ILFORD FP-4 PLUS; CORRECTING FOR RECIPROCITY FAILURE

[wskmosaic]

Does anyone know if reciprocity failure correction computed for Ilford HP 5 Plus will apply to Ilford FP-4 Plus?

Ilford's data sheet on these films, which declares correction factors for all its films to be equivalent, was never meant to be a precise guide, and is very old.

In addition, does anybody know, for either of these films, what the reduction in developing time for each range of exposure increases to compensate for reciprocity failure?

tnx

Warren

 

[Oren Grad]

Howard Bond's article...

http://www.phototechmag.com/index.php/archive/reciprocity/

...unfortunately didn't address FP4 Plus. But it's worth a read anyway, for its insight into the utility of the manufacturers' published correction factors.

 

[Shawn Dougherty]

I go by the Howard Bond data for HP5+, it has worked well for me so far.
For FP4+ I have been using the Kodak reciprocity chart for general black and white film (Not the TGRAIN CHART) and it has been working great.
Don't forget to decrease development as well!

 

[dnjl]

I use the following formula to calculate reciprocity compensation for classic Ilford films (PanF+, FP4+, HP5+):

exposure time^1.48

For example, a 15sec exposure after correction will result in a 55sec exposure. I found this works well.

I don't remember where I picked this up, but thanks to whoever came up with it originally.

 

[wskmosaic]

Re: Recip Failure and FP-4 Plus

Thanks for the quick and thoughtful responses.

Oren: I have read Bond's article. I trust him implicitly and rely on that article--or as much of it as I can handle. Which is why I'm so down on the Ilford figures.

Walter: I believe that ^1.48 is the Ilford formula precisely. I can't imagine how it can work for all the films they list it for. I'm afraid I'm not going there.

And Shawn:
I'll take a look at those Kodak figures, but I'm curious to know why you've never given the Bond figures a run with FP-4+. If you ever do, I'd love to hear about it. I think Bond might, too.

tnx

Warren

 

[wskmosaic]

I go by the Howard Bond data for HP5+, it has worked well for me so far.
For FP4+ I have been using the Kodak reciprocity chart for general black and white film (Not the TGRAIN CHART) and it has been working great.
Don't forget to decrease development as well!

Quick further question, Shawn:
At what ASA do you shoot FP-4+ and what is your normal developer and development time?
tnx
Warren

 

[Shawn Dougherty]

And Shawn:
I'll take a look at those Kodak figures, but I'm curious to know why you've never given the Bond figures a run with FP-4+. If you ever do, I'd love to hear about it. I think Bond might, too.

tnx

Warren

As far as I know Bond did not work with FP4+ or I certainly would.... If I'm missing it somewhere please point it out!

Quick further question, Shawn:
At what ASA do you shoot FP-4+ and what is your normal developer and development time?
tnx
Warren

I rate FP4+ @ ISO 64. However, I tend to error on the side of more exposure. I am developing FP4+ in Pyrocat HD at 1:.5:100 (note that B is POINT FIVE ((.5)). 8 Minutes for N. I develop 4x5 in small tubes gently rolling them in water. And I stress the importance of using N- development in various degrees for reciprocity corrected exposures.

Edit. HERE is a link to the Kodak graph I have been using for FP4+, it is on page 3.

 

[wskmosaic]

As far as I know Bond did not work with FP4+ or I certainly would.... If I'm missing it somewhere please point it out!

I'VE SEEN SEVERAL SETS OF DATA FOR FP-4 PLUS, AFTER MUCH SCROUNGING, SURFING AND ASKING. ONE IS AT
http://www.film-and-darkroom-user.org.uk/forum/showthread.php?t=2678&highlight=McLean+reciprocity , THOUGH YOU MIGHT HAVE TO LOG IN TO THE FDU FORUM TO SEE IT. IN A PINCH, AT THAT FORUM, SEARCH 'McLEAN RECIPROCITY TO COME UP WITH IT.

