A few question on CPL filters

[Roy C]

First day out with a new CPL filter today -not ideal as there was little sun so the polariser did not make much difference which is fair enough but I have a few nobbish queries:-

1) I understand that leaving a CPL on when not really needed will lost a stop or two of light but is there any detrimental effect on IQ by leaving it on?

2) I noticed that several on my shots were under exposed - I would have thought that with TTL metering the filter would not make a difference OR should there be any special compensation when using a CPL?

Thanks in advance.

 

[odd jim]

A polariser should still make improvements even without sunlight. It still cuts down on reflections and should still improve contrast and saturation.

The camera should compensate and it shouldn't really be underexposing, either via manual metering or any of the auto/semi auto modes.

I would say to remove it though when you don't need it. Theres no point in leaving it on if you don't want it as all you'll donis slow the shutter speed down...