Why Are Automatic Roll Film Processors Not Recommended For Push & Pull Processing?

I've seen several mentions here at PN regarding the unsuitability of automatic processors, such as those from

PhotoTherm & Jobo, for push & pull processing..

I am curious as to why these machines are suitable for processing B&W films at their recommended ISO's, but not

if the photographer wishes to push or pull process the film..

Can I assume (there's that word that gets me into trouble!) that the answer to my question might have something

to do with the type & duration of the agitation required for push & pull processing compared to processing the

same film stock at the normal ISO?..

Thanks for any & all answers to this question..

Bruce

Pushing involves compensating for underexposed film by increasing processing time (and/or I suppose, temp, but that's not

how it's usually done). As long as the processor can be programmed to a longer time cycle for the developer, you can push to

your heart's content. I've never heard of pushing or pulling by varying agitation--but if I'm ignorant I'm sure someone will pipe

up to school me.

I use a Jobo ATL-1500, and solution times are fully programmable. With the ATL-1000, you get a series of development times

with allowance for plus/minus 10%, so you can usually find what you need. Don't know about the Phototherm processors.

Hi Bruce.

Rotary processors like the Jobos are very flexible but extending development alone will likely result in increased contrast more than increased film speed, especially with standard developers and continuous agitation. In short, there are better ways to push process film. Pulling (increased exposure with reduced development), on the other hand, does not suffer with continuous agitation. Push processing is a very specialized endeavor, and unless you push regularly it should not deter you from using an automated processor with their many and significant advantages.