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I had an e-mail from a gentleman called Danny the other day, who was wondering where my film development database had gone - and to be honest, I was sort of wondering it that myself.

My black and white film development database is designed to look up times for combinations of black-and-white film and a specific developer. If it can’t find it, it does it best to calculate a likely development time for any given combination of film of developer.

Seeing as it was one of the very first things I ever coded in PHP, the code was a bloody mess, and it used a horrible tables-based layout, so I’ve spent a fair bit of time tonight not only tidying up the PHP code, but I’ve also given it a bit of a CSS-driven layout update, which means that the HTML pages went down in size significantly.

So, Haje, how did you come up with the idea?

Well. 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 my film and another developer, and I could find the combination of my developer and another film. However, I also found the combination of the other film and other developer. I thought: There has to be some way to interpolate the data so I can make an educated guess as to how long the films need to be in the developer!

So I came up with a clever 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 only about 30-60 seconds. Which is obviously not perfect, but significantly better than just taking a wild guess. Of course, some times the times would be off by WAY 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!

Wow, that sounds pretty amazing

I have my moments.

Don’t you feel pretty daft, interviewing yourself like this?

Yeah, I do, but I’m so damn tired I can’t think straight, and it seems like a good idea right now. We’ll see if I feel the same way tomorrow, and if I don’t, I guess I could always go in and edit this article to be sober and boring. For now, I’ll just stick with it…

But I see that film X or developer X 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!

See also the - Digital Truth Dev Chart, which my database nicely complements.

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Categories: Film and dev
Tags: Film and dev

This entry is © Haje Jan Kamps / Photocritic.org, and was posted on Tuesday, December 2nd, 2008. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.