Do you use the viewfinder 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 

[Ramsden]

According to my EOS90D user guide, it says 'Cover the view finder to prevent light from seeping into the camera and affecting exposure' 

It goes on to explain that the camera ships with a cover for this purpose.

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First day on, so I'll check this out and see if my zone project photography improves.

Ramsden 

[Waddizzle]

“ Thanks, Waddizle, for the very helpful diagram. “

I don’t know where my original caps are, either. I don’t have a need for them. The caps are only needed when the camera is controlling one or more legs of the exposure triangle. 

i typically shoot in M mode with ISO auto. If I neeed to use an OVF cap, then I will put my face on the OVF and read the ISO.  I will then dial in the ISO and take the shot.  This is what I do for most landscape shots and longer exposures.

[ebiggs1]

"..  I'll check this out and see if my zone project photography improves."

Yeah, let's see if you can tell the difference. I'm betting you won't see any or can't see any. There is no issue for  normal daytime photos. None. Your eye and head is in the way. Now perhaps if you are doing a long exposure on a tripod you might have an issue. I never have or had any personally. Long exposure means several to many seconds or minutes.

[Ramsden]

You're absolutely right.

It was raining here in Yorkshire this morning, so I put my research hat on. 

Camera on tripod, flowers on the table and did the test. One shot with the cap on in Live view. Then exactly same composition through view finder. To get the same spot on the exposure meter, I  had to shorten the exposure by 2/3rd of a stop. 

But, as you rightly point out, you can't tell the difference.

I would get out more...

Ramsden