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Photo Forum / Film Photography / Darkroom / May 2005How Does Agitation Affect B&W Film Contrast
I'm curious. How's does agitation affect contrast during film development? How much or how little can one agitate and still get acceptable results? > I'm curious. How's does agitation affect contrast during film development? > How much or how little can one agitate and still get acceptable results? Kodak and Ilford recommend intermittent agitation for best overall results. See the data sheets for recommended procedures. Agitation that varies a great deal from the recommended methods and periods can cause uneveness and streaking. > > I'm curious. How's does agitation affect contrast during film > development? [quoted text clipped - 5 lines] > varies a great deal from the recommended methods and periods can cause > uneveness and streaking. I agree the manufacturer's recommendation are usually pretty close to achieve an adequate result. What I'm after is the finding the latitude one can vary parts of "the process" to achieve different outcomes. What's the point of having a darkroom if you can't take control of the mix and tweak it to achieve a particular effect or to achieve an outcome which is superior to the recommendations? Yes, I could spend a lot of time trying this myself, but I'm pretty short on time these days. I'm not looking for shortcuts or handouts, rather I like to think of it as a map of other people's experiences in this area. Learning if you will. It seems to make sense that if you start diluting the developer you need to add time to allow for more chemical reactions to take place. I've been reading statements which seem to suggest that lessening agitation allows the developer to exhaust or starve faster in the dark areas of the negative (print highlights) while the light areas of the neg (print shadows) continue to develop. So what I'm after is a rule or guideline i.e. if I triple tank time do I or should I also lessen agitation by the same factor i.e. from once every 30 seconds to say once every minute and a half or two minutes? >> > I'm curious. How's does agitation affect contrast during film >> development? [quoted text clipped - 28 lines] > time do I or should I also lessen agitation by the same factor i.e. from > once every 30 seconds to say once every minute and a half or two minutes? Agitation should be done at regular intervals to ensure uniform development, the manufacturers recommendations are generally good practice, at least every minute should be considered as normal. You mention about taking control of the mix and tweaking it to achieve a particular effect, I assume that you mean the control of dilution and contrast. If you need more contrast, then increase the developing time a little, if you need less contrast, then reduce the developing time. How you dilute your developer makes a difference too, but don't over do it or you will find that you could end up with negatives that are a pain to print. >Agitation should be done at regular intervals to ensure uniform development, >the manufacturers recommendations are generally good practice, at least >every minute should be considered as normal. Ilford recommends once a minute, but Agfa says every thirty seconds. Has anyone noticed any significant difference? > > [quoted text clipped - 6 lines] >Has anyone noticed any significant difference? > I have taken to agitating about 50% of the time for the first two minutes, then agitating about 5 turns every 45 seconds thereafter. I have been happy with the results. This experiment resulted from someone's comment that agitation is most effective at the start of development. I am afraid I cannot recollect who said it but I think it was in this newsgroup. Francis A. Miniter >>Agitation should be done at regular intervals to ensure uniform >>development, [quoted text clipped - 3 lines] > Ilford recommends once a minute, but Agfa says every thirty seconds. > Has anyone noticed any significant difference? Kodak recommend every 30 seconds as well Andrew, I use the Ilford recommendation. I don't suppose it really matters that much as long that you get consistently good results. That is what really matters. Its just a case of what works for you. There's different strokes for different folks. There are so many films and developers and possible dilutions that such a request is impossible to fulfil. I invert twice, once per minute. > > > I'm curious. How's does agitation affect contrast during film > > development? [quoted text clipped - 23 lines] > time do I or should I also lessen agitation by the same factor i.e. from > once every 30 seconds to say once every minute and a half or two minutes? >I'm curious. How's does agitation affect contrast during film development? >How much or how little can one agitate and still get acceptable results? Depends on the developer. Weaker developers (Rodinal 1:150) or developers specifically formulated for low agitation (FX2) will work but a high powered developer such as HC110 used at Dil.B should probably be avoided. You see the irregularities even out over the course of development. JD - www.puresilver.org I was reading a tread which