opteka professional wrist grip strap review
I bought this strap to use with my 40D. I was shooting a lot of bouldering competitions and was playing with holding a remote flash in one hand and the camera with the other. I got some great shots, but the trouble was, I couldn’t really operate the camera with one hand. For example, after shooting a couple of frames, I would want to switch to playback mode and review the images. I found I couldn’t press the “play” button with the hand holding the camera. So I was left juggling the camera and the flash.
I thought that with this strap, I would be able to completely hold and operate the camera with one hand. Unfortunately when you have your hand in the strap and the camera is completely hanging off one hand, you CANNOT reach any of the buttons. You can BARELY reach the shutter release button. The problem is the camera hangs down, leaving your thumb way above any of the buttons. If you want to press any of the buttons on the camera, you need to hold it with your other hand.
As you can see, none of my fingers are anywhere close to the buttons they need to reach! The only way to use the camera, is the same way you would with any other strap: hold the grip, and use both hands.
Once I came to the realization that this strap was nothing special, I immediately removed it and went back to using the stock strap that came with the camera 
Here’s some more pictures for anyone who’s interested:
