I own a Canon EOS 40D (bought slightly used) and overall I'm pretty happy, but there's one thing that's not right: according to the specifications, the buffer for continuous shooting should be able to hold around 17 RAW pictures before continuous shooting slows down.

With my camera, however, the slowdown hits after 7 frames. Does my camera for some reason have less than the usual 256 MiB of memory? Any suggestions on how I can figure out why I'm not able to use the full image buffer?

ETA: The buffer size indicator in the lower-right of the viewfinder always says 6 for me, although it should say 17 normally.


2 Answers 2


This is due to the High ISO Noise Reduction and/or Highlight Tone Priority filter being set to on; if you turn this off you should get back to about 17 RAW frames in the buffer.


  • \$\begingroup\$ Aaaaah, thanks a lot. Indeed, that's the culprit. I'm going to bang my head against a wall and when I return I'll accept the answer (SO says I cannot, yet :-)). \$\endgroup\$
    – Joey
    Commented Jan 10, 2011 at 15:57

You should check the speed of your CF card. It may be the bottleneck. Also, I am not sure (don't have the manual in front of me now), but maybe the max continuous rate is for smaller RAW files, and not max size RAW?

  • 1
    \$\begingroup\$ +1 this might not be the problem for the questioner but card write speed has a big effect on continuous bursts! \$\endgroup\$
    – Matt Grum
    Commented Jan 10, 2011 at 19:39
  • \$\begingroup\$ @Matt That's right. The clue here is that the viewfinder says 6. I believe the Canons don't attempt to account for SD write speed in their estimates, so that 6 must reflect some internal settings, as @stark indicated. \$\endgroup\$
    – whuber
    Commented Jan 10, 2011 at 19:59
  • \$\begingroup\$ Good detective work all round! \$\endgroup\$
    – Matt Grum
    Commented Jan 10, 2011 at 21:21

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