Why does my Canon 5D Mark III viewfinder get darker and blurrier when I remove the battery?
Asked 2/20/2015
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On my Canon 5D Mark III, I can focus normally through the optical viewfinder with a battery installed. But if I remove the battery while looking through the viewfinder, the image immediately becomes dimmer and less clear. Is this normal? Also, do any lenses require camera power for manual focus to work?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
11y ago
2 Answers
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Yes, it's normal behavior. The reason you're having problems is that the 5DMkIII has an LCD overlay in the viewfinder. This overlay is used to give you grid lines you can turn on and off and different AF point displays. Without power, the LCD becomes opaque. This behavior is identical in Nikon cameras with an LCD overlay in the viewfinder, and has long been noted.
From the Canon Learning Center's article on the 1DX's & 5DMkIII's intelligent viewfinder display:
The LCD overlay does require a tiny amount of electrical power to operate. This is obviously no concern when the camera is turned on, but if the battery is removed the transmissive LCD suddenly loses a lot of brightness and contrast. This is perfectly normal and will return to full brightness once a battery is reinstalled in the camera (the camera doesn't have to be turned on; it only requires a functioning battery pack to draw power for proper viewfinder operation).
Originally by user27440. Source · Licensed CC BY-SA 4.0
user27440
11y ago
0
Generated from our catalog & community — verify before relying on it.
Yes — this is normal on the 5D Mark III. Its optical viewfinder uses an LCD overlay to show items like AF points and optional grid lines. That overlay needs a small amount of power. When the battery is removed, the overlay loses power and becomes less transmissive, so the viewfinder appears darker and lower in contrast, which can make the image seem blurrier.
So the issue is not that the lens suddenly lost optical focus; it’s that the viewfinder display is no longer bright and clear without power.
Also, some Canon lenses use focus-by-wire manual focus, especially STM lenses. On those, turning the focus ring does not mechanically move the focus elements unless the camera is powered and supplying power to the lens. In practice, that means manual focus may not work at all with no battery, even if the lens is set to MF.
So both behaviors can be normal: the 5D Mark III viewfinder gets dimmer without a battery, and certain electronically focused lenses also need camera power for manual focusing.
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AI11y ago
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