I have never really been into ‘view finders’ when plein air painting. These are usually square cutouts you hold up to frame and isolate the scene so you can get a better handle on the composition and how to paint it. Many artists make their own just by cutting a square out of a piece of cardboard or matting board. Here is some info on using a viewfinder. While in the field if I need an aid, I usually just hold my hands up or use my camera as a viewfinder.
When I was at the PAPA paintout several weeks ago, Kevin Macpherson was using a viewfinder which I thought was really worth getting…well actually, I just had to have one!! It is made by Artwork Essentials. It comes with a dry erase marker, so you can actually draw your scene on the viewfinder as you hold it up. It also has a value bar with three peepholes to better isolate and judge values in the scene. It comes in two sizes, a 6×8 and a 3×4, so I ordered both.
I tried it out yesterday at Elkhorn Slough and it worked great! I did find if you are sketching on it, you need to prop it on the top of your easel or other support to get a good sketch.
One of the other features I especially liked was the hairline partitioning of the viewfinder. The hairlines partition the scene by thirds both horizontally and vertically. On the larger viewfinder, the “Golden Section” is also indicated with slightly smaller hairlines. I won’t go into details about these rules of composition other than saying generally put the center of interest somewhere along the one third line intersects. This viewfinder makes doing so a snap. You can read more about these composition rules here.
All-in-all, this is the handiest tool I have seen in a long time! Both viewfinders are very affordable at around $10 and $4.50 depending on size. You can get more info and order it at:
http://www.artworkessentials.com/products/accessories/Viewfinder/VF68G.htm