View finder cap

[Ramsden]

When I bought my EOS90D it arrived with a small strap with a view finder rubber cap attached. I thought this was just for protection, and fitted an eye piece and a better strap (or two). 

Only today I read that the cap is to prevent light leaking into the camera and interfering with exposure. 

So my question is, do you guys regularly use these caps and what are the benefits?

Ramsden 

[March411]

Hey Ramsden, not only do I use them on each camera I upgraded them to give me a better seal and fit. The Canon is OK but there are several soft silicone ones that are in my opinion better.

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[Ramsden]

Hi Marc

Thanks for your prompt response. I'll check these out over here.

Ramsden 

[kvbarkley]

That is not what he is talking about. He means the cover that replaces the eyecup when you are not at the camera, like on a tripod. Pentamirrors can leak light back to the exposure chip. 

[March411]

Interesting, thanks for the heads up @kvbarkley. I have never purchased a body that had any supplied cap or type of cover over the EVF/eye piece as Ramsden mentioned and I purchased most of my bodies including my 90D new. Learn something new every day..... 

[Waddizzle]

“ That is not what he is talking about. He means the cover that replaces the eyecup when you are not at the camera, like on a tripod. Pentamirrors can leak. “

Correct!  Your face is not there to block light from entering the OVF.

This diagram below shows where the metering sensor is located at the top of the viewfinder in a SLR or DSLR. Number 7 is the pentaprism. The metering sensor is located on the right side, where the vertical light path is reflected towards the left.

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The cover is most useful when shooting in Live View, depending upon your shutter mode. The default Live View shutter mode drops the mirror and uses the metering sensor. You need to cover the OVF. 

Or, you can have mirror remain raised, and use the image sensor for metering. No cover needed. 

[stevet1]

Ramsden,

These are most useful in Long Exposure photography.

If you've got a baseball cap, you can accomplish the same thing by draping it over the top of your camera, if it's not too windy.

When you bought your camera, did it come with a camera bag? Sometimes Canon will also provide a rain cover for your camera and stick it in the pouch of your camera bag. I didn't realize mine had one for like two years. If a camera bag came with your camera, check the pouch. Those rain covers will accomplish the same thing as your eyepiece cover.

Steve Thomas

[Ramsden]

Thanks guys

I have reattached the small strap and cover and it will get used on a regular  basis. But I can envisage quite a few eyecaps going missing on my daily meanders. 

I'm just annoyed at myself for not knowing the correct purpose when I bought the camera, new.

Ramsden 

[Ramsden · Accepted solution]

Thanks, Waddizle, for the very helpful diagram.

I'm currently working on using zones, so need an an accurate reading. My exposure meter is a critical part of that procedure.

I consider this a step forward.

Ramsden