Hack 47 Judge Image Sharpness by File Size

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With a series of photographs of the same subject in hand, you can judge which shot is sharper without ever opening a file.

Figuring out which photo in a series is the sharpest can be a laborious task. If you have five shots of the same subject, you typically open each in turn in the image editor, examine them all closely, and then make a judgment call as to which one is the keeper.

If you have to work quickly, this approach can be quite frustrating, not to mention time-consuming. There's got to be an easier way! And indeed there is.

You can make solid judgments about image sharpness without ever opening the file. Both Windows and Macintosh computers provide you with all the information you need by simply opening the folder that contains your pictures and viewing some of their basic data. Eyeballing sharpness is all a matter of size?file size, that is. The larger the file, the sharper the picture.

When you're shooting in JPEG mode with your digital camera (which you usually are, unless you explicitly switch to TIFF or RAW), the files are compressed in the camera so that they don't take up too much room on your memory card. Fine, sharp detail is harder to compress than softer, duller images. So, the resulting file for a slightly sharper image will be a little bigger.

Under Windows, open the folder of images and choose the Details view, as shown in Figure 5-1. In the Size column, you'll see how big each image is. In this example, IMG_1005 and IMG_1006 are of the same subject, but IMG_1006 (1,803 KB) is a little sharper than IMG_1005 (1,775 KB). Windows enables you to preview the image in the Details box in the left column. All you have to do is click once on the filename, and the preview for that file appears. This makes it easy to make sure you're comparing pictures of the same subject.

Figure 5-1. The Details view in Windows

This process on Mac OS X isn't much different. Choose Column View, as shown in Figure 5-2, and click the image you want to examine. Finder will generate a thumbnail, along with the image's file size and other details. Click another image to compare. Again, file size should inform you which shot in the series is sharper.

Figure 5-2. Column View in Mac OS X

This hack assumes that you usually shoot more than one frame for each subject; I highly recommend this. For people shots, I always shoot at least two frames, just in case someone looks away, closes her eyes, or otherwise contorts her face in one of the shots. But even for landscape and other nonpeople compositions, I shoot more than one frame and then choose the absolute best version of any subject. I don't hold the camera as steady for every shot. And sometimes, things happen in the background that I don't notice in the camera's small LCD monitor.

Multiple shots ensure that I come away with the best picture possible. And if you can get away with finding the sharpest version without opening a single file, why not do so?