Center filter for wide angle lenses
How important is the use of a center filter to avoid light fall-off in the corners with wide angle lenses, f.ex. 75mm on 4x5?
It depends on whether you're shooting B&W or colour, particularly colour transparency.
I shoot with a 65mm f8 Super Angulon and no center fiter on my Wista for B&W work but I can compensate at the printing stage, same goes for my 75mm SA on my 617 camera. However ideally I would need use a center filter for transparency work where there's less leeway.
So I've got away with out owning a center filter for 20+ years with the 65mm and had no problems, I don't use the 65mm that much though. However I may well get one to use on the 617 & 75mm lens but so far it's mainly been used for hand held work where the loss of speed due to the filter factor would make it less practical.
Ditto what Ian says.
I often find the fall-off pleasing for some subjects.
FWIW, I often make a note at the time of exposure about where the optical center of the image I'm making is (necessary when using movements, although a 75mm doesn't give you much room for movements) when I want to compensate at the printing stage. Then, when printing, I can dodge the edges using a hole in a piece of mat board. I hold the board low over the optical center of the print (which may be off-center depending on movements/composition), start the exposure and lift the board to the lens moving faster to begin with and then slower the higher the board goes for about 20-25% of the basic exposure time for the center of the print ending with the hole at the lens and the entire print showing on the easel. This approximates a center filter really well.
I use a 4:1 center-weighted filter with my 72 mm Super Angulon XL, which I often use at almost full vertical shift on a Cambo 4x5 monorail. Be careful to check how the mount works to avoid vignetting due to the extension of the filter from the front of the lens. It does a good job of flattening the intensity on E-6 film.
I was unable to get any useful information from Nikon on such filters for my 90 mm Nikkor SW (when they still made LF lenses), and I have seen some discussion that the Nikon designs do not need as much filtration as other makers' designs. Specifically, the Nikon representative said that they did not recommend the use of such filters, but were unwilling to give me the angular curves for their lenses.
The Nikon 90SW is virtually identical in this respect to the Super-Angulon, the Rodenstock, and probably the Fuji SW. It need one and a half stops of center compensation. In fact, I use the Schneider 82mm CF with it and the results in terms of field illumination are virtually perfect (densitometer tested). With all CF's you need to stop down a ways. Any 75mm lens is going to have
much more significant falloff, so unless this effect is something you deliberately want in your images,
and particularly with chromes, a CF is pretty much essential. Just be aware of quality issues - best
to buy one specifically dedicated to that particular lens.
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