Last updateFri, 06 May 2016 1pm

Sending images: The curse of large attachments

The other day I received an email from a client who said she was having trouble sending emails with attachments. 

When I asked her the size of the attachment she was trying to send, she answered “250 megabytes.”  My response to that was “Good GRIEF!!!!”  A file that size is only one hundred times bigger than some email systems can handle.

When sending emails with attachments there are two limits to consider.  There is a limit to the size your computer can send, and there is a maximum size the recipient’s computer can receive.  So, even if your email system allows you a very generous 10 or 20 megabytes maximum, the person you are emailing may have a limit of only two megabytes.  Enough about that.

My client was attempting to email a photograph, and sending a super high-resolution image file is a waste of electronic resources.  I will explain this in layman’s terms rather than technical:  When an image file is displayed on the screen of a computer, it can probably display only 50,000 bytes (50 kilobytes) of sharpness.  Smart phones would need even less.  If you send somebody an image file with 16,000,000 bytes of sharpness (16 megabits), that is at least 15,950,000 bytes more than necessary.  There is just no use sending someone an image that is thousands of times bigger than it needs to be.

Smart users know the thing to do is reduce the resolution of image files before emailing them.  There are some programs that do this automatically, Picasa being one of the most popular (albeit only for users of Gmail).  There are also free utility programs that can resize images; my favorite is the easy to use “Image Resizer” available for Microsoft Windows.  I have never found a comparable easy-to-use utility for OS-X so if anyone reading this knows of one I hope you will let me know.

Mac users still have an option because OS-X comes complete with a way to resize images.  Simply use Apple’s Preview program; click on Tools and Resize Image.  Your goal is to end up with a file that is much smaller than the original, in the case of super high-resolution originals the reduced file could be only onepercent as big as the original … but that is all that is needed to display properly and that may be emailed easily.

By now some alert readers will be asking “Why does my camera make image files that are so huge that I cannot email them?”  The screen on a computer or smart phone can only display image quality up to the maximum resolution of its screen, and that is a very small amount of data.  However, if you ever want to print out on paper an image in National Geographic Magazine quality that does require much more sharpness, ergo the need for a much bigger file.  This explains why sometimes you may hear someone say a certain snapshot looked great on the tiny screen of their smart phone but the same image file looked awful when they printed an 8x10 hard copy on paper.

So, your camera makes large image files in case you need the sharpness for printing.  If you know the recipient of your email is only going to view an image and not print it, you might as well reduce the size of the file in order to be able to send it as an email attachment.

Charles Miller is a freelance computer consultant with more than 20 years IT experience and a Texan with a lifetime love for Mexico.  The opinions expressed are his own.  He may be contacted through his web site at SMAguru.com.

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