Canon 7D: Format v. Frame Rate

Over the weekend, I was talking with Kellie. She asked me if it was true that:

Shooting both raw and jpegs lowers the frame rate per second of her Nikon D300s like she was told.

1. I’m not an expert in Nikon. I don’t own one, I’ve occasionally used Nikon and all of my experiences, with Nikon, were very positive. I still chose to buy Canon because of one lens that I really, really, wanted: the 70-200L-IS f/4 that doesn’t exist in the Nikon line-up (and the higher resolution.)
2. This is not a matter of expertise in Nikon or Canon but of understanding the technology. This applies to all DSLRs such as Olympus, Pentax and Sony.

Shooting raw vs raw + jpeg will result in the same frame rate as shooting in raw only or in jpeg only. Her Nikon D300s does 7 frames per second with a buffer of 17 raw frames at 12 bits or 100 frames in jpeg (without the MB-D10 battery grip.)

This means that, in just raw, she can hammer the shutter for 2.4 seconds before the buffer fills and the D300s needs to empty the camera buffer to the memory card. Or in just jpegs, she can hammer the shutter for 14 seconds before the buffer fills and D300s needs to empty the camera buffer to the memory card. The speed is still 7 frames per second.

When she switches to raw + jpeg, the speed is still 7 frames per second, but the buffer will hold less “independent” photos because the camera buffer also has to hold the raw and the jpeg photos.

The question is how big are the jpegs? That will depend on the photo. The jpegs are compressed. A photo with mostly blue skies will compress a lot more than a very dark and stormy sky…

When we tried some street photos, we got 11 frames in 1½ second before the camera buffer was full, but the shooting speed was still 7 frames per second.