One of the things I get asked about the most is my developing methods, especially my use of Rodinal in stand development. Rodinal has become my go to developer for almost all my souping needs. It’s flexible, economical, produces negatives that are great for scanning and almost idiot proof when used in stand development. But before going through my workflow, it’s helpful to know a bit about what’s going on when you develop film.
In traditional developing methods the goal is to immerse your film in a fairly concentrated developing agent for a specific time and temperature indicated by the manufacturers (or garnered from experience and experimentation) for the given combination of film and developer. Agitation performed semi regularly throughout the development period refreshes exhausted developer next to the film as exposed areas leech out the active chemicals as they develop. With this method time, temperature and agitation all play very active rolls in how the end product will turn out. Development time, which is usually between 3-12min needs to be extremely precise, especially with times down around the 3-5 minute mark, which makes sense if you think about it. If your development time is only 3 minutes a change of +/- 30 seconds means your film is roughly 17% lighter or darker than you wanted, assuming a fairly constant rate of development over the souping time. The amount you’re off by has a diminishing affect the longer your overall development time is; this is going to be key later on.
The temperature of your developing solution dictates how active it is. Basic chemistry: warmer molecules are more active and react more quickly. So a warmer-than-indicated solution will develop the exposed areas of your film faster than you want, resulting in overdeveloped negatives. The opposite happens with a colder solution. Again, this effect is more noticeable with short soup times and more concentrated developing agents.
Agitation is probably the least understood factor of developing. The basic purpose is to refresh exhausted developer with fresh stuff as the film uses up the active chemicals around it as it develops, but it plays a more subtle role as well. Most people get taught ten inversions to start, then three inversions every minute for the rest of the time and leave it at that, which is pretty much the standard manufacturers expect you to use when they post their recommended development times for their chemicals. There’s really two main things going on when you agitate your film. First, every time you agitate you’re starting off a mini development cycle: fresh developer rushes in and hits the film; development starts quickly and slows down as the developer gets used up. Then you agitate and start this cycle over. So the more often you agitate, the more time your film spends next to highly active developer. Agitate less and your film gets more of the tail ends of each mini cycle when the developer is getting depleted. So if you want to agitate less, you have to lengthen your overall development time to compensate for this, agitate more, and you have to decrease your soup time… make sense so far? Good, it gets a little more complex than this.
Agitation also affects the level of contrast in your negative. To understand why this is, you have to look at how different areas of your negatives react to the developing agent. The highlights, those areas that got exposed to higher amounts of light during exposure, eat up developer faster than the shadows, areas that didn’t get a lot of light. This means right after each agitation, when the developer is concentrated and is reacting quickly with the film, your highlights start to use up active developer very quickly, while the shadows consume developer at a much slower rate. Consequently development of the highlights slows down and can even stop if the time between agitations is extended, while the shadows keep chugging along much more evenly during each agitation cycle. In a nutshell this means the more you agitate, the more your highlights will develop compared to the shadows, as they’re given fresh developer more often and don’t get a chance to exhaust their supply, giving you a more contrasty negative. Conversely, if you give your film less agitation as you develop, the shadows will have more time to continue developing while the highlights have exhausted their surrounding developer, narrowing the gap between the lights and darks, giving you a more flat looking negative.
So in summary:
more time = more development (darker negatives)
less time = less development (lighter negatives)
higher temp = faster development
lower temp = slower development
more agitation = higher contrast, faster development
less agitation = lower contrast, slower development
So that’s the basics of what’s going during the normal development stage of your workflow. Next time I’ll talk about Rodinal and stand development, my personal favorite, which takes advantage of the above rules to turn standard development on its head to give you really nice, consistent results, every time.