perspective correction issues (X6)

[beutelwolf]

When using perspective correction (in X6) I noticed that the resulting pictures are very often too narrow.

I know this, because I typically do this to photographs of magazine covers found on ebay, and for some of these mags I know their standard aspect ratio - and I have observed that issue a fair number of times over the years. As a rule of thumb a subsequent resize with a height reduction to 94% is fairly good repair.

Is this a bug, a principal problem with perspective correction, or am I missing a trick somewhere? Would also be interesting to hear whether subsequent versions of PSP behave differently.

A related question: these photographs often also have lens distortion issues. Is it advisable to do the lens distortion correction before the perspective correction, or the other way around, or does it make very little difference?

[Joelle]

I don't think it's a bug, but it is annoying.
Promote the Background Layer and apply the Pick tool (K on the keyboard - it used to be the Deform tool D, but you can use either now), then pull the image back into shape.
That's what I do, although I often only the Deform Tool instead of the perspective Correction Tool, I activate the grid (the icon is on my toolbar), to make sure everything turns out right.
With the Deform Tool/Pick Tool, hold the Shift key and pull on one corner node, this will stretch just that corner, if you do the same but hold the Ctrl key, it will move two nodes at once.
Very handy

Joëlle

[beutelwolf]

I never quite got the hang of that feature (GIMP does it in a similar way), but even when I do that does not really help - at best this gives a quick and simple way of turning something that ought to be rectangular into something that is, but the perspective tool does that as well. In fact, it does that job better, because I do not have to do that in a single mouse movement - I can zoom in till I run out of pixels and make that really precise. That applies in particular when the image has clear rectangular features - and with photographed mag covers that is pretty much the case 98% of the time.

Problem is: in either case I get (would get) a rectangle that is potentially too wide or too narrow.

My gut feeling is that the perspective tool views the problem in a similar way as a Pick Tool problem, and breaks it up into a series of 2D affine transformations. My incling is that one might get better results viewing it as a single 3D transformation.