gliderbee
Well-known
this chart gives different development times depening on what you are developing: 35mm, 120 or sheet. Why is this ? Are the emulsions different ?
Thanks,
Stefan.
Thanks,
Stefan.
sevo
Fokutorendaburando
They often are - at least the base substrates must be different.
Besides that there are traditionally different densities and gamma values targeted for in small and large format black and white. Large format once was mostly used for contact copies, and there also was a escalation of enlarging contrast with growing negative size due to the relatively smaller light source. A matte bulb is approaching point light dimensions in relation to the area of a 8x10", while it is, at twice the negative area, almost diffuse in relation to 24x36mm - and that affects the print contrast from a silver negative.
For modern use where diffuser heads (colour or multicontrast) and scanners are dominant, there is no safe rule of thumb by size any more - you'll have to know the peculiarities of your enlarger or scanner to develop to ideal contrast regardless of format.
Besides that there are traditionally different densities and gamma values targeted for in small and large format black and white. Large format once was mostly used for contact copies, and there also was a escalation of enlarging contrast with growing negative size due to the relatively smaller light source. A matte bulb is approaching point light dimensions in relation to the area of a 8x10", while it is, at twice the negative area, almost diffuse in relation to 24x36mm - and that affects the print contrast from a silver negative.
For modern use where diffuser heads (colour or multicontrast) and scanners are dominant, there is no safe rule of thumb by size any more - you'll have to know the peculiarities of your enlarger or scanner to develop to ideal contrast regardless of format.
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wintoid
Back to film
Anyone can submit a time/temp/ISO/format for a given film/dev/dilution combination. You may find the 35mm time was submitted by one person, and the 120 time by someone else.
Massive Dev is a great starting point, but that's it.
Massive Dev is a great starting point, but that's it.
sevo
Fokutorendaburando
The manufacturer data for different formats often are or were different, too.
charjohncarter
Veteran
And that's right.