How to focus a soft focusgreenspun.com : LUSENET : Large format photography : One Thread
OK, I got the 7" Wolly Verito diffused focus. It is a BIG lens. It sharpens up pretty good by f11 and I can still see enough light to operate. At f4 it blasts light through but the full softness is there. I have heard of lenses that require different focus at different stops. So, my question is, can I compose at f4, focus at f11, and go back to f4 or f6 and shoot so I know it is focused? I can focus at f4 but I'm a bit more comfortable focusing a sharp GG. (No digs please, soft focus still needs to be in focus) Thanks Dean
-- Dean Lastoria (email@example.com), July 20, 2000
Hi Dean, after playing around with this for awhile myself, I think the answer to your question is: what you see on the ground glass is what you get on the neg. I'm not real certain with the Verito; I've just gotten a Veritar. If they are the same, then it seems like you are forced to give up the effect of soft focus when you stop down unlike the other SF lens I have which produces its affect by increasing the distance between to two front elements. I think focus, as in how well defined the image is, is a relative thing at that particular f-stop. With the dial in your degree of soft focus lens I have I notice the biggest difference is in the highlights, so the sparkles on the water are blurry where the tree branches are still well defined, and so you can split the interaction between the SF and the depth of field to achive SF at say f-16, but I don't have much experience with the chromatic abberation type yet. IMHO it seems composing & focusing at the stop you then shoot at is the proceedure for the SF lens otherwise the change in f-stop is going to change the degree of chromatic shift which will change the composition. Good Luck, David
-- david clark (firstname.lastname@example.org), July 23, 2000.
I guess you're right about the GG being king. Just to close out this thread, here is what I dug up in case some poor sap in the future gets to looking for a Soft Focus lens: --------- From American Photography Feb 1921 "The Manipulation of the Diffused-Focus Lens" (pg. 82) Carrol B. Neblette. This applies to Verito, and Pinkham & Smith "It is no easy matter to tell just when the image is in the correct focus, because it is never sharp, and each movement of the lens introduces another degree of diffusion The worker who uses his lens at the sharpest focus that he can obtain and depends upon regulating the degree of diffusion with the stops is not using the widest range of the lens. There are pleasing degrees of diffusion to be had by focusing before or behind the plane of sharpest focus. Never stop your lens down much, as you loose the fine qualities. All of the lenses I have ever used, if properly focused, will seldom need to be stopped down more than to f5.6, or f6, to give all the firmness desirable. It might be mentioned that if after focusing to the sharpest possible focus with the lens open, then lens be brought in towards the plate about one-eighth of an inch, the exact distance depending on the lens, a greater sharpness will be obtained. By focusing in this manner the chromatic aberration is allowed for and thus a firmer image secured."
---------- From American Photography Aug 1921 "Soft Focus Lenses" Arthur Hammond "In focusing with an anastigmat lens we sometimes get the required sharpness by looking carefully at the important parts of the image rather than by taking in the whole of it, for there is a definite point at which the definition will be at its best, but in the soft-focus image it is sometimes hard to determine an exact point, for it is possible to move the lens a considerable distance backwards or forwards without affecting the definition on some parts of it to a marked degree, yet the general effect will vary a little at different positions. As a general rule it will be found best to rack the lens forward till the image is all out of focus and then rack slowly back until the most pleasing effect is secured. (pg 426)"
"That there is considerable scope for variation may be demonstrated by the following incident. When the Smith lens first was put on the market a well-known photographer was showing his new, long-focus Smith lens to some friends who also were photographers, and in order to get an idea as to its capabilities, each one in turn focused the same picture on the ground glass. When each had decided what he considered was the best effect, the baseboard of the camera was marked and when all were through it was found there was a difference of about three inches between the nearest and the farthest mark. (pg. 428) ------- I guess that means there is no correct way and you just have to experiment - at least that means I'm not doing it wrong Dean
-- Dean Lastoria (email@example.com), July 25, 2000.