RECIPROCITY BLACK & WHITE FILM

hortense · May 24, 2006

It appears Digital Truth has posted incorrect reciprocity data according to my experience with exposures less than 15-minutes. Have NOT tested Ilford for reciprocity but used their formula meter reading ^ 1.49.

BLACK & WHITE FILM
Digital Truth for ALL B/W film (http://www.digitaltruth.com/techdata/reciprocity.php)
1 sec reading: expose 2 sec and N-10%
10 sec reading: expose 1 min and N-20%
100 sec reading: expose 20 min and N-30%
Kodak for 320TXP
1 sec reading: expose 1 sec and N-0%
10 sec reading: expose ≈18 sec and N-1
100 sec reading: expose ≈4-min and N-1 1/2
Ilford
1 sec reading: expose 1 sec and N-0%
10 sec reading: expose 30 sec and N-10%
100 sec reading: expose ≈15 min ^1.49=15 min ≈N-30%

colrehogan · May 24, 2006

I would just download the tech sheets for each film you are using or plan to use and they include reciprocity information.

hortense · May 25, 2006

colrehogan said:
I would just download the tech sheets for each film you are using or plan to use and they include reciprocity information.

Kodak 320TXP and Ilford reciprocity data are documented by each company. More specifically Ilford states that there film reciprocities are based on Uncorrected Time or Meter Reading seconds ^1.49. However, if you have some information that would substantiate or correct what Digital Truth has claimed it would be helpfut to forum viewers. Perhaps other viewing this verify?

RalphLambrecht · May 25, 2006

My co-author conducted a reciprocity test lately, but the data is not evaluated yet. So I can't post anything right now. Nevertheless, I have a working reciprocity chart for Kodak films and it matches the above table closely.

One factor needs to be considered. What is the color temperature of the low-light condition, which is causing the reciprocity failure? Film has a very different sensitivity to blue, green or red light. If we are facing a tungsten low-light condition, the reciprocity chart made with dim daylight data will give false results.

Remember, film is very forgiving to over-exposure. When in doubt, just double the exposure. It won't hurt.

Roger Hicks · May 25, 2006

RalphLambrecht said:
Remember, film is very forgiving to over-exposure. When in doubt, just double the exposure. It won't hurt.

Dear Ralph,

Oh dear! Giving away trade secrets!

Couldn't agree more!

Cheers,

Roger

hortense · May 25, 2006

RalphLambrecht said:
One factor needs to be considered. What is the color temperature of the low-light condition, which is causing the reciprocity failure? Film has a very different sensitivity to blue, green or red light. If we are facing a tungsten low-light condition, the reciprocity chart made with dim daylight data will give false results.

Remember, film is very forgiving to over-exposure. When in doubt, just double the exposure. It won't hurt.

Thanks Ralph. I did not realize this factor was involved. I thought that the increased exposure requirements took this into consideration - but, you tested - that settles it. Sounds like you and a coleague are doing some in depth reciprocity testing. I would be nice to do better than a very broad estimate. Keep us informed as you get more data?

Digitaltruth · May 25, 2006

Hi Hortense,

The data on our site comes from many reliable sources, but there can always be errors or inconsistencies. The reciprocity data is a guideline only and testing needs to be done with individual films.

We are happy to accept any improvements to our site, and will credit all contributions, so if anyone can supply better data, then please send it to me and we will make it available on our information pages.

--Jon

hortense · May 25, 2006

Digitaltruth said:
Hi Hortense,

The data on our site comes from many reliable sources, but there can always be errors or inconsistencies. The reciprocity data is a guideline only and testing needs to be done with individual films.

We are happy to accept any improvements to our site, and will credit all contributions, so if anyone can supply better data, then please send it to me and we will make it available on our information pages.

--Jon

Jon - You site is fine. Pardon my comments - not intended to throw spears. We value the service your site provides. I was hoping others would chime in with the reciprocity data they have used successfully.

hortense · May 25, 2006

Jon - Here is what I have successfully used for TriX. Ilford calculations are
Meter Readiing in seconds ^1.48.

hortense · May 25, 2006

320TPX

Here it is.

Digitaltruth · May 30, 2006

hortense said:
Here it is.

Thanks.

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