Agitation: does it affect contrast or grain?

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kcf
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Agitation: does it affect contrast or grain?

Postby kcf » Fri Oct 09, 2009 2:52 am

I'm guessing agitation does not affect grain or contrast, since the purpose of agitation is merely to remove bromide from the surface of the film so that it doesn't get between the film and the developer thereby preventing development from continuing. I am assuming developer cannot be made more aggressive or active through increased agitation, even though this is often stated to be the case in black and white forums and discussion groups on the internet. Am I correct?


Keith Tapscott.
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Re: Agitation: does it affect contrast or grain?

Postby Keith Tapscott. » Mon Oct 12, 2009 9:52 am

Ilford recommend up to 15% less time for rotary-tube processors than for intermittent agitation in small-tanks, so it can affect the contrast of the negatives.
This is only a general guide as some developers are more active than others.

Lowell Huff
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Re: Agitation: does it affect contrast or grain?

Postby Lowell Huff » Tue Oct 13, 2009 11:07 am

Agitaion, absolutely, affects both contrast and grain! More agitation results in faster development has the effect of increasing the shoulder, increased contrast. Greater development does increase grain, not beecause the silver-halide grains "grow"; they dissolve to smaller sizes. Thus the small grains are gone leaving only the larger grains, hense the seeming appearance of "large" grain.

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Re: Agitation: does it affect contrast or grain?

Postby Keith Tapscott. » Thu Oct 15, 2009 2:15 pm

Lowell Huff wrote:Agitation, absolutely, affects both contrast and grain! More agitation results in faster development has the effect of increasing the shoulder, increased contrast. Greater development does increase grain, not because the silver-halide grains "grow"; they dissolve to smaller sizes. Thus the small grains are gone leaving only the larger grains, hence the seeming appearance of "large" grain.
Lowell, yes of course.
By "a general guide" though, I meant that a 15% shorter development time for continuous agitation is only a general guide.
Some rapid acting developers such as Kodak HC-110 at dilution `B` might need more than a 15% correction while slow working low energy developers of the D-23/D-25 type like Microdol-X and Perceptol might be OK with less than a 15% correction, depending on temperature and dilution etc.

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Re: Agitation: does it affect contrast or grain?

Postby Lowell Huff » Thu Oct 15, 2009 2:57 pm

Yes, Kieth the physical reaction of agitation does remove the inhibitors. Bromides and other inhibitors do not prevent the chemical reaction just slow it.
Yes, you are also correct, saying that agitation does not make the developer more aggressive. Agitation brings more chemicals in contact with the emulsion, a chemical reaction, thus speeding development. More development therefore directly increases contrast and disolves more silver.

Ornello
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Re: Agitation: does it affect contrast or grain?

Postby Ornello » Fri Oct 16, 2009 11:36 am

kcf wrote:I'm guessing agitation does not affect grain or contrast, since the purpose of agitation is merely to remove bromide from the surface of the film so that it doesn't get between the film and the developer thereby preventing development from continuing. I am assuming developer cannot be made more aggressive or active through increased agitation, even though this is often stated to be the case in black and white forums and discussion groups on the internet. Am I correct?
Agitation does not directly affect graininess, but it does affect contrast. Gentle intermittent agitation is preferred with 35mm work.

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Re: Agitation: does it affect contrast or grain?

Postby Keith Tapscott. » Fri Oct 16, 2009 1:20 pm

Ornello wrote:Gentle intermittent agitation is preferred with 35mm work.
Yes, but I do that with 120 film as well.

Ornello
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Re: Agitation: does it affect contrast or grain?

Postby Ornello » Mon Oct 19, 2009 5:02 pm

Keith Tapscott. wrote:
Ornello wrote:Gentle intermittent agitation is preferred with 35mm work.
Yes, but I do that with 120 film as well.
Of course one can use softer, thinner negs in 120 too. The point is that the soft thin neg is mandatory for 35mm for optimum results.

pirateoversixty
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Re: Agitation: does it affect contrast or grain?

