On Jun 15, 2006, at 12:17 PM, Tom C wrote: >> I've tested TIFF output against JPEG highest-quality on four >> different cameras. There are differences, certainly, but >> insignificant to image quality. >> >> I see absolutely no point to saving TIFF files in-camera. They're >> huge, they are just 8bit RGB rendering (same as JPEG), they take >> forever to save, and they don't provide anything useful over JPEG >> highest-quality. >> > > There are not losses of data when saving any .jpg?
As I said, there are differences between the out-of-camera TIFF and JPEG highest quality, in all the cameras I did the comparisons with, but they're not significant. You can see how the JPEG compression changes pixel by pixel values slightly if you examine the pixels individually, but the differences are quite small and not significant. Technically, JPEG-2000 compression algorithms include lossless compression, if desired, but JPEG-2000 has not been broadly adopted. JPEG is, however, a scalable compression standard. Take a JPEG file, make a simple change (like selecting a block and erasing it) to force Photoshop to recompress it, then Save As that file to several JPEG versions from minimum quality to maximum quality. If you then open each of the files and do a calculation against the original (subtraction or difference), you will begin to see artifacts and changes to detail around JPEG quality '4' or lower. Above that, the losses are so small as to be insignificant. I find Photoshop's JPEG output at quality '5' or '6' to be perfectly suitable for high quality photographic rendering in all but the most sensitive areas, like very subtle tonal variations in the sky and clouds. Then I have to bump the quality up to 8 or 10 to eliminate tonal blocking. Godfrey -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
