When you edit any image from any source, it is recomended that you save your working files on a non destructive way on a non destructive format. I'm adding this part for one comment you posted on another answer. We are still strugling with another oh my gosh prehistorical myth. The "reason" in my opinion, is just a mixture on Mercadological-Historical-GneralPublic/Use, where you "needed" to show that PhotoMightyShop could deliver a well compressed file, (back in some early dial-up web days) without any visual noticable compression artifacts. Some time ago (I don't recall the source) I read a coment on a design magazine, that if someone used a maximum quality settings on a jpg file "they had no clue of what they were doing!" well, that ignorant comment made me make the initial tests on how a jpg compression behave. I have no idea! There are sooooooooo many misconceptions on the jpg file! Some programs can detect (or gess) the original compression level and use one simmilar acordingly.ĭepending on the modifications, a new jpg saving could be considered as the first one, for example a resamped image. But if you save it lets say 2 times with the same settings, the data loss on the 2nd saved is not that significant as the first one. Save for Web, but now the results looks the same, so they are using the same algorithm when using Save For Web with maximum quality.Ī jpg file is recompressed everytime you re-save it as jpg. In older versions of Photoshop they used a different algorithm when you used Save As vs.
with a compression, compared with an uncompressed tiff (or bmp) file of 34.6%.ī) But here you have the settings as 10/12 with a "significant" data loss, with a compression of 20.4%. Here are some compression tests following my methodology explained here (In spanish, please use google translate if needed): Ī) Using the compression (save as) 12/12 you have a slight data loss 1/255 aprox. The reason you have a higher settings than 10/12 is becouse 12/12 is a higher setting.
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