discussed reducing agitation while extending development time to, in effect, push film without affecting the contrast which one would normally associate with extended tank times. It was in fact Rodinal at a higher dilution. My question I guess is how little agitation can I use without jeopardising the film to problems like streaking or uneven development. Is there a rule of thumb? Why would this work for some developers but not others? Has anyone tried this with D-76? > >I'm curious. How's does agitation affect contrast during film development? > >How much or how little can one agitate and still get acceptable results? [quoted text clipped - 5 lines] > > JD - www.puresilver.org > I was reading a tread which discussed reducing agitation while extending > development time to, in effect, push film without affecting the contrast [quoted text clipped - 3 lines] > development. Is there a rule of thumb? Why would this work for some > developers but not others? Has anyone tried this with D-76? Part of it I suspect involves the oxidization rate of the given developer. Some will work slowly and gradually build contrast. It also depends upon the "look" one is trying to achieve. What I like you might say "thats way too soft or hard" Probably the best way is to test film yourself, its a no brain answer but one that works.  SignatureLF Website @ http://members.verizon.net/~gregoryblank "To announce that there must be no criticism of the President, or that we are to stand by the President, right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public."--Theodore Roosevelt, May 7, 1918 Use Rodinal 1:200 for any film with no agitation for 55 minutes and be happy. Yeah, that's a bit of a troll, but I'd like to see someone put up an _experienced_ rebutal, not impressionistic bull. Well, being that you can develop a BW neg in tea, coffee, Yak urine, and others, it is no stretch to do stand development as you put forth in Rodinal (which I like for LF)... So, what is your question? cheers ... denny > Use Rodinal 1:200 for any film with no agitation for 55 minutes and be > happy. Yeah, that's a bit of a troll, but I'd like to see someone put up > an _experienced_ rebutal, not impressionistic bull. > Use Rodinal 1:200 for any film with no agitation for 55 minutes and be > happy. Yeah, that's a bit of a troll, but I'd like to see someone put up > an _experienced_ rebutal, not impressionistic bull. What are the pros & cons? How does it affect contrast? Signaturehttp://www.petezilla.co.uk >How's does agitation affect contrast during film development? Easiest way to understand the effects is to look at the extreme cases. If you don't agitate at all, there will be areas of the negative that are underdeveloped because they didn't receive "fresh" developer after the developer is exhausted in that area. This means the highlights won't be as dense as they would be otherwise. Overall effect is that you'll have lower contrast since the highlights are compressed. If you agitate constantly, the highlight areas that would create local developer exhuastion are continually being exposed to fresher developer, so these areas will develop faster than they would with normal agitation. So, you'll get denser highlights and increased contrast. -- Eric http://canid.com/ >>How's does agitation affect contrast during film development? > Easiest way to understand the effects is to look at the extreme cases. > If you don't agitate at all, there will be areas of the negative that are > underdeveloped because they didn't receive "fresh" developer after the > developer is exhausted in that area. This means the highlights won't be as > dense as they would be otherwise. Overall effect is that you'll have lower > contrast since the highlights are compressed. > If you agitate constantly, the highlight areas that would create local > developer exhuastion are continually being exposed to fresher developer, so > these areas will develop faster than they would with normal agitation. So, > you'll get denser highlights and increased contrast. you will normally also get more grain > -- > Eric > http://canid.com/ SignatureJan Keirse - +32 (0)485/089.786 http://jankeirse.free.fr Without having read all the answers given by now and apologizing for repeating others: The agitation method and frequency do influence contrast, but so do development time and temperature. I was recommended to keep all contrast influencing parameters constant except one: development time. Keep temperature and agitation consistantly and meticulously the same and only vary with time to adjust contrast. For agitation I follow the manufacturers instruction (eg. 2 complete 180° inversions in 10 seconds every 30 seconds). I always develop at 20°C (68°F) with some exceptions in hot summers when it's to warm in the darkroom, and adjust time to reach the desired contrast. If your film is too contrasty, just decrease time. If it's too flat, increase time. Keep the rest as it is to avoid confusion and unpredictable results. Jan | I'm curious. How's does agitation affect contrast during film development? | How much or how little can one agitate and still get acceptable results? |
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