What is the difference between a file that has only one layer and a file that is flattened and thus also has only one layer? Anything?
#1
Flattened = smaller file but no transparency
One layer = transparency option available
#2
Flattened = locked single layer
One layer = movable and scalable within the document size due to the transparency Ronald mentioned.
Just experiment, you'll find allsorts of differences.
#3
you can't use the one layer file in Quark
but you can use it in InDesign.
#4
One of my printers said he received an InDesign file with a linked PSD that had almost 100 layers in it. He said it printed fine. Brand X is definitely on its way out.
#5
All that InDesign, sees is the flattened composite of the PSD.
It has no idea how many layers are in a particular PSD file.
#6