alongside, but I dug out one image that sows some purple that needs fixing -- not as much as here, but some.
Way up in the thread I explain what the issue is that requires re-shimming; it appears to be specific to GFX cameras. I explored why the lens requires a closer spacing of the cells in this thread: https://www.dpreview.com/forums/thread/4752119 The conclusion from the participants in that conversation is that the problem is the very thick cover glass on GFX cameras, which is effectively part of the optical system. Wide symmetrical or near-symmetrical lenses like the SK APO-Digitar 35/5.6 and my Mamiya N 43mm f/4.5 don't play nice with that thick cover glass because their exit pupil is so close to the sensor. Back in the early days of mirrorless, people putting Leica lenses on Sony A7 cameras ran into this, and discovered that attaching a corrective lens on the front, in addition to re-shimming (in some cases). https://phillipreeve.net/blog/rangefinder-wide-angle-lenses-on-a7-cameras-problems-and-solutions/ Thankfully I don't need a corrective lens to get excellent performance with my problem lenses.
I have two thoughts.
1 The PP of branches with purple fringing or the blues flowing from the blue heaven to the branches. Interestingly the input profile in the raw converter makes a big difference in this. If you use the Camera Standard or any more vivid input profile like Landscape in LR, or default input profile in C1 you'll have this kind of problems ( There's a neutral profile in C1 too). If you take a neutral input profile you can add alot contrast and saturation w/o seeing any purple fringing. And if you see it you can correct it by taking back a little.
2 You are all the time speaking of the problems with symmetrical lenses. That someway irritates me, maybe because I love symmetric lenses. The problem with those lenses comes from the angle the light rays hit the sensor, not from the symmetric lens design. Thick cover glass on GFX or other cameras/backs amplifies that effect , but not causes it. ( I read that DPReview thread). My 150mm SK Apo-Symmar serves me well with digital sensors.
Btw. all "symmetrical" lenses are "near-symmetrical" ones. If not, they were worth of nothing.
rdeloe
Well-known member
Short of monochrome camera profiles, the purple is always there, but you are right that it is emphasized with profiles like Adobe Vivid and the Fuji Velvia simulation in LR.
There's no need to be irritated. Every lens design involves compromises. I also talk about the problems of wide angle retrofocus lenses, which have difficult moustache distortion (like my Pentax-A 35/3.5). It's a feature of the design.
I'm not quite sure what you mean here. Some lenses have the property of being symmetrical designs, some do not, and some are "near" symmetrical, like my Mamiya N 43. It's just a term.
rdeloe
Well-known member
The diameter of the housing seems to be the same. However, if you undo the three screws on the rear that hold that little ring on around the back of the rear group, the actual lens cells are loose inside. You have to take it out gently to see the shape. Here's what my L-88 cell looks like out of the housing. If you don't want to take the risk of tipping it out, just undo the screws and remove the cover. Look at @kinglang 's picture in this post and note the bevelled edge of the one on the right. You'll see that bevelled edge if it's an L-88 cell like mine. The one on the right, from the XL-102, has much less bevel on the edge.
dchew
Well-known member
So that’s why the flange is thicker on the L-88; to cover the bevel.
Dave
rdeloe
Well-known member
Yes, that makes sense.
Seeing that you have your copy handy... with it mounted on a board, I'm reading 17.4mm from the rear of the lens (top of the plate, not the screw) to the flange surface. Schneider gives 17.4mm for the XL in a Schneider Elec 0 shutter.
dchew
Well-known member
I’m just now flying out of town. I can do it this weekend.
Dave
4x5Australian
Well-known member
The differences in external dimensions and shape being described here do not prove that the optical formula itself is different. That is yet to be established.
I've seen differences between individual copies in the exterior dimensions and shape of a number of SK lenses. The Super-Digitar HM 28 XL and SA 90 6.8 Classic come to mind.
Rod
I've seen differences between individual copies in the exterior dimensions and shape of a number of SK lenses. The Super-Digitar HM 28 XL and SA 90 6.8 Classic come to mind.
Rod
rdeloe
Well-known member
I have a hunch that we've reached the "We will never know for sure" stage, but I've certainly satisfied myself that my L-88 will serve me well. I'm amazed that such a simple design can hold its own against much more complex modern designs that benefit from software correction.