Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,002   Posts: 1,524,424   Online: 1046
      
Page 2 of 4 FirstFirst 1234 LastLast
Results 11 to 20 of 33
  1. #11

    Join Date
    Oct 2004
    Location
    Cambridge, MA USA
    Shooter
    Multi Format
    Posts
    895
    Regarding Rodinal's long-ish development times....

    Agfa publishes their times for a gamma of about 0.65. Depending on who you talk to you will get two explanations for this rather odd choice of gamma:

    a) That gamma is typical for a diffusion enlarger
    b) That gamma is close to the ISO gamma for testing film speed

    IIRC, every box of Rodinal has a data sheet that includes dev times for APX 100 and 400 for gammas of 0.55, 0.65, and 0.75 for Rodinal 1:25 and 1:50.

    I've found that a time for a gamma of 0.55 minus about 7% works well for Rodinal 1:50 on APX 100 with a fairly contrasty subject when I print on a condenser enlarger and Forte Polygrade V.

  2. #12

    Join Date
    Oct 2004
    Location
    Cambridge, MA USA
    Shooter
    Multi Format
    Posts
    895
    Quote Originally Posted by jdef
    I understand that there is a difference between gamma, and CI, and that average gamma is.7. Am I misinformed?

    Jay
    Not at all - in fact I think Agfa may be the confused party! An "average" (typical?) gamma of 0.7 sounds about right if you're developing to a CI around 0.50 or a bit higher with something like Tri-X in 35 mm.

    A "typical" CI for a condenser enlarger and for a 35mm neg could be around 0.5 but perhaps 0.65 or so for a diffusion enlarger.
    The corresponding gamma, I think, would be up around 0.83 or maybe a bit more - so I really don't know why Agfa furnishes that diffusion enlarger explanation. So is that 0.65 really a CI or a gamma as far as Agfa is conerned? Well it seems to provide a plausible CI for a diffusion enlarger but too low a gamma for the same - though it would be in the ballpark for a condenser.

    I placed a call down to Ridgefield Park, NJ to ask them about it a couple months back and I got the "its close to the gamma for an ISO film speed test" explanation. Others on Photo.net recall getting the story about the diffusion enlarger.

  3. #13

    Join Date
    Oct 2003
    Location
    Århus, Denmark
    Shooter
    Medium Format
    Posts
    2,102
    Images
    16
    Quote Originally Posted by TPPhotog
    I prefer FP4+ rated at 64 in Rodinal 1+100 for 15 mins at 20C. Invert for first 30 seconds and then invert once every 30 secs.

    Jeanette beat me to posting Mortons times for Delta 100 - I think he's in the darkroom today lucky man
    I WAS in the darkroom today making the last print for a friend. After that I did some fibre (5x7) to get trained in this. Quite a bit og hassle there.

    But for the stuff in this thread:

    I recommend using it 1+50 to get comfortable times and great contrast. For Delta 100 jeanette published my times (13:30-14:00 in 1+50) and they are correct (of course! Jeanette is from the inner circle in the CHURCH). I have done some further testing and now I find 12:30 quite pleasing with flash heads, but the contrast is on the low side.

  4. #14

    Join Date
    Nov 2004
    Location
    Italia
    Shooter
    Multi Format
    Posts
    4,680
    Quote Originally Posted by aldevo
    So is that 0.65 really a CI

    I placed a call down to Ridgefield Park, NJ to ask them about it a couple months back and I got the "its close to the gamma for an ISO film speed test" explanation. Others on Photo.net recall getting the story about the diffusion enlarger.

    See if you can find Agfa's numbers for things other then small tanks. I don't know if they still do but they used to publish a bunch of different times for different types of processing. But the easily found numbers were only for high contrast index.

    Is Agfa USA really part of Agfa or a independent group that handles Agfa products?

    http://www.agfaphoto.com/en-GB/profe...ing/index.html


    Click on data sheet and download it.

    You'll see 0.55,0.65 and 0.75 for APX 100 in rotary drums. Is that symbol contrast index?

  5. #15

    Join Date
    Oct 2004
    Location
    Cambridge, MA USA
    Shooter
    Multi Format
    Posts
    895
    Quote Originally Posted by Nick Zentena
    See if you can find Agfa's numbers for things other then small tanks. I don't know if they still do but they used to publish a bunch of different times for different types of processing. But the easily found numbers were only for high contrast index.

