Red Filter compensation

[Jaime Marin]

Im going to be using a Tiffen red #25 filter and wanted to know how much filter compensation I should put in my light meter. Does it block out -1 or -2 stops of light????

[Bill Burk]

#25 Red is 3 stops

[Jeff Kubach]

I agree, it is 3 stops.

Jeff

[2F/2F]

Three stops is standard for a Wratten #25A, but you should always check each filter manufacturer's recommendations in case there are slight differences from the Wratten filters.

[Kevin Kehler]

I often do while using my spot meter is meter a scene, then hold the filter up and and re-meter the scene, using the exact same reference points. While 3 stops is the calculated average, depending on subject matter and lighting conditions, I have sometimes used between 1.5 to 4 stops for the same filter. If in a hurry, I use 2.5 stops; if you are using a camera with TTL metering, the camera will compensate for you.

The other thing to remember is that filters do not always work equally on all areas of the a photograph - if I am taking a picture with trees against the sky and put a red filter in front of the camera, the filter will darken the sky 3 stops. However, the shade under the trees is more blue than the sky: the sky has a blue background but is lit by sunlight, which consists of a number of colours whereas the shade is lighted only by the reflection off of the blue sky (and not the sunlight) and thus has less colours in it. As such, the shade might be darkened by 3.5-4 stops; this is important when placing shadow values.

[Rick A]

TTL metering does not always compensate fully for a #25 wratten filter, most will only compensate up to two stops. It is best to meter a specific scene without and then with the filter to se the difference, then check the results against the manufacturers specs for the filter. Film choice also plays an important part, not all films react the same to filters.

[Pinholemaster]

http://www.tiffen.com/camera_filters.htm

[benjiboy]

According to Tiffen the filter factor of their 25A is 3, and they recommend you open up two stops to compensate for the light loss.

[Jeff Kubach]

BTW if you are going to use the 25A for infared film it might not be dark enough.

Jeff

[Adrian Twiss]

In his book Using the View Camera Steve Simmonds outlines the method used by gordon Hutchings. He meters through the filter and then applies the appropriate factor for filter being used. In the case of a #25 it is two stops.

He expalins that Hutchings developed this system to make sure that a scene's shadow areas receive enough exposure as shadow areas are primarily illuminated by blue light. I have used this method for some time and it works for me.