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johnh
06-Aug-10, 09:15
Does the Compression setting in the Output Tab (by default on 90) mean that compression is high or low?:eyebrowlift2: Thanks, JH

Richard Marklew
06-Aug-10, 09:19
http://wiki.blender.org/index.php/Doc:Manual/Render/Output_Formats#Compression



Compression
Some formats can compress the image to use less disk space. This compression might be lossless (PNG, ...) or lossy (Jpeg, ...). Lossy formats don't store individual pixel information, thus reducing image quality. All the other formats are more or less equivalent, each having advantages and disadvantages. Make your compression selection using the button or field located beneath the format selector. For example, if Jpeg is selected, you can specify a compression level (Quality:90 by default). Higher quality takes more disk space, but results in a better looking picture with less compression encoding artifacts.
The default image type is Targa, but, since the image is stored in a buffer and then saved, it is this is only valid for static images, not when rendering animations!).

johnh
06-Aug-10, 09:29
Thanks for your quick reply Richard. So it sounds like moving the slider to 100% gives you better quality. Maybe the slider should say Quality rather than Compression. By saying 100% Compression that to me seems like fully compressed, therefore poorest quality...John

loopduplicate
06-Aug-10, 12:36
Compression is always measured this way. On a scale from 0 to 100, 100 being the best. It doesn't matter what program you use. Therefore, Blender should stay with this naming convention.

sundialsvc4
07-Aug-10, 23:46
I will take it for granted, from the discussion, that you must be doing the entire render "basically 'all at once.'" So, all's well. But on the general subject of file-formats I would make three important comments:


If you are building up a project out of multiple components that are generated at different times, all of your intermediate files should be in the "MultiLayer" (OpenEXR-based) format. (And "frankly, my dear, you don't give a damn" how big or small they are.) Your workflow should build the complete "finished image" in this format, and then, separately, create the deliverable file (or files) in whatever format (or formats) are appropriate. (Those formats can be "lossy" because the master-print final file ... which is the actual "finished output" ... is not.)
Remember that not all image formats support an Alpha channel. JPG, for example, does not; PNG does. Especially if you are doing it "all at once," be sure that the output format which you select will be appropriate to its intended purpose.
Don't overlook gamma. Formats such as PNG (IIRC...) do apply gamma to the output so that an "ordinary" picture viewer can easily handle it. Formats like "MultiLayer," which are really intended to hold intermediates, don't. As always, you need to know how, where, and when, gamma is entering into your process at any step.