Above image: Sk 60xl, two-image stitch shifted 18mm L/R (98mm image circle)
Schneider Kreuznach Apo Digitar Lens Data
This is a collection of data sheets for legacy Schneider-Kreuznach (SK) digital lenses. Unfortunately, SK abandoned the market for large-format digital lenses in and around 2017. The symmetrical designs of their wider lenses limited their use on the sensors available at the time due to color casts and crosstalk. Since then, the BSI sensor designs now being utilized have greatly reduced the color cast issue and the associated main drawback of the wide angle SK designs. Many photographers using medium format digital sensors with technical cameras have renewed interest in using some of those legacy SK lenses. At least as of this writing in 2021.
Because SK left the market, their data sheets are difficult if not impossible to find. I've been using SK lenses since 2010, and have a collection of data sheets related to many of them. Links to them are below. Many thanks to Steve Hendrix of Capture Integration, Rob De Loe and Dominique Ventzke for their contributions.
A note about naming. Lens manufacturers like to change the names of their lenses, sometimes because of actual design upgrades and/or coatings, but also just for marketing reasons. To complicate this, lens manufacturers often make marketing deals with camera brands. Sinar and Alpa are good examples. All this means the names of data sheets may not match the name printed on the lens. This can be difficult to navigate. Many of the data sheets linked here are from Alpa's old website, so this naming complexity applies to at least the document titles. It may take some internet searching and cross-reference to ensure the lens you are interested in is indeed the same lens referenced here.
This first batch of pdf's are brochures that include technical data but no MTF curves. They are good for cross referencing names, comparing image circles and other mechanical design info:
- Older analog lens brochure, including Super-Angulon, Super-Symmar Aspheric, Apo-Symmar, Makro-Symmar and Apo-Tele-Xenar: Schneider Analog Large Format Lenses
- Original Apo-Digitar lenses: Schneider Apo-Digitar
- Newer Apo-Digitar lenses (5.6/28xl, 5.6/43 XL, 5.6/60 XL, 5.6/100 Asph and 5.6/120 Asph: Schneider "new" Apo-Digitar
- 2006 Sales manual for digital applications: Schneider Digitar Manual
Below are individual data sheets with MFT curves:
- APO DIGITAR 5.6/24
- APO DIGITAR 5.6/28
- DIGITAR 2.8/28
- APO DIGITAR 5.6/35XL
- APO DIGITAR 5.6/43XL
- DIGITAR 5.6/47
- APO DIGITAR 4.0/60
- APO DIGITAR 5.6/60XL
- APO DIGITAR 5.6/72 (75)
- APO DIGITAR 4.0/80
- APO DIGITAR 5.6/80 Macro
- APO DIGITAR 4.5/90
- APO DIGITAR 5.6/100
- APO DIGITAR 5.6/120 ASPH
- APO DIGITAR 5.6/120N
- APO DIGITAR 5.6/120Macro
- APO DIGITAR 5.6/150
- APO DIGITAR 5.6/180
- APO DIGITAR 6.8/210
Here are several brochures for Schneider Kreuznach enlarging lenses. Many thanks to TimoK for supplying these:
Some General, Very Opinionated Comments About Schneider vs Rodenstock Lenses
I have some experience using both Rodenstock and Schneider-Kreuznach lenses on technical cameras with medium format sensors. I think it is safe to say SK got beat by Rodenstock in this market space largely because SK’s symmetrical wide-angle designs caused more color cast issues than the equivalent Rodenstock asymmetric or “retrofocus” designs. If you want more info about wide angle lens design, Roger Cicala of LensRentals has a good history and explanation here: lensrentals.com-blog There was a period in sensor technology from ~ 2010-2020 where pixel design, size and well depth made the sharp angle of incidence associated with wide-angle symmetric lens design a real problem. Here is a Samsung paper that explains the issue: Imagesensors.org It could largely be corrected by Capture One's LCC / Adobe's Flat Field process, but only to a point. And, many photographers just didn't want to deal with the hassle. After 2020, most modern sensor designs incorporated back-side illumination (BSI) technology. The associated (relatively) shallow pixel well greatly reduces color cast, cross-talk and vignetting associated with the interplay of angled light and sensor. This puts SK lenses back in the picture, so to speak.
