Tri-x reciprocity

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X-mas holidays and time to experiment with pinhole.
My second home made camera uses roll-film and gives a negative size of (almost) 6 X 9 cm. I've done some shooting at home with kodak tri-X (the new one). The correction for reciprocity suggested by kodak requires an adjustment in development that varies with the exposure and is difficult to apply if your time varies greatly from shot to shot. I've applied the exposure correction but developed the film with my usual tri-x time/developer/temperature (i.e. ignored the development adjust). The negs I've obtained are a bit too dense in the long expositions. Does any of you can point me to set of correction values that do not requires to adjust the development time?
Ciao,
Marcello
 

dr bob

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There was an extensive article in PhotoTechniques July/Aug last year concerning reciprocity of several films ( TX was included, but I don't remember if it was TX-400 or TXP-320) by Howard Bond. I can look up details if you wish. PM me. or email.

dr bob.
 
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Thank you (Dr) Bob,
after searching the net on reciprocity I have come to some conclusions (maybe an expert pinholes already knows all that):
1) reciprocity failure tables have been calculated for night-shots where contrast is much higher (the road is dark but a lamp can be very bright). Probably the table should be reconsidered in the light of this (no pun intended);
2) tri-x is not the best film for B&W pinhole as it has a very bad reciprocity curve. Tabular grain films will in theory perform better. Fuji across (impossible to find here in Italy) with no reciprocity up to very long time and tmax with very few reciprocity in the range 1 to 100 seconds. I'll make some test with t-max. Oddly Ilford gives the same reciprocity for delta, hp and fp
 

Jim Chinn

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TMAX is much more forgiving with Reciprocity characteristics than TriX but i don't know if that applies to exposures in the many minutes that you can get with a pinhole exposure.

Here are a couple of sights that may interest you if you have not seen them before:

http://www.thenocturnes.com/index2.htm
http://www.pinhole.com/
 

Donald Miller

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marcello.brussard said:
X-mas holidays and time to experiment with pinhole.
My second home made camera uses roll-film and gives a negative size of (almost) 6 X 9 cm. I've done some shooting at home with kodak tri-X (the new one). The correction for reciprocity suggested by kodak requires an adjustment in development that varies with the exposure and is difficult to apply if your time varies greatly from shot to shot. I've applied the exposure correction but developed the film with my usual tri-x time/developer/temperature (i.e. ignored the development adjust). The negs I've obtained are a bit too dense in the long expositions. Does any of you can point me to set of correction values that do not requires to adjust the development time?
Ciao,
Marcello

In order to have a negative of manageable density range when encountering reciprocity considerations the development must be compensated in some fashion. The reason is that brighter objects receive much greater relative exposure then objects that are lower in luminance. This creates greater contrast by the very nature of the exposure.

If it were me, I would tend to think in terms of the tabular grain films that others have mentioned and additionally I would move away from strict time and temperature development and toward developing by inspection. I would probably give great consideration to a pyro or catechol based developer. Highly dilute or water bath development may also be of benefit in your situation.
 

Lex Jenkins

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With some practice you should be able to get satisfactory results using Tri-X with long exposures. I've done so several times photographing under moonlight with exposures ranging from 10 seconds to one hour.

While I've read articles about the reciprocity characteristics of various films (including the excellent article by Mr. Bond referred to earlier), I don't work with films in any technical manner for night photography. I'm familiar enough with Tri-X to be able to estimate a baseline exposure under most conditions and I'll usually bracket around that baseline.

One trick that I find helps me is to use a development technique that helps control contrast. I develop in either Diafine or use stand development in very dilute Rodinal. Either method essentially eliminates time as a factor in development. Diafine (a two-part developer) is used for 3-5 minutes; the time is not critical. With Rodinal and stand development I typically use a 1:200 solution for two hours but, again, the time factor is not critical.
 
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