RAW - Why two files?

[Malok]

I am just getting started with photography and am beginning to see the benefits of working with the RAW format rather than the jpg format. However, I am a little confused about one aspect of the RAW format.

Each photo seems to have two files, one ends in .crm and the other in .thm. Do I need both of these files? I would guess that the .crm file is the main raw file, but what is the .thm file? When archiving, do I need to keep both of these files?

[darrylr]

The THM file is a low resolution (160x120 pixels I believe) thumbnail JPEG of the image in the CRW file (the file with the full size image). The one advantage is that the THM file contains the full EXIF information and can be used by just about any program to grab the EXIF. Not all viewers support reading CRW files. Other than this I can't see why you would need to keep it but hey they are only 5KB or so and compared to a 3 or 4 MB file for the CRW it isn't going to cause you any storage problems.

-Darryl

[JayB]

Hi.

Being just slightly off topic, the "thm" file may only show up in your file viewer as 5/6k but it can take a lot more space depending on how you have set up / formatted your hard disk. Fat32 (WindowsMe/XP [not NTFS]) equates to 16k or mutliples thereof for a file.
i.e. a 5k file takes the same amount of space as a 1k, or 14k file

Other operating systems/file structures have different sized clusters as it is known as

Jay

[Malok]

Many thanks Darrylr!

It wasn't storage space I was worried about as much as the fact that I like to rename my files to something more meaningful and I was worried that if the two files were connected that it would mess things up to change the name. Thanks for clearing up my confusion!

Malok

[Bean]

If you lose the thumbs, or if they get out of sequence,some programs like Breezebrowser will regenerate them for you.

[s00pcan]

Oh, is that why when I playback raw files on my camera that they look compressed?

[sdommin]

s00pcan wrote:
Oh, is that why when I playback raw files on my camera that they look compressed?

Yes. When you look at a RAW file on your camera, you are actually looking at the small THM file.