Remaining Image Counter

[zackojones]

Greetings,

 

I know there are lots of variables on the number of images that can be stored

on a memory card but I was curious to know how accurately your camera estimates

the number of images remaining. Yesterday I went to a triathlon with two

buddies to photograph them while they raced. Before using the 2 gig memory card

I formatted it in the camera (Digital Rebel XT). Normally when I do this the

camera shows I have 233 images remaining. At the triathlon I shot a total of

257 photographs and the counter said I had 17 remaining when I started

downloading the images. I use RAW images only.

 

Does anyone know (or really care) how the cameras calculate the number of

images remaining? I know it's really nothing to worry about but I was just

curious to see if anyone else noticed this before with your camera.

[steve_dunn2]

<p>I've never paid that much attention to what it said at the start of the card. I only really care when it gets down towards 0 so that I know I need to swap cards soon. And since I don't care, I've never compared its estimate with the card empty to what actually fits on the card. As well, it's rare for me to fill a whole card with shots at the same ISO, so even if the initial estimate is highly accurate, it wouldn't necessarily match what I'd end up fitting on the card in real-world shooting anyway.</p>

 

<p>I haven't seen any documentation on how the estimate is produced. Obviously, ISO factors into it, as you can see by changing ISO without taking any (more) pictures. It must have been programmed with whatever Canon considers to be a typical file size for each combination of ISO and file type(s). Whether it tries to learn from the actual size of your files as it goes or not, I don't know, but I suspect it probably doesn't; my guess is that it simply takes the space remaining, divides it by the preprogrammed estimated average file size for your currently-selected ISO and file type(s), and displays the result.</p>

[PuppyDigs]

Higher ISO and longer exposures require more storage space than lower ISO and shorter exposures due to increased data. Also, a complicated landscape creates more data than a simple blue sky. So it would be impossible to calculate the exact number of frames remaining unless you repeated the same image over and over. The estimate is conservative as I can usually squeeze a dozen or more in than the starting estimate.

[mendel_leisk]

At least it's better than the old days when you managed to crank the film one last time for frame 37, only to have the lab put a big clamp through it ;D

[colinsouthern]

Puppy Face,

 

I'm curious - why would longer exposures & ISO affect the size of a file?

 

I would of thought that it would have simply come down to how compressible the data was? (assuming identically exposed images).

 

Cheers,

 

Colin

[phule]

<<I'm curious - why would longer exposures & ISO affect the size of a file?>>

 

Because longer exposures and high ISO have more noise.

 

<<I would of thought that it would have simply come down to how compressible the data was? (assuming identically exposed images). >>

 

See above.

[rainer_t]

Besides the variables named above, the image content has big influence on the filesize ... "white eagle on white background" or "black chimney sweeper in dark chimney" are typical situations for images that compress very well.

[zackojones]

All,

 

Thanks for the replies. I appreciate your feedback.