By: Erik Vlietinck
Wed, April 11, 2007 - 8:18:00
Pros: 0

http://www.expoimaging.com
Score: ">

Imagine a scene that you want to catch with the object closest to your camera in focus, and all the rest out-of-focus. Or imagine that you want to capture as much of a scene sharply. Traditionally, you’ll have to calculate the depth-of-field or look it up in a table. Enter the ExpoAperture, a rotating dial guide that will tell you the maximum and minimum depth of field for a given focal length and aperture size.

We’ve learned that the smaller aperture will give you the larger depth of field, while the larger aperture (smaller f-number) will give you the smaller depth of field value. However, this is not always correct, at least not one-on-one. In fact, every lens type has its hyperfocal distance, which will give you the largest depth of field at a given aperture. You can calculate this distance by carrying a calculator with you, every time you go out to take photographs. Or you could buy ExpoImaging’s ExpoAperture guide.

The ExpoAperture depth-of-field guide is a set of rotating discs made in sturdy plastic the size of a man’s hand. It is small enough to carry with you in a breast pocket, and it will tell you in an instant the depth-of-field value for any given aperture, the aperture you’ll need to get a specific depth-of-field, and the hyperfocal distance of your lens type at any given aperture.

The Guide works with focus zones. If you want to know how large your depth of field will be at an aperture of f11 with a 50mm lens, you can find out by first selecting your “circle of confusion”, then dialing to your lens size and reading the number of focus zones under the f11 mark. Flip over the DOF guide and you’ve found distances between which the photo will be in sharp focus.

You can work in a number of ways with the Guide, including finding the right aperture for a desired depth of field. The only disadvantage that I found with it is that the distances are all in feet and inches. This is fine for people living in the US and the UK, but much of the rest of the world --and certainly continental Europeans-- live with metric measurements. If the Guide were available in metric units, it would be perfect.

As it is now, it requires an extra conversion from feet to metric which is not very comfortable. On the other hand, the Guide does make tables with depth of field values a thing of the past. It ‘s much easier to carry around a small dial than it is to carry around a booklet with values, or worse to calculate these values from the top of your head.

I for one found the conversion from feet to meters a small effort to know what I can expect in terms of depth-of-field in any given situation.