[belowm]

After a short period of training, I got to the point where I can see the third image which I can focus on. However, the differences are very subtile and don't stick out at all :/

[drdo]

Try the second test image (the one labelled "Hard", with the snow). That one was far easier for me than the first (the cat one).

[belowm]

Indeed, that did the trick. Thanks!