Digital Camera Aspect Ratio and Photo Print Size

May 16, 2008

What You Saw Is Not What You Got - You take your brand new digital camera along for your European vacation, shoot hundreds of photos, and start printing them when you get back home. To your shock and dismay you discover that all of your photos, many of which you carefully composed to include nice backgrounds, are cropped, missing either portions of the top or bottom, or both. What happened?

History of Photo Sizes - Going back in time recall the widespread 35mm format film used in almost every camera. The actual size of the negative was 36mm wide x 24mm tall, resulting in an aspect ratio of 1.5 (36/24). Next you took your film to be developed and have photos printed, most likely 6 inch x 4 inch in size. Since 6/4=1.5 is the same ratio as the negative, the image on the negative would be enlarged untill it filled the size of the photo paper. Perfect match. If you had your photos printed at 7 inch x 5 inch (aspect ratio of 7/5=1.4), a bit of cropping would be done either manually or automatically, amounting to less than 1/4 inch on each side. You probably never noticed.

Digital Camera Aspect Ratio - Fast forward to digital cameras. Initially manufacturers assumed photos taken with digital cameras would be primarily used for display on computer monitors. Many monitors have resolutions of 800 x 600, 1024 x 768, 1280 x 960, and so on. The common factor among all these is the aspect ratio of around 1.3 (800/600 for example). Looking at resolutions for typical consumer digital cameras such as Nikon Coolpix or Canon Powershot, you’ll find that these cameras have resolutions similar to the ones listed above. This means that they’re a good match for displaying your digital photos on computer monitors, but not so good for printing, in which case they should have an aspect ratio of 1.5 to transfer the complete image to a 6 x 4 photos. Note that DSLRs (digital single lens reflex, i.e. cameras with the flip up mirror) don’t suffer from this problem. Being essentially digital versions of the SLRs, their image sensors have the same ratio as 35 mm cameras.

Digital Image vs Printed Photo Proportions - This image shows an 800 x 600 digital image frame overlayed on a 6 x 4 print. As you can see a portion of the original image needs to be trimmed to match the size of the underlying 6 x 4 paper size. It may be equal amounts on the top and the bottom, or less on the top and more on the bottom, as long as the total pixel rows trimmed add up to 140. Automated processing will trim equal amounts from top and bottom of photo. If a human is assisting this process they may ‘move’ the photo up or down so as to capture what they believe are the important portions of the picture, but there is no guarantee. Most photo processing places now have the option of 6 x 4-1/2 prints, in which case the image and the paper are a near perfect match. The cost per print however is about double of a ’standard’ sized photo.

Composing Your Photo - So what to do? When you compose your pictures in the viewfinder or preview screen, be sure to leave a little extra space above and below the subject of interest, such as a person’s head. That way you won’t end up with the top of the photo annoyingly close to the head.

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