THE OTHER IS ASCRIBED TO JOHN SEXTON AND LOOKS LIKE THIS (METERED/ADJUSTED):

2/3
4/7
8/19
12/33
16/50
24/93
32/145
45/250
60/378
90/853
120/1670

THEY BOTH APPEAR TO BE MORE GRADUAL THAN THE KODAK DATA AND CONSEQUENTLY APPEAR NOT TO REQUIRE SO MUCH (IF ANY EXCEPT AT THE LONGEST EXPOSURES) REDUCED DEVELOPMENT.

AT LEAST THAT SEEMS TO BE THE CONSENSUS; I'M ABOUT TO LAUNCH MYSELF INTO THEM.




I rate FP4+ @ ISO 64. However, I tend to error on the side of more exposure. I am developing FP4+ in Pyrocat HD at 1:.5:100 (note that B is POINT FIVE ((.5)). 8 Minutes for N. I develop 4x5 in small tubes gently rolling them in water. And I stress the importance of using N- development in various degrees for reciprocity corrected exposures.

Edit. HERE is a link to the Kodak graph I have been using for FP4+, it is on page 3.

AND THANKS FOR THE KODAK GRAPH; I HAVE THEIR DATA.

AND THANKS FOR ALL YOU HELP.


WARREN

 

[Rick A]

http://www.ilfordphoto.com/Webfiles/2010712125850702.pdf

 

[Regular Rod]

Does anyone know if reciprocity failure correction computed for Ilford HP 5 Plus will apply to Ilford FP-4 Plus?

Ilford's data sheet on these films, which declares correction factors for all its films to be equivalent, was never meant to be a precise guide, and is very old.

In addition, does anybody know, for either of these films, what the reduction in developing time for each range of exposure increases to compensate for reciprocity failure?

tnx

Warren

I use the chart that ILFORD supply but I print it with more grid lines to make it easier to read across. It has never let me down. Here's my pdf of it to print off, cut out, laminate and keep with the exposure meter.

RR

 

[Rick A]

Their product, their research.

 

[ic-racer]

http://phototechmag.com/black-and-white-reciprocity-departure-revisited-by-howard-bond/

That article seems to have a serious flaw. He is testing for aperture correction and plotting time correction. The entity that tie aperture to time is reciprocity! When he converts his results from aperture to time correction his equation (1 stop light = 1 stop time) is only valid if reciprocity holds true at all times! If you convert his table back to f-stop correction, then it is a valid table for what he is testing (dim-light photography at 1/4 second).

 

[Ian Grant]

Sorry Rick but I can't buy that curve. Ilford has used that reciprocity curve for nearly every one of their films for many years, and I just can't believe that to be the case. But then Kodak also provided info for b/w films in general as well (seems Acros and T-grain films would almost certainly not conform to that).

There is no way to produce an accurate Reciprocity table because the variables in light type, intensity, spectral composition, scene contrast etc are just too wide. It makes a difference if it's Daylight or Artifical light particularly Tungsten where a film has a lower EI anyway.

It's far better to do your own personal tests in the lighting conditions you intend to work with. Failing that the Ilford chart will get you close it probably has a degree of safety factor built in.

Ian

 

[Regular Rod]

Sorry Rick but I can't buy that curve. Ilford has used that reciprocity curve for nearly every one of their films for many years, and I just can't believe that to be the case. But then Kodak also provided info for b/w films in general as well (seems Acros and T-grain films would almost certainly not conform to that).

There is no way to produce an accurate Reciprocity table because the variables in light type, intensity, spectral composition, scene contrast etc are just too wide. It makes a difference if it's Daylight or Artifical light particularly Tungsten where a film has a lower EI anyway.

It's far better to do your own personal tests in the lighting conditions you intend to work with. Failing that the Ilford chart will get you close it probably has a degree of safety factor built in.

Ian

I can only repeat that "It has never let me down"...

RR

 

[Shawn Dougherty]

In my experience the most accurate info I've found (info that I've tried and has led me to good results) is the Howard Bond data... (who did not test FP4+).

The info provided by Ilford is, as stated earlier, a big generalization which they have used for years on multiple films. Following it led me to overexposure. Testing yourself (or at least bracketing like crazy and keeping careful notes) is your best bet. Of course it can be very time consuming...