All About Digital Photos - Changing the Size of a Digital Photo

At some point or other you're likely going to want to change the size of a digital photo. This will usually be to serve an intended purpose such as emailing a smaller sized version of your original photo. In most instances you will be reducing the size of the image. The details of various size changes are described below:

Original Photos
Your original digital photos, whether they be from your digital camera or from a scanner are your "negatives" and should never be touched. Keep them in a safe place and always work on copies of your originals. See the Storage Page for details about how to properly save and archive your originals.

Enlarging Digital Photos
Digital photos do not take well to being overly enlarged and this is generally to be avoided. If you want to print an image it is usually best to first try printing using the original size and quality of your digital photo. Your printer software will make the adjustments.

If you really want to digitally enlarge a digital image then the best bet is to either use proven workflow routines to optimize enlarging or get software specifically designed for this purpose (i.e. Genuine Fractals or SI Pro). If you are using a program such as Adobe Photoshop, the "quick & dirty" way to do a reasonable digital enlargement results is by doing the enlargement in increments of 10%. Keep doing 10% enlargements until the distortion that results becomes too great for you and then step back one step and save the resulting enlarged image. There are much better, but more complicated Photoshop techniques. An excellent one can be found on Digital Outback (update: a free Photoshop Action that does this routine in one mouse click is now provided on that website). For others, do an Internet search for "Upsizing Digital Images" and "Enlarging Digital Images."

Reducing Digital Photos
The most common size adjustment for a digital photo is to reduce its size, either for a specific purpose (i.e. emailing, posting to a website) or to crop the photo. Specifics regarding cropping and size reduction for emailing are in the two sections following this one.

One note is that after a digital photo has been resized, it will need to be re-sharpened. Sharpening comes in many flavours and sometimes it can be a bit hard to find in a program. For instance, in Adobe PhotoShop (CS or Elements), the most effective sharpening tool is the "Unsharp Mask" that you will find under the "Filter" menu using the "Sharpen" option. In IrfanView it is under the "Image" menu but for greatest control you'll have to open the "Effect" option and choose "Effects Browser" in order to visually control the amount of sharpening. In Breezebrowser it is part of the "Proofs" dialog box and uses settings similar to Adobe PhotoShop's "unsharp mask". There is a whole science to doing high quality sharpening, do an Internet search for "Sharpening Digital Images."

Cropping Digital Photos

Top: original photo with a 1.33:1 aspect ratio. Cropping marquee is shown
Bottom: Cropped to a 1.5:1 aspect ratio

A common size change for a digital photo is cropping. This can be done to either "zoom in" on a section of the photo (create a new photo of just a portion of the original photo) or to change the aspect ratio of the photo. We'll discuss the latter first.

Aspect Ratio: the aspect ratio is the ratio of the width of a photo compared to the height of the photo. A square photo would have a 1:1 aspect ratio (width is the same as the height). Conventional 35mm film has a 1.5:1 aspect ratio. Most "point & shoot" digital cameras produce photos with a 1.33:1 aspect ratio while digital SLR cameras generally use the 35mm 1.5:1 aspect ratio. You can determine the aspect ratio of your digital images by looking at the pixel dimensions. A photo with dimensions of 2048 x 1536 would have an aspect ratio of 1.33:1. The problem with this ratio comes when you want to print a digital photo. A 6" x 4" print has an aspect ratio of 1.5:1, an 11" x 8.5" print has a ratio of 1.3:1, a 7" x 5" print has a ratio of 1.4:1. The answer to printing your original 1.33:1 aspect ratio digital image to various paper sizes is either bordering (printing the full image and leaving white border space to make up the difference in ratio) or cropping.

Cropping: this involves selecting a portion of the image and removing the rest. This creates a new smaller image with just the portion of the image that you want. Cropping can be used to remove annoyances in the photo, to "zoom-in" on a selected portion of the photo, or to change the aspect ratio of the photo so that it can be printed full frame on a selected paper size. Most good photo programs have a cropping tool. In Photoshop Elements for instance you would use the "Rectangular Marquee Tool" to select an area of the photo. Note that this tool can be set to be a fixed aspect ratio (i.e. 6:4). Once selected you would use the "Image > Crop" function to produce an image with only the selected portion of the photo.