    Is Agfa USA really part of Agfa or a independent group that handles Agfa products?

    http://www.agfaphoto.com/en-GB/profe...ing/index.html


    Click on data sheet and download it.

    You'll see 0.55,0.65 and 0.75 for APX 100 in rotary drums. Is that symbol contrast index?
    Those figures are identical to those included on the datasheet that came with my bottle of Rodinal - save the inclusion of APX25 on my bottle's data sheet.

    That symbol is "gamma" which is a measurement of film contrast as specified on the characteristic curve. It's similar, but not identical to CI.

    Gamma measures the slope of a line tangent to a point on the film characteristic cuve that is part of the straight-line portion of the curve.

    The CI measurement is a bit different - it includes more of the cuve (essentially, most of the toe and the entire straight-line region - which is considered to be the portion most useful to photographer's) in its slope calculation.

    The values for gamma are higher than that for CI because they are a measurement of the region where the slope is greatest whereas CI includes the lower-contrast toe portion of the curve.

    As far as the Agfa data sheets are concerned - we were discussing the validity of Agfa's explanations for selecting a gamma of 0.65 on which to base their film development time.

    A gamma of 0.65 is too low to support the explanation that it is a typical gamma for a diffusion enlarger. Since a CI of 0.65 is quite typical for a diffusion enlarger, I was postulating that somebody at Agfa USA had got CI and gamma confused.

    As far as Agfa USA goes - I imagine it is a wholly-owned subsidiary of the parent. I guess we should now be talking about AgfaPhoto USA and AgfaPhoto given recent developments.

  6. #16
    Max Power's Avatar
    Join Date
    Sep 2004
    Location
    Aylmer, QC
    Shooter
    Multi Format
    Posts
    598
    Images
    5
    Quote Originally Posted by modafoto
    I recommend using it 1+50 to get comfortable times and great contrast. For Delta 100 jeanette published my times (13:30-14:00 in 1+50) and they are correct (of course! Jeanette is from the inner circle in the CHURCH).
    So, if my quick math is correct, the Agfa published time of 16 mins ought to be reduced by about 15% or 144 seconds which gives around 13:30 or so. Aldevo, if I understand you correctly, with a condenser enlarger, this would be somewhere around your recommended time too.

    Again, I want to thank everyone who has helped so far, because what I'm looking for is a springboard; a place to start and experiment from.

    Cheers!
    Kent
    Max Power, he's the man who's name you'd love to touch! But you mustn't touch! His name sounds good in your ear, but when you say it, you mustn't fear! 'Cause his name can be said by anyone!

  7. #17
    Max Power's Avatar
    Join Date
    Sep 2004
    Location
    Aylmer, QC
    Shooter
    Multi Format
    Posts
    598
    Images
    5

    So, have I been overdeveloping then?

    I realise that this is a newbie question, but I am a newbie, and I have nobody but all of you out there on APUG to help me...

    I have been using Delta 400 and 100 in ID-11 at 1+1 developed at the prescribed Ilford times and temp using 4 agitations every minute. My negatives are naturally contrasty, and roughly match a grade 2.5 to 3 filter. In other words, I don't need a filter for most work.

    Why I wonder if I'm overdeveloping is the simple fact that the surrounding frame of my negatives (in 35mm) is always a darkish grey; not black, not light grey, but a solid darkish grey. Without sounding paranoid, have I perhaps been overdeveloping my negatives?

    Thanks, again
    Kent
    Max Power, he's the man who's name you'd love to touch! But you mustn't touch! His name sounds good in your ear, but when you say it, you mustn't fear! 'Cause his name can be said by anyone!

  8. #18

    Join Date
    Jul 2004
    Shooter
    Multi Format
    Posts
    3,042
    Kent, My 35mm surrounds are almost clear except for the grain. If they are black then I'd suggest that they are over-cooked.

    On the subject of times I usually subtract 10% to 15% from the recommended dev time as a starting point. Also I fix for 3 minutes non-delta films and 6 minutes for Deltas.

  9. #19

    Join Date
    May 2003
    Location
    Valley Stream, NY
    Shooter
    Multi Format
    Posts
    3,216
    Quote Originally Posted by Max Power
    I have been using Delta 400 and 100 in ID-11 at 1+1 developed at the prescribed Ilford times and temp using 4 agitations every minute. My negatives are naturally contrasty, and roughly match a grade 2.5 to 3 filter. In other words, I don't need a filter for most work.
    To make sure that I understand, most of your work prints well with the equivalent of grade 2.5 to 3? If that's the case then you're doing it right.

