Odd center filter question

[Harlan Chapman]

I'm shooting a project where I often use a Nikkor SW 120 f8 on 5x7 film in portrait orientation at the limit of coverage for lens rise.
Unfortunately the compositions I need often include large amounts of clear sky. I'm printing with an enlarger. As one would expect, vignetting is a problem in the prints.
I find it difficult to correct well by dodging/burning. It is easy to moderate but difficult to control well enough to make a decent print. Experiments with using digital negative gradients above the negative in the enlarger have helped but, for me, are very difficult to get right. Not expecting a perfectly even sky as that isn't reality. But a simple solution to moderate the vignetting so the prints can be made without contortions would be nice.
The Nikkor 120 takes 77mm filters.
I have Heliopan 0.45 and Schneider IVB (0.6) center filters both with 95mm threads. I'm wondering if one of these adapted to the Nikkor would be a good solution for the vignetting in spite of the lens vs filter size differential? An advantage to the big center filters is that there is no mechanical vignetting by the filter when the lens is stopped down to shooting aperture.
Obviously shooting through the filters into clear sky and checking the resulting negatives would answer the question. My problem is that, where I live, I haven't had a cooperative sky for weeks to do a shooting test and am planning a trip with the camera in a few days.
Am getting tired of suggestions that involve digital shooting and/or scanning and correcting in Photoshop to make the shooting work. That is not what I want to do.
Your thoughts?
Thank you,
-Harlan

[Corran]

Your question got me thinking. I have often used my Nikkor 120 on 8x10 and while the fall-off towards the corners doesn't bother me generally, I've thought it might be nice to have a CF. I had not considered the idea of stepping up the 77mm thread to 95mm and using my 4b. Considering I have all of the referenced equipment it was easy enough to try it, at least visually. Looking at the GG with a bright lamp shining towards the lens and stopped to f/22 it seems the entire field is very evenly illuminated. There was much more obvious fall-off sans filter. With some rise I found the edge of the visible IC and from my observation the coverage was restricted a couple of millimeters when the filter and step rings were on. However, I will note that I don't have a direct 77-95mm step-up ring - I have a 77-86 and then 86-95 stacked, so that might cause a tiny bit more loss than a direct 77-95mm ring.

Without actually taking any photos, it seems to me that it works fine.

[Pere Casals]

I'm shooting a project where I often use a Nikkor SW 120 f8 on 5x7 film in portrait orientation at the limit of coverage for lens rise.
Unfortunately the compositions I need often include large amounts of clear sky. I'm printing with an enlarger. As one would expect, vignetting is a problem in the prints.
I find it difficult to correct well by dodging/burning. It is easy to moderate but difficult to control well enough to make a decent print. Experiments with using digital negative gradients above the negative in the enlarger have helped but, for me, are very difficult to get right. Not expecting a perfectly even sky as that isn't reality. But a simple solution to moderate the vignetting so the prints can be made without contortions would be nice.
The Nikkor 120 takes 77mm filters.
I have Heliopan 0.45 and Schneider IVB (0.6) center filters both with 95mm threads. I'm wondering if one of these adapted to the Nikkor would be a good solution for the vignetting in spite of the lens vs filter size differential? An advantage to the big center filters is that there is no mechanical vignetting by the filter when the lens is stopped down to shooting aperture.
Obviously shooting through the filters into clear sky and checking the resulting negatives would answer the question. My problem is that, where I live, I haven't had a cooperative sky for weeks to do a shooting test and am planning a trip with the camera in a few days.
Am getting tired of suggestions that involve digital shooting and/or scanning and correcting in Photoshop to make the shooting work. That is not what I want to do.
Your thoughts?
Thank you,
-Harlan

In the darkroom you have a way to compensate taking lens falloff, this is an enlarger lens with falloff. Use the shorter enlarging lens that covers your 5x7 negatives, it will have pretty falloff, and that falloff will throw less light in the (density) thinner corners of the negative. Depending on enlarging lens aperture you may adjust more or less falloff.


There is a second way I've tested for a difuser enlarger, this is printing a transparency with a laser printer, you place that transparency on the white translucid plastic of the difuser, acting like a center filter, but the counter as the center is clear and the borders are darker. Those "filters" can be generated with Photoshop.


At least this may solve the printing of the negatives you still have with falloff.


In the far past, when cameras where used as enlargers, it was recommended to use the same lens for enlarging that the one that was used for the taking, as distortion and falloff could compensate.

Graflarger device is a late example of that era...



Regards.

[Dan Fromm]

Harlan, I recently wrote an article on center filters that will, I hope, eventually be published on the French LF site. In it I discuss which CFs are right for Fuji and Nikon wide angle lenses.

