DxO Optics Pro uses custom-made lens correction profiles to fix the distortion issues inherent in nearly all lenses, but it goes further than that – it can also correct the perspective distortion created when you photograph a rectangular object at a slight angle, thanks to the DxO Force Rectangle tool . You often don’t notice this kind of misalignment at the time, only later on when you’re looking at the picture on your computer.

• Note that the latest versions of DxO Optics Pro do not have perspective correction built in – you now have to buy the separate ViewPoint 3 application. Once installed, this integrates perfectly with DxO Optics Pro.

DxO ViewPoint 3 review

DxO Optics Pro 11 review

This marvellous old poster is a good example. It was shot using an 18-105mm kit lens near its minimum focal length, so the original shot suffers from quite severe barrel distortion. And even though the camera was mounted carefully on a tripod, there wasn’t time to get it exactly perpendicular to the poster.

DxO Force Rectangle tool

The safest thing to do, then, was allow a little space around the edges of the poster with the aim of fixing the picture later on.

01 Initial correction

DxO Force Rectangle tool

DxO will apply a default correction preset as soon as you select an image to work on. You can quickly view the original version to see the difference by selecting the arrow tool then clicking and holding on the image – when you release the mouse button the corrected image is displayed again.

Alternatively, use the side-by-side view icon on the top toolbar to display the original (left) and the corrected image (right). You can see that the barrel distortion has been completely removed, and the lens’s vignetting (corner shading) has been fixed too, so the corrected image now has even illumination right into the corners.

02 Force Rectangle

DxO Force Rectangle tool

But this correction also makes it obvious that I wasn’t quite square-on to the poster when I shot it. You can fix horizontal and vertical perspective issues separately, but when you’ve got both, as I have here, it makes more sense to fix both at the same time, using the Force Rectangle tool on the top toolbar (circled).

Again, DxO displays a before-and-after image, but this time you apply the correction to the left image, and the right image shows you the result. The image is surrounded by a rectangular marquee with a control handle at each corner, and you drag the corner handles individually (also circled) to line up with the corners of the rectangle you’re trying to correct.