Polarizing Filters

MightyMike wrote:

manual_focus wrote:

PeterPentax wrote:

manual_focus wrote:

One additional note is that while the camera settings were the same, the shutter speed was two full stops difference (1/1600 sec vs 1/400 sec) without and with the filter. The CPL is removing a lot of polarized light which accounts for the differences

CPL's darken the light from an image. Due to their nature, they darken polarised light more than non-polarised light.

You need to take this into account when you use CPL filters. Your shots with the filter look under-exposed to me.

Yes, the CPL reduces the amount of light getting to the sensor because it is not clear glass and because it blocks light of a particular polarization. With my CPL I needed to increase the amount of light to the sensor by four fold (2 stops). Your description of a CPL may need some more thought. See: https://en.wikipedia.org/wiki/Polarizer#Circular_polarizers

Interesting as to your comment that the filtered images (on the left) look under-exposed.

I disagree, the pictures on the left look decently exposed, the effect makes them appear a bit darker but check the whites, they're still exposed ideally.

Who am I to argue? I can say this. The highlights would blow out with a longer exposure. Take a look, I used multi-pattern metering and still had to dial it down -1.0 to -1.3 eV. so as to not blow the highlights (white columns) out. The RGB luminous values for the columns are around 240s. It is not under-exposed.