Lossless 16bit file comparison

Started Jul 1, 2004 | Discussions thread
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Kalus Senior Member • Posts: 1,683
Lossless 16bit file comparison

Havn't seen one around so I thought i'd compare the various lossless file formats for 16bit images to see which is the best to use based on wether your more concerned about file size or the time it takes to save and open the image.

Scroll down if you just want to see the speed and size results.

For those that don't know lossless means the image is saved without any degredation of the data (unlike a JPEG) so no matter what size the file is the opened image will look exactly the same as if it was saved with another lossless file format even if the format is 3 times the file size of it. It is for this reason that lossless file formats are used to save the original of an image as you don't want to lose any of the data in the image.

Typically people save an Uncompessed TIFF file for this purpose but I thoguht i'd look to see if or when it is the best option to use.

I don't think machine specification are worth posting as everyone system is different and will effect the times differently however the relative times will remain the same and hence why it's worth doing a comparison eg if it takes 1 format twice as long to save then another on a 1ghz system it will still take twice as long to save then the other on a 3ghz system.

The formats I look at are as follows:
TIFF uncompressed
TIFF LZW compression
TIFF ZIP compression
JPEG 2000 lossless
Photoshop PSD format.

The 2 compressed TIF and the JPEG 2000 formats all compress the data to reduce the file size but inlike a regular JPEG they don't lose any information in the compression so you don't have any artifacts in the image and it is exactly the same quality as an uncompressed TIFF or Photoshop PSD file.

For testing I rebooted the computer and closed everything that was running. For the save and open process I saved and opened the file 4 times averaging the 3 closest results to come up with the time to save or open. Besides recording the times to save and open as well as the file sizes I did 2 more comparisons and did them to various files as follows:

Time / None - is the time it takes that format to save or open compared to the time it takes an uncompressed TIFF to save or open so you can see % wise how much faster or slower it takes to save or open the file.

Size / None - is how big th fle size is compared to an uncompressed TIFF so you can see % wise how much smaller the resulting file will be.

Low Dynamic Range - the image didn't have a large dynamic range which the image consisting of mosltly just mid tones.

High Dynamic Range - the image contained as wel las the midtones alot of dark shadows and bright highlights giving it a large dynamic range (which also usually increases the size of a file)

I also did the test on a full sized D70 image and a cropped image 33% of the size incase someone doesn't usually use the whole image to give an indication of the performance of smaller images.

It should be noted that JPEG 2000 unlike the other formats can not save layers. I included it since alot of people save the original NEF conversion they do bt if you do edit the image and have layers or adjustment layers in it then saving as a JPEG 2000 will flatten the image and you'll lose those layers.

Analysis of results on next post due to psot character limit.

Conclussion:

From the results if you don't have layers in the image then JPEG 2000 seems like a dream reudice the file to half its size in most cases however the time to save an open the images is far too slow usually 7 - 10 times as slow as a PSD or uncompressed TIFF file. On that basis i'd never use JPEG 2000 since the cost of cd's and dvd's is so cheap that the extra time it takes to save and open isn't worth it especially if you edit alot of images where it's just out of the question.

TIFF zip compressed files seem to compress the file nicely but are still pretty slow to save and open compared to an uncompressed file and doesn't seem worth it however if you have many layers in the file then it might be a better option to use it asa 200meg file is better then a 400meg however the speed is still an option as it'll take around 3 to 4 times as long to save the image and if its that large that will be a long time not to mention opening it as well.

LZW well unless the image has alot of dynamic range and its a large image then the small reduction in file size isn't worth the extra time in my opinion, not to mention the wierd bit of the 1003 x 667 images actually producing a file quite a bit larger then an uncompressed file :os so i'd stay away from LZW even if just to be safe.

So whats the format to use..... overall i'd personally use PSD since I'd only be opening hte images in Photoshop so an uncompressed TIFF doesn't really hold anything over a PSD file since its slower to save and open. If running low on space i'd use a ZIP compressed TIFF but as long as i've got plenty of HD space and blank discs laying around i'd always use PSD jnless I know i'll be giving the file to someone that can't use a PSD file.

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