Yellow, Orange, Red Filter Factors?

[jamgolf]

I have a simple (or perhaps not so simple) question. I've purchased Heliopan Yellow #8, Orange #22, and Red #25 filters. According to the specs, Yellow has a compensation factor of 1.5 stops, Orange 2-stops and Red 3-stops. However, when I take a spot meter reading in EV mode with a Sekonic 758, the difference in readings between a straight reading and one through the filter is 0.6 stops for Yellow and 1.1 stops for Orange filter.

I want to trust my own readings, but I am confused by the difference. I have taken readings from different subjects ... sky, stuff around the house, ground, etc. and the difference in EV readings is never 1.5 stops for Yellow or 2 stops for Orange.

This has me puzzled. What am I not getting? What is the correct compensation factor to use?

[paulbarden]

The filter factor given by the manufacturer can be trusted.

[jamgolf]

Thanks, Paul.
I usually trust whatever the manufacturer specs say, and will probably just use the compensation factors per specs, but I am definitely confused by the EV readings.
I mean I trust the light meter to provide a correct exposure value when not using a filter, it feels very strange to ignore the meter when using a filter.

[Mark Sawyer]

I want to trust my own readings, but I am confused by the difference. I have taken readings from different subjects ... sky, stuff around the house, ground, etc...

Use a grey card in daylight, not colored subjects in whatever light source is around the house. Also, meters wander. Paul is right, trust the manufacturers.

[jamgolf]

Thanks, Mark
I have actually taken readings in daylight and the difference in EV values is ~0.6 for Yellow and ~1.1 for Orange filter.
For instance, on a sunny day, I take a reading off a puffy cloud in the sky the reading might be 15.7 EV and if I put a Yellow filter in front of the spot meter the EV value is 15.1 - for a 1.5 stop compensation I would expect the reading to be 14.2.

While I do not have a Kodak 18% gray card, I do have something close to it.

[Sal Santamaura]

There are three variables involved. The spectral response of your light meter. The spectral response of each film. And the spectral composition of the scene, which is a product of both the subject and the light falling upon it.

Therefore, there's only one answer: test, test, test.

[Alan Klein]

Do you trust the film manufacturer's recommendation on their specification sheet or the filter manufacturer's recommendation?

[jamgolf]

Alan, I would like to trust both the film manufacturer's recommendations and the filter manufacturer's recommendations.

But as Sal said "test test test" and that's what I have been doing with films and developers etc. and same thing here - instead of blindly accepting the compensation factors, I thought let me check the differences in EV values with/without filters - but I am a bit surprised and confused by the EV readings - so I thought I should ask if I am misunderstanding something.

[Pieter]

Just shoot some film with the factor as specified and the metered-through-the-filter reading (not always accurate, by the way) and maybe bracket, too.

[Tobias Key]

I got a similar set of filters recently and I found the readings I got putting the filter over my spot meter did not correspond to the filter factors at all. I just used the manufacturer's recommendation and haven't had any problems.