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Not all eyes are created equal. For those without “normal” 20/20 vision, this may be a problem when you look through a camera’s viewfinder—either optical or electronic. Your view into the camera might be blurry even when the camera’s lens is in focus. Because of this, your camera’s viewfinder likely has a diopter adjustment (some older cameras do not have diopter adjustments and require the addition of add-on viewfinder lenses to provide the same function).
The diopter adjustment allows you to customize the viewfinder so that you can see a clear, focused image inside the viewfinder without using eyeglasses or contact lenses to correct your vision.
I used to spend an inordinate amount of time at a fantastic camera store in San Diego. At least twice a day, a customer would come into the store and say, “My camera is broken… the viewfinder is all blurry.” Their camera was not broken; their diopter was out of adjustment.
The only way to tell if your diopter is accurately adjusted for your eyes is to look around the viewfinder symbology (grid, exposure information, focus points, digital data, etc.) and see if that is in focus. If the numbers, letters, and grid of your viewfinder are tack sharp and the image is not, the camera is out of focus or the autofocus is not working. If both the accurately “focused” image and the symbology are out of focus, you need to adjust your diopter.
Different viewfinders have different adjustments, but there is likely a small wheel or slide in close proximity to the viewfinder (sometimes labeled with a + and -) that allows you to adjust the view. There are different techniques for adjusting the diopter—feel free to share your own in the comments section below—but here is one that should work well:
1. Mount the camera. If you can, put the camera on a tripod and point it toward a bright scene with sharp straight edges and a fair amount of contrast—something that the camera should focus on easily.
2. Focus the camera. If it is an autofocus camera, activate the autofocus. If you have a manual focus camera, attempt to focus the image (using electronic focus indicators, if available).
3a. AUTOFOCUS CAMERA Are both the viewfinder image and symbology blurry to your eye? Then you need to adjust the diopter. Rotate the wheel or slide the slide until everything is sharp.
3b. MANUAL FOCUS CAMERA If the symbology is not sharp, you’ll need to adjust the diopter. Only then can you achieve accurate manual focus (unless you have electronic focus aids). Once the symbology is sharp following a diopter adjustment, adjust the manual focus as needed to ensure you can get the image in focus.
• When adjusting a camera diopter (or a diopter on a set of binoculars, for instance) you should adjust the diopter to make the image sharp, and keep adjusting until it goes back out of focus. Then, work back toward focus and stop. The reason to turn or slide past the focus is to ensure that you have made the adjustment far enough and not ended up short of true focus.
• Truth be told, if you are confident in your camera’s autofocus, you can likely do a quick and accurate diopter adjustment in the field by just looking at the viewfinder symbology and adjusting the wheel or slide until it is sharp.
If the camera is out of focus, you see a blurry image in the viewfinder. Then you either focus the camera using autofocus or manual focus and everything is sharp; but is it? What if you didn’t manually focus accurately? Or, worse, what if the autofocus is inoperative or erroneous?
If your camera’s viewfinder gives you sharp viewfinder symbology, but a blurry image, there are likely problems with the camera lens. If the image and symbology are crystal clear, but the image is slightly out of focus, you likely have a minor autofocus error. Verify this by switching to manual focus and see if you can achieve clear manual focus.
Depending on the camera’s diopter adjustment design, the wheel or slide can easily get knocked out of position. So, if you peer into a blurry viewfinder, don’t panic—it might just be your diopter.
If your eyesight is such that a diopter adjustment cannot help you get a clear image in the viewfinder, some cameras can accommodate more extreme adjustment with add-on diopter accessories. Also, some cameras do not include diopter adjustments and the accessories exist to provide the same function as the adjustment dials and slides.