[mattt]

Although the ND400 might appear to be a cap, it is actually a 9 stop ND filter - the reason the image is so dark is the camera in Av mode measures light from the view finder as well as what makes it through the ND filter.

[123jippo]

In my k5 no need to cover viewfinder anymore, no light leaking anymore. This is handy

[paranoia23]

ok now i got it ^^

[JimJohnson]

...But not entry level ones like the Kr - I have one now after seeking it out (and getting it for free thanks to Windsor Photo Outfitters in Windsor, ON)

I pointed out to Pentax USA that my past cameras came with the viewfinder cap, and its use is recommended in the K-r manual. Further I pointed out the ridiculous cost for a replacement cap. Pentax sent me a cap as a freebie.

By the way, I haven't lost a Pentax viewfinder cap yet after 30 years. I drill two small holes through the cap and sew it like a button on the inside of my camera strap, just past far enough up from the camera to make for an easy loop over to the viewfinder.

[smigol]

... I drill two small holes through the cap and sew it like a button on the inside of my camera strap, just past far enough up from the camera to make for an easy loop over to the viewfinder.

I'm going to do this for my gear. Seems like a good way to get the strap up and secured to keep it from dangling and moving in the breeze. Great tip!

[lister6520]

I'm curious how this occurs.. when taking a photo, the viewfinder is obscured by the mirror which flips up to expose the sensor.. so is the mirror simply not fully blocking the focusing screen?

The mirror has a number of semi-transparent patches to allow light to reach the autofocus sensors, which are at the bottom of the mirror box (unlike the exposure sensors which are in the viewfinder side)

There is a flap (with also some mirrors on it) on the underside of the main mirror which folds when the mirror goes up and it covers the semi transparent parts but apparently it is not 100% effective.

That said, even if it were't for the semitransparent parts I think it is quite difficult to achieve a perfect light seal around the edges of the mirror without causing friction that would hinder the rapid movement of the mirror. I remember having the same problem a long long time ago with a Ricoh Kr-10, which didn't even have autofocus. However the problem only occured in extreme cases, shooting in bright sunlight with a piece of welding glass used as an affordable ND filter. I eventually figured out that it was light leaking past the mirror (there were no internet forums back then, or even computers) and started to cover the viewfinder with a hat - which seemed to work perfectly.

Nowadays with the K-30 I use a rear lens cap which seems to hook on very nicely to the viewfinder rubber cup, when I remember.

[adwb]

I long since lost ( if I every had) the viewfinder cover for my k5 and apart from my long gone k100d which did come with one I don't actually remember getting one with Kr,,Kx,km,k30 either.
What I do remember was that you had to remove the rubber viewfinder surround to fit it and that was a p.i.t.a.
I just stretch a bit of black insulation tape over the rubber as I always have a roll handy in my bags

[Clavius]

This phenomenon is not restricted to long exposures only. It's just more prominent there. I've had it happen with normal shots on bright sunny days, when I don't press my eye against the VF hard enough too. And it's also a nuicance when taking studio macro shots for focus stacking.

I know about the VF cap, but it's such a clumsy solution, having to pull off the VF optics to replace it with that cap. And it's so tiny, it's always lost in the camera bag. I just use the black tape that I cover the Pentax logo with.

[JimJohnson]

What I do remember was that you had to remove the rubber viewfinder surround to fit it and that was a p.i.t.a.
I just stretch a bit of black insulation tape over the rubber as I always have a roll handy in my bags

The was fixed with the K-30. Yes, you still have to remove the eyecup to use the official viewfinder blind, but unlike earlier models, the eyecup has a rigid plastic back plate that slides off and on the viewfinder just like the viewfinder blind. Especially in combination with my previously mentioned approach to attaching the viewfinder blind to the strap like a button, you can make the swap in the field much faster than digging in your bag for a roll of tape and tearing off a piece. No sticky residue either.

[lister6520]

A rear lens cap fits perfectly onto the rubber eye cup of the K-30. After discovering that I never used the 'official' cover again.

[123jippo]

I did writethat my k5 not need viewfinder cap, i was wrong. When taking long exposures like 2 minutes and sun or street light is shining straight to viewfinder then light from viewfinder will ruin photo if not use cover. I did try lens rear cap, most cases works okay but sometimes sidelight will reflect inside viewfinder and ruins photo. So Now i use original pentax viewfinder cover cos its 100% safe light protection.

[dwalker19]

Matt - the OP. Thanks for bringing this up when you did. I posted a long exposure shot in Post Your Photos the other day and discusses this. I took a bunch of photos on the OR coast and when I remembered to bring the cap with me I had much better results. I would not have had in OR if not for your post. I had decent results putting my thumb over the eyepiece, hanging my hat over the camera or draping a black lens cloth over it, but like 123jippo said, only that little cap gives you the 100% seal. Funny how it lead to some wacky meter readings and lots of dark photos before I figured out what was confusing the meter.
DW

[JimJohnson]

when I remembered to bring the cap with me I had much better results

Never forget or lose your viewfinder blind again .... drill two small holes in the blind, and sew it like a button on the inside of the camera strap just far enough from the camera to easily reach the viewfinder. It never gets lost, it is always ready for use. Just loop your strap over the viewfinder.