Preview not opening images at full resolution?

[generalist]

In the past, when I opened an image in Preview I would expect it to be scaled to fit but rather large. Now if I open an image that's say 2000x1000 it's tiny-tiny and when I check view it says 'Actual Size' but it isn't, in reality.

What have I done to screw up my Preview?

 

[Partron22]

You have Preview's Image prefs set to Define 100% scale as: 1 image pixel equals 1 screen pixel?

 

[generalist]

You have Preview's Image prefs set to Define 100% scale as: 1 image pixel equals 1 screen pixel?

Curiously, no. Define 100% scale as = Size on screen equals size on printout.

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Another thing I should throw in here is that I installed a trial edition of Adobe Acrobat recently and coincidentally that is when this 'issue' with Preview started.