# Film Reciprocity Tables

Here you find some Reciprocity tables for the most used Films. (others may follow)
I took the data from the original data sheets of the Film or collected them on other places on the internet.

### What is Reciprocity and why do u need this table?

Most of the time, when you plan to do a long-term exposure, longer than one second, you will see the effect of reciprocity.
In simple terms, Reciprocity means, that when you expose your film to the light for (most of the time) longer than one second,
the effect that the light has on the emulsion is reduced. Therefore you have to alter your exposure time to get a correctly exposed image.
Also, reciprocity could take effect, when you expose your image for a shorter time than 1/1000s.

The following tables give you the start time (the exposure time you plan to shoot at) and the corrected time (the altered exposure time).

### How to calculate reciprocity correction.

Most film manufacturers provide you with graphs on which you can search for your measured time and then read your corrected time. But most of the time you do not find the exact time you measured, that ´s why some of the manufacturers provide you with the so-called (most of the time) “P factors”.
With that given “P factor” and the following Formula, you can calculate your exact corrected exposure time. Please note, that with some Films, the reciprocity curve is not linear. Means that most of the time the formula only works with higher measured exposure times. Mostly 50s+ (usually you find further information in the datasheet of the Film.)

Here is the Formula.
Tc=TM^p (TC= Time Corrected TM= Time Measured p=1,31 (P is a factor calculated following a range of exposure times) )

Warning: Some of the times were as already mentioned taken from other online resources, some were calculated by myself. I can’t give you any guaranty! Use at own risk!

### KODAK TRI-X

Kodak´s official Reciprocity Diagram ends at 100sec measured time (1,40min).

Thankfully the friendly support of Kodak, provided me with “P factors” so you will be able to calculate values from 50s+ with that factor.
Note until a measured time of 50s the formula will not work, since until 50s the light curve is not linear. Keep that in Mind. :-)
For Tri-X, the “P factor” is 1.54.

The values of them are calculated using the given “P factor”. I stopped calculating at 20m measured time
since to me it started making no sense to use even longer times.

 start time 2s 3s 4s 8s 10s 15s 20s 30s 40s 1m 1,40m 3m? 4m? 6m? 10m? 15m? 20m? 30m? 1h? corrected time 4 8 15 36 50 1,35m 2m 3,3m 5m 9m10s 20m 49m 32s 1h 17m 2h 24m 5h 16m 9h 50m 15h 20 XXX XXX

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### KODAK T-MAX 100 (TMX)

Times were taken from another online resource, I could not find an exact table in Kodak´s datasheets.
I calculated the times from 1m with a “P factor” for T-Max 100, which was also given to me, directly by Kodak.
The “P factor” is 1.15

 start time 2s 5s 10s 15s 20s 30s 1m 2m 4m 10m 20m 1h corrected time 3 7 15 25 35 50 1m 50s 4m 6s 9m 6s 26m 6s 57m 55s 3h 24m

### KODAK T-MAX 400 (TMY)

For Kodak T-Max 400, I Also got the “P factor” directly from Kodak.
The “P factor” for Kodak T-MAX 400 is 1.24. Also, keep in mind that this value only works from 50s (measured time ) up.

 start time 1s 10 15 20s 20s 50s 1m 2m 4m 10m 20m 1h corrected time +1/3stop 15s ca. 25s ca. 25s ca. 35s 2m 8s 2m 40s 6m 18s 14m 54s 46m 25s 1h 49m 39s 7h 08m

### ILFORD HP5 Plus

I calculated the times based on the datasheet of Ilford with the following formula also mentioned in the beginning of the article: Tc=TM^p (TC= Time Corrected TM= Time Measured p=1,31 (P is a factor calculated following a range of exposure times, provided by Ilford) )

You can find the Values for the different Ilford film HERE

The Reciprocity calculator app for Ilford gives me extremely different times. So I decided to go with the values directly from Ilford’s data sheet.

 start time 5s 10s 15s 20s 25s 30s 1m 2m 4m 6m ? 10m ? 20m ? 1h ? corrected time 8s 20,4s 34,7,6s 50,6s 1,08m 1,26m 3,33m 8,49m 21,52m 37,12m 1h 12m ? 3h 7sec ? 12h 39m ?

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