Many photo printers come with software that allow the easy printing of photos and include a built in cropping tool, allowing you to crop the photo to the desired printing size.

Emailing Photos

One of my pet peeves is digital photo bloat and this is especially true when it comes to emailing photos. There is no point in sending "just to see" photos of a larger viewing size than a normal computer screen - it's just annoying. These images should be reduced in both pixel dimensions and computer file size. Some of you will have software that came with your camera that will automatically do this for you. Others will have to rely on separate photo software. My recommendation for emailing size is a photo with a horizontal dimension of about 800 pixels and a JPEG compression of between 35 to 50%. My favourite program to change digital photos for emailing is Breezebrowser, but I'll outline procedure for Windows XP, Adobe Photoshop and Irfanview as well:

Windows XP

You will first have to download and install Microsoft's Image Resizer Powertoy for Windows XP: www.microsoft.com/windowsxp/downloads/powertoys/xppowertoys.mspx
Open up a view of your images using Windows Explorer or My Computer
Select the image(s) you wish to resize
RIGHT mouse click on the selected images
In the dialog box that pops up, choose "Resize Pictures"
Choose the size you want and click OK
Copies of you new resized images (with a size ( ) in the filename) will appear in the folder with your other images

Adobe Photoshop Method

Adobe - image size dialog box - resample image

note that both the "Resample Image" and the "Constrain Proportions" boxes are CHECKED and that the WIDTH box in the Pixel Dimensions section has been set to 800 (the program will automatically set the height).

Load a copy of your photo into Adobe Photoshop (or Photoshop Elements).
Select the "Image > Image Size" menu option (may be "Image > Resize > Image Size" in Photoshop Elements).
In the image size dialog window, make sure that the "Resample Image" and the "Constrain Proportions" checkboxes are selected (checked).
In "Pixel Dimensions" section type in 800 in the Width box (assuming that the image you are working with has a width greater than 800
Click the "OK" button - Sharpen the image if required
Your photo will be resampled using its original aspect ratio (which is what Adobe means by the obtuse "Constrain Proportions").
Use "Save As" to save this photo in JPEG format with a new name - I suggest adding a -email extender (i.e. "345-2365-email.jpg"). Click "OK"
The next dialog box are your JPEG options, choose Quality 5 or less.

Newer version of Photoshop have a "Save to Web" which can do the above in a single process and make a smaller file to boot. If you have this option use it. It will allow you to change the image size and select your JPEG compression in one step. Note though that "Save to Web" will strip out any IPTC data you have in the image.

Irfanview Method

Load a copy of your photo into Irfanview
Select the "Image > Resize/Resample" option
In that dialog window make sure that "Preserve Aspect Ratio" is selected
In the "Set New Size" section, make sure that "pixels" are selected and input 800 for width
Click on the "OK" button. Sharpen the image if required.
Use "Save As" to save this photo in JPEG format with a new name - I suggest adding a -email extender (i.e. "345-2365-email.jpg"). In the flyout box select 50 as the quality

You can also change the size of multi photos using the Batch Conversion routine in Irfanview (also accessible from the thumbnail view).

Breezebrowser Resize (Proof) Window

Breezebrowser Method

View your photo directory with Breezebrowser (thumbnail images)
Select all the images you want to change
Under the "Tools" menu select "Proofs"
Make sure that "Resize" image is selected and set Max Size to Width of 800 and height of 600
Set any image enhancement options you want (i.e. sharpening). You might also want to add a watermark (your name, EXIF photo date, IPTC caption, etc.)
In output settings, choose JPEG with Quality 50. The default output directory is a subdirectory called "proofs" but you can change this to whatever you wish.
Click on "Proof Selected" then use Breezebrowser to look at the results in your "Proofs" directory (or wherever you have put them).

More Options

Do an Internet search (i.e. Google) for "resizing photos for email software" and you'll get lots of hits, including dozens of free software packages designed to resize photos and even some services that will do the conversion on-line.