To use a polariser or not

merv

merv

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Mervyn
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Was out today in lovely sunshine by the sea with blue skies and white clouds. Put a polariser on my Nikon 24mm f2.8 AF D lens on my D4. Yes the photos came out lovely and blue but they were often really underexposed. I know to use the polariser at 90 degrees to the sun. Perhaps I should also have used ND grads to tone down the sky but had neither time nor tripod or filters.
Beginning to think a polariser is not always necessary. Any comments would be appreciated
MERV
 
A little more info would be helpful. Was it a circular or linier polariser .Linier can confuse the metering. Were you using manual setting . maybe your calculations were out.
 
A polariser will usually take up to 2 stops of light depending on its rotation so if you're not letting the camera meter you'll need to add compensation for that. The benefit of shooting digital is that you can see you're under exposing as you shoot and adjust.
 
Also, sounds like you might have been metering off the sky which is always going to give you underexposed land on a sunny day whether you have a polariser or not, without using a grad. You don't need to use a tripod to use filters. Standard Cokin p holder with stacked grads/cpl can be left on to walk around with.
 
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Thanks. It was a circular Hoya polariser. I was on Matrix metering and aperture priority and do realise that this is trying to average the scene and if the sky is bright, which it was this will dominate the overall exposure and stop the camera down darkening the land. Yes filters would have been the answer. I normally find there is always a 2 or 3 stop difference at least between sky and land.

Good point I should have looked at the histogram and it would have been staring me in the face. I suppose I could have tweeted the exposure compensation but there again this would have blown out the sky - maybe.

Thanks guys
 
I suppose its never necessary as such. I must say I may use it for the wrong reasons. I tend to put it on to enhance colours and blue skies but sometimes it does seem to overdo it. I know it can be used to cut glare on water. I always set it to the maximum effect and thats probably the wrong way to use it. Ive been going through my shots today and am noticing that in the viewfinder the exposure looks great but on my Macbook the photos definitely look darker. The histograms are also fairly spread out from left to right. Is this a monitor brightness or calibration issue?
 
merv said:
I suppose its never necessary as such. I must say I may use it for the wrong reasons. I tend to put it on to enhance colours and blue skies but sometimes it does seem to overdo it. I know it can be used to cut glare on water. I always set it to the maximum effect and thats probably the wrong way to use it. Ive been going through my shots today and am noticing that in the viewfinder the exposure looks great but on my Macbook the photos definitely look darker. The histograms are also fairly spread out from left to right. Is this a monitor brightness or calibration issue?
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A polariser will make things darker. It darkens blue sky, and removes reflections off the shiny surfaces of foliage. There are always some leaves or fronds of grass etc that randomly fall at the right angle (30-40 degrees to the surface for reflections) so the polariser removes those reflections, making them darker, greener, more lush. That's why landscapers love them. Exposure may still be technically correct, but if that's too dark, then increase exposure.
 
In theory shooting in Av the camera should automatically take into account there is reduced light reaching it & set exposure accordingly but obviously as said one effect of a CPL is to darken/richen the blues & greens in a scene.
 
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