Straightening & Cropping 101

Work flow is the one thing that Photoshop isn’t very good at imposing on
you (nor should it), or leading you through, but it doesn’t take a beginner
very long to work out that pretty much the first thing you will want to do
with your photographs, once you have loaded them into Photoshop, is either
Crop or Straighten them (or sometimes both). Although Photoshop
provides a tool specially for this job, it’s not very good at doing either
one of these essential tasks. The Crop Tool will straighten a photo, but you
have to rely on your ability to rotate the crop accurately. The Crop Tool
will also allow you to correct any perspective problems in your image, but
again, it’s not a very good method of doing so. The thing about Photoshop is
that it provides about six different methods to achieve nearly every task – which
method you use and when to use it, is left entirely up to you. Unfortunately
this approach causes Photoshop’s user interface to be mind bogglingly
complex to navigate.

Cropping and Straightening your images

The technique I’ll outline below relies on two unrelated, but very powerful
methods, of achieving a more controlled and precise crop and straighten, but
first things first. Your camera probably has a nice little feature on it
that allows you to view a rule-of-thirds grid through the viewfinder, which
you may use to help you compose your shots, but Photoshop doesn’t give you
this grid set up, does it? Well, yes actually, it does; it just doesn’t
come out of the box set up for you, so here’s how to set it up.

Create yourself a new blank document or load a photo so that you have
something on screen to look at, and then go to the Edit menu. At the
bottom of this menu is the Preferences item with an arrow next to it. The
fly out menu lists all the different things you can configure for
Photoshop’s default preferences (actually, they all call-up the same Dialog Box). Select the Guides, Grid & Slices item and you will be presented with a dialog which allows you to set your preferences for… guessed it – Guides, Grids and Slices.

Now unless you’re into web page design you can forget
about Slices, and I have to admit, I’ve never really investigated what Smart Guides do for you, but the Guides and Grid sections are important. You don’t really have much control over the Guides bit, just the colour and appearance of the guides; I have mine set to 100% Cyan and Lines. The Grid part of this dialog allows you to set your Rule of Thirds grid up, you just need to set the colour (I use bright yellow to match the grid on my camera) and dashed lines. Here is the important bit – set the ‘Grid line every:’ box to 33.33 and the drop down box next to it to ‘percent.’ For those of you who didn’t pay attention in maths at school, that’s one grid line for every 1/3 of the image – you can subdivide the grid if you like, although I don’t – and I have my Subdivisions box set to 1. Now click on the OK button to close the dialog and voilà! your rule of thirds grid should appear over your image (if it
doesn’t, you need to press ” Control + ’ ” keys and it will show the grid – this acts as a toggle, so just press ” Control + ’ ” again and the grid disappears).

Now don’t worry, I’m not going to go into how to actually use this Rule of
Thirds grid to aid composition, as there are better explanations of the rule
available on line than I can give you here. I just thought you may like
to configure your copy of Photoshop to show you this grid so that at least
you can attempt to follow the rule, or see when your image breaks it.

Now, the method I use to straighten my photos is as follows: on your Tools
pallet you will find the Measure Tool (I know what you may be thinking, but I
don’t want to measure anything, I just want to straighten the horizon on
this pic, so bear with me!) It’s one of the tools that’s hidden
underneath the Eyedropper Tool; armed with this go to your picture and
choose a horizontal or vertical element of the image – it may be the horizon
in your sunset, or the corner of a building, or whatever (but don’t choose
something that’s not straight because the perspective of the shot needs
correcting – converging lines are corrected later on in this method). Use a
window sill, the base of a building or anything that should either be
horizontal or vertical, but isn’t, because you didn’t hold the camera
straight, or you’d had too many glasses of wine! Zoom in on this part of
your image and with the Measure Tool draw a line across the two end points
as accurately as you can – the longer this line is, the more accurate the
result will be. Now go to the Image menu and select the Rotate Canvas item
and choose Arbitrary from the fly out menu. A small dialog will appear
telling you the angle of rotation and direction needed to straighten your
image, so that the line you drew with the Measure tool ends up sitting on
either a Horizontal or Vertical plane. All you need to do is click OK and
Photoshop will rotate your image for you. Now you will probably find that
your image has transparent areas around its edges where the picture has been
rotated, but don’t worry about that, because you will be fixing that in the
next bit.

Okay Cropping; probably my favorite filter in Photoshop is the Lens
Correction filter found in the Filter menu under the Distort section. This
is where I do the rest of my cropping work – this filter is underrated in
my opinion, but with it you can correct:

Lens Barreling – apparent when you have your lens set to wide angle.

Chromatic Aberration or lens fringing – apparent in areas of high contrast
on your image (go on, zoom in on that tree, see the blue fringe on the edge
next to the sky? Yuck! Get rid of it with the aid of the sliders here).

Vignetting – your camera may not suffer from this problem (mine doesn’t),
but you can also use it to ADD vignetting to your image for a pleasing
effect and it’s a good way to experiment.

Perspective problems – converging lines on buildings which make them appear
as if they are going to fall over. Two sliders here allow you to correct the
perspective of your shot both vertically and horizontally.

And lastly, you can use the Scale slider to get rid of those transparent
triangles at the edges that we introduced before.
You could also use this filter to straighten the image, but frankly, I don’t
think it’s as accurate as the Measure tool method – just my personal
preference, but hey!

Go on give the Lens Correction filter a try, and see whether you like it!

The only problem with this filter is it’s a destructive one (in Photoshop
CS2 at least), and by that, I just mean that once you click on the OK
button you can’t go back and tweak the settings – well, you can, but it’s
not very easy because you need to have saved them separately first.

The important thing to remember about this Lens Correction filter is that it
only works on the active Fill Layer (the one you have selected in your
Layers Palette), so if you not sure about something make a copy layer first
(Control + J) and work on that. You can always delete the layer afterwards
if you don’t think it worked for you.

Since areas of a layer can exist outside the bounds of your canvas you will
find that the bits of your image that you can no longer see are actually
still there! It’s not till you flatten your image that Photoshop gets rid of

Well I think that’s about it for cropping and straightening and anything
else comes under another title for another day. If you found this useful
then let me know, and I might be tempted to write about some other aspect of
Photoshop. (I saw a tee on RB which said “starving.. will web design for
food” well that’s me! )

I hope you found this useful and informative, now go out and create
something stunning!

Journal Comments

  • allisonberryart
  • Trevor Patterson
  • AllyL
  • Russell Fry
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