THM files from Digital Rebel

[Curtis N]

Shooting RAW with the DRebel produces two files of each shot: One with a .CRW extention and one with a .THM extension, which I presume is for viewing on the camera's LCD screen.

I have been downloading the files with a card reader, copying and pasting the files to my harddrive with windows explorer. I sort by file type, then select only the .CRW files to transfer. I then use Digital Photo Professional to convert.

Is there any reason to download the .THM files also?

[AccidentalArt]

i need an answer to this also...

Thanks

[dputz]

Nope.

[René Damkot]

I'd say THM stands for THuMbnail...

[Curtis N]

Glad to see it only takes 17 months to get an answer around here. ;)

Kudos to AccidentalArt for using the search button!

[PacAce]

Glad to see it only takes 17 months to get an answer around here. ;)

Kudos to AccidentalArt for using the search button!

You must have not done a search the first time you posted that question, Curtis, because it's been asked and answered several times previously.


;) :lol: :mrgreen:

BTW, I thought the THM file contained all the EXIF info generated by the camera whereas the CRW onlt contains partial (incomplete) EXIF info. But it's been a while since I'v e worked with them and I ain't gettin' any younger.

[Curtis N]

BTW, I thought the THM file contained all the EXIF info generated by the camera whereas the CRW onlt contains partial (incomplete) EXIF info.I have read that here as well.

Now can we assume that if you convert with one of Canon's programs like DPP, you'll get all the EXIF in the converted file if both (CRW and THM) files are in the same folder, whereas if you use other software like RSP or ACR, you won't get it all?

My (wife's) 300D doesn't get much use anymore, and I never much worried about saving EXIF after conversion anyway, but it might be useful to some people.

[300Dplus]

Glad to see it only takes 17 months to get an answer around here. ;) :lol: :lol: :lol: :lol: :lol:

Chris Breeze, the developer of the must-have (for PC users anyway) utility, BreezeBrowser (http://photography-on-the.net/links/a-c/breezebrowser.htm), says emphatically, "yes, keep THMs" and offered these reasons for users of BreezeBrowser to archive the THM file as well as the CRW file. Some of them, at least, may apply to those of you who are using other software to convert their raw image files:

The thumbnail generator is faster, if you keep the THM's. THM's are used to generate the small and large thumbnail images and this is much faster than generating them from the larger JPEG embedded in the CRW file. (Extra large thumbnails are larger than the THM image and use the embedded JPEG).
EXIF data stored in converted JPEGs and TIFF's is more accurate if you keep the THM's. This is because THM's contain the full EXIF data including the undocumented Canon MakerNote and this is simply copied to the converted file. If you don't keep the THM's the EXIF data has to be generated from the CIFF data held in the CRW file and this is less accurate. Don't believe what other people may claim, the Canon MakerNote has not been fully decoded (outside of Canon) and so the only way to guarantee the accuracy of the EXIF data is to copy it from the THM file.
You can't write IPTC data to raw files if the THM's are not present. Since the THM file is really a JPEG file with a different extension it is used to store the IPTC data. The CRW file is a proprietary format which has no provision for storing IPTC data.

[Curtis N]

Thanks for the info, Tom!

[300Dplus]

Glad it help. Just a little payback for your regular great contributions.;)

[golferchck234]

so do we need to keep the thm file even if we keep the movie? i've always wondered this and i'm not very technical so it's hard for me to decipher what you guys are saying in previous posts...

:oops: :confused: :?:

any help is appreciated...and my apologies if this has been answered many times before...also, if you could e-mail me the response, that would be wonderful...mashfreak4077@hotmail.com. thanks :)

[JWright]

:lol: :lol: :lol: :lol: :lol:

Chris Breeze, the developer of the must-have (for PC users anyway) utility, BreezeBrowser (http://photography-on-the.net/links/a-c/breezebrowser.htm), says emphatically, "yes, keep THMs" and offered these reasons for users of BreezeBrowser to archive the THM file as well as the CRW file. Some of them, at least, may apply to those of you who are using other software to convert their raw image files:

The thumbnail generator is faster, if you keep the THM's. THM's are used to generate the small and large thumbnail images and this is much faster than generating them from the larger JPEG embedded in the CRW file. (Extra large thumbnails are larger than the THM image and use the embedded JPEG).
EXIF data stored in converted JPEGs and TIFF's is more accurate if you keep the THM's. This is because THM's contain the full EXIF data including the undocumented Canon MakerNote and this is simply copied to the converted file. If you don't keep the THM's the EXIF data has to be generated from the CIFF data held in the CRW file and this is less accurate. Don't believe what other people may claim, the Canon MakerNote has not been fully decoded (outside of Canon) and so the only way to guarantee the accuracy of the EXIF data is to copy it from the THM file.
You can't write IPTC data to raw files if the THM's are not present. Since the THM file is really a JPEG file with a different extension it is used to store the IPTC data. The CRW file is a proprietary format which has no provision for storing IPTC data.

I don't find this to be the case. I use BreezeBrowserPro as well as Adobe Photoshop. Perhaps this information is now a bit out of date... My D60 creates a THM file at the same time as a RAW. I usually delete the THMs immediately after downloading. I'm able to write IPTC data to the D60 RAW file using the "File Info" tool in Adobe Bridge without the THM files. The EXIF data present in the D60 RAW file is exactly the same as the EXIF generated by my 20D RAW file (which doesn't create a THM).