Ethol UFG-fill strength or diluted? E.I. ? : LUSENET : B&W Photo - Film & Processing : One Thread

Hello. Is there a noticeable difference in negatives processed in UFG full strength and those processed in UFG diluted (1:5)? Also, Ethol recommends I.E.'s that are higher than the film's manufacture. Is this similar to "push" processing? Thank you.


-- Francis T. Knapik (FKNAPIK@MAIL.NYSED.GOV), March 15, 2000


Not knowing the developer in question I can only give a general statement: The actual internationally standardized (ISO) speed of a film depends, to some extent, on the developer used. It is determined by measuring density at the toe of the characteristic curve (density over exposure) of the film, or rather the film/developer combination, i.e. by the minimum exposure needed to generate a printable density.

When pushing a film, you are not really changing its speed, but changing its contrast, the slope of the characteristic curve. In other words: The minimum exposure needed to produce a printable density remains the same, but an increase of one f-stop in exposure will give you a greater increase in density than with "normal" development.

Sounds rather complicated, right? So let's consider an example:

Suppose you are shooting a Gray Card. With normal processing, the film you use will give the minimum printable density when exposed at say f/11, 1/60 s. Now shoot the Gray Card at f/4, 1/60 s, i.e. at an exposure of 3 f-stops more. Then print the first negative so that it produces a tone that is a little less than the maximum black the paper is capable of. Then print Gray-Card negative under the same conditions as the minimum-density negative, and you will get a tone that will closely resemble that of the gray card. When you push-process the film, the minimum density will still be at f/11, 1/60 s (or perhaps 1/3 f-stop below that, which we can neglect here), but you will produce a negative for a Gray-Card print at f/5,6, 1/60 s, i.e. giving the film one f-stop less exposure than was needed with normal development. If you usually expose for a mid gray, pushing has then increased your effective speed, not the actual speed of the film/developer combination, though. The price for this is this: whereas the normally processed film may have a range of printable densities from three f-stops below mid gray to three above, the pushed one will limit this from two below to two above, which means it gives you about two f-stops less to accommodate the tones of your subject.

By changing to a different developer, you may increase the actual speed, leaving the gradient unchanged.

-- Thomas Wollstein (, March 16, 2000.

Thomas Wollstein: For the first I understand push processing...I think. Thank you very much.

Francis T. Knapik

-- Francis T. Knapik (FKNAPIK@MAIL.NYSED.GOV), March 16, 2000.

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