Metering question regarding filter use...

I was reading that you can simply place your color filter over your spot meter lens when taking a reading... to account for the filter factor. Using a red filter, they say add about 3 stops to your exposure, but if I meter thru the filter itself...it usually tells me different (more or less).

Is this possible to do this with all filters and all spot meters? Or, is this only possible with meters like the Pentax Zone VI and Pocket Spot Meter which are made for black and white film.

Thank you.

A lot has to do with what you are measuring. Since a red filter will darken the sky, you don't want to use it to meter the sky. Similarly, a yellow filter shouldn't be used to measure a blue sky or you will have overexposure in the shot.

Figure out the effect you want and then play with it a bit. Meter a gray card to see what your compensation is, but it still takes a bit of experimentation to get things right. tim

This was a highly touted feature for the Zone VI modified meter. I used it that way until I finally figured out that it didn't work. Use the filter factors. You will save yourself a lot of thin negatives.

In addition to the points already mentioned, there is an issue with the spectral sensitivity of the meter itself. With some, the sensitivity drops off at the red end of the spectrum, so it's easy for the meter to be fooled. I'd agree that filter factors, after some personal testing, is the way to go.

I agree with most everyone else. I get better results by simply applying a filter factor than through measurement for an individual shot.

What sparked my interest in this was reading one of the ZONE VI Newsletters regarding their spot meter, and how you can meter it at different things, using a color filter on the end, and get different readings for what the correct exposure would be.

Fred went thru a project of trying to get separation from a sky and a gray building. He metered with a yellow filter, and they came out the same zone. He metered with a orange filter, they came out the same. finally, he used a red filter, and when he metered the suject and sky...it said there was finally a tonal separation between the two.

I thought this might be useful, but I guess I will stick to the normal methods.

Thanks.

Supposedly, the Zone VI-modified Pentax meters were "corrected" to provide even response across the visible spectrum. If so, what you describe might work. But, not having tested one, but having read conflicting reports, I'm still in the dubious camp.

With either the Z6 modified or Pocket Spot, I know that metering through the filter gives the correct reading for what might be called BW films with average or normal spectral sesnsitivities. It will not work for IR, red enhanced, or UV sensitive films without some experimentation. This is the point and it does work. To test my Pocket Spot, I photographed a gray card based on the meter reading and then added different filters to the mix. Measuring the density on the developed negative showed almost no variation, less than 0.05.

Hard to know what other meters do. Most meters made today use a silicon cell that sees light very well in the red and near IR. I think meters should (I hope) as a minimum, filter out the near IR (650nm to 1050nm and beyond). To further correct the spectral responsivity of the silicon sensor requires a filter or filters to take out the red, besides the near IR, and shape the green and blue to get the correct 'gain' silicon cell.