(Image) Size Matters
Parentheticals and double entendres are 'big', in that they are common, at least to these pages. What is also common is for people who regularly work with image files to have no idea what they are doing. It's okay, it is the fault of our highly-specialized economy and a lack of any common computer literacy curriculum, which results in a lot of self-teaching and a litany of 'unknown unknowns' that plague every computer user (save the one who started by reading the manual.) But it can be a 'big' problem when it comes to efficiency, budgets, and sanity if people don't know how to determine the dimensions of an image file.
How Big Is That Image File, Anyway?
If you are working on a Windows-based PC, it is relatively painless to find the resolution of an image file, though, because it is a Windows-based PC, it is neither obvious nor intuitive how to do this.
Right-clicking an image file, selecting 'Properties' and clicking the 'Details' tab will give you a wealth of details, including the 'dimensions', which is the same thing as resolution. Confusing? Yes. But I have faith you can accommodate this contradiction.
Note that these values are always written with width first, followed by height. Also, If there is sufficient demand in the comments, I can go in to the other strategies for viewing the 'resolution/dimension' properties for you power users out there.
Mac OS users have it perhaps a little easier. The finder window, when set to 'Icon' or 'Column' view will have the dimensions of an image file clearly listed, either below the icon or in the 'Preview' column. In 'list' or 'cover flow' views, you may have to highlight the file in question and hit 'Command+I' to bring up the file's Info panel. You will see the dimensions under 'More Info:' as below.
Is It Big Enough?
And now for more confusion. The common definition of 'resolution' is synonymous with 'dimensions'. The other definition of 'resolution' has to do with print media, and introduces the aspect of 'DPI' or 'dots per inch.'
Without getting too technical, suffice it to say that the dimensions of an image file are related to the 'DPI' settings. Images meant for display in a video, web page or other screen should have a 'DPI' setting of 72. Print applications, like brochures and posters, require a DPI setting of 300 (or better) to look their best. It is best not to think about 'dpi' unless you want your head to explode
In the dimensional sense, a file is 'big enough' if the dimensions of the image match the area you would like it to cover. If you want something to be 'Full Screen' ask yourself, how big is the screen? An HDTV screen's resolution (see, there it is, the common usage again) is 1920 x 1080 (unless it is 1280 x 720, but we're trying NOT to have your head explode, if you'll recall.). So your image better be close to that size. Oh, and that dimension is sometimes referred to as the 'raster size'. You're welcome.
For print, there's a little math you can do. Let's say you want to print an 8″x10″ photograph. You need 300 dots per inch of real resolution, as you recall. So your image file would need to have dimensions of 2400 x 3000 or risk looking yucky.
The web has fewer hard-and-fast rules. Old displays would max out at 800 x 600. A 4th generation iPad screen dimensions are 2048 x 1536. And your cell phone screen? That could be any of 10+ specific dimensions. Designers argue over whether to size everything for the lowest common denominator, or adopt standards that scale to the size of the – new term alert – viewport. That's the size of your web browser's viewable area and doesn't have anything to do with how big your screen dimensions are. Check your head – is it pulsing or creaking? If so, step away from this article. Hopefully you'll know a little more about how big things really are, and that's enough for now.