Yup. Your polarizer usually costs you 1.5 stops. Last year I got a Sekonic 558 meter that's almost smart enough to hold down a job. It can be set-up to factor in this compensation thru a second ISO button, giving exposure readings with and without the polarizer.
I had a go with the circ. pol filter on yesterday, with confusing..results?
I set my light meter up to test out what the exact compensation factor would be,
so I had it set to give me readings 1.7/stop wider than normal.
I took two shots in a 10 minute period, right after each other. For the first polaroid
I had the filter turned so that it was un-polarized-looking (?) through the lens.
Exposed that one according to the meter's compensated reading, 1/6 @ f22.
It looked normal enough, sky plain, pretty flat light.
The second polaroid I turned the filter round so it was showing up the contrast
through the lens visibly. Exposed that one for 1/6 @ f16 because the light
was quickly fading and the reading had gone down one stop in the space of
4 minutes. That second polaroid gave me the sky/cloud contrast you associate
with polarizers, but the overall exposure looks muddy, and underexposed.
? Am I not using it right?
You shouldn't meter through a polarizing filter.
Just take a meter reading without the filter (ideally an incident meter reading), and then apply the fixed filter factor to that reading.
Generally speaking, the orientation of the filter should not affect the exposure setting you choose, although every once in a while you'll be working with a subject where there is so much glare from the (unfiltered) subject that a reflected light reading will be distorted.
I have always been under the impression that it was autofocus and not the meter that had problems with linear polarizers, hence the reason older manual focus cameras are fine with the linear variety.
It wouldn't surprise me if there are auto-focus systems that are affected by polarizers. My personal knowledge is based on somewhat dated experience - I worked as a camera salesperson in the 1970s and early 1980s. At that (pre-autofocus) time there were some systems whose metering systems required circular polarizers (Canon and Leica SLRs spring to mind, IIRC) while others didn't.
Originally Posted by chrism
Since then, I haven't had reason to keep track of the issue, because it never has been an issue with my 35mm equipment (Olympus OM - no autofocus) and my medium format equipment isn't autofocus and, with the exception of one metering finder, is also without meters.
Maybe I didn't explain that right..I was using a separate handheld light meter?
Originally Posted by MattKing
Which I had set up to calculate the filter compensation in-meter for me.
You may have run into why polarizers are generally not a good thing.
First (and this is not the bad thing about polarizers), polarizers have an overall darkening effect, because they cut out half of the light (at least - more depending on the material used in the polarizer). They do that always, no matter which way the polarizer is rotated. This is your fixed filter factor.
Secondly (also not quite the bad thing, but already part of it), polarizers darken bits selectively. That's why you use them.
That can however already lead to images appearing too dark, depending on how big the part of the scene is that is affected by the polarizer. The fixed filter factor (of course) does not compensate for the selective darkening effect of the polarizer. But (in a worse case scenario) your entire scene is affected by the filter... If you do not like that, use less polarizer.
Thirdly (another part of the bad thing about polarizers), polarizers can remove reflections. That includes specular highlights in your scene. And there are very many of those in outdoor shots. The result (even if the overall appearance of the resulting image is not too dark) is a dull, flat looking image.
Combined, the effect of a polarizer can be quite horrible.
And it is easily mistaken for underexposure. That, because it is, but selective underexposure. You elected to do that, and it is not (!) fixed by exposing more, but by using less polarizer.
So only use a polarizer when absolutely necessary.
If you should think it is necessary quite often, use your head and eyes, and don't just go for maximum effect.
If you go for maximum effect anyway, look at what that does to parts of the scene you did not pick the polarizer for (it's o.k. to want to darken the sky, but what does that do to leaves, grass, etc.?) You may then want to rethink what you want to do to the sky.
The result (even if the overall appearance of the resulting image is not too dark) is a dull, flat looking image.[QUOTE]
Originally Posted by Q.G.
Thing is, I want to take out the kind of highlights that make an outdoor image look 'normal', because I'm aiming for a look which conjures up the kind of light you might only see in a weird dream, if that makes sense. These are art photographs I'm taking, I'm not a landscape photographer, but I use the outdoors as a 'set' for staged photographs I guess along the lines of Jeff Wall for want of a better reference. So I'm not too worried if I get a weirdly 'flat' light, but I don't want thin, crappy colours that are muddy and bland either.
(And I am phobic about post-production techniques, although I have that option for achieving the right light, but I'd way prefer to get it on film not through a computer.Hmph.)
I certainly don't want it to look underexposed! Maybe there is another filter option I don't know about which would be better for my type of look? I like what polarizer does to the sky, but not much else so far. Like you say, what's happening to the grass/earth/skin, they're just going to be flattened if I take it too dark.
PS. quote thing is not my friend today, sorry. ^
1.7 stops would be the minimum exposure change for your filter. Depending on how you rotate it and the scene it could easily drop the light another 3 stops or more. All depends on the polarization of the light before it tries to pass thru the filter. This is where ttl metering really helps. There are some very good pol filters made where the extinction of crossed pol filters is nearly 100% of visible light, but they are not usually sold for general photography. The effectiveness of pol filters for general photography vary quite a bit, the usual indication of effectiveness is the brand and retail price.
Metering with an external reflected or incident meter just isn't going to work very well. You could get a second filter and mount it in front of a reflected light meter and set the rotation angle to match the one on your camera, but it is a pain and you would really need matching filters with degree markings on the perimeter for it to work very well.
End of ramble. :)