Agitating – With Film

When developing film, you need to agitate the tank every so often to refresh the developer that’s right next to the film. It might seem like it’s an insignificant step in the process. After you have carefully measured the temperature and time, and thoughtfully selected your developer, everything should be good, right? The way you agitate the film will also affect the results. There are so many different methods, and opinions, about film agitation – some work, some are not the best. Everyone who develops their own film will find a way that works best for them after some trial and error. My opinion is that if it is working for you, and you are consistent with your process, it’s good.

When an image develops, the light sensitive silver halides that were affected by exposure to light are reduced/oxidized and converted to metallic silver, forming the image. There is more to it than this and it’s worth reading about if you are interested in the intricacies of developing film. For now, know that the development part of the process is the most important in terms of your negative density and contrast. Different developers also have an effect on the results, but that is for another day and another blog post.

To see what the differences are with agitation methods, I thought I’d do an experiment and share the results. Note that I don’t have a full roll of film in the developing tank for all tests and this could have an effect on the outcome. I didn’t want to use up so much film with all the same image! These are not super scientific experiments, I don’t have a densitometer, and didn’t use a scale to precisely measure the chemicals, but I did measure as accurately and consistently as I do when mixing photo chemicals. I did only change one thing for each test so I know the changes in the negatives should be a result of the agitation method, but I did shoot the film outside and the lighting situation could have changed over the time it took me to shoot all four rolls. It is interesting to see what changes between the agitation methods. some of the finer details might only be discovered when the negatives are printed in the darkroom.

The film – Flic Film Ultrapan 400. Shot in my Nikon FM2 that I got many years ago when I graduated from high school. It still works pretty well.
The scene – Fairly evenly lit in bright shadow. The back garden with ferns, flower pots and a brick path. (The image shows more dappled light than I thought there was at the time I was making the exposures.)
The shots – All exposed with the same shutter speed and aperture. I didn’t use a tripod so the frame moves around a little.
The developer – Black White & Green from Flic Film. Mixed 1:49. 300 ml fresh for each test.  All tests developed at 20C. The HVAC system here keeps the temperature at an even 20C all the time.
The agitation – I agitate (film at least) very gently. Tilting the tank about 45 degrees and slowly turning it, then upright, then tilt and turn again. Lots of people do it differently, more aggressively. I don’t want to cause strong currents around the film that might cause uneven development. I see it as a meditative exercise, and a chance to do a little stretching in between.
The rest of the process – Stop 30 seconds, fix in Flic Film Allergen Free Fix for 4 minutes. This fixer doesn’t have that strong fixer smell and is great for people who are sensitive to the rapid fixer.

It is obvious by looking at the negatives that agitating constantly produced negatives with more density than intermittent agitation. It also caused the base to have a bit more fog – you can see it in the film rebate. This isn’t necessarily bad, you can still print or scan it and make adjustments. There also appears to be more contrast in the continually agitated film, which is expected. Under agitating will reduce contrast and over agitating will increase contrast. In this experiment, I didn’t change the development time with different agitation methods, but if you are developing your film, you would adjust the time and develop longer with less agitation, and shorter with more. This can be a way to control contrast and get the effect you want. If you are printing in the darkroom, it’s easier to print flatter negatives as you can increase the contrast with filters. It’s harder to print high contrast negatives since some of the deep shadow or bright highlight detail may have been lost.

The unexpected result is that it looks like I have more shadow detail in the film agitated every minute than the film agitated every 30 seconds. Generally, more agitation should produce more density in the shadows too. I think because this was a fairly informal test and I was outdoors, the light may have changed more than I realised. I can see it in the light on the tree trunk too.

I was expecting more of a difference between the agitation methods. Film stocks will respond in different ways, and the way you agitate your film could have more of an effect than what you see here. There are differences though, and these will affect your prints, especially in the darkroom. With different agitation methods, you have another way to control the final outcome of your images. I plan to do a more controlled experiment in the future using lighting and a colour checker. Stay tuned for these results! In the meantime, do some experiments yourself with your favourite film to find an agitation method that works best for you.

Negatives showing differences in agitation methods. #1 – Gently agitate once every minute. #2 – Gently agitate once every 30 seconds. #3 – Gently agitate for full development time. #4 – Shake to agitate once every minute.

Positive of negative image. No adjustments have been made to the file to show the differences between the strips. You could make adjustments to each strip to account for the extra base fog.