How to Create THM Extensions for a Canon

A THM extension indicates a thumbnail file. Most Canon cameras create a THM file for each picture. The thumbnail is a smaller version of the actual picture and provides a preview of the photo. If you're missing THM files on your Canon camera, you can create them using photo editing software. Adobe Photoshop is the industry-standard photo-editing software that is capable of creating THM files.

Instructions

1. Insert the memory card from your Canon camera into the memory card slot on your computer.

2. Click “Start” located in the lower left area of the screen. Click “All Programs” and then click “Adobe Photoshop.”

3. Click “File” from the upper left area of the Photoshop screen. Select “Open” from the File drop-down menu.

4. Click the photo of choice from your Canon memory card and click “Open.”

5. Click “Image” from the upper menu of Photoshop and select “Image Size.”

6. Enter a width of 160px, height of 120px and resolution of 72px.

7. Select “JPEG” as the file type in the Save for Web dialog box. Check the box next to “Optimized” and enter “100” for the Quality.

8. Select “JPEG” as the file type in the "Save for Web" dialog box. Check the box next to “Optimized” and enter “100” for "Quality."

9. Click “Save.”

10. Locate the JPEG file on your computer.

11. Right-click the file and select “Rename.”

12. Type the file name of choice with an extension of THM.