Using Perceptol at box speed.

So one thing I have always heard is that Perceptol is generally considered a speed reducing developer causing you to have to shoot your photos at lower ASAs. But on the factsheet provided by Ilford, there are times listed for Perceptol used at normal box speed. Has anyone here tried this? How does it compare to developing at a lower ASA?

I have found that if I used perceptol stock, then I needed to cut box speed in half. If used at 1+3, the dilution I prefer, then for some films I got box speed and others close.

when I use it now, I prefer to use it at 1+3, half box speed and cut development time about 25% from recommended.

Part of the fine grain effect is achieved from using a lower film speed.

Athiril said:

Part of the fine grain effect is achieved from using a lower film speed.

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I always thought over-exposing (down rating film) slightly increased the grain? I used the word "slightly" too! At least that's what I have seen with many of my negatives anyway??? John W

I would just like to point out that if your subject is for example 7 stops range and you half film speed, then all you have done is shift everything up the slope 1 stop. So there will be 6 stops of that range which are within the same range of film density as they were before you halfed film speed.
So would those of you claiming halving film speed either increases or decreases fim grain please explain why.

Diluting Perceptol will increase grain but that is not a function of your EI.

RobC said:

So would those of you claiming halving film speed either increases or decreases fim grain please explain why.

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Textbooks say that increasing development time increases grain, eg:
https://books.google.co.uk/books?id...e&q=granularity development time film&f=false
Quantitative measurements of grain size appear to have been started by Jones and Higgins in 1951 but AFAIK there are no readily available charts of grain size vs time.