Photography Tips - Cropping Images

As the old saying goes "Less is More."

This is certainly true when it comes to certain images.  Cropping an image can eliminate distracting elements, improve composition or even shift the focal point to a different area of the image.  Today's image editing software makes cropping images relatively painless.  An image can be quickly copied and cropped.  Any cropping applied to the copy can be quickly undone as long as the copy has not been saved.

This process can be repeated to create any number of images, each with an alternative crop.


Tips for Cropping Images

1)  Use an image program with transparency and layering capabilities.  
This allows you to place a cropping stencil above your image.  This stencil is basically a frame with a transparent square or rectangle cut out of the middle.  The part of the image visible is what will remain after cropping.

2)  Prepare stencils with desired aspect ratios in advance.
Start with an image equal in size to images produced by your camera.  (This does presume you want to crop photos.)  Fill with a single color, black works well.  Enable transparency if not already enabled.  Create a second layer on top with a different color.

Decrease the scale of the top layer.  The aspect ratio can be altered if desired.  Merge the shrunk layer with the first.  Use the color selection tool to select the middle area and cut.  (The editing software I use places the layer in the middle of the image when shrunk.  If second layer is placed at a corner you will have to move it.  The placement does not have to be precise.)

3)  Save file using format that preserves transparency.
Saving using the editing software's native format should do this.  Exporting to png format is an alternative as this saves transparency settings.  Other formats will result in the transparent area being replaced with the background color.

Stencils with different aspect ratios can be saved as different files or images.  They can also be saved in a single file as different layers.  Make sure each file or layer has a description of the aspect ratio.

Using a crop stencil
1) Import Stencil
Open the image you want to crop in your image editing software.  (Again, it needs to support transparency and layers.)  Follow by importing the appropriate stencil.

If you saved the stencil as as individual files, just open the desired stencil as a new layer.

If all stencils are saved in one file, open that file then copy the desired stencil.  Paste this on top of the image as a new layer.

The stencil can be moved around once it is on top of the image to be cropped.  This helps give a good idea of what the cropped image will look like.  The stencil can also be rotated to change orientation or scaled up or down to change how much of the image will remain after cropping.

2) Select Transparent Area
Use an area selection tool targeting the transparent area of the stencil.  Make sure the selection tool is set to select transparent areas.

3) Use Selection to Crop Image.
The quickest way to do this is simply selecting "Crop Image to Selection."  The image can be saved with a different name after this so that the original image remains unaltered.  Of course, the quickest way is not always the best way.

An alternative method is to copy the selected area and then paste as a new image.  This image will have a different name from the original so there is no chance of overwriting the original file.  The copy and paste method works well if uncertain that the selected area is the best choice.  The original file still has the stencil in place and this can b quickly altered if the crop is not quite correct.

The stencil can still be used if the software refuses to select transparent areas.  Select the colored portion of the stencil instead.  Switch to the image's layer.  Then invert the selection.


Why Not Just Use a Rectangular Selection?

This may seem like unnecessary work when you could just use a rectangular selection tool to select the area you want to keep.  There are some reasons to use a crop stencil when cropping images.

First, it's easier to tell what the end result will be when using a stencil to block out portions of the image.  Using a selection by itself will require a certain amount of guessing as to how the crop will turn out.

Second, using a stencil results in an accurate aspect ratio after the crop is applied.  This is useful in some circumstances.  The most obvious reason for using a specific aspect ratio is because the image will be printed and framed.  The aspect ratio changes based on the size of print desired.


A 4" x 6" print requires a 3:4 aspect ratio.  An 8" x 10" is a 4:5 ratio.  Compare the lengths as percentages to understand what that means.  The first ratio results in the short side having a length 75% that of the longer side.  The second result in the shorter side having a length 80% as long as the longer side.

Using an image with a 3:4 ratio to print an 8" x 10" requires one of two options.  First, the image can be stretched in one direction.  Second, the print can have blank borders along two edges.

Cropping the image before allows the image to be printed without choosing one of those options when printing at a specific print size.