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Choosing the right compression level

MIRROR™ imaging software uses JPEG compression to reduce the size of stored image files. JPEG allows the user to select an optimal balance between file size and image quality. By taking some time to experiment with the compression setting in your Canfield software, you may be able to reduce the required storage space and improve system performance with no noticeable impact on image quality.

The following is a general procedure for determining the best compression setting for you:

Using your digital camera, capture one or more test images. Be sure to capture images that are representative of your typical patient photos.
Select "Set Program Options" from the "Options" menu and click the "Images" tab.
Drag the "Image compression" slider all the way to the left. The text below the sample image should read "Approximate compression ratio = 1:4."
Click "OK."
Create a new patient record store temporary test images.
Import the test image(s) into the test patient chart. (DO NOT select the "Delete source images after import" check box.)
With the new test image(s) selected in the chart, enter "1:4" in the Notes field and click "Save."
Select "Set Program Options" from the "Options" menu and click the "Images" tab.
Drag the "Image compression" slider to the right until the text below the sample image reads "Approximate compression ratio = 1:10."
Click "OK."
Import the test image(s) into the test patient chart. (DO NOT select the "Delete source images after import" check box.)
With only the new test image(s) selected in the chart, enter the compression ratio (e.g., "1:10") in the Notes field and click "Save."
Repeat steps 8-12 two more times, changing the compression ratio to "1:15" and "1:20."
Using the Side-by-Side tool, compare the images two-at-a-time on screen. Start with the two lowest compression ratios and work your way up (i.e., compare 1:4 to 1:10, then compare 1:10 to 1:15, etc.). Note the highest compression ratio that offers acceptable image quality. Repeat this step on each computer that runs Mirror.
Print each image at the largest size that you use in your practice. Compare the printouts to determine the highest compression ratio that offers acceptable image quality.
Based on your results from steps 14 and 15, determine the highest compression ratio setting that produces acceptable image quality for all methods of viewing. This is the best compression ratio for your clinical photos.
Select "Set Program Options" from the "Options" menu and click the "Images" tab.
Drag the "Image compression" slider until the text below the sample image indicates the appropriate compression ratio.
Note the number that appears above the slider and click "OK."

The new compression ratio will be in effect for all images saved from this point forward. Images that have already been saved will not automatically be recompressed. If you wish, you may recompress all images in the current database as follows:

IMPORTANT: Recompressing images with an improper compression setting can have a negative impact on image quality and cannot be reversed.

Make a backup copy of the entire image (pics) folder. Keep this backup as an archive and do not cycle the media back into a regular backup cycle.
Choose a time when the Canfield software will not need to be used.
Select "Recompress Images" from the "Utilities" menu.
Confirm that the number above the "recompression factor" slider is the same as the number noted in step 19 above (this may not be the same as the compression ratio).
Click "Check All," then click "Recompress." For larger databases, recompression may take a substantial amount of time.