None of Rodenstock's and Schneider's center filters is right for the 120/8 Nikkor SW. Heliopan's 77mm ND Center Filter 3X is the one you want. Using a CF with larger mounting threads on a lens with smaller, e.g., with 95 mm threads on a lens with 77 mm, isn't a good idea. Trying is cheap, so by all means try it, but its the wrong solution to your problem.

Edit: error reading table, Schneider's CF IV will do. It is threaded M82 and is for the 120/8 SA. Schneider recommends it for the 121/8 SA, threaded 77 mm, with a step ring. Steve Goldstein pointed out Schneider's CF IV in post #5 below. Rodenstock doesn't seem to have offered a CF with 77 mm rear threads but, following Schneider's reasoning, R'stock's E82/112 1.5x (= ND 0.45) should also do. Since I didn't think of this when I wrote, I have a little revising to do.

[Steve Goldstein]

Harlan, Schneider's older CF literature recommends the IV (not IVb) for use with the 121mm Super Angulon, so it should also be appropriate for your Nikkor. You'll need a 77-82 step-up since the IV has an 82mm male thread. I realize this may not help much if you don't have a IV filter at hand...

[Dan Fromm]

Steve, thanks for popping up. I misread my own table, you're right, Schneider's CF IV will do too.

Schneider and Rodenstock follow a couple of simple rules for CFs. If the lens covers less than 110 degrees, 1.5x. If it covers more than 110 degrees, 2x. They don't agree about 110 degrees, Schneider says 1.5x, Rodenstock says 2x. And there's an anomaly, Rodenstock's first CF for Apo Grandagons is 2.5x, the current one is 2x.

[Eric Woodbury]

Given the cost of CFs, it sure is worth the try. It won't work well if close to the lens, but if you match the angle of view to the CF by moving the CF away from the lens a bit, it should be better. Move the CF out until it interferes with the image circle (angle of view) of the 120. It might take a couple extension rings to get it right. Look through the junk box or make something with foam core and tape (just as a try).

[Harlan Chapman]

Here are some answers from an unscientific field test now that the weather has improved and I drove to a favorable spot for the shoot.

First thank you all for your thoughtful replies.
Pere's enlarger vignetting solution is clever. Unfortunately, that creates centered vignetting and, as I'm working at the edge of coverage, my vignetting is well off center of the negative.
Dan, do you intend to publish your article on center filters so we can see it here?

For the test I set up the camera with the Nikkor 120SW at full rise (limited by lens, not camera) and made three shots: with no filter at f/32 and 1/8, with the 0.45 Heliopan at f22.5 and 1/4, and with the 0.6 Schneider IVB at f32 and 1/2. The sky metered very roughly 1.5 stops darker at the top of the tower than at the base at the time of the shot. Measuring the negatives with a densitometer, with no filter the top of the sky is about a stop too dark compared to "reality".
The 0.6 Schneider overcompensates with the sky actually appearing lighter at the top of the negative than the center. The 0.45 Heliopan looks about right with a roughly 1 1/3 stop difference between the bottom and top of the sky. That is plenty close for me!
So I'll continue shooting the 120 using the Heliopan 95mm 0.45 center filter.

The filter was attached to the lens using a single 77mm to 95mm step up ring. All negatives are 5x7" Delta 100 developed together in Pyrocat HD 2:2:100 for 7 minutes in a rotary drum. The shots were made off of Radio Road in Foster City, California. The main tower is about 500' tall, FYI.

Please excuse the vignetting at the base of the shots. Got too focused on checking for vignetting at the top of the image where the coverage limits out, forgot to check the bottom and missed the bag bellows getting in the way.

Thank you again for your help.

https://photos.google.com/share/AF1Q...JyQ1VjTnVzczNn

https://photos.google.com/share/AF1Q...JyQ1VjTnVzczNn

[Dan Fromm]

Harlan, all being well the article will appear in English and French on the French LF site around the end of June. Look for it on galerie-photo.com.

I expect it will be most useful to people with Fuji and Nikon ultrawides who want to know which CF to use.

Eric, you're right that list prices of new CFs are very high. Some are higher than very. I bought all of mine used, was patient, watched eBay and was alert to other sources. Used ones sometimes turn up at reasonable prices on forums like this one and, believe it or not, on the few dealers' sites left.

[xkaes]

Does anyone know of a website that has a table of the numerous center filters that are, and have, been manufacturered? There is a nice website that has an extensive table of achromatic and apochromatic "close-up" lenses (filters), and I thought a similar one containing information on center filters would be a good idea.