In general, most users agree with the following comparison between Schneider-Kreuznach and Rodenstock. None of these are true across the board; there are always exceptions:
- Wide open, Rodenstock lenses perform better; they are sharper across the field with more contrast at the edges.
- Rodenstock lenses tend toward retrofocus designs, while SK tend toward symmetric designs.
- For a given focal length, Rodenstock lenses are larger and heavier.
- Wide angle SK lenses have less distortion vs their Rodenstock equivalent.
- For wide angles, Rodenstock lenses will have less color cast and less vignetting vs their SK counterpart.
- Center filters are more important on SK lenses. Unless you are using a newer BSI sensor, assume a center filter is necessary for all SK lenses < 72mm.
- Rodenstock stated image circles are hard and fast; they utilize a mechanical “stop” that defines the edge of the usable image circle. SK stated image circles are more liberal; some may argue the usable image circle is not as large as stated due to a falloff in image quality. Again, there are exceptions like the f/5.6 60XL and the f/5.6 120 ASPH. The usable image circle will depend on whether a center filter is applied, the specific digital back used, the LCC process, image content and the photographer's sensitivity to color and/or image quality in the corners.
- Some Rodenstock lenses are more susceptible to flare.
I love SK lenses because of their compact size. In my opinion, many of them "punch above their weight." I don't use them exclusively. I have a few cases of direct experience with comparable focal length lenses in both SK and Rodenstock. I’ve owned and used the SK 35XL, Rodi 40HR and SK 43XL; the SK 60XL and Rodi 70HR; Rodi 90HR-SW and SK f/4.5 90 Apo-Digitar; also the Rodi f/6.5 138 float and SK f/5.6 150 N. In some focal lengths I've sold Rodi versions to get the SK equivalent, while in other cases I've done the opposite. My current active list of lenses includes: SK 35XL, SK 60XL, SK 90 N and SK 150N. I also use the Zeiss f/5.6 250 SuperAchromat.
35XL / 40HR / 43XL:
- 40HR is 42mm; the 35XL is 36.4mm; the 43XL is 44.6mm. Each is a bit longer than the name implies.
- The 40HR is the sharpest wide open to f/8. Above f/8 they are all similar with a slight edge to the 40HR.
- On a 54x40mm sensor, the 40HR has the widest useable image circle ~ 92mm; 43XL ~ 87mm; 35XL ~ 84mm
- 35XL is incredibly small and light weight (360 gm in Alpa mount)
- On a BSI sensor, the 43XL is a very good combination of size, image quality and image circle. Excellent choice for the 44x33mm sensor, and particularly the 100mp version used in the Fuji GFX 100/100s.
60XL / 70HR:
- 60XL has a very large 120mm image circle.
- 70HR is sharper wide open to f/8. Above f/8 it depends where you are in the image circle.
- You should get the center filter with the 60XL for all except BSI sensors.
90 HRSW / 90 Apo-Digitar:
- The HRSW is sharper wide open to f/8. Above f/8, the Apo-Digitar stays even out to ~ 70mm image circle then falls slightly behind out to ~95mm. Beyond 95mm the HR is the better option.
- The 90 HRSW has a very large, incredibly sharp image circle out to 120mm.
- The Apo-Digitar is 1/3 the size, weight and price of the HRSW. 40.4mm filter threads vs. 67mm for the HRSW.
- The non-Copal shutter, aperture-only version of Apo-Digitars use a 5-blade aperture. This renders annoying pentagons in some out of focus areas. Not that these lenses are known for buttery bokeh, but it is something to be aware of. Rodenstock's aperture-only version uses 9 blades and has much smoother out of focus areas.
Rodi 138f / SK 150:
- The 138f is the best lens I’ve ever tested. Very sharp wide open throughout 110mm stated image circle. The image circle goes at least to 123mm. It does get slightly better at f/8 out at the edge of that 123mm image circle.
- The SK 150 is very good; it just does not stand up to the modern design of the 138f. Solid image circle out to 85mm, with slight fall off in sharpness out to 100mm
- The SK 150 is light and compact without a helical. Even with a helical, weight is only 706 gm. Again, 40.5mm filter threads vs 67mm for the 138f.
- The 138 does have a small amount of field curvature at f/6.5, but that is in the context of a 123mm image circle.