Back in February 2007, when I was working with a lot of darkroom and black and white developing, I had a brain-wave: Why is it so bloody hard to find a complete resource for film developing? And so, like the good little geek I am, the Photocritic Film Developmet Database was born. My black and white film development database is designed to look up times for combinations of black-and-white film and a specific developer. The extra special ingredient, however, is this: If there isn't a lookup for a particular film and developer combination, it does it best to calculate a likely development time for any given combination of film of developer.
I came up with the idea when I was doing some processing with some obscure films. I could find processing times for a combination of film A and developer B, and I could find the combination of developer B and film A. However, I also found the combination of Developer B and film B. I thought: There has to be some way to interpolate the data so I can make an educated guess as to how long film A needs to be developed in developer A.
So I came up with a formula that calculates how long any given film needs to be in any given developer, as long as you have the information for a known film in both developers.
But how accurate is it?
Surprisingly, actually. Most of the time, I’d find the time to be off by up to 15%. Which is obviously not perfect, but significantly better than just taking a wild guess.
Of course, some times the times would be off by more than that, in which case I’d ruin my films, but at least the formula gave me a starting point.
As I started refining my formula, I discovered that some combinations of films and developers have predictable deviations (T-Max, for example, tends to need 15 % less than other films in similar developers), and I started adding this data into the formula, rendering it even more accurate
But you use lookup tables as well, don’t you? Damn right. You can’t beat looking up the developing time in a table. Which is why the Photocritic Developing Database first looks up the combination of films and developers in a database, before it tries to calculate.
This way, you are guaranteed either a 100% accurate processing time (provided I entered the information correctly in the first place, of course), or a very well educated guess as to how long the processing will need to be!
When you run the look-up, you are given a warning if I've calculated the developing time for you, or a 'congratulations' message if the developer time was done with a lookup.
Film X or developer Y is missing from your database! My bad. Send me an email with all the available information you have about the film, and I will add it both to the calculations and to the available lookup tables.
I want to give the developer Database a shot!
No problem it is right here!
Photo credits: The 'retro' camera and dev reels is (cc) by Jim Sneddon, and the lovely, scantily clad lass is Kelly, photographed on my favourite film, Ilford Delta ISO 3200 (cc) by Sean McGrath