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Never Use Quality ‘7’ For Saving A JPEG In Photoshop

What many people don’t know is that there is a quirk in the way that Photoshop defines its quality range. […] Quality level 6 is the last point in which chroma subsampling is used.

At Quality level 7 and higher, no chroma subsampling is used at all. With the amount of color information encoded now doubled, the file size would have naturally increased significantly at this level versus the previous level.

However, it is likely that Adobe decided to allocate the various quality levels with some relationship to the final compressed file size.

Therefore, Adobe chose a poorer luminance and chrominance compression quality (i.e. higher level of compression) in Quality level 7 than Quality level 6! What this means is that the image quality of Quality level 7 is actually lower than Quality level 6.

“What they’re saying is that there’s a different compression strategy is used for a quality of 7 compared to 6. Holding the JPEG image quality constant, this change would normally drastically increase the file size of the photograph.

However, not wanting to have a giant leap in file size between 6 and 7, Adobe actually reduces the image quality when going from 6 to 7 in order to compensate for the larger file size!

So basically, don’t ever use a quality of 7 when saving JPEGs with Photoshop. Either use 6, or something higher than 7 if you want to actually increase the quality of the photo.”

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