PhotoVision Calibration Target vs Expo Disc

Yesterday I read a long forum post where a couple of folks were debating the virtues of both of these tools, the PhotoVision Calibration Target and the Expo Disc. 

I own both tools but I largely use the PhotoVision Calibration Target.


Both sides of the argument were making some sense (to me anyway) so I thought I do my own tests. I know I did this a while back but wanted to redo this as I did not recall the original results.

So I put my Canon 7D/24-105mm on a tripod tethered to Lightroom. Using a 3 light setup with a 36" octa as the main, a 30" brolly box and 20 degree grid spot as an accent light. Having metered my setup with my flash meter I know the correct exposure is f/5.6 ISO 100 at 1/125 shutter speed. So let's see what the White Balance tools say.

First photographed the PhotoVision Calibration Target at f/5.6. Here is the result:

As you can see from the histogram this is pretty much what I expected to see. A perfect exposure. I sometimes like to underexpose a tad so I re-shot the target at f/6.3:

Again about what I expected to see. Next I shot several Expo Disc images:

 What I found was that in order to get a center spike I had to open up to f/5, which would over expose my image. Not what I want to do.

Here are the results of both tools shot at f/5.6, the LR settings on both images are identical except for WB which was based on the respective tool:

PhotoVision Calibration Target

Expo Disc

The skin tone is slightly off here.


I guess I'll be staying with the PhotoVision Calibration Target. I suppose I may have done something incorrect in my test here but if so someone will have to point it out to me, as I don't see it. I'll upload these files to my Flickr site if anyone wants to see the full size image. If you have comments or questions please post them.