Film development with continuous agitation

Updated: Apr 20

In this manual you learn about how to develop film with continuous agitation and what the benefits and disadvantages are.


Why a manual about this?

Our ars-imago Lab-Box makes film development very easy - and if you develop your films with continuous agitation, it becomes even more convenient! Even with other tanks, you safe time, chemicals and effort - so let’s take a closer look:


What is continuous agitation?

Other than with regular „inversion“ development where you agitation your filmtank only every 30 sec or every minute and then let it sit, with continuous agitation the tank is in motion during the whole developing process. The best way to achieve this is to roll the tank in the direction of the film reels, always back and forth. You can do this on the edge of your table, on rollers or in a machine. The ideal rotation speed would be about 1x rotation per second and changing direction every 10-15 turns (if possible).





What are the benefits?

Since the tank never stands still, there is no need to fill it up entirely. Depending on the tank you use, it sometimes only needs half of the volume you would otherwise use when the tank is filled up to the brim.


Examples:

  • Lab-Box: 490 ml when filled entirely - only 300 ml with continuous agitation

  • Jobo 1520 Tank: 483 ml filled entirely - only 240 ml with continuous agitation

  • Kaiser Universal Tank: 650 ml filled entirely - only 350 ml with continuous agitation


Since the film always comes in contact with fresh developer, you can also shorten the developing time for about 10% - 15%. The exact shortening of the time needs to be tested and adjusted individually (according to your film and developer choice). Just try to be consistent with every development and then review the negatives: too dense negatives -> shorten time / too light negatives -> longer development time is needed.



Negative too dense - shorten dev Time

Negative too light - longer development needed

One additional benefit is also, that once you start rolling your tank, you don’t have to always check your time, just set a timer and „let it roll“.


Benefits in short:

  • less chemistry

  • shorter developing times

  • less effort

  • more consistent results

  • a bit smother grain (see below)


What are the disadvantages?

Since the film needs to sit motionless in the developer to build up sharp edges on the silver grains, the negatives will look a little bit smoother in continuous agitation. So if you are looking for the sharpest, crispest negatives, continuous agitation is not the best way to achieve this. But if you like smoother grain, it's perfect!


In addition, high acutance film developers are not ideally suited for continuous agitation process, they can cause streaks. Avoid using Rodinal (ars-imago #9), Diafine or D-76 diluted 1+3.


Disadvantages in short:

  • less apparent sharpness (It's a matter of taste)

  • risk of streaks with certain developer


Want to start continuous agitation, here are some ideas to get going:

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