70D buffer - number of shots decreases with reduced RAW sizes?

Just playing around with a 70D right now and with quality set to RAW only (all JPEG options turned off) the viewfinder indicates 12 shots available in the buffer.

Changing to mRAW reduces it to 9 shots. And changing to sRAW makes it 11.

Can someone replicate this and if so, why is this happening?

My preferred shooting mode is mRAW because 10MP is about all the resolution I need for my purposes.

That is a good question. My best personal guess is that the resampling process takes up a chunk of extra memory and is done in-buffer, rather than pre-buffer. So the camera would read the whole sensor output into the buffer, then run through that data to re-calculate the down-sampled copy, which in turn takes up its own chunk of memory. Then the original file gets dropped from the buffer's memory as the down-sample gets written to the card.

I've never seen this behaviour before on other cameras.

I grabbed a 60D nearby and these are the buffer values seen in the viewfinder:

RAW - 14
mRAW - 18
sRAW - 22

That makes sense, that the smaller file size would allow more shots before the buffer is filled. The 70D doesn't seem to have any consistency in the values I posted at the top?

What are you actually getting when you take a burst of photos? (You'll get a few more than the buffer indicator shows due to streaming to card while still shooting, which depends on how quickly the camera can write to the card of course.)


Possibly a software glitch in the display number that just slipped through. (I know I've never really paid much attention to it on my 7D. 20 something when I have a 'full charge', and will drop quickly during a burst, but then again the 7D's buffer is big enough that you don't really have to think about it unless you're really abusing the shutter button.)

Also possible that they changed how they're doing their processing in camera. Fun quirk of programming is that there are usually several 'efficient' ways to do something, but they may be inefficient in other ways. (Using more memory to process something faster for example)

And then again it could just be that something has gone funky with your camera. I did message a friend of mine who has a 70D, but they seem to be offline for the evening. Hopefully someone else can provide some better help in sorting out what is going on for you.

14, 9 and 11 on mine. Never thought about it because I rarely use that many shots in a burst.

Luckless wrote in post #17306474
What are you actually getting when you take a burst of photos? (You'll get a few more than the buffer indicator shows due to streaming to card while still shooting, which depends on how quickly the camera can write to the card of course.)

Test results as follows. I recorded the sound of the shutter and counted the spikes in the corresponding waveform in an audio editor to be sure.

Sandisk Ultra (30MB/s) 32GB card:

RAW - 18
mRAW - 19
sRAW - 27

Sandisk Extreme (45MB/s) 16GB card:

RAW - 21
mRAW - 22
sRAW - 38

So yes it looks like a glitch in the viewfinder display. Probably will be fixed in a future firmware revision.

I checked my 70d out of curiosity last night and my disply numbers were exactly what yours showed. Very weird.

I'm curious to hear what Canon support might have to say about the issue.

Could easily be an undocumented bug. I work in software testing, and honestly this is the kind of thing that can somehow manage to get overlooked by a half dozen professional testers working full time for a few months. It could also be known, but still, it is very hard to fix bugs you don't know about.

Luckless wrote in post #17311910
I'm curious to hear what Canon support might have to say about the issue.

Could easily be an undocumented bug. I work in software testing, and honestly this is the kind of thing that can somehow manage to get overlooked by a half dozen professional testers working full time for a few months. It could also be known, but still, it is very hard to fix bugs you don't know about.

I'm with you there - so does anyone know what's the best way to report this to Canon?