Why Use a Diopter?

By David Cobb

I photograph flowers, mushrooms, and small creatures often, and I like to make them look larger in the image and also create an even background or a nice bokeh. For this effect my primary tool is to use a Canon 500D diopter. The diopter simply screws onto your lens like any filter, and acts as a magnifying glass on your lens. Don’t be confused, there are two diopters in photography and I’m writing about the close-up filter not the eye piece on the back of your camera.

I like to use this on my 100mm macro lens sometimes with a combination of extension tubes and also on my Canon 70-200mm lens in conjunction with my Kenko Pro 1.4x teleconverter. For techniques such as selective focus and “cramming” this tandem of a zoom lens and diopter combines for a wonderful effect. It also enlarges my subject to fit my tight compositional style. The skunk cabbage seen above was only a few inches high and in pristine shape. When these flowers get larger they lose their rich color and have too many blemishes, but when they are small they are beautiful subjects. My goal was to make my small subject seem large, so in tandem with my zoom lens I added a diopter (see above). Of course, putting more glass in front of your lens hurts quality, but I don’t lose speed like I do when using an extension tube. I find the Canon 500D to have the best quality out there and you can use it on any make of lens.

Cramming or “shoot-through” is a technique I often use during wildflower season. I use my Kenko Pro 1.4x, my Canon 70-200mm lens and a diopter. I place my lens directly against a flower and simply shoot through it to create a nice wash of color within the composition. I prefer to use a diopter whenever I use this technique (see below).

Using a diopter on a lens cuts down on depth-of-field and this can be a good and a bad thing. So, use it when you don’t need much. I like it on my 100mm macro after stacking extension tubes too, which creates some nice abstracts when photographing the Yellow Salsify seed pods.

The diopter also allows me to get closer to critters, and makes this tiny Rough-skinned newt seem like marauding giant.

Diopters are fun and just another tool in the box, but for me they’ve become an important tool in my creation of images.