  10. #20

    Join Date
    Oct 2004
    Location
    Cambridge, MA USA
    Shooter
    Multi Format
    Posts
    895
    Quote Originally Posted by Max Power
    So, if my quick math is correct, the Agfa published time of 16 mins ought to be reduced by about 15% or 144 seconds which gives around 13:30 or so. Aldevo, if I understand you correctly, with a condenser enlarger, this would be somewhere around your recommended time too.

    Again, I want to thank everyone who has helped so far, because what I'm looking for is a springboard; a place to start and experiment from.

    Cheers!
    Kent
    Well...I'm not sure where the 15% number comes from exactly. Basically, I've used Rodinal 1:50 w/ APX 100 in some fairly contrasty lighting. When I computed by development time I figured that I'd be conservative (remember, constrasty!) and take a minute off the time published for a gamma of 0.55 - figuring that would be a CI of 0.40 or so. I figured that that CI might work (and, fortunately, it did work ) for my 35 mm negs that were to be printed on Forte Polygrade VC with Polymax filters. Given that most of these negs seem to print nicely with a filter grade of 2 1/2 or 3 - I'd say its been successful.

    I tend to agree with jdef in that your ability to print at paper grades of 2 or 3 (or filter numbers of the same - though VC filter #s and paper grade #s aren't really the same thing) is a good sign that you've matched development time to your subject contrast and materials.

    Just to sum things up regarding all the stuff that flys through my head when I try to nail a development time based on the manufacturer's published time:

    What sort of light source do I have on my enlarger? Is it condenser or diffusion? I figure as a rule of thumb a condenser requires about 20-25% less development time than for a diffusion enlarger. How or even whether you adjust your development times from published figures to account for your light source depends upon which type of light source they used to devise the published times. Very often, incredibly, it isn't listed.

    Not all condenser light sources are the same, but the differences among them don't seem to upset the apple cart all that much.

    How contrasty is my scene? Basically, I use my 35 mm SLR's spotmeter (or wing it if I'm shooting with my Yashicamat 124G for MF) to try to determine the SBR. If the "typical" scene on that roll seemed to include more than 7 stops - I might give it 10% less development time. In extreme cases I'd reduce it more than that but I've yet to encounter any. If its significantly less than 7 stops I might add 10% or even a bit more to the time I devised in the first step.

    Of course, the needs of the many outweigh the needs of the few. If I've got a bunch of contrasty subjects and a few flat ones, the constrast ones win out; or, if I'm really certain that the subject in front of me is a keeper I'll change film rolls anyway to avoid having to compromise. Film is (still) cheap.

    What's the relationship between my film and paper curves? I'm typically going to try to print on Forte Polygrade V and this paper seems to have a fairly lengthy toe. Rodinal is probably going to give me pretty strong highlight separation so I figure its a wash and won't adjust anything. On the other hand, were I printing on a really short-toed paper like Kodak Polycontrast III (dead and buried) I might drop that development time a little bit. If I were going to use a developer that tended to shoulder off the highlights agressively (and there aren't many that will give me any real shoulder in the useful density range with the films I use) and print those negs on Forte Polygrade (long, sweeping toe = subdued highlight contrast) I might increase the development time a little bit.

    In truth, though, I always have two papers in both RC and FB with me in the darkroom. I also make sure I have Agfa Multicontrst papers at hand because these papers seem to have more aggressive highlights separation than the Forte paper and a bit smoother transition to deep shadows. What doesn't work on one usually will do reasonably well on the other. I always start with the assumption that I will print it on Forte Polygrade V.

    I suppose I could add the question of which format am I using to the above. But since I always print on a condenser enlarger, I've found developing to a higher CI for MF vs. 35 mm doesn't really buy me anything. YMMV, of course.

    If this sounds serendipitous - you're not wrong. The Zone System it is not, but I do make an effort to keep notes of what works and what does not. In any event, I don't use sheet film or own transmission/reflection densitometers so a "Cumulative Experience Factor Adjustment System" works better for me.

Page 2 of 4 FirstFirst 1234 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin