Sharpen Downsized Images

Did you ever look at a photo online and it doesn’t look quite sharp?  It is kind of blurry and you aren’t sure if it is the photo, the screen, or just your eyes.

Well, there is a good chance that the image was downsized from high resolution (300 ppi – pixels per inch) to screen resolution (72 ppi) and was not sharpened.

Simply put, when a digital image is downsized, the computer interpolates the image; it throws away pixels and does its best to determine what the picture should look like smaller.  Unfortunately, sharpness is a casualty of this process.

Thankfully, there is an easy remedy.  Sharpen the downsized image.
Please note:  Sharpening an image will not correct an out of focus image!  If a photo was shot out-of-focus, it will always be out-of-focus.

For those who want the technical low down, here it is:
Digital photographs are made up of millions of little pixels (or dots).

High Resolution (Hi Res) – 300 ppi which is suitable for printing.
Low Resolutions (Lo Res) – 72 ppi which is suitable for websites, emailing,
and computer viewing.
Megapixel – 1 million pixels

Example –
High Resolution:
An 8 inch x 10 inch image at 300 ppi  =  2400 pixels x 3000 pixels
multiply those two numbers and you get 7,200,000 pixels or 7 megapixels

When you downsize that same image from high resolution you get –
Low Resolution:
An 8 inch x 10 inch image at 72 ppi  = 576 pixels x 720 pixels
multiply those two numbers and you get 414,720 pixels or approx. 1/2 megapixel

7,200,000 pixels  – 414,720 pixels =  6,785,280 pixels

That is a loss of a whopping 6 1/2 million pixels!!!  And thus you get a soft image.

But I don’t know how to sharpen an image,” you say.  Don’t worry.  Any experienced professional photographer or graphic designer should know how to do it for you.  When in doubt, ask.

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One Response to Sharpen Downsized Images

  1. Jon says:

    I always wondered why so many photos online look fuzzy. The question is, how many are just out of focus and how many simply need to be sharpened? Good post.