The Red Filter as a Plein Air Painting Tool: A Problem

Like many outdoor painters, I keep a red filter in my backpack.  A red filter is just a piece of plastic colored red.  I've seen it in many forms - cardboard eyeglasses, a rectangle of lucite, and also framed nicely with an accompanying perspective grid.   The eyeglasses are cheapest at about 50 cents each, and I used to give them away free at my workshops.  The perspective grid model is perhaps the most expensive at around twelve dollars.

Lucky students with their red value eyeglasses

Just as a reminder, the purpose behind it is to help a painter determine relative values.   If you look through it at a scene, everything - trees, lawns, buildings -  will all be seen as different shades of red.  If one shape is a lighter shade of red than another shape, you paint it accordingly.  (Not in red, of course, but in the observed actual color.)

But although it's a great teaching tool, you can't rely on it as an accurate interpreter of values.

It alters vales for certain colors.  Reds turn a little lighter.  Lights, especially white, turn darker.  Green trees and gree fields are observed as being much darker.  If you were to paint them this way, your landscape would look stunningly wrong.  Here's what a scene looks like through mine.  The white reads as darker and the reds a little lighter, and so the letters disappear:

Although there are ways around this - taking an image with your digital camera and viewing it in greyscale might be one way - the best approach is simply to learn how to distinguish values in the landscape.  It's not hard, but it does take practice.

By the way, I mentioned in my last post that the Spring Sale is on!  Visit my Studio Store.