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Optimizing Images

Basic Image Optimization for the Web

by Laurie McArthur Wilderness Landscape Photography

Living in rural Australia, I'm not on broadband. Rather, I'm on dial-up with a 56k modem. You'll understand that, being an impatient old bloke, it really gets up my nose when I visit a website that takes for ever to load, or when someone e-mails me photos that, similarly, take too long to download.

The answer: Resize and optimize your photos. Here are the basics on how and why.

Why Resize and Optimize Photos for the Web

Minimize transfer time.
The larger the file size, the longer it takes to upload and download.
Save on storage space.
The larger the file size, the more storage space required.
Save on bandwidth usage.
The larger the file size, the more bandwidth used in uploading and downloading the photos.
Deter image theft.
A photo resized to 640px x 480px at 72 dpi, and optimized to 80% quality will not make a very good print, even at half the size of a 6" x 4" mini lab photo, yet will retain quite acceptable quality for on-screen viewing and will be large enough to appreciate.

Software for Resizing and Optimizing Photos

Your computer probably came with a basic graphic arts or image viewer application. Study the help file and you'll soon get the hang of it.

A good alternative is IrfanView, a free program that I use all the time, for most everything to do with photos. Again, study the help file and you'll soon be on track.

Aims of resizing and optimizing photos

Of course, you'll be aiming to reduce the file size of your images. This reduction occurs in four forms.

Reduce the physical size of the photo.
A suitable size for viewing a photo on the computer screen may be 640px x 480px. This is particularly relevant for the photos that you e-mail to friends or family and is also a good maximum size to keep in mind for an online gallery. Unless you had a good reason, you wouldn't go any bigger than this for a web page and may choose to go as small as 250px. x 187px. if there are multiple images on the page.
Reduce the resolution of the photo.
Most computer screens, that's yours and mine, have a screen resolution of 72 dpi. That's dots per inch or pixels per inch, if you like. This resolution is adequate for the human eye. Therefore, there's no point in maintaining a higher resolution in your images for on-screen viewing. So, when you're setting your new image size, also set the dpi to 72.
Reduce the image quality.
Yes! Reduce the quality of your precious masterpiece. This is the main part of the optimization process.
The great advantage of the JPEG or jpg file format is that it compresses file size by loosing unnecessary information. Even at 100% quality, a JPEG file is vastly compressed. If you save your photos at 85% quality, the loss in quality will be imperceptible. In some situations you can go lower, down to 70% or even 60% and still have a usable image with vastly reduced file size. Experiment for yourself and see the results.
Remove the EXIF data.
Your digital camera records quite a lot of information about the camera settings, as a text file, whenever you take a photo. This EXIF information is attached to your image file and should be removed as part of the optimization process. This will probably occur by default in your application but if need be, adjust the settings accordingly.

So that's it. Nothing to it really, once you get the hang of it.

A few things to consider

Try and "Save as," only once.
Every time you save a JPEG file, you loose more quality. That's it's nature.
IrfanView is a great choice.
With Irfanview, you can make certain image adjustments in the same operation as resizing and optimizing, thus reducing the number of "saves."
Work on a copy.
Always keep your original file in tact for when you want to make a print, manipulate the image in some way or make a different sized copy for the web or e-mail.
Reduce file size in the camera.
Your digital camera settings will allow you to reduce the size and image quality of the original file, when you take the photo. This is fine if you are sure that the only use for the photo is on-screen viewing. It will save space on your memory card, too.
Relating this to scanned images.
While this little tutorial is directed mainly to digital camera photos, much of the information will be useful if you scan negatives or prints.
About the Author Laurie McArthur

Laurie is a passionate digital photographer. He captures the landscape around his home on the New South Wales Far South Coast, also known as the Sapphire Coast, the high country of the Monaro and Snowy Mountains, a little way inland, and also the Australian outback. Laurie also gets involved in social documentary from time to time.

A range of Laurie's photography and stories can be seen on his websites: Wilderness Landscape Photography, ATV Camping and Portrait of a Dairy Family.