Don Edrington  PC Columnist for the San Diego Union Tribune  Home Page  Profile
Share/Bookmark

The text on this page was created with Google Docs, the free word processing program available at: Google/Drive/Docs.
The computer used was a Google Chromebook.

I Love Working with My Chromebook and Google Drive




Reducing a Digital Photo's File Size

   A reader recently wrote: "How do I reduce a 2-megabyte JPG photo to a few hundred kilobytes? I don't want to resize the picture; just make the file size smaller so it can be emailed as an attachment more easily."

   Well, it's helpful to understand why digital photos are usually saved in the JPG format to begin with. There are file size choices that range from very small to very large (lower quality resolution to higher quality resolution). Surprisingly, going from a high bit count (hi-res) to a lower bit count (low-res) often results in an image that shows little discernable difference in quality.

   By default, each time a JPG is saved (in many image-editing programs) it is compressed to a file size of about 80 percent of the previous save. Well, an image thus compressed once will usually not noticeably have the quality of its appearance diminished. However, additional 80% saves can make a picture look very splotchy.

    The original reason for compressing images was to accelerate their emailing speed and to conserve disk space. However, in today's digital world of huge hard drives and high-speed internet service, compressing a JPG is rarely helpful.
        Also, once a picture has been compressed it can never be "uncompressed."

        Therefore, you should give subsequent saves incremental name changes such as, say, Sunset-1.jpg, Sunset-2.jpg, etc. Better yet, use Irfanview (free image-editor from www.pcdon.com/irfanview) which lets you choose your own JPG compression ratio, including the option of saving an image at 100 percent (i.e.: no compression at all).
   
Various image-editing programs have different ways of letting you adjust the bit count, but my favorite is Irfanview, which is a free download from Irfanview.com

   Open a picture in Irfanview, go to File>Save As, and choose JPG from the "Save As Type" list. A sliding "Save Quality: (Best to Lowest) bar will appear that displays a percentage number as it is moved.

   Experiment with different percentages to see how small you can make the file, yet maintain an acceptable image.

   IMPORTANT: be sure to change the file name with each attempt (such as Mary1.jpg, Mary2.jpg, Mary3.jpg, etc.). Always retain a copy of the original image with its name unchanged. If the original's file size is reduced and then saved with the same name it can NOT be returned to its previous status. This is why JPG is known as a "lossy" image format.



    Before saving an image in IrfanView be sure "Show options dialog" (at the bottom of the page) is checked, whereupon "Save Quality" options will appear, displaying different compression ratios. (I normally use 100%.)



Free Newsletter
Don's Newsletter

If you would like to receive our newsletter just send an email
to Don Edrington at: DonEdrington@gmail.com.
and put newsletter in your Subject Line.
  We've been sending out this PC Help Newsletter since 1994
and your email address is safe with us – we don't share it with anyone!
Read Current Newsletter

© Donald Ray Edrington - All Rights Reserved
Top of Page
Mission Statement - Privacy Policy

This page is supported by advertisers who create and post ads here via Google Adsense.