Let me suggest something else to you. When the light won't allow you to shoot at a higher aperture, you may need to resort to something called "focus stacking." It's a process whereby you take multiple images of a scene focused at different distances from you and using a special software to blend all the focused images together. Often, due to a lack of the ability to select an appropriate aperture and shutter speed to achieve what you want in focus, that's the only way you can get a totally focused image from the front to the back. Google "focus stacking" and read about it. There is free software available for download that will stack images or you can buy software for it. Here's a good url to read about it:

http://www.cambridgeincolour.com/tutorials/focus-stacking.htm

Gessman,

Without an understanding of DOF, none of that will make any sense.

Ron,

Here is a link to a tutorial that MWAC did last summer that will get you started on Depth of Field.

http://www.uglyhedgehog.com/t-41242-1.html

Enjoy and keep taking photos!

According to your EXIF, you were actually a distance of .56m from the butterfly that was in focus. That equates to 21.84", not 5 feet. Therefore, the butterfly that is in focus is tack sharp, however, the butterfly that was an inch or two closer (the one on the left) is no longer in focus.

The EF-S17-85mm lens is an 1: 4-5.6 lens. To get both in focus, you will have to shoot at about f8 to get away from the DOF issue. In other words, a macro type lens. My EF-S18-135 1:3.5-5.6 is marked as a macro (.45m - 1.5 ft) or 18 inches, however, that is at focus point, not necessarily at the DOF I would desire. I'm not sure if you have the same marking on your lens barrel or not, you might look.

In reality, you have a very sharp photo of the butterfly on the right...enjoy that. Sorry that you didn't get them both in focus, but hope this helps resolve your question.