Viewfinder cover

[tandeejay]

The other morning before I got up, I thought I would enjoy some light reading, and was browsing through my camera's manual, and came across a section talking about an optional addion of an optical view finder cover, for use to stop light entering in through the view finder when you don't have your eye up to the view finder.

So my question is, how much of a problem is light entering in through the view finder? (eg, when you have the camera on a tripod, or using live view)

and does anyone ever make use of the view finder cover?

[ricktas]

It is a problem, but not really one worth worrying about. But if you are looking through the viewfinder as you take your shot, your face is doing the job of limiting light getting in that way. Also if you are on a tripod and not looking through the viewfinder, you can easily place your hand over the viewfinder if you are concerned about light leak.

Some cameras seem to be more prone to it than others.

I have never, not even once, had a viewfinder light leak problem.

If you do want to get something, sure buy one, but your hand, some duct tape, a small bit of cardboard, anything like that will do the trick too.

[tandeejay]

If I was having a light leak problem, what would I see in my images?

[ameerat42]

An improperly metered image; probably underexposed. But, you've got to ask why, if this is such a problem, don't the camera
makers do something (significant) about it? IMO, a piece of black cloth draped over the viewfinder would suffice. You can try to test
for this effect yourself:

Put camera on Shutter Priority, then take two pics of exactly the same scene.
1) with eye at viewfinder (to block stray light), and
2) with eye away from viewfinder.

Look at EXIF and see what - if anything - changes.

I would be interested in the results.

[tandeejay]

The manufacturer put a comment about it in the cameras manual, so must be an issue to some extent.



Perhaps for the test I should point the camera directly away from the sun..



And you're right, my D5500 has a sensor near the eye piece to detect when you've got the camera up to your eye. Should be trivial to use that same sensor to trigger an automated block of the view finder when you don't have your eye up to the camera... .

[ameerat42]

I wonder if that sensor is coupled to some compensator for when you take an exposure with the eye removed?
Am.

[tandeejay]

As far as I'm aware, the only reason for the face proximity sensor is to turn off the LCD screen when you look through the view finder.

[Kerrick]

I thought it was to protect your metering being thrown off when not looking through the viewfinder. If you are backlit more light might enter that way than what lights the scene.
I guess you could test it indoors, where you compare a normal shot with one where you shine a torch through the viewfinder.

If you have live view enabled, the mirror will be locked up and block that light from entering anyway?

[Cage]

Where light intrusion through the viewfinder will be very noticeable is with long exposures, and particularly when using ND filters.

This first shot was taken using a cheap 3 stop ND filter, f13 at 3sec. Actually it didn't turn out too bad.

Cheapie 3 stop.jpg

The second shot was taken using a rather expensive B&W 10 stop ND filter, f8 at 25sec. To say I was disappointed when I uploaded it to my computer would be somewhat of an understatement. That magenta cast, particularly visible on the LHS of the shot, is caused by light intrusion through the viewfinder.

B+W SOOC.jpg

Fortunately the good folk on here put me right about light bleeding through the viewfinder during long exposures. The silly thing is that my Nikon D800 has an inbuilt shutter which covers the viewfinder for use during long exposures. If I too had done some light reading I may have been aware of the shutter's existence, and saved myself some frustration.

This was my first outing using filters and suffice to say I learnt a fair bit about their use, and when to use them and when not to.

This last shot was with no filter, f13 at 3sec.

No Filter - Copy.jpg

[tandeejay]

Thanks Cage, so it really is more than just a metering issue, as your image clearly shows light bleed during exposure. That makes it look like an old color print that has started fading.

So without covering the view finder, that sort of light bleed would be there in live view mode as well?

[Cage]

So without covering the view finder, that sort of light bleed would be there in live view mode as well?

Can't really comment on that.

But as you can see from the last shot above at 3 seconds there doesn't appear to be a problem at all. It would seem that the issue only rears it's ugly head with longer exposures.

[tandeejay]

Not enough light bleed during exposure to be noticeable until you start going longer exposure. Sounds like a method of covering the viewfinder without having to touch the camera during long exposures is a must.