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What happens when you use a CircPolarizer in low light
Hi everyone,.

Just got a new Sony A700 and took some shots of a sunset, I mistakenly left a circular polariser filter on the lens. The shots are very very noisy, is it the filter doing this?.

I'm quite dissappointed with the shots, my Sony A100 took better pictures. I;m hoping it's the polariser that has caused the noise and lack of sharpnessThanksJoBal..

Comments (8)

The filter will typically lose you a full stop of light and sometimes 2 stops of light.If the camera is set to AutoISO then the ISO will ramp up and thus the noise.A member of the rabble in good standing..

Comment #1

Joanne Balchin wrote:.

Hi everyone,Just got a new Sony A700 and took some shots of a sunset, Imistakenly left a circular polariser filter on the lens. The shotsare very very noisy, is it the filter doing this?.

You can lose around 2 stops of light with a typical polarizer, depending on how it's rotated (IOW, only 1/4 the light gets through to the sensor)..

So, you may need ISO 1600 with a polarizer to get shutter speeds as fast as you could using ISO 400 without one..

If the Auto ISO was set to where it was using higher ISO speed in dim lighting, then you'd see more noise. You also tend to see more noise in underexposed areas of a photo. So, that could also have been part of your problem shooting into the Sun (which can cause the metering to underexpose an image)..

In addition, if DRO was turned on, that would have increased noise levels (since it's "pushing" some of the shadow areas which increases effective ISO speeds). Anytime you brighten an image later, you're using higher effective ISO speeds..

JimChttp://www.pbase.com/jcockfield..

Comment #2

It's very difficult to talk about a picture if you can't see it. Please post one (with EXIF-data). At the moment I think that this is due to higher ISO, as mentioned before...

Comment #3

Sorry StefH! How stupid of me....here is a sample...be gentle with me, I'm new to DSLRs.

1/30 S @ F/4 ISO 250 - Sigma 10-20m with CircPol.

Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window..

Comment #4

Thanks LM2 & Jim, this info is sooooo helpful to me..

I'm fairly new to the DSLR world, I've just upgraded to a Sony A700 and I was getting really worried that I had wasted my cash. I just needed some reassurance that the problem was me rather than the camera...

Comment #5

As stated you lose about two stops with a polarizer. Also a polarizer does nothing when looking towards or very nearly towards the sun. It needs to be at approximately 90 to 180 degrees angle to the sun. 180 giving the strongest effect. It is good to darken sky, take the shine off leaves and water, take the reflection off of windows if used at the correct angles.http://www.pbase.com/galleries/sascIn the Arkansas Ozarks..

Comment #6

I really don't see a lot of noise in the image, where in particular are you seeing excessive noise?.

It seems a little noisy for ISO 250, but not greatly so. The things other than high ISO that would affect noise levels would heat (was it a hot evening, had there been several shots in close proximity?), long duration (1/30 s isn't that long), and post-processing (has the luminosity level been increased using levcls, curves, etc?)..

The shadow areas in any digital image are always going to be noisier than the highlights..

Brian A...

Comment #7

S Clark wrote:.

As stated you lose about two stops with a polarizer. Also apolarizer does nothing when looking towards or very nearly towardsthe sun. It needs to be at approximately 90 to 180 degrees angle tothe sun. 180 giving the strongest effect. It is good to darken sky,take the shine off leaves and water, take the reflection off ofwindows if used at the correct angles..

90 degrees, NOT 180. The effect is strongest at 90 degrees to the sun and drops of on either side, and is minimal at 180..

Dave.

Http://www.pbase.com/dsjtecserv..

Comment #8

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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