Emaling Images

Keeping with this week's photography theme (I'll try and have more variety soon), I have an explanation for a common problem with sharing pictures.

The Problem:

When people send other people (particularly those with little image editing knowledge) pictures from digital cameras or scanners they often are displayed very large. This problem has even effected some friends of mine who I have sent pictures, because I don't like to loose quality any more than necessary. If you view the picture in older versions of Internet Explorer, and your webmail provider doesn't scale images automatically, you will have a very small portion of the image, which looks awful, and a huge amount of area to scroll.

Why:

This involves a bit of theory about how digital images work. Most digital images are bitmaps (as apposed to vector drawings), groups of tiny dots called pixels. Digital cameras these days are often sold by their number of MegaPixels (not as important as some other features, cameras with good optics, image stabilization, and good processing, are often better than those without these features but with a high MP rating). A MegaPixel is 1Million Pixels and is a measure of area (Length * Width), for example my 6.1 Megapixel camera produces images 3039 pixels by 2014 pixels. If you multiply that out, you will find that it comes out to about 6.1 million pixels. Those 6.1 million pixels are either reduced to something that can be more easily displayed/printed or compressed into tighter bundles. The number of pixels in a given area (usually an inch), or its resolution is what is important when displaying images (often expressed in DPI or dots per inch). To get a reasonably sized print, I would have to use a resolution of at least 600 DPI; However, many monitors (and older imaging programs) display images at 72 DPI. This spreading out of the pixels (dots) is the cause of your huge photo problems. Of course, spreading the pixels out in this way also makes your picture look very bad, unless you have a very good camera/scanner.



What to do about it?

Well, you have two choices, you can reduce the number of pixels, or increase the resolution. Many programs can do both. For displaying the picture, look for a zoom function, and zoom out. I find that 30% zoom or less works well, for my 6 MP pictures. If you are sending pictures, it may be a good idea to scale them. In GIMP, the option is called "Scale Image", and I would expect it to be similar in most programs. I would start with a value around 1024x768 or 800x600 (these are common resolutions of monitors, so the resulting image should just about fill the typical screen), be careful not to stretch the image, type one number in and make sure that the option to keep the aspect ratio the same is enabled (often an image of a chain, or a check box), the program should fill the other value in with something appropriate. This is also good because it will drastically shrink the file size, just be sure to keep a copy of the original, because since you are throwing away pixels, you are lowering the overall quality (save as). The same thing goes for printing, many image editing packages, have an option to adjust the print size (including the default image viewer in Windows XP).

If you don't have any image editing software on your computer, you can always import an image into your Word Processing program (in Word use Insert -> Object -> From File). Size it by using its properties dialog or by dragging the small boxes on the corners, just be sure no to stretch it.

This should get you started, but if you want more info about megapixels vs. camera features, and print resolution, take a look at this article or search google.

If you don't want to deal with all this, you could just use a photo sharing program like picassa or a photo sharing site like flickr or ophoto (there are many more, do a search)