I am interested in 'agitation'. Does anyone know if there is a noticeable difference when agitating film more often but for less time compared to agitating less often but for more time?

-- Andy Laycock (agl@intergate.bc.ca), October 25, 1998

Answers

Contrast will change.

What happens is that as the highlights in the negative receive fresh developer, they will develop faster than the lows. The same effect would be achieved by keeping agitation and time constant, but raising developer temperature. Or using a stronger developer dilution.

Back around the turn of the century, there were a number of photographers who photographed the interiors of cathedrals. The speed of the plates they used was so slow and the light was so dim inside the churches, that they used highly dilute developers with a development time of something like eight hours. Oh yes, and very little agitation.

-- Brian C. Miller (a-bcmill@exchange.microsoft.com), October 25, 1998.

agitation cont.

Thanks for the info Brian. I guess specifically I was wondering how much of a difference in contrast you should notice between something like 2 inversions of the tank every 30 seconds compared to 4 inversions every minute with the same film and developer and for the same time. The reason I was wondering is that with D-76 and Delta 400 you agitate 10 sec every minute but with Xtol you agitate 5 sec. every 30 seconds. I don't really notice much of a difference except the grain 'seems' finer with more frequent agitation.

-- andy laycock (agl@intergate.bc.ca), October 25, 1998.

I think that the biggest difference is between constant agitation and intermittent agitation. If you were using a rotating drum system (Jobo) with fast revolutions, then you would see a real difference.

Between agitation in 30 or 60 second intervals, I believe the biggest difference is in the shadow values. The high values will not be that strongly affected.

The best thing to do is burn some film, all of the frames being the same subject. A still life of egg, orange, grapefruit, and Kodak grey scale card against Kodak grey card is good. Have enough of the grey card showing in the scene so that it can be measured if need be (1/4-in. of film area). This way you will be able to judge what you are seeing, and obtain impirical results.

Remember: Film is cheap, the scene of your life isn't.

-- Brian C. Miller (a-bcmill@exchange.microsoft.com), October 26, 1998.

I'm not convinced that there would be much difference between 2 inversions of the tank every 30 seconds compared to 4 inversions every minute. The total agitation is the same, just more spread out. If anything, I suppose the fourth inversion of the 4-every-minute might have less effect than the first, so this regime might give a little less overall agitation, giving lower contrast and slower speed.

When I try a new film/developer, I usually test it with my own regime (which is 5 inversions every 30 seconds for 35mm). It's bad enough keeping notes of different temperatures etc, I can't keep track of agitation regimes as well.

-- Alan Gibson (gibson.al@mail.dec.com), October 26, 1998.

Andy the general rule is that the more agitation the film recieves the higher the contrast of the negative. This would be more noticable if you were using a higher energy developer such as rodinal or HC 110. Or if you were to increase your method to the same number of rotations every 30 or 15 seconds.

-- jim megargee (mvjim@interport.net), October 27, 1998.

I presume you're asking about the difference between five seconds every 30 seconds and 10 seconds every minute. If the developer you're using is weak enough to give some exhaustion/compensating effects (eg Rodinal 1:100) then you'd find a decrease in highlight contrast with the 10 secs/minute regime, or iow put more of a shoulder in the curve shape. With a standard developer such as D-76 or Xtol then there'd be virtually no difference. The big drawback about depending on a weak developer for compensating effects is the strong tendency toward unevenness.

-- John Hicks / John's Camera Shop (jbh@magicnet.net), November 17, 1998.

Yes, this is exactly what I was asking but I guess I wasn't very clear. Thanks for the information it was what I wanted to know.

-- andy laycock (agl@intergate.bc.ca), November 18, 1998.