Photoshop Flip: destructive edit?

[mbalensiefer]

Hello!
 
 When one opens an image (.jpeg) and performs a "rotate" in Photoshop:

Image > Image Rotation > Flip Canvas (horizontal/vertical)

 Is this affecting metadata orientation information only--or is this a destructive edit?

 Michael

[gromit]

If you open a JPEG, make NO changes at all, and save it again as a JPEG it's still destructive.

[mbalensiefer]

Traditionally, yes; I think that that is the case.

However, resampling is not always performed, is it? See:

 http://www.luminous-landscape.com/forum/index.php?topic=46581.msg391142#msg391142

[gromit]

However, resampling is not always performed, is it?

It has nothing to do with resampling. JPEG throws image information away to achieve the desired compression ratio. Each time you save as JPEG, more information gets thrown away.

Don't take my word for it, compare the results with Image->Calculations selecting Difference blending mode and look at the (uncached) Channel in the Histogram panel.

[jeremypayne]

Traditionally, yes; I think that that is the case.

However, resampling is not always performed, is it? See:

 http://www.luminous-landscape.com/forum/index.php?topic=46581.msg391142#msg391142

You are confusing the mechanics of what happens inside photoshop with what happens when you save out the image to a file.

[madmanchan]

Michael, it is a destructive edit. You can check this for yourself by making a copy of the original, doing your proposed edit on the copy, then comparing the results to the original. They are not the same.

In contrast, doing a rotation in Bridge (or Lightroom) only affects the metadata. Pixel data is 100% intact; no loss.

[Joe S]

Is this the case with JPEGs only or does it apply to TIFFs?

[jeremypayne]

Is this the case with JPEGs only or does it apply to TIFFs?

TIFFs can be saved losslessly.