I noticed that the images delivered by my Canon 5D at maximum quality gives me files rather small something between 1.5 mb and 3 mb. Though I know compression sizes depend also on image content, I find these to be a little too small. My 1DsMII gives 12+ mb jpeg files at max quality. This leads me to suspect that either I haven't been able to find how to configure my 5D properly or that it's default compression at max quality is greater. Any thoughts on this?

Here are the rough expected sizes from 5d files (from DPReview)
• RAW: approx. 12.9 MB
• Large / Fine: approx. 4.6 MB
• Large / Normal: approx. 2.3 MB
• Medium / Fine: approx. 2.7 MB
• Medium / Normal: approx. 1.4 MB
• Small / Fine: approx. 2.0 MB
• Small / Normal: approx. 1.0 MB

the default compression may be "normal" - so change it to "fine"

Hola Sergio!

at 100 ASA the Large/Fine setting i have also produced images around 2.7-3.2 MByte with my 5D. At the Large/Normal setting somewhere around 1.6 MByte for the same image.
With certain image content these figures might go up or down.

File size also increases as you push up the ASA dial.

Hasta pronto,

Andrew (y Juanes)