Black and white contrast filters.

[Gary Holliday]

How much of an increase in contrast do the basic black & white camera filters (yellow/ orange/ red) increase in strength with relation to graded darkroom paper?

To make myself clearer, does the jump from an orange to a red camera filter relate to whole increase of grade in printing paper?

Perhaps there are too many variables in the process for an accurate comparison?

Thanks

[Nick Zentena]

Red blocks everything but red. Orange blocks all blue and various amounts of green.

So the increase in contrast depends on the scene. A red cloak wouldn't change. A green one would go all black with a red filter. A blue would go black with both.

So how much has contrast changed?

[Gary Holliday]

I'm aware of the effects of filters on colour. I'm asking how does this relate to in contrast grades?

If you have the same blue sky and use a yellow, then an orange filter. Could this relate to a 1 and a half grade increase? Perhaps no-one has tried to measure this.

[David Brown]

Perhaps no-one has tried to measure this.

Perhaps because there is not a direct relationship. As I understand it, color filters in B&W photography effect the relationships of the various colors' "values", but not contrast across the entire spectrum.

[JBrunner]

How much of an increase in contrast do the basic black & white camera filters (yellow/ orange/ red) increase in strength with relation to graded darkroom paper?

To make myself clearer, does the jump from an orange to a red camera filter relate to whole increase of grade in printing paper?

Perhaps there are too many variables in the process for an accurate comparison?

Thanks

Hi Gary.

The filter won't alter any real contrast beyond some gain from reduced chromatic aberration, depending on the lens. It can alter apparent contrast, by the transmission effect, but it is a printers choice once you get to the darkroom. In general, I don't print at a grade any different than I would have without, for the way I exposed and developed a particular neg. A color filter can raise or lower apparent contrast just as easily, depending on your decisions, and the scene before you, hence the lack of a defining parameter for printing.

[matti]

Interesting question. I suppose if an orange filter cuts the colour of the sky by four stops you could measure it with a spot meter to actually place it in the right zone to calculate the contrast change. Is it possible to read out the filter diagrams like that and calculate it?
/matti

[matti]

Hm, I wrote contrast change... what I ment was a need to change the contrast by development to place the dark stuff in the right zone.
Contrast is a bad word... I will never get it.
/matti

Interesting question. I suppose if an orange filter cuts the colour of the sky by four stops you could measure it with a spot meter to actually place it in the right zone to calculate the contrast change. Is it possible to read out the filter diagrams like that and calculate it?
/matti

[Thomas Bertilsson]

I suppose you could measure through the filter to accurately meter your shadows. But I don't think the shadows would change much since they reflect so little light anyway.

Since white light is a component of all kinds of light, some of that will be filtered out by an orange filter. So it would depend on the colors of light that your subject matter reflects. If you had a blue wall and you photographed it with an orange filter and compensated for the extra 'density' the filter presents, should you change how you print it? If you have a wall that's half white and half blue, would that make a difference? What if you have a wall with the rainbow painted on it? Lots of questions. Use of filters I think is more about suppressing certain colors and bring forward others. That could well increase the contrast between clouds and blue sky, but at the same time it could lessen contrast somewhere else in the same scene.

I don't think it can be measured that way.

- Thomas

[Michel Hardy-Vallée]

If you photograph a grayscale step wedge through various filters (yellow, orange, red), you will find that the resulting negative will not show differences in contrast.

Color filters simply change the relative amount of specific wavelengths in the light falling onto your film. What's more, different films react differently to the color of light (that's their spectral sensitization).

With real-life subject, a color filter will thus change the distribution of tones, but not the contrast.

[Gary Holliday]

I believe that some answers are purely academic arguments! The filters are termed 'contrast' filters throughout the entire industry. I will run a film through with each filter and do a test in the darkroom to compare 'apparent contrast'. This will help finely tune the print.