I love the effect a polarizing filter can have when used appropriately; less so the need to rotate the filter around to work out its current orientation.
I like the idea of adding a clearly visible notch or dot to the top and bottom of the rotating ring when the filter is aligned exactly horizontally or vertically, so that I can see at a glance how the filter is oriented and develop a better instinct for the effect (on sky, reflections on water, shop windows, vehicle windshields, etc) before even putting my eye to the viewfinder.
Have any serious photographers marked their polarizing filter for this reason? Do you find it helps you to anticipate the effect, and mentally plan which way to rotate the filter for your desired result, before raising the viewfinder to your eye?
If this is a common practice, can you recommend a way to add a bright mark to the outer ring without risk of damaging the filter or the ring? (A small dot of paint on opposite sides of the circumference ought to be enough, but the thought of wielding a wet paintbrush around the filter makes me very nervous.) Also, what is the best way to determine true horizontal or vertical orientation whilst applying such a mark?
My CP has a mark from the manufacturer but I don't pay it any attention. I rotate it until I like the effect then shoot.
Experimenting with my Highly Scientific™ method, I point it at my computer screen with the mark at 0 degrees top I see a bright screen. Rotating so the mark is at 90 degrees has the strongest effect.
Without this mark would I be able to detect the minimum and maximum effect with high precision? Very unlikely, so I'm not likely to place a new mark very accurately.
If I were to try I'd start with a pencil so I could adjust the mark before making it permanent.
Worth a try. If you want to mark it try this.
Put a rim of tape around at half the rim on the outside. You still want the filter to rotate, so don't stick to the threaded portion.
Aim at a water (use a puddle) when the sun is closer than 45 degrees to the horizon. Stand downlight from the puddle. Orient the filter to minimize the reflection. At this point your filter has vertical polarization. Put a dot or other mark on the tape.
Put a sheet of wax paper on the table.
Put a mark on the wax paper by scratching it with a pen or pencil or kitchen knife.
Remove the tape and set the filter front side down on the wax paper, keeping track of where the mark was, and putting that on top of the scratch on the paper.
Using a toothpick transfer a drop of either white out or finger nail polish to the outside of the rim.
Let it dry. I mean it. Really let it dry. Go have a beer or something.
It's face down so that it's harder glue your polarizer to the threaded slip ring.
It's on wax paper so that you have less capilarity sucking at a spilled drop of goop. You really don't need a 1 inch wide band of your sister's Passion Pink polish on the front of your filter rim.
Might be better to prop it up on a pair of tooth picks. Your choice.
Both goops mentioned are soluble in acetone. Acetone also dissolves many plastics.
Cut a narrow strip of masking tape. Put a dot on the middle of the strip. Apply strip to filter ring.