Filter EV change

[esearing]

If I use a red filter to darken green foliage. I know I have to open up 2 stops for more exposure.

But if my foliage metered unfiltered EV 7-9, what EVs should I consider it when filtered? Is the density difference the same as the increased exposure requirement?

Assume that I would place EV7 on Zone IV without filtration.
I still want texture in the foliage so would not want to place it lower than zone III along with other shadow details.
I might use this to darken foliage across a river so the white water and midtone rocks stand out more.

[koraks]

Logically EV5-7 (2 stops less)...or am I being too simple minded?

[Bill Burk]

Literally filter factors are intended to compensate for the density difference. But the purity of the color of your foliage could influence your meter reading and the filter factor was meant for average color, but you have a specific color that is the complement of the filter (so you made things complicated).

I often find meters (at least the old "non-Zone VI converted" Spotmeter V and Weston meters) indicate foliage has more luminance than I would have guessed. That further complicates the idea of basing exposure on foliage, and was a major selling point for the Zone VI meter conversions.

This would be a good place to substitute a gray card. Or at least base your reading off of something that isn't the color you want to suppress.

Simplest approach might be to try the Hutching's method.

These are Gordon Hutching's filter factors you could use. Take meter reading "through" the filter and ... then open up according to which red filter you used.. (*21 light red + one stop) (*25 med red + two stops) (*29 deep red + two stops)

[esearing]

These are Gordon Hutching's filter factors you could use. Take meter reading "through" the filter and ... then open up according to which red filter you used.. (*21 light red + one stop) (*25 med red + two stops) (*29 deep red + two stops)

backyard test. My deep red filter is 3 stops per manufacturer. Measuring different greens in different light the meter difference was 2.5 stops +or- 0.1, while Medium grey card was 3 stops regardless of light.

[Bill Burk]

backyard test. My deep red filter is 3 stops per manufacturer. Measuring different greens in different light the meter difference was 2.5 stops +or- 0.1, while Medium grey card was 3 stops regardless of light.

To use Hutchings' factors, you meter with the filter over the meter... so some of the light is already cut. Then you adjust.

Did you ever notice how with an SLR using it in automatic or with match-needle exposures, the pictures through a red filter are often underexposed? That's because the meter and film don't react the same. So Gordon Hutchings devised a way to adjust for what would otherwise be bad meter readings.

Normally when you do it the other way, filter factors are taken from meter readings without a filter, then you adjust.

[Doremus Scudder]

I've advocated metering through the filter and applying exposure factors for years now. There are inherent inaccuracies due to the different spectral responses of meter and film that affect other things besides exposure (e.g., how a particular color will be rendered, etc.). Still, I think it's the most practical method if one wants an approximate idea of how a particular subject/color will be rendered in B&W.

So, for the OP: meter your foliage through the meter and place it where you want it. This, of course, after you've done a couple of tests to determine your exposure adjustments. FWIW, my exposure compensations for red filters are less than Gordon Hutchings, but I might be using different film/meter than he. Your individual adjustments will depend on your meter and film combination.

If you just want to apply the filter factor, keep in mind that colors complementary to the filter color will be darkened more than the factor, so, if that's what you want fine, otherwise give even more exposure than the factor to retain detail (or don't use the filter at all...).

Best,

Doremus

[LabRat]

Let's rewind, a colored B/W filter creates effect by affecting the spectral response/curve the film sees, with the colors it passes or cuts...Yes, there is a density of the filter itself to be factored for, but the changes happen to the film's spectral response to produce cuts that produce contrast...

So if you wanted to meter through a filter, it means that the meter cell should have to have exactly the same color response curve as your film (but don't)... And different panchromatic films have slightly different curves than other films, and IR + ortho films are different, and at different times of the day, conditions etc... Even the filter factors listed on your filter are suggested starting points, but usually not too far off... So your meter is blind as to what your film is doing...

Then there's tho overall color of the ambient light, time of day, new contrast where the light might be flat or dim, where your shadows get too dark, and needs even more exposure...

You can do testing to see how they compare, and establish new factors for yourself... I have shot some 35mm TTL exposures with good cameras, got lazy about metering with filter on and used heavy filters, and got exposures over 1 1/2 stops underexposed, so IMHO is is risky...

Maybe ok with a pola screen, or light filter, but...

Steve K

[Sirius Glass]

If I use a red filter to darken green foliage. I know I have to open up 2 stops for more exposure.

But if my foliage metered unfiltered EV 7-9, what EVs should I consider it when filtered? Is the density difference the same as the increased exposure requirement?

Assume that I would place EV7 on Zone IV without filtration.
I still want texture in the foliage so would not want to place it lower than zone III along with other shadow details.
I might use this to darken foliage across a river so the white water and midtone rocks stand out more.

1 EV = 1 f/stop
1 Zone = 1 f/stop

But no one can figure that out from the articles and books about the Zone System. Please treat this like highly classified information, because the Zonestas do not want to the world to know that the Zone System can be simply explained. Many Zonestas can only exist if they are doing endless meaningless testing. [/Cone of Silence

[Sirius Glass]

If I use a red filter to darken green foliage. I know I have to open up 2 stops for more exposure.

But if my foliage metered unfiltered EV 7-9, what EVs should I consider it when filtered? Is the density difference the same as the increased exposure requirement?

Assume that I would place EV7 on Zone IV without filtration.
I still want texture in the foliage so would not want to place it lower than zone III along with other shadow details.
I might use this to darken foliage across a river so the white water and midtone rocks stand out more.

*******************************************************************************************

[Cone of Silence]



1 EV = 1 f/stop
1 Zone = 1 f/stop

But no one can figure that out from the articles and books about the Zone System. Please treat this like highly classified information, because the Zonestas do not want to the world to know that the Zone System can be simply explained. Many Zonestas can only exist if they are doing endless meaningless testing.


[/Cone of Silence]