FP 4 reciprocity.

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Jorge

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Does anybody have a reliable reciprocity table for FP4, I will be shooting a really dark place on monday and would like to have good numbers.....pretty please...:tongue:
 

lee

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I have one and it is at the darkroom and I will get it for you and post it for your tomorrow.


lee\c
 
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Jorge

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Thanks Lee....aint APUG wonderful?!?...
 

Lex Jenkins

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I have no reciprocity data for FP4+, only anecdotal observations.

This has quickly become one of my favorites for nighttime photography. I prefer it in Diafine for that usage.

The maker of Diafine suggests an EI of 250 for use with FP4+. Instead, for nighttime use I halve that and rely on my F3HP's AE mode to establish a baseline exposure. I also estimate exposure based on the EV for a given scene (metered when possible, estimated otherwise). From there I'll bracket in full stops one up and one down.

So far this has given me at least one and usually more than one usable exposure. I simply treat the lighter or darker exposures as different interpretations of the scene.

For 35mm or rollfilm use I believe this is a viable method if you have enough time. If you're using sheet film or time is short and you can't bracket, by all means you'd want the reciprocity data.
 
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Jorge

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Thanks Lex, but I plan to do it in 12x20, so bracketing is out of the question..:smile:
 

philldresser

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Jorge

I have been told by a reliable source from Ilford that to get the correct exposure on FP4 when under reciprocity failure conditions that you multiply the selected exposure time (in seconds) to the power of 1.49. So if you have a decent scientific calculator or an excel spreadsheet why not create your own table


Excel formula =POWER(A2,1.49) where A2 is the time in secs


Phill
 

dr bob

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philldresser said:
Jorge

Excel formula =POWER(A2,1.49) where A2 is the time in secs

Phill

That is close to the SQRT of 2 (1.41 et c.). I have been using that (SQRT 2) as a guidline for years. I discovered the same factor is useful in determining zone development times. Maybe a paper is in order? Ever notice the frequency of occurrence of this factor in photography and optics?
 
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Jorge

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ah....Thanks Phil and Bob, seems like I could make a table that I could carry with this formula.....
 
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Jorge

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The Ilford chart you mention is what I have used in the past with terrible results, and from what I understand I am not the only one. In addition it only goes to 30 seconds exposure. I am guessing the place I want to photographs will have soemthing in the 2 minute range for which I will have to compensate for reciprocity. While I am sure that FP4 and FP4+ would probably behave very similar at these exposures, when you are doing 12x20 it pays to be as accurate as you can...:smile:
 

Black Dog

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For a 1-7 sec exposure I DOUBLE the indicated time on the meter.
For 8-59 seconds I QUADRUPLE it.
For 1 min plus I multiply by EIGHT (from a table published in Photo Art a few years ago). This has served me well for several years and I'm very happy with the negs-a touch dense sometimes but if it's not on the neg you can't print it can you ? I've generally used FP4/HP5 or Fortepan in 4x5 devved in PMK or a 2 bath.
 
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Jorge

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Thanks Black, I will keep your exposures in mind, seems like a simple thing to remember....:D
 

lee

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Jorge,
This is what I have:
meters reads shoot at
1 1
2 3
3 5
4 8
5 11
6 15
7 20
8 25
10 35
12 45
15 60
30 2m40s
45 7m
60 10m
2m 15m
These work very well. There is some thought that you don't need to change the development with the Ilford products like you do the Kodak stuff. I think I might do that to about 20%. After that I would not fool with it if it were me.

lee\c
 
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Jorge

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Thanks a lot Lee! I really apprciate it. I am curious now as to how the little formula and the chart compare, I think I will work on that tomorrow and let you know.
 

lee

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I printed it out and had it laminated and keep it in my shooting vest. I have HP5+ the delta films an d tri-x tmx and tmy on the same chart. BTW, the chart I posted for you will work for Pan-F also.

lee\c
 

djkloss

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Jorge

I have been told by a reliable source from Ilford that to get the correct exposure on FP4 when under reciprocity failure conditions that you multiply the selected exposure time (in seconds) to the power of 1.49. So if you have a decent scientific calculator or an excel spreadsheet why not create your own table


Excel formula =POWER(A2,1.49) where A2 is the time in secs


Phill

I suppose there's a similar way of calculating for Ilford Ortho Plus IF the number were available? That would be so helpful. I'd much rather use the formula than a graph. fwiw, I have searched the internet and have found very little regarding this film and its' reciprocity

Thanks,
Dorothy
 
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