Canon 7D Frames per Second Analysis

Conclusion: The Canon 50D, when shooting with manual exposure and manual focus, will deliver the rated 6.5 frames/second no matter how dark it is. However, the Canon 7D has a different behavior and under very dim light conditions, will reduce its shooting speed from 8 to 4 frames/second. Again, this is with the camera in full manual - so while the 50D is "dumb", the 7D is trying to do something "smart" that causes it to slow down under very low light conditions.


I've been pretty happy with the Canon 7D I recently acquired, and the eight frames per second is like a machine gun. However, some Internet postings mention under certain low-light situations (and when using slow glass), the frames/second drops dramatically, even when using manual exposure and manual focus. Here's a quick test to find out.

First, I downloaded XNote Stopwatch which is a Windows application that will display the time in hundreds of a second running on a laptop. The Canon 7D is mounted on a tripod with an 18-200 lens zoomed at full telephoto with max aperture of F/5.6. An ND4 filter is attached to cut the light even more. I shot three sequences, all with manual exposure and manual focus ... so the camera (standard settings with JPEG only) should just rip through the frames, not worrying about anything.

I turned the laptop brightness all the way down and at F/5.6 & ISO 6400, the image was still underexposed at 1/100 second, but I didn't want to go any slower for burst shooting. The Canon 7D would consistently only shoot four frames/second!

If I cranked the laptop brightness back up, (but changed nothing on the camera), it would then shoot eight frames/second. For grins, I shot a third sequence with the ND filter removed at ISO 1600 and 1/200s ... it squeezed in one more shot, but probably more due to the faster shutter speed.

I did the same tests with the Canon 50D, and no matter what the light conditions, it would shoot at 6.5 frames/second when in full manual, even when shooting in a pitch black room. I consider this an interesting oddity of the camera since I'd rarely "machine gun" in light as low as F/5.6, ISO 6400, and 1/100s (which underexposed), but there does seem to be something different about the Canon 7D versus the 50D. Assuming the metering is the underlying issue, an easy firmware fix would be to stop the "meter check" when in full manual after the first frame of a burst ... since you really only need it before shooting. The Canon 7D images are below with EXIF. You can also look at the shot times (they both record to a 1/100 second), and the summary data is:
    13 shots in 2.90 seconds - Sequence 1 demonstrating slowdown
    23 shots in 2.98 seconds - close to rated 8fps, even with 1/100s shutter speed
    24 shots in 3.01 seconds - shutter speed bumped to 1/200s
Note: You can also simply shoot in a pitch black room to see this behavior! ;-)

Use the controls to play, step, pause, slow-down, and/or speed-up the animation.

I welcome any comments/suggestion on all this - back to the main Canon 7D versus 50D page