Grey Card and Dynamic Range

A bit late with this blog post, oops!

I spent quite a bit of time trying to track down a grey card. I needed the grey card for my third assignment from "The Photography Institute" course I'm doing. Grey cards (or at least the one I bought) are a complete rip-off for what they are. But now I have one.

I used the grey card to measure the dynamic range of my camera - here's how: Fix the grey card to an object (outdoors in the shade) and then completely fill the viewfinder of the camera with the card. Set the camera to manual, manual focus, f8 exposure, and then change shutter speed to expose the scene correctly. Take a shot. Increase shutter speed by one stop and take another shot - repeat about 6 or 7 times. Then return to a correctly exposed photo and repeat in the opposite direction. After this is complete, import photos to your computer and you'll see a range of photos from completely black to completely white. Set up a little table of results and get an average RGB reading for each photo (but discard any duplicate completely black or completely white shots). Then count up the number and you have the dynamic range in stops.

Here's the results of this experiment that I did with the Nikon D300.
http://spreadsheets.google.com/pub?key=pJtsF7O3f1aq0Lho49IZQVg

I also repeated the exercise at different ISO's to see what difference they made, but as you can see from the chart, it made no appreciable difference. The shots for the ISO 200 were made about an hour before the other shots, and at a different part of the garden which might account for the slight differences.

I went along to a meeting of the Canberra Photographic Society on Tuesday evening. They had a competition night, which was quite interesting. Many people displayed their works around the room on a pinboard, and then a judge commented on each photo finally giving it a score out of 5. The night was very informative, and the judge very entertaining! Next month I'll be submitting some photos for some constructive criticism.