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Development Time Constants
This question is within the context of the subject title.
ALL things being equal, if HP5+ is given X minutes to develop, what is the value of the constant K in the equation X times K equals Y. Y is the time needed to develop Delta 3200. I think the value of K may hold steady for all films in the same developer. If so, some film, Plus X perhaps, may be used to establish base times and a constant K applied to each of any other films in that same developer. To the point, I've from the woods ONE roll of Delta 3200 to develop. If ten minutes will do for a roll of HP5+ how many minutes should I give the Delta? Or, by what factor should I multiply the ten minutes? Dan |
Development Time Constants
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Development Time Constants
One other variable that may need to be considered (based only on my empiric
data). You may need to group films into "families" to get anything like an easy "k" factor. Perhaps grouping films by characteristics: High resolving microfilm types perhaps including TechPan Slow speed fine grain films like Pan F and Panatomic-X Medium speed conventional films FP-4 Medium speed tablet grain films Delta 100 TMax 100 Acros(?) 400 speed conventional films Tri-X, HP-5 plus High Speed T-grain films TMax 3200, Delta, etc. Kodak's Darkroom Data Guide once had a dial used to figure time and temp for all their films, by extrapolation I included films by other makers but ran into problems when the TMax films came out. -- darkroommike wrote in message oups.com... REUC wrote: There is no such universal 'constant'. Each developer will react differently. Time and temperature compilations are taken by most to be ballpark figures. A not too inclusive compilation might be worth while. A type of developer and perhaps eight or ten films might be accurate enough across the board. Dan |
Development Time Constants
Michael Gudzinowicz wrote:
wrote: To the point, I've from the woods ONE roll of Delta 3200 to develop. If ten minutes will do for a roll of HP5+ how many minutes should I give the Delta? Or, by what factor should I multiply the ten minutes? Dan If you're trying to estimate a time for Delta 3200 based on a known HP5+ time for a certain temperature, EI and CI, check the Ilford film PDF's for both films and the developer you intend to use. The developer is ACU-1 and the films are the HP5+ and Delta 3200. ACU-1 and the Delta is not a combination listed in the Massive Chart. For a K I'll check the two films in D-76 and likely another developer or two in which both films have been processed. Dan |
Development Time Constants
wrote:
Michael Gudzinowicz wrote: wrote: To the point, I've from the woods ONE roll of Delta 3200 to develop. If ten minutes will do for a roll of HP5+ how many minutes should I give the Delta? Or, by what factor should I multiply the ten minutes? Dan If you're trying to estimate a time for Delta 3200 based on a known HP5+ time for a certain temperature, EI and CI, check the Ilford film PDF's for both films and the developer you intend to use. The developer is ACU-1 and the films are the HP5+ and Delta 3200. ACU-1 and the Delta is not a combination listed in the Massive Chart. For a K I'll check the two films in D-76 and likely another developer or two in which both films have been processed. Dan If some data was available, I guess you wouldn't have asked. I assume that you don't have more D3200 to run a clip test, or a developer for which Ilford provides data. There is a "constant" called the Waller coefficient which varies markedly for different developers, but is fairly "constant" for similar types of films. The coefficient is the ratio of the required or total development time to the time of emergence of the image. That observation is the basis of "factorial" development of paper. And of course, we don't know the value for Acu1, and apparently there's no D3200 film to waste. What I would do, would be to clip a section of leader from HP5+ or the last 1/4" of the tail of 120 film, and reroll it. Expose to light and develop in a tray and note the emergence time for a light gray image. I'd let development continue for the same period of time (2X emergence time total), stop and fix the HP5+. The film should be underdeveloped to a grey tone rather than opaque black. Divide your known development time by the time to emergence, and use this as your constant. Get a scrap of D3200 film from the leader or non-image area of 120, in light determine the emergence time, and stop at 2x that time as with HP5+. Compare the fixed films and see if the densities are the same. If they are identical, use the factor to calculate a D3200 development time. If they are "close" (within 10% using a densitometer), use the optical density ratios to tweak the time calculated with the factor. If they are no where near agreement, try again with scraps you've saved. This is a rather oblique approach, but it avoids the comparison of two films in different developers where the ratios of development times will differ. In those situations, the ratio of emergence times differs. If you don't post, let me know where this goes by email. |
Development Time Constants
Mike King wrote:
Kodak's Darkroom Data Guide once had a dial used to figure time and temp for all their films, by extrapolation I included films by other makers but ran into problems when the TMax films came out. The dial works (in my not very well tested experience) for time versus temperature, while film and developer are held constant. That is, if you know the right time at 68 F, you can predict a reasonable time at 72 F. But you already need to know a right time for your film+developer combination. For Tmax, I used the film box or datasheet value as a starting point. The dial is basically just a convenient version of a time/temp chart like this: http://www.digitaltruth.com/chart/timetemp.html Dan wants a formula that lets him convert times from one developer to another, or one film to another. I don't think this is possible with a simple conversion. If this were possible, the time for film X would always be a constant factor times that for film Y, and some study of a dev chart will show exceptions. For example, a very small amount of data from the Massive Dev Chart: 35mm,20C HP5+(400) FP4+(125) Tri-X(400) Acufine 4.5 4 - D-76 7.5 8.5 7-8 D-76 1:1 13 11 10-11 HC-110 B 5 9 4.5-6 Rodinal 1:50 11 15 13 Now, maybe these times are all crap, although I think some of them are from manufacturer's datasheets. But my point is you can't come up with blanket statements like FP4 takes 50% as long as HP5, or HC-110B takes 2/3rds as long as D-76. And I deliberately picked three films that are fairly similar, so the difference isn't regular vs T-grain or anything like that. |
Development Time Constants
wrote:
Dan wants a formula that ... I've the formula. What's needed is a method of establishing the values of k. I think I've Got It! All films through the STD developer and the STD film through All developers. The chart looks like this: Films l--------l---------l----------l------- D l--------l---------l----------l------- E l--------l---------l----------l------- V l--------l---------l----------l------- l--------l---------l----------l------- Top row STD developer, Left column STD film. Fresh off the top of my head. I think it makes sense. What do you and ... think of it? Dan |
Development Time Constants
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Development Time Constants
David Nebenzahl wrote:
spake thus: All films through the STD developer and the STD film through All developers. The table looks like this: Films l--------l---------l----------l------- D l--------l---------l----------l------- E l--------l---------l----------l------- V l--------l---------l----------l------- l--------l---------l----------l------- Top row STD developer, Left column STD film. Fresh off the top of my head. I think it makes sense. What do you and ... think of it? Dan Yes, wonderful, Dan: ......... But what you forgot, ........... *there's no data in it*. And even if you do get data plugged in, will it mean anything? Yeah, it makes lotsa sense ... That format may be an improvement over the Massive ---. A source of data is that supplied by manufacturers. I've still that 120 roll of Delta 3200 to develop in ACU-1. A 3x5 index card will do for the table and some values off the WWW can be found and pluged in. HP5+ and Delta 3200 times in the STD developer will be entered in the table. Times for HP5+, as the STD film, in the STD developer and ACU-1 will be entered. The ACU-1 time I must derive. The value of k computed and applied I'll know the development time for the Delta 3200 in ACU-1. It's worth a whirl. I'll let you know. Dan |
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