Memory card help

[digital gurl]

I am having some weird issues with my memory cards and I cannot find any info on the web that is useful. So hopefully one of you out there can help me. Okay here it goes:
A few jobs ago I noticed that when I downloaded my images off my cards that the file name had changed on all my files. For example, instead of the file being named "IMG_001.jpg" the file was named "_MG_001.jpg". All my files are missing the "I". I didn't think it was too big a deal at the time. I talked to my friend about it who also shoots with a Canon 5D and she had never experienced it before. I searched through my camera manual and repeatedly reset the numbering on the camera. Well, last weekend my friend helped me with a huge wedding. I gave her some of my cards to shoot in her camera to help me cover the reception. I noticed when I went to download her cards that her files were missing an "I". So it isn't the cameras, it must be the cards! Right?! Why is this happening? Is there one corrupt card that is screwing up everything? I shot 15 cards from and all of them are missing the "I" in the file name. Is that weird or what? Any insight would be greatly appreciated. Oh and for the record, I always reformat my cards in camera.
Many thanks in advance.

[OTRphoto]

I don't know what causes it - but my 30d has the I and the ones from my 20d dont...

[KdLaneJr]

This is determined by the colorspace set in your camera. sRGB puts the I at the beginning of the file. Adobe RGB puts the _ at the beginning of the file.

[OTRphoto]

hmmm - I guess that means I'm shooting in 2 different color modes between the two cameras, huh?

[digital gurl]

Wow! Mystery solved! (I just shot a couple of images in each color space.) Thanks so much Ken for clearing that up for me. I thought I had a bad card or something. Whew!

[KdLaneJr]

Originally Posted by mjae69

hmmm - I guess that means I'm shooting in 2 different color modes between the two cameras, huh?

Yep!

It won't hurt in the long run.