Filter compensation?

[Skinny McGee]

I can't remember my Filter comp. I am going to shoot in the morning and some times when it is really bright out I need a filter.. also I would like to see some of the effects that my filters give..


yellow
orange
25a red
blue

These are all leica filters but i assume they are standard.

Thank you for any help you can give me as far a compensating for the loss of light do to the filter I am using a spot meter .

Thanks
Skinny

 

[VictorM.]

What works for me (but will vary with the actual filter and the film): yellow 1 stop, orange two stops, red 3 stops, blue?. The reality is, I use filters far less than I did thirty years ago. The need to adjust the tonal response of b&w film just doesn't seem to be the same. I find neutral density filters to be the most useful, especially with Tri-X outdoors.

 

[richard_l]

I have some old Leitz filters. I've measured their effect in different lighting conditions, and I think my numbers are in the ball park. Your filters may be different, however. Nothing is very standard about filters, not even Leica filters. Fortunately the exposure compensation needed is not very critical.

Leitz yellow (1) - filter factor: 1.5x (+2/3 stop)
Leitz orange (Or) - filter factor: 2.5x (+1 1/3 stop)
Hoya red (25A) - filter factor (according to Hoya): 2.5x (+1 1/3 stop)
Hoya yellow (K2) - filter factor (Hoya): 2x (+1 stop)
Hoya orange (G) - filter factor (Hoya): 2.5x (+1 1/3 stop)
B+W red (090) - filter factor (B+W): 5x (+2 1/3 stops)
B+W red (091) - filter factor (B+W): 8x (+3 stops)

I don't have a blue, but the B+W light blue filter is 1.5x (+2/3 stops). If the 1/3 stop increments bother you, just use 1/2 instead of 1/3, and 1 instead of 2/3.

Richard

 

[Roger Hicks]

Interesting, Victor, I use 'em more than I did 30 years ago -- and almost never ND.

Richard: what's the spectral sensitivity of your meter? Some are over-sensitive to red and will give falsely low readings for red; yours look a bit low to me.

And there's always the point that Kodak T-grain films are disproportionately sensitive to orange/red and disproportionately insensitive to blue and will therefore show far less effect under yellow-orange-red filters.

Then there's the color of the light you're shooting under. In warm morning or evening light the Y-O-R range will have less effect, a blue (which I never use) more.

My own rule of thumb with anything except T-grain, all for mid-range filters, is Yellow 1 stop (2x) Orange 2 stops (4x) and Red 3 stops (8x) but a weak Y can be 1/3 or 1/2 stop and a strong Y over a stop, with comparable variations for the others.

Incidentally Richard is dead right that it's not very critical anyway.

Cheers,

Roger (www.rogerandfrances.com)

 

[richard_l]

Richard: what's the spectral sensitivity of your meter? Some are over-sensitive to red and will give falsely low readings for red; yours look a bit low to me.

That's probably true. It's a Gossen Digisix, which uses an SBC sensor. However, except for the two Leitz filters, the filter factors are from the manufacturers. The Hoya 25A red seems especially low. I'll try to remember to check it with my meter.

When using Scala slide film, I just trust the M6 meter to have a sufficiently flat spectral sensitivity curve. Life's too short to agonize over filter factors. 😎

Richard