Developing Acros to a Specific Negative Density

[tgtaylor]

Is there any was to tell fom the published characteristic curves for Fuji Acros (below) how long to develop the film at 68F to achieve a negative density of 1.8?

75296

Thanks,

Thomas

[Mark Woods]

If you're talking about shooting a gray card, look where the line crosses the 1.8 (or approximately) and that is the time. Gamma is a different story, but can be surmised.

[Drew Wiley]

You might get a rough clue from some published chart, but really have to equate it to your
own personal processing method. Hopefully you are good at tight temperature control and other variables. Then you simply waste a few sheets (or a few darkroom sessions) until you hit your target density and can reliably repeat it.

[Shen45]

Is that a total negative density of 1.8 or a negative density above base fog? Different developers will give different base fog and different developers will "look" more or less dense to the eye with the same film. You may eventually arrive at a result that satisfies your requirement but will it be 1.8? Who knows? If you have a densitometer then yes you will know. Density and densitometers go hand in hand. Even if your thermometer is inaccurate you will read actual density and adjust time if needed. If you are using a staining developer you need either a blue channel or UV to read correct density.

[tgtaylor]

Thanks for the replies so far!

For further clarification I'm looking to achieve a Density Range of 1.5 to 1.8 which would result in a negative that would print fine on a Grade 0 paper for certain alternative processes. Ilford's Delta 100 has a published maximum density (depending on development time) of 1.8 regardless of how long you develope it. Acros continues well beyond 1.8 going over 200. I'm trying to determine how long to develope Acros to achieve such a range.

Thanks,

Thomas

[Drew Wiley]

Are you planning to use a staining or conventional developer?

[Vaughn]

Would it not depend greatly on the range of light one is photographing?

I usually take the contrast range of the scene into account when developing negatives for carbon printing and platinum printing. A scene with a range of 9 stops of light gets much different treatment than one with only 5.

[Jay DeFehr]

Thomas,

The short answer is; no you can't extrapolate from the Ilford chart a reliable time for a specific negative density range. The kind of control you desire requires some investment -- ie, more than glancing at a published chart, and more than a forum query. Even if I told you I developed Acros to a density range of 1.8 in 510-Pyro 1:100, 10:00, 70F, rotary agitation (hypothetical numbers), and read the negative with the blue channel of my Xrite 810 densitometer, I still would not have told you much that might transfer to your specific image and process -- I would only have given you a starting point for your own testing. If you want to control your process to the degree stated, you have to learn to control your process to the degree stated, and there are no real shortcuts to doing so. If you have a densitometer, and some time, it's not so difficult to learn a testing procedure. I recommend BTZS as an excellent primer.

[tgtaylor]

Thanks again for the repliues everyone.

The published curves above specify D-76 as the developer, Small Tank Development as the method, and 68F as the temperature. Since Fuji doesn't consider it necessary to dilute the developer, I consider the curves were generated using D-76 stock and not diluted 1:1 (for which the development time is published), and a typical "normal" well-exposed negative. Is there anyone out there that can extrapolate from the given curves?

Thomas

[sanking]

Thanks again for the repliues everyone.

The published curves above specify D-76 as the developer, Small Tank Development as the method, and 68F as the temperature. Since Fuji doesn't consider it necessary to dilute the developer, I consider the curves were generated using D-76 stock and not diluted 1:1 (for which the development time is published), and a typical "normal" well-exposed negative. Is there anyone out there that can extrapolate from the given curves?

Thomas

If you were able to exactly duplicate the conditions of development described by Fuji, and assuming you are interested in an alternative process like vandyke, kallitype or pure palladium, you should develop for a Contrast Index of about 80 - .95. This should get you in the ball park with vandyke, kallitype or pure palladium for scenes of average contrast.

However, if you want to do it right you should first determine the ES (exposure scale) of your specific process and chemistry, then learn to develop your negatives to a CI that matches the ES, adjusting for conditions of subject brightness. Purchase of a 21 step transmission step wedge, and learning to use it, would be a good first step. You would answer a lot of your questions with this exercise.

Sandy

[tgtaylor]

If you were able to exactly duplicate the conditions of development described by Fuji, and assuming you are interested in an alternative process like vandyke, kallitype or pure palladium, you should develop for a Contrast Index of about 80 - .95. This should get you in the ball park with vandyke, kallitype or pure palladium for scenes of average contrast.

However, if you want to do it right you should first determine the ES (exposure scale) of your specific process and chemistry, then learn to develop your negatives to a CI that matches the ES, adjusting for conditions of subject brightness. Purchase of a 21 step transmission step wedge, and learning to use it, would be a good first step. You would answer a lot of your questions with this exercise.

Sandy

Thanks Sandy! That makes mathematical sense from the published graphical data. I've put off purchasing the step wedge but I really should get one.

Thomas

[sanking]

Thanks Sandy! That makes mathematical sense from the published graphical data. I've put off purchasing the step wedge but I really should get one.

Thomas

I have found step wedges to be extremely useful tools in alternative printing. Stouffer has them in various sizes. http://www.stouffer.net/TransPage.htm.

Sandy