SnapperTalk

November 5th, 2006

Straightening Images

Posted by Ben in General, Imaging

Measure tool

I’ve been meaning to write about this Photoshop tip since I read about it a few months ago in an issue of the PhotographyTech newsletter. It was one of those moments when you realise that despite using Photoshop almost every day for many years, there are still things to learn…

If you have an image with a horizon that isn’t quite horizontal, the usual method is to use the crop tool and rotate the crop.

Try this instead:

1. Select the Measure Tool (usually hidden under the eyedropper tool) in the tools palette.
2. Draw a line along the edge of the part of the image that you want to make horizontal.
3. Go to Image > Rotate Canvas > Arbitrary, ignore whatever value has been entered into the “Angle” box, and just hit “OK”.
4. The image will now have been rotated so that the line you drew is a perfect horizontal, and all that’s left is to crop the black canvas out of the frame.

I still use the normal method most of the time - but do find this useful for pictures where you need an accurate horizontal or where you need to visualize the rotated image before cropping.

3 Responses to ' Straightening Images '

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  1. Jeremy said:

    A good tip to know, but then i probably only use about 20% of what Photoshop is capable of…but it’ll come in handy straightening my squinty horizons that I shoot…
    cheers.

    November 7th, 2006 at 03:21 PST

  2. Erin said:

    One thing about this arbitrary rotation is that it is “destructive” and it will soften your image. It is no free lunch, so use it with care and perhaps only on image files where you can afford to lose some pixels. Add this to other lossy jpeg functions and you just end up losing ever more pixels. Perspective control is another lossy tool, amongst others in PS.

    December 29th, 2006 at 21:56 PST

  3. Ben said:

    Erin,

    You are of course correct that this type of rotation is destructive but the same is true with rotation using the cropping tool - which for most people is the alternative…. Pixels are square and any type of rotation is going to lose some quality, the exception being rotations at exactly 90, 180, 270 degrees using an application that supports non-lossy rotation such as Photo Mechanic. Thanks for your comment. Ben

    December 30th, 2006 at 10:33 PST

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