Are Quantization Tables ever Optimized?
When you select optimized JPEG in Photoshop or other photo editing programs you are almost certainly not getting any optimization (or change) of the quantization tables. Nearly every program includes some predefined quantization tables that are used (and a scaling thereof), depending on the user’s desired quality setting. Trying to calculate an optimum quantization table (given targets in file size and knowledge about the characteristics of the human visual system) would be very difficult. I believe this has been the focus of a few published theses, but not adopted in any popular computer software.
