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  1. #11
    gainer's Avatar
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    Contrast of pyro negatives.

    Quote Originally Posted by Snapshot View Post
    Hi Sandy,

    I have a pH value close to 10 for the formula (estimated from test strips as I don't have a digital meter yet). I was surprised at the 'relatively' high pH but that's what the test strips indicated at 1+100 dilution. The HQ was to bump up the contrast a bit. It's my understanding that pyro-metol formulas tend to be of moderate contrast. Since I use VC paper and the pyro stain acts a contrast mask, I wanted a little more contrast to compensate.

    The formulation that I used is as follows...

    TEA...............100ml
    Metol.............2.0g
    Hydroquinone...5.0g
    Pyrogallol........10.g
    Where did the myth arise that you cannot use printing filters with pyro negatives on VC paper? If you have a yellow, orange or red stained negative where the stain is proportional to the silver image, you could in fact use a blue separation filter to get the same printed image you would get from blue sensitive graded paper. The stain of a pyro or pyrocatechol negative would have to be inversely proportional to the silver image to get a reduction of contrast, or else the blue sensitive emulsion of the paper would have to be the low contrast emulsion. You don't have to believe me. You can prove it for yourself.
    Gadget Gainer

  2. #12
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    Quote Originally Posted by gainer View Post
    Where did the myth arise that you cannot use printing filters with pyro negatives on VC paper? If you have a yellow, orange or red stained negative where the stain is proportional to the silver image, you could in fact use a blue separation filter to get the same printed image you would get from blue sensitive graded paper. The stain of a pyro or pyrocatechol negative would have to be inversely proportional to the silver image to get a reduction of contrast, or else the blue sensitive emulsion of the paper would have to be the low contrast emulsion. You don't have to believe me. You can prove it for yourself.
    Ahh... it seems I'm operating under a mistaken belief. I thought that contrast filters would not be as effective for pyro negatives.
    "The secret to life is to keep your mind full and your bowels empty. Unfortunately, the converse is true for most people."

  3. #13
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    BTW, the less pure grade of TEA could give considerably higher pH than the best grade because it contains as much as 15% diethanolamine. (I wonder why I never see it as DIE for short?)
    Gadget Gainer

  4. #14
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    Quote Originally Posted by sanking View Post
    A pH of 10 is much higher than I would have expected from TEA at this dilution. I have an electronic pH meter and would get no more than about pH 9.2 with this dilution.

    However, there could be significant synergism between the three reducers that activates the hydroquinone at a lower pH?

    But why HQ and not ascorbic as the third reducer? Were you concerned that there would be a loss of sharpness as Hutchings suggests with Pyrogallol + ascorbic?

    Sandy
    I avoided ascorbic acid because I've had difficulty obtaining a source that was reliable in quality. It seems that the quality/content of store bought ascorbic acid varies. I suspect that what ascorbic acid I did purchase contained dehydroascorbic acid, which isn't effective as a developer but acts like ascorbic acid in the body. This affected the development qualities of the formulas I used.
    "The secret to life is to keep your mind full and your bowels empty. Unfortunately, the converse is true for most people."

  5. #15
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    Erythorbic acid is the isomer of ascorbic acid, its mirror image, that developers can use but the body cannot. I got it from KICgroup. You can get ascorbic acid from The Chemistry Store or from NOW foods. Usually, the label tells whether the drug store vitamin C is ascorbic acid, dehydroascorbic acid, sodium or calcium ascorbate (may be labelled "Ester C".
    Gadget Gainer

  6. #16
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    Following the advice of TheFlyingCamera, it printed some negative frames. What I found was blown highlights but acceptable shadow detail. So, it would appear my answer is that the negatives are too dense, as my printing time was extended as well. I'd like to thank everyone for their contribution.
    "The secret to life is to keep your mind full and your bowels empty. Unfortunately, the converse is true for most people."

  7. #17
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    Sounds like a second test is in order, using the same exposure settings, but cutting your dev time by about 15-20%. See if that works for you, and if your highlights are still blown out, maybe it's time to adjust the chemistry.

  8. #18
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    Quote Originally Posted by TheFlyingCamera View Post
    Sounds like a second test is in order, using the same exposure settings, but cutting your dev time by about 15-20%. See if that works for you, and if your highlights are still blown out, maybe it's time to adjust the chemistry.
    I'll give it a try today (time permitting). I reshot some scenes this morning so a near direct comparison is feasible.
    "The secret to life is to keep your mind full and your bowels empty. Unfortunately, the converse is true for most people."

  9. #19
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    Well, I cut processing time by 30% and it appears to be resolving the issues I've been having. There are deep blacks, shadow detail and highlights that aren't blown. I'm getting near the appropriate developing times but I may even cut it down even more. Right now, I'm souping APX 100 (at EI 100) for 7 minutes using a 1+100 dilution, which seems very quick. Grain has reduced so that it is very comparable to the results I've seen with FX-37, with at least equal sharpness.
    "The secret to life is to keep your mind full and your bowels empty. Unfortunately, the converse is true for most people."

  10. #20

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    Quote Originally Posted by Snapshot View Post
    Well, I cut processing time by 30% and it appears to be resolving the issues I've been having. There are deep blacks, shadow detail and highlights that aren't blown. I'm getting near the appropriate developing times but I may even cut it down even more. Right now, I'm souping APX 100 (at EI 100) for 7 minutes using a 1+100 dilution, which seems very quick. Grain has reduced so that it is very comparable to the results I've seen with FX-37, with at least equal sharpness.
    If that approach does not work out for you, try replacing the Hydroquinone with Ascorbic Acid and the Pyrogallol with Catechol.

    However, it would probably be easier to just mix some Pyrocat (either HD or MC). Pyrocat is great at clamping the highlights.
    Tom Hoskinson
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    Everything is analog - even digital :D

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