Tag Archives: JotNot

Perspective Correction on the iPhone

Although I rarely use it, every now and then I want to do a bit of perspective correction (or perspective control) with my images. In Lightroom I’d gotten used to using the perspective correction feature, but I hadn’t yet seen anything like this in any photo apps that I’d liked*.

If you aren’t familiar with perspective correction, it basically means adjusting the image so that lines that are parallel in the real world stay parallel in the image. Your eye and mind are very good at “perceiving” parallel lines, but cameras can’t do that, so anytime you are not pointed directly at the main plane of an object (such as directly above a piece of paper), the perspective won’t be ideal. These images give you a quick idea of what this means.

Typical snapshot with no perspective correction.

Typical snapshot with no perspective correction.

Snapshot after perspective correction.

Snapshot after perspective correction.

In the left image the sides of the building seem to slant towards the upper middle portion of the picture. When viewing the actual scenery your mind knows that the sides of the building go straight up and it perceives it that way. To make the snapshot show what your mind perceives you need to do a bit of correction. You’ll then end up with the image on the right.

It almost looks as if the camera was moved up in to the sky so it is sitting right in the middle of the building. This is a correction to the perspective (or view).

Can you do that on the iPhone/iPad? In an email exchange with the developer of the Image Straightener and Image Blender apps (both superb apps) he pointed me towards JotNot Scanner. This app is for the iPhone (runs fine on my iPad 2) in the business/productivity category, but it turns out it is useful in photography.
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