How to adjust a circular polarizer

ElizaMM · Oct 17, 2017

My lens is a Canon IS 24-105 to which I have attached a Hoya Pro 1 circular polarizer for sky/water, etc. How much change in a scene should I see through the viewfinder, or on the LCD? Seems nearly impossible to detect a change, when rotating.

tirediron · Oct 17, 2017

It depends on the circumstances. The maximum change will happen when the sun is low in the sky (shortly after sunrise / before sunset) and at 90 degrees to the lens axis. The higher in the sky, and closer to the lens axis the sun is, the less you will see. In other words facing south 30 minutes after sunrise on a clear morning, the blue sky will turn almost black. At noon, with the sun at your back? Probably 0.0% change.

photo1x1.com · Oct 17, 2017

What are you trying to photograph? Polarizer filters work best on a sunny day, in an angle of 90° to the sun (to achieve a blue sky).
If you have an overcast day, it hardly works at all for landscape photography. You will however still be able to reduce reflections e.g. from glass.
What does not work is reducing reflections from metallic surfaces btw.

benhasajeep · Oct 17, 2017

To get the absolute maximum effect of a c-pol filter. Take your index finger and point it towards the sun. Stick your thumb out to the side to make a 90 degree angle. Anywhere you thumb points is the direction the c-pol will have the most effectiveness. So as you rotate your wrist while pointing at the sun will let you know the 90 degree angle (if you could spin your wrist 360 degrees that is). It will work at other angles but to a lesser degree.

KmH · Oct 17, 2017

As the sun gets 30° above the horizon a CPL starts losing effectiveness at darkening the sky.
The higher in the sky the sun is the less effective a CPL is, and the CPL cannot affect the sky equally across the image frame. and only part of the sky gets darkened.
So on a mid summer day when the sun is about directly overhead and at 90° to the long axis of a level lens a CPL is least effective.

When using a CPL to reduce reflections it's again all about the angles - the angle of the sun to the long axis of the lens, the angle of the sun to the surface the problematic reflection is on, and the angle of the lens long axis to the reflecting surface.

photo1x1.com · Oct 17, 2017

We must not forget about water reflections in all these calculations. I´m a huge fan of polarizer filters and even though the angle to the sun might not be perfect to create the blue sky (even at noon), it still does a lot on reflections in the water - especially in turquoise blue lagoon images of travel brochures. So when shooting landscape: as long as the sun is out and I´m not shooting a sunset or sunrise, I always have the CPL on.

Derrel · Oct 17, 2017

Wow! The original poster has received some most excellent reply as above, covering almost everything there is to know about using a circular polarizer. Yes, it can be difficult to discern the change when looking through the viewfinder. Wow! The original poster has received some most excellent replies above, covering almost everything there is to know about using a circular polarizer are. Yes, it can be difficult to discern the change when looking through the viewfinder.

petrochemist · Oct 18, 2017

Derrel said:
Wow! The original poster has received some most excellent reply as above, covering almost everything there is to know about using a circular polarizer. Yes, it can be difficult to discern the change when looking through the viewfinder.

Well there's nothing yet on combining two for a variable ND.
If both are CPLs it won't work properly mounted normally (the one in front should be a linear pol.) but CPLs front to front works.
CPLs mounted back to back can give some very weird effects.
Finally for the sake of completion polarizers usually transmit NIR significantly more than visible, not relevant unless you shoot IR!

When actually looking to boost or kill reflections I usually find it very easy to see the effect in the viewfinder, but for skies/increasing saturation etc. the effect is fairly subtle & can be much more difficult to see.