Postby pirateoversixty » Mon Oct 19, 2009 6:55 pm

Haven't really thought this through, but why would a softer thinner neg be better for 35mm? I would think that a neg that was softer would not enlarge as well to, say, 11x14. Thinner, ok, but grain as mush? Or am I misinterpreting what you are saying?
Jim

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Re: Agitation: does it affect contrast or grain?

Postby Ornello » Tue Oct 20, 2009 6:00 pm

pirateoversixty wrote:Haven't really thought this through, but why would a softer thinner neg be better for 35mm? I would think that a neg that was softer would not enlarge as well to, say, 11x14. Thinner, ok, but grain as mush? Or am I misinterpreting what you are saying?
Jim
Softer contrast, less development will give better results due to shorter development times. Give a slight increase in exposure (1/2–2/3 stop) and cut development time by 1/3 from the recommended, print on grade 3 paper. You will be stunned at how good the results will be!

miha
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Re: Agitation: does it affect contrast or grain?

Postby miha » Thu Oct 22, 2009 7:41 am

Ornello wrote:Softer contrast, less development will give better results due to shorter development times. Give a slight increase in exposure (1/2–2/3 stop) and cut development time by 1/3 from the recommended, print on grade 3 paper. You will be stunned at how good the results will be!
Or not. It depends on the contrast of the light in which the photo was taken in the first place. A good compromise is gamma 0.62 or what film manufacturers sugest.

Ornello
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Re: Agitation: does it affect contrast or grain?

Postby Ornello » Thu Oct 22, 2009 4:30 pm

miha wrote:
Ornello wrote:Softer contrast, less development will give better results due to shorter development times. Give a slight increase in exposure (1/2–2/3 stop) and cut development time by 1/3 from the recommended, print on grade 3 paper. You will be stunned at how good the results will be!
Or not. It depends on the contrast of the light in which the photo was taken in the first place. A good compromise is gamma 0.62 or what film manufacturers sugest.
No, that is too high. A gamma lower than that is better. Probably around 0.38-0.42.

For the most part I make very minor adjustments in contrast. It is a myth that you need to do so (adjust contrast a lot). If the scene is flat (i.e., if the lighting is flat)...well it should appear so in the print.

miha
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Re: Agitation: does it affect contrast or grain?

Postby miha » Fri Oct 23, 2009 8:22 am

Ornello wrote:No, that is too high. A gamma lower than that is better. Probably around 0.38-0.42.

For the most part I make very minor adjustments in contrast. It is a myth that you need to do so (adjust contrast a lot). If the scene is flat (i.e., if the lighting is flat)...well it should appear so in the print.
Too high for you, and only you.

Standard is 0.62 for printing on grade 2 or 3 paper, depending on enlargement.

Ornello
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Re: Agitation: does it affect contrast or grain?

Postby Ornello » Fri Oct 23, 2009 8:26 am

miha wrote:
Ornello wrote:No, that is too high. A gamma lower than that is better. Probably around 0.38-0.42.

For the most part I make very minor adjustments in contrast. It is a myth that you need to do so (adjust contrast a lot). If the scene is flat (i.e., if the lighting is flat)...well it should appear so in the print.
Too high for you, and only you.

Standard is 0.62 for printing on grade 2 or 3 paper, depending on enlargement.
No, it isn't. Kodak recommends CI of 0.42 for condenser or 0.55 for diffusion. I think those values are too high by one-half to one grade.

miha
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Re: Agitation: does it affect contrast or grain?

Postby miha » Fri Oct 23, 2009 10:00 am

Ornello wrote:No, it isn't. Kodak recommends CI of 0.42 for condenser or 0.55 for diffusion. I think those values are too high by one-half to one grade.
As you are very well aware of, Contrast Index (CI) is not gamma.

Kodak recommends CI of 0.56 in every tech sheet for their various B&W films.


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