This question already has an answer here:

I just read the manual of my camera, and it says that if you are using the LCD display to take shots, you should close the viewfinder with the plastic piece (I don't know its proper name), so the shot does not receive additional light coming from the viewfinder, and overexpose your shot.

Is this true?

And BTW, this is the viewfinder, right? enter image description here

EDIT: My camera is Nikon, I just found this picture on the internet. EDIT2: So what if I am using only the LCD display for displaying the shot, for taking long exposures, or self-timers, will then light enter through the optical viewfinder?

marked as duplicate by mattdm, MikeW, Philip Kendall, NickM, James Snell Oct 3 '15 at 8:52

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • I think what your camera manual says is more along the lines of "When you are not using the viewfinder" and it is said in a chapter where the context is when using the light meter in the pentaprism housing to determine exposure for the shot. – Michael C Sep 30 '15 at 17:48

The light entering the camera from the viewfinder will only affect metering when the mirror is down. When the sensor is exposed, either to take a picture or to enable Live View, the mirror will be up and will block pretty much any light entering the viewfinder from reaching the imaging sensor. This is true of just about any DSLR with a reflex mirror whether it is a Canon, Nikon, Pentax, Sony, etc. (The only interchangeable lens cameras that I am aware of that have an optical viewfinder and no reflex mirror are the Sony SLT designs. For the Sony SLT cameras it probably wouldn't hurt to cover the viewfinder when not using it.)

The only time you need to use the eyepiece cover is when you are using the self timer, shooting a bulb exposure, using a remote trigger, or any other times when you are using automatic metering with the mirror down but not placing your eye to the viewfinder. You don't need to use it in Live View because metering in Live View is done by the image sensor with the mirror up, not by the light meter that is inside the prism housing near the viewfinder.

If you are shooting in a very dark environment with a very strong light behind the camera a little light may leak around the edges enough to bounce around the light box and affect the image, but under normal use it will be much less light reaching the camera sensor than what is reaching the exposure meter through the viewfinder when your eye is up to the viewfinder and you are looking through it.

From page 187 of the EOS 5D Mark III Instruction Manual:

When you use the self timer or shoot bulb exposures and do not look through the viewfinder, stray light entering the viewfinder can cause the image to come out dark. To prevent this, use the eyepiece cover (p. 27) attached to the camera strap.
During Live View shooting and movie shooting, attaching the eyepiece cover is not necessary.

Similar statements are included in pretty much every Canon EOS DSLR manual. Among the ones I have handy at the moment are the 5D II, 7D, and 7DII Instruction Manuals. The concept is the same for any DSLR with a mirror.

The early version of this statement did not include the last sentence clarifying that using the cover is not necessary when using Live View. But in every case I can find, the instruction is included immediately following the instructions on how to take bulb exposures that assume the mirror is down between shots. It is not included in the chapters regarding Live View.

  • check my edit please – Sartheris Stormhammer Sep 30 '15 at 18:16
  • It really makes little difference if the camera is a Nikon or Canon. In both cases when the mirror is up it blocks virtually all of the light entering the viewfinder from reaching the light box. If you are shooting in a very dark environment with a very strong light behind the camera a little may leak around the edges enough to bounce around the light box and affect the image, but under normal use it will be much less than it would when your eye is up to the viewfinder because you are looking through it. – Michael C Oct 1 '15 at 6:16

Yes, this is the viewfinder. And from what I see on the picture this is Canon camera. They have such unit (to "close" the viewfinder) on the strap. To put it your should remove the rubber element from viewfinder

The general recommendation is to block viewfinder in case of long exposures and during low light shoots

P.S. And this side light will not overexpose your shoots, its not so much. But can provide unpleasant effects when shoot in above situations

P.P.S. I have no experience with Nikon, but there is high probability they provide such element for their cameras as well. At least for mid and highend models. But the rest continue to be true (for long exposure)

Not the answer you're looking for? Browse other questions tagged or ask your own question.