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  1. #41

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    Mrred, I don't get it : you develop and fix a strip of unexposed film. Then why develop it when there will be nothing to develop if it's unexposed, and you'll end up with a blank strip ? How do you recognize the correct first development time from this ?

  2. #42
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    What you are looking for is fog. That's the point when the developer shows something from nothing, or in DigitalIze - noise. Look at any of your negitives, they all have a varying degree of it.

    To demonstrate, take some unexploded ( ) film and put it in your developing can. Use PQ or Dektol 1:1 (or the strongest of whatever you have) and do a time of 20 mins or so. Fix it and have a look. That would be fog.
    Get it right in the camera, the first time...

  3. #43

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    Quote Originally Posted by Tofek View Post
    Mrred, I don't get it : you develop and fix a strip of unexposed film. Then why develop it when there will be nothing to develop if it's unexposed, and you'll end up with a blank strip ? How do you recognize the correct first development time from this ?
    Tofek. My take on it is, that with Mr. Red's method, you do a series of developer time tests. Say 4, 6, 8, 10, 12... (or smaller increments) until you get fogging on the base. Then with the last one that shows no fog or just a touch of fog – that's the max amount of silver you can ever get out of the film with your developer before you've begun to lose the shadow detail and contrast. Because even with blank film the developer will eventually start working on unexposed/unexploded halides – to preserve the clear base you have to stop development at that point.

    I've been thinking about this and decided that i could take 6 or so small strips of tri-x and then put each one in turn into the dev, time it , stop it, fix it and then compare them at the end. I thought I could try and mark the strips with numbered notches. Use one mix of dev for the whole test and it's done - ideal development time is sorted for good. (Then perhaps do it for a other dilutions for completeness or if the contrast needs adjusting in the final exposed image tests.)

    It separates out the question of ideal development time from the one of exposure.
    Last edited by mr.datsun; 02-12-2013 at 08:43 AM. Click to view previous post history.

  4. #44

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    Ok I see, thank you. However, the silver that is reduced (developed) in the first development will actually be bleached. And the ''fog+non developed silver'' is then the part left for positive developing. So if some of the positive part is bleached away, you'll lose on final density. And you don't want that. Do I get it right ?

  5. #45

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    I see your point. As the bleach is before any slight fogging might be taken care of by the clearing bath. Maybe you have to get it just right before fogging shows. Maybe a slight fogging is negligible in terms of the final result anyway, but I think the idea is to avoid it getting to that point if possible. Over to Mr Red, I think.

  6. #46
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    You have to recognize that in reversal processing, the first developer does not go to completion but the second developer does. Therefore, the first developer must have a tad of silver halide solvent in it to ensure that whites are white. To do this, a slight amount of fog is normally needed in the first developer to ensure that the second developer does not give gray whites.

    There is still plenty of Silver Halide to get black blacks in the final positive.

    PE

  7. #47
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    yes. You expect some fogging but too much will cause the bleach step to work too hard and effectively strip away the latent image thus reducing dynamic range. Not so much "pushing you off a development cliff" but more of a "no real gain" situation.
    Get it right in the camera, the first time...

  8. #48
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    Mrred, not sure what you are talking about. The latent image is only used in the first developer. And, silver is silver as far as the bleach step is concerned. Any and all Silver metal is converted to Silver Sulfate which washes out. By the time the film hits the bleach, there is no latent image to be concerned about.

    Fog is not related, in this instance, to latent image in the sense that you are forcing a silver halide solvent to cause physical development and concomitant fog, to allow an overall increase in density that then allows the clean out of the final white areas. Without the fog, caused by the solvent, the whites would be very gray in the final image.

    Now, there are some developers that work without solvent action, but I am not going into that here.

    PE

  9. #49

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    Ok. I'm confused. But aside from that for the moment, I just spent two hours trying to get fog on Tri-X. I took my dev (PQ Universal mixed at 1+5) from 6m to 16m in 2 minute steps. (I normally have been using it for 10m). Nothing. No fog. Is the PQ dev not energetic enough? What's happening? Remember that Ilford recommended it at 1+5 10m for their FP4 film. Do I need to go all the way to 20mins, double the concentration, or go for Dektol?

  10. #50
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    Try 1:1 or 1:2. I don't use much less than this with Dektol which should have the same activity level. Even then it's at the suggested time of 12. Time is less critical than when developing negatives as the density is much greater. With D-19 I had to use 1:1 which was why I stopped using it; it got much more expensive than Dektol.

    try jumping up more in times. I would use increments of 10. When you get fog, try backing off half way from the last point. If that is good, bump it forward half way....and so on.

    You should get the similar results with PQ. It looks like you are just using a strong enough dilution. In theory you should be able to use any developer. Getting it to work well or with a reasonable cost is another story.
    Get it right in the camera, the first time...

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