If you ask photographers what they consider important when choosing a camera, the aspect ratio of the sensor seldom enters the conversation. Megapixels? Yes. Sensor size? Yes. Burst rates? Yes. Aspect ratio? Seldom.
Aspect ratios are determined by the form factor of the camera’s imaging sensor, which among consumer cameras are typically 3:2 or 4:3 rectangles. And while photographers weigh the pluses and minuses of MFT, APS-C, and full-frame sensor formats, few photographers care about the actual shape of their camera sensors.
"Aspect ratios are determined by the form factor of the camera’s imaging sensor..."
Photographs do not enter this world as rectangles and squares. The light image exiting the rear element of a lens is circular and it doesn’t become a square or rectangular until it’s recorded by the camera sensor or film.
The aspect ratio of a sensor, a photograph, or the LCD on your phone, laptop or tablet is the proportional relationship between the width and length of the sensor or screen. Separated by a colon—and always represented width first and height second—aspect ratios determine the form factor of the images the camera captures.
Full-frame and APS-C format cameras have 3:2 aspect ratios.
Micro Four Thirds cameras and many point-and-shoot cameras have 4:3 aspect ratios.
Videographers live in a wider-format 16:9 world.
Until Instagram came along, square 1:1 aspect ratios were the domain of medium-format film cameras and for a short time in the 1960s and ’70s—Kodak Instamatics.
Most digital cameras offer you a choice of aspect ratios apart from the camera’s native aspect ratio. Depending on how or where you plan on displaying your pictures, you can often improve the visual impact of a picture by changing its aspect ratio to a format that allows you to fill the frame more efficiently.
Aspect ratios weigh heavily on how we compose photographs. The dimensions of the image’s horizontal and vertical frame lines influence how we angle the camera and how close we can get to our subject.
Squares and rectangles present different challenges. Some images lend themselves better to square frame lines while others work better as rectangles. The good news is that, depending on the camera, you can often preset your camera to an aspect ratio that better fits the compositional needs of the image.
3:2
The native aspect ratio for full-frame, APS-C, and 1" imaging sensors is 3:2. Photographs captured at 3:2 can be printed with little, if any, cropping onto 4 x 6", 6 x 9", 8 x 12", 10 x 15", 12 x 18", 16 x 24", 20 x 30", and 24 x 36" paper sizes.
Though no longer widely available, 6 x 9 cm roll-film and 5 x 7" sheet-film cameras also have 3:2 aspect ratios.
Most photographers find the 3:2 format to be a comfortable compositional workspace.
4:3 (Universal Video Format)
Originally intended for motion picture and TV production, the 4:3 Universal Video Format is most commonly associated with the Micro Four Thirds (MFT) mirrorless cameras from Olympus and Panasonic. MFT-format cameras are also incorporated into the latest-generation drones from DJI.
With the advent of widescreen motion pictures and HDTV, the wider 16:9 ratio has greatly replaced the 4:3 as the standard for video and TV productions.
Though most people associate the 4:3 aspect ratio with digital imaging, 4:3 is also the aspect ratio for 645 (6 x 4.5cm) film and digital camera backs.
A big selling point for the 4:3 format is that it allows you to output traditional print sizes–i.e., 4 x 5", 8 x 10", 11 x 14", 16 x 20", and 20 x 24", without having to crop the original image file.
Generally speaking, most shooters find little difference between composing pictures at 4:3 compared to the less “boxy” 3:2 ratio.
16:9 (Universal HDTV Format)
The widest standard aspect ratio found in consumer cameras is 16:9. Created for widescreen movies and HDTVs, digital cameras automatically default to 16:9 when you switch your camera to HD video mode.
Some landscape shooters set their cameras to 16:9 to give their images a wide-field appearance. Do 16:9 pictures really have wider fields of view than the same image captured at 3:2 or 4:3? Not at all, but by lopping off the upper and lower portion of the frame, you get the appearance of a wider field of view.
1:1
Hasselblad and Rolleiflex cameras used to be the cat’s meow among medium format film shooters. The square 6 x 6 cm images they captured were the domain of wedding, portrait, and commercial photographers. Nowadays, 1:1 is available mostly on point-and-shoot and consumer-oriented cameras though, practically speaking, any image can be easily cropped to a square.
For wedding shooters, the square format eliminated the “vertical or horizontal” dilemma. Square-format wedding albums that could be made up in a variety of sizes and prints up to and beyond 24 x 24" were possible. In most cases, the pictures could also be cropped to fit more conventional 4 x 5", 8 x 10", 11 x 14" and 16 x 20" print sizes.
Aside from Holgas, Lubitels, and Dianas, the only square-format cameras currently being manufactured are the light field cameras from Lytro.
Perhaps the best use for the 1:1 aspect ratio setting is for shooting images intended for Instagram. Similarly, many websites defer to square-format avatars and portrait fields.
Panorama
Many cameras offer a panorama mode, which captures a series of 60 or more still images when you hold the shutter button and pan the camera to the left or right. These images are then stitched together in-camera to produce panoramic images with up to 360 degrees of coverage. Due to the nature of the process, panoramic images have variable aspect ratios.
The trick of capturing successful panoramic images is to pan slowly while maintaining a level horizon line. The bugaboo of stitched panoramas is that repeat patterns, vertical lines, and moving objects can confuse the image processors, resulting in visual “hiccups”—some more obvious than others. But when all of the visual elements fall into place, the results can be outstanding.
So what’s the best aspect ratio to use?
"Switching from 3:2 to a wider 16:9 aspect ratio doesn’t make the image wider—you’re simply cropping the top and bottom of the frame to fill the full length and width of your 60" HDTV."
If you’re shooting film, your camera determines the aspect ratio of the photograph. In the case of digital cameras, most offer you the option of changing aspect ratios.
When you change the native aspect ratio of a camera, all you are really doing is pre-cropping the image. Switching from 3:2 to a wider 16:9 aspect ratio doesn’t make the image wider—you’re simply cropping the top and bottom of the frame to fill the full length and width of your 60" HDTV.
Want to shoot square? No problem, but keep in mind you’ll be losing the left and right sides of the total image field.
If you’re looking for maximum levels of resolving power, the best aspect ratio to use is the camera’s full sensor area, regardless of format, and do keep in mind that if you decide to change the aspect ratio of any pictures that follow, they will be cropped and lower in resolution.
JPEG or Raw?
One last item worth mentioning has to do with your choice of image files. If you select an aspect ratio other than the camera’s native aspect ratio and only capture JPEGs, your image files will be cropped accordingly. Whatever was cropped out of the picture is history.
If however you shoot raw (or JPEG+raw), your JPEGs will be cropped but you will be able to access the entire image when you open the raw file. If in doubt, you should shoot raw, JPEG+raw, or simply crop your final image post-capture.
Changing aspect ratios post-capture
Changing aspect ratios of existing images is simply a matter of cropping. For precise aspect ratio cropping, your best bet is to open your image in Lightroom.
In Lightroom, go to Develop, click on Original, and choose from the list of default ratios or create a custom ratio.
You can also crop JPEGs to alternate aspect ratios in Photoshop CS, but you have to crop the image manually to the desired ratio. Raw files can be cropped in Adobe Camera Raw, similarly to the way you would change the aspect ratio of an image in Lightroom.
At the end of the day, unless you have to follow a firm layout, your final image should be cropped in a way that optimizes the compositional impact of the photograph, regardless of how square or elongated it may be.
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