Following on from a discussion on the Picture Window Pro message board, I have undertaken some tests into the compression of TIFF files.
I took 6 images, selected from my collection for being a selection of shooting scenes, ranging from darkness through to very light; from detailed backgrounds to smooth. Some of the images are direct from RAW from my camera, others are resaved JPEG crops.
In Photoshop CS, the 'ICC Profile' option in the "Save As" dialogue was ticked. The "Save Pyramid" option was unticked and the IBM PC byte order was chosen.
| File | PWP /KB | LZW /KB | ZIP /KB | Saving using LZW | Saving using ZIP |
|---|---|---|---|---|---|
| 2005-03-30_21h38m38s17_filtered.tif | 17865 | 10856 | 10117 | 39.23% | 43.37% |
| 2005-06-10_17h30m48s54_1.tif | 6782 | 3155 | 3028 | 53.48% | 55.35% |
| DSCF0001 bluer sky with glow.tif | 17862 | 10230 | 9554 | 42.73% | 46.51% |
| DSCF0009.tif | 17865 | 6767 | 6480 | 62.12% | 63.73% |
| DSCF0107.tif | 35867 | 41648 | 31563 | -16.12% | 12.00% |
| DSCF0112.tif | 4755 | 2101 | 2054 | 55.81% | 56.80% |
| DSCF0258.tif (new RAW conversion) | 35864 | 44817 | 34649 | -24.96% | 3.39% |
I also tested to see how the file size changed if I enabled the Pyramid option when saving TIFF files. As the table below shows the file size is increased.
| File | LZW w. Pyramid | ZIP w. Pyramid |
|---|---|---|
| 2005-03-30_21h38m38s17_filtered.tif | 14968 | 13823 |
| 2005-06-10_17h30m48s54_1.tif | 4431 | 4245 |
| DSCF0001 bluer sky with glow.tif | 14213 | 13155 |
| DSCF0009.tif | 9527 | 9099 |
| DSCF0107.tif | 44332 | 34171 |
| DSCF0112.tif | 2956 | 2858 |
PWP is currently slow at reading LZW-compressed TIFFs in comparison to uncompressed ones, much slower than Photoshop CS.
Photoshop CS takes a second or two longer saving ZIP compressed TIFFs than LZW compressed ones, particularly when the image pyramid option is ticked.
The above data shows that in the majority of cases a good saving in disk space usage can be made by compressing TIFF files where the original data has been compressed - eg crops from JPEG files resaved as TIFF after editing to prevent extra loss of quality.
Because a lot of these images were saved from JPEGs it is obvious that they will compress better than the average TIFF file. Due to IMatch's lack of versioning support in 3.4 it is hard for me to tell which images originated as RAW and which as JPEG.
http://www.ee.cooper.edu/courses/course_pages/past_courses/EE458/TIFF/