[UMC]

Does the viewfinder stray light actually make it to the sensor?...

As others said, it probably will during long exposures. However, this is not the primary reason for using a viewfinder blind.

All (D)SLRs that I know have the light meter somewhere in the pentaprism housing. Therefore, unless you use Live-View, strong backlight through the viewfinder will influence the metering. A classic situation where this comes into effect, is the camera being mounted on a tripod, sun from the back - and there you have an underexposed picture.

Don't believe it? Well, take your camera, turn it on with the lens cap in place. Tip the shutter button and watch the metering. Now take a maglite and direct its beam into the viewfinder....

[MJKoski]

Even if you use the plastic cover which came with K-1, then watch it! Because, it is not very tight fit. And when you take vertical long exposures etc. it might slide a bit thus ruining your exposure.

[Qwntm]

As others said, it probably will during long exposures. However, this is not the primary reason for using a viewfinder blind.

All (D)SLRs that I know have the light meter somewhere in the pentaprism housing. Therefore, unless you use Live-View, strong backlight through the viewfinder will influence the metering. A classic situation where this comes into effect, is the camera being mounted on a tripod, sun from the back - and there you have an underexposed picture.

Don't believe it? Well, take your camera, turn it on with the lens cap in place. Tip the shutter button and watch the metering. Now take a maglite and direct its beam into the viewfinder....

Well, that's why I use my thumb and suggested it.


I don't do astrophotography so I learned something if I ever do.

[stevebrot]

Does the viewfinder stray light actually make it to the sensor? I ask because I don't do that kind of photography and don't know.

It can. It depends on how careful one is with one's flashlight. There are also potential issues with light leakage from adapted lenses and poorly designed adapters (Sony A7 users mostly). What you see is similar to veiling flare. For a quick and dirty test, set up your camera in a dark room with the lens cap on and the shutter open on B and pass a bright flashlight across the viewfinder opening.


Steve

[stevebrot]

As others said, it probably will during long exposures. However, this is not the primary reason for using a viewfinder blind.

All (D)SLRs that I know have the light meter somewhere in the pentaprism housing. Therefore, unless you use Live-View, strong backlight through the viewfinder will influence the metering. A classic situation where this comes into effect, is the camera being mounted on a tripod, sun from the back - and there you have an underexposed picture.

Don't believe it? Well, take your camera, turn it on with the lens cap in place. Tip the shutter button and watch the metering. Now take a maglite and direct its beam into the viewfinder....

This is the classic reason for using a viewfinder cap or blind. It was not an issue before exposure automation, but is something to be aware of when shooting on tripod, particularly if the viewfinder is exposed to fairly bright light. The problem is exacerbated when doing stop-down metering with standard K-mount of M42 lenses. Under those conditions the contribution of light from the viewfinder opening may be greater than than coming through the lens!

I use my thumb.


Steve

[funktionsfrei]

I'll have to experiment, I have the Magnifying eyecup on mine, so don't know if plastic will slip behind it or not.

It does; that's the eyecup I'm actually using. The plastic piece has to be smaller than for the "original" eyecup. The optical element in the magnifying eyecup is recessed, so there's absolutely no danger of scratching anything.

Attached is an image of the plasticky light blocker and of it's use on the O-ME53 on my old K-5.

[MJSfoto1956]

It does; that's the eyecup I'm actually using. The plastic piece has to be smaller than for the "original" eyecup. The optical element in the magnifying eyecup is recessed, so there's absolutely no danger of scratching anything.

Attached is an image of the plasticky light blocker and of it's use on the O-ME53 on my old K-5.

Sweet!

M

[BigMackCam]

It does; that's the eyecup I'm actually using. The plastic piece has to be smaller than for the "original" eyecup. The optical element in the magnifying eyecup is recessed, so there's absolutely no danger of scratching anything.

Attached is an image of the plasticky light blocker and of it's use on the O-ME53 on my old K-5.

Nice job - great idea, and well executed!

[loco]

I'm ghetto. I just keep a piece of black gaffer tape on the pentaprism at all times. It's hardly noticeable to me. It's there when I need it.

[csa]

I agree, a very nice job! Thanks for posting those photos!

[Tan68]

Bubble gum?

Tongue

I use the type of blue tape intended for masking glass or molding when painting. This is common in US, anyway.. I use two layers of the tape, cut it roughly in some trapezoidal shape to fit the viewfinder, and store them pasted them onto the case that holds my ND filter.

Of course, I remove the blue tape from the filter case when I want to use it.
'Them' because I made 3 in case one falls onto dirt or loses its 'sticky'