Red filter compensation

[gmed]

Red filter requires a 3 stop compensation (factor 8). But to me, this is 2 stops too much. Using my meter, I only get one stop. Ive used 3 stop compensation when metering, and this totally over-exposed my photo.
I use the Expo dev app, and I usually put it on the Yellow filter instead of red.

What do you guys think about this?

Gevork

[E. von Hoegh]

Red filter requires a 3 stop compensation (factor 8). But to me, this is 2 stops too much. Using my meter, I only get one stop. Ive used 3 stop compensation when metering, and this totally over-exposed my photo.
I use the Expo dev app, and I usually put it on the Yellow filter instead of red.

What do you guys think about this?

Gevork

Three stops sounds about right (IIRC) for a red 29. Some films need more, some less. I'd go with what the film manufacturer reccomends for starters. You didn't say which film, or which red filter, r23, r25, or r29? It makes a difference. I'm not familiar with your app.

[vinny]

If it works, why the hell not.
Filter factors vary by film type, it's not cut n dry.

[gmed]

Sorry, its a red 25. HP5. Red 29 may need 3 stops, but 25A, 3 stop seems too much.

[Andrew O'Neill]

For me, a 1 2/3 stop increase is enough with the 25 and HP5. BUT, I increase development as there is some loss of contrast with this combination. It really depends on the film.

[cowanw]

It also depends on the subject. A red rose may need no compensation at all.

[Drew Wiley]

Three stops is standard with 25 red and any typical pan film, including HP5. If you're using
a different factor, it's probably because your meter is reading things funny. 29 red is a
little different story because certain films, namely Fuji ACROS and Efke 25 are othopan
and can't take this degree of red without truncating shadow values. Then a few extended red films have been made, like Tech Pan. But otherwise, the performance of a 29 red is quite predictable, that is, per gray scale, though the presence of certain strong colors
in a scene might warrant creatively skewing this formula per "previsualization" (in case
you're an AA wannabee).

[gmed]

I dont think its reading funny things. I have a brand new Sekonic 758.
Ive read in other threads than red filter needs more like 1.5 stops, rather than the stated factor of 8 (3 stops).
My main subject is landscape. I use it to daken the sky. I have since switched to Tmax 100.
Mybe I should just meter through the filter, that way there is no guess work.

[Bob Salomon]

A filter factor is just a guide. Read through your meter and, if you like what you get, use it. But your final result will vary with exposure and development. So test and see what you like and then use it. Tailer the results to your liking. But a filter factor of 8 is the usual starting point. Heliopan states that if you are metering with a TTL system that you should set the exposure correction on the metering system to +1, except with Tech Pan film. They also state in their guide that the filter factor is "approximately 8x". Not that it is 8x.

[Steve Smith]

Mybe I should just meter through the filter, that way there is no guess work.

But there is more uncertainty as meters vary in the way they work through a coloured filter. Some are more sensitive to red than others.


Steve.