View Full Version : Falloff: 75mm Rodenstock vs 80mm Schneider

Eric James
26-Apr-2006, 23:46
I'm planning to replace my 90mm lens with a wider compliment to a 110mm lens. For reasons or bulk, weight and filter compatibility, the 72mm Schneider is out of the running. I'm looking closely at the Rodenstock 75mm f4.5 Grandagon-N and Schneider's 80mm Super Symmar XL. Weight, image circle, and flange back have me leaning toward the Schneider lens but the lower price and slightly wider view of the Rodenstock are confounding the decision. I will be using the lens on a 4 by 5 rig for landscapes and will swing and tilt accordingly.

My question: which lens will be less likely to require a center filter? Discussions of optical design and statements like: "entrance pupil diameter increase when viewing at an angle" may prove helpful to future readers of this thread (so by all means, don't hold back), but I have no formal training in optics and am hoping to hear: "I've owned both lenses and absolutely never needed a center filter with lens A and always needed one with lens B."

Thank you in advance!

Leonard Evens
27-Apr-2006, 08:59
I have a 75 mm f/4.5 Grandagon-N. In fact I just used it within the last hour. Whether or not you can get away without a center filter depends on the subject. I've used mine in the past without a center filter, but I found that generally speaking, things work out better for me with the center filter. (I got the Rodenstock 67 mm center filter, which also works with my 90 mm f/6.8 Grandagon-N.) This is particularly true with color negative film because along with the decrease in intensity, there is a slight color shift. (The same is probably true with transparency film, but I haven't used my 75 mm with such film.) For landscapes, the shift in intensity may just darken the sky and not be otherwise objectionable. For architectural photography where you want a fairly accurate rendition of a building facade, it will probably be necessary to use a center filter for best results.

The 75 mm Grandagon-N does have a relatively small circle of coverage (195 mm), so you need to be careful about movements.

Eric Leppanen
27-Apr-2006, 09:08
I find that with my SS80XL, I need a center filter when using transparency film, and don't need it when using color print or B&W film. This goes for pretty much all subjects (landscapes, architecture, etc.).

See also this thread: www.largeformatphotography.info/lfforum/topic/498879.html (http://www.largeformatphotography.info/lfforum/topic/498879.html)

Michael S. Briggs
27-Apr-2006, 09:14
LF lenses fall into two categories of illumination behavior. The lenses that you are considering are examples of both categories: the Grandagon-N series uses a design (tilting pupils) that improves the illumination off-axis to cosine to the third, while the Super-Symmar-XL series follows the faster falloff of cosine to the fourth. I and others have written about this before, for example, Center filter for Nikkor 90mm f4.5 at http://www.largeformatphotography.info/lfforum/topic/501033.html
and Image circle and fall-off at http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=005gK2.

Understanding the implications for these two lenses is even easier since by Rodenstock and Schneider publish the illumination curves, either on the web or in paper brochures. As an example, here are the figures for the corners of a 4x5 film (153 mm diagnonal) with no movements. From the graph for the 80 mm SS-XL, the illumination falloff is 28%, or 1.9 stops. This matches very closely the prediction of the simple theory: cosine the fourth of 43.5 degrees is 28%.

The Rodenstock graph for the 75 mm f4.5 Grandagon-N shows a falloff of 33% at the same point, or 1.6 stops. This may not seem much different, but the Rodenstock has the disadvantage of being 7% wider. This falloff is much better than a hypothetical 75 mm SS-XL lens would have: cosine to the fourth of 45.4 degrees is 24%. The Rodenstock is close to the predictions of the cosine to the third theory: 35%.

So at the corners of a 4x5 film, without movements, the 75 mm f4.5 Grandagon-N delivers 1/3 stop more light. That isn't much, but it is a wider lens than the 80 mm. And the differences will widen when you use movements. Maybe it would make the difference in not needing to use a center filter, esp. if you use negative film.

Bob Salomon
27-Apr-2006, 09:19
The lenses have fall off.
'What you shoot, what you want to do with the image and how you process the image.

While one person may always have lots of sky or sand at the corners another may always have dark edges. Another may always overlight the edges.

What one user finds may have no bearing on your work with the same lens.

If possible rent both and see for yourself.

Just remember that the lens must be stopped down at least 2 stops for a center filter to work. If you want to shoot at larger openings then a center filter won't help at all.

Bruce Watson
27-Apr-2006, 09:49
I use the 80mm SS-XL for landscape work. Next up is the 110 SS-XL, and I find the two to be nicely spaced for my needs. I don't have a center filter, and have never used one for either lens. Just doesn't seem necessary. This photograph (http://www.achromaticarts.com/big_image.php?path=sequoia&img_num=2) was taken with the 80mm lens. The trees required that I level and plumb the film stage, and this in turn required a fair amount of front rise to bring the tops of the trees into the frame.

I didn't make any corrections for light fall off. I've got a print of it that's 150 x 92.7 cm that's amazing. The print is razor sharp, and has been seen by countless people including other photographers and a couple of gallery owners. No one has ever commented on or otherwise indicated they see any fall off. But clearly, YMMV.

Brian Ellis
27-Apr-2006, 10:02
I've never used the Rodenstock but I can tell you that with b&w and color negatives I didn't think I needed a center filter on the 80mm XL.

Leonard Evens
27-Apr-2006, 15:34
In view of Michael's comments, let me add that I do usually use my 75 mm Grandagon-M with a significant rise. So that would increase the need for a center filter. The cosine cubed drop-off at the edge of the 195 mm image circle would be over 2 stops. Be that as it may, even without a rise, a drop of 1 stop, which is what the cosine cubed fall-off gives at each edge, will be noticeable for some subjects, particularly architectural subjects.

Harley Goldman
27-Apr-2006, 16:33
I have the 80mm and shoot nothing but trannie, mostly Velvia. I have not felt the need to use a center filter.

Eric James
28-Apr-2006, 14:06
Thank you all very much for your input - all answers were helpful!

Michael, your answer was just what I was looking for. You had hinted at this conclusion in previous postings - now the answer is clear: If I hope to do without a center filter, the Rodenstock 75mm f4.5 is the better choice.

Still, I'm encouraged by the many anecdotal accounts of the 80mm Schneider not requiring filter correction - for some, even with transparencies. Renting in Alaska isn't too convenient but I think I should take Bob's advice before I buy.