Push processing: is there a generic formula?

<p>Sorry if this is basic, but there are some things about processing I haven't got figured out yet. I got a deal on some Shanghai GP3 film, which I kind of like but there's very little info on it out there. It's only in 100 and I'd like to see how it works pushed, so is there a generic rule-of-thumb formula for push dev times?</p>

<p>Pulling is better than pushing, but if you do push I got these figures from Kodak years ago. Plus-X and Tri-X increase development 10% per stop. T Max, increase 5% per.</p>

<p>As a rule of thumb, if it's an 'old technology' film (i.e. not tabular/delta grain) I give it an extra 50 percent per stop uprating. For new technology films, I give 20-30 percent extra. That said, these are only a starting point so you would need to adjust these times on the basis of the results you get.</p>

<p>The Massive Dev Chart has some general / rule of thumb information about push processing:<br>

http://www.digitaltruth.com/devchart.php?doc=pushproc<br>

I've followed their numbers when I tried pushing film for the first time, and the results were IMHO perfect. I shot some APX100 at ISO400, developed in T-Max according to the dev chart with 2 stops compensation, and the negs came out perfectly.<br>

Cheers!</p>

 

<p>Or you could do it another way, shoot it at 200 (perhaps more) and dev in Diafine. Pretty easy. This generally works the same way with diafine and most films.</p>

<p>I guess with all that disagreement, the question wasn't to basic :) Time to experiment...</p>

<p>I'll have to dig out an old Kodak pamplet on pushing. IIRC, it gave general guidelinges to follow.</p>

<p>I've always thought that pushing was more art than science as some/most (?) folks don't like the looks of pushed films, but here goes:<br>

according to the Kodak Publication AJ-30, (they mean Kodak film, but it's still a good starting point) for a 1 stop push, increase the dev time by 50%. The pamphlet says you can use any developer listed with the film except Microdol-X. D-76 used to be the "standard" for pushing<br>

Now, Digital Truth recommends a 1.5x increase in time. I think you'll have to play around with it a bit. This is why Diafine is so easy...</p>

 

<p>"Pushing" is just overdeveloping film that has been intentionally underexposed. This results in a contrastier, but more printable negative than "standard" development would have yielded. This allows films to be rated faster than box speed for low-light situations, etc.; the tradeoff being loss of shadow detail and increased grain.</p>

<p>Therefore, the "rule of thumb" for pushing is "underexpose and overdevelop." The exact amount of overdevelopment needed to produce a printable negative depends on a number of things; film, developer, how much underexposure is present, your printing skills and preferences, etc.</p>

<p>A 50% increase per stop of underexposure seems to be a common starting point assuming you have a standard EI/developing time combination for a specific film already (film speeds and developing times are highly personal). </p>

<p>Shoot, bracket, develop at different times and see how your negs print. </p>

<p>Good luck,</p>

<p>Doremus Scudder</p>

<p>...another way of dealing with this: You're unlikely to hurt anything by adding 50% to "standard" development time, and you may well effectively double iso. Me, I'd develop it in Rodinal 1+100, invert for the first 5 minutes and take a walk for 45minutes without further agitation. And my test shots would envision ratings of 100, 200, and 400 with some low contrast skin tones (outdoor, shadow or overcast). What the heck.</p>