What is the little window for?

[ricksplace]

I have a Pentax KX. I have always wondered what the little window is on the front of the prism. Doesn't seem to be for the meter since I can cover it and the meter doesn't change, and I can't see anything in the viewfinder that would make me think it affects the viewfinder image. I think I have seen it on other models of Pentax too. Can someone enlighten me?

 

[bobwysiwyg]

Aperture reading window according to this..

http://mcfaddenphoto.com/camera_manuals/kx_man.htm

 

[ricksplace]

Thanks Bob. I've been playing with the critter indoors and I can't see an aperture anywhere in the viewfinder. Maybe it's my eyeglasses, maybe it's not bright enough in here, maybe that feature of the camera doesn't work.
One of my colleagues at work bought a lens from ebay for his K10D, and this body came attached to it. Since he doesn't shoot film anymore, he gave me the KX body, and a spotty body too (same story). Both have appropriate sounding shutter speeds and working meters. Definitely my lucky day.

 

[Chan Tran]

You should be able to see the aperture number even in door. The number is on the top center of the viewfinder. The number is kind of distorted a bit, it's kind of keystoning effect and has a blueist cast.

 

[bobwysiwyg]

Any chance it is not the stock lens and the aperture marking is not in the correct position in relation to the window?

 

[nickandre]

Aperture. I was mystified by the ingenuity of these 70s cameras and finally realized how it got the aperture number to appear in the finder. I loved that camera. I was very sad when mine died. It was my dad's which he bought new in 1976.

 

[Mike Kennedy]

The little window might be a tad dirty.Mine was when I picked it up.A little clean up might improve the view.
Blow it off with compressed air and use a Q-Tip treated with windex.

 

[phenix]

Any chance it is not the stock lens and the aperture marking is not in the correct position in relation to the window?

Yes, it is possible, not to often, but it happens. It does more with zooms than with single focal lenses. Of course the lens has to have an aperture barrel (newer ones don't) with clearly written aperture numbers, and the window to be clear too, as the reading is optical. Try with another lens.

 

[paul ewins]

It is possible for the little prism that sits behind that window to be knocked out of allignment and thus nothing shows up in the viewfinder.

 

[ricksplace]

It is possible for the little prism that sits behind that window to be knocked out of allignment and thus nothing shows up in the viewfinder.

I think you got it Paul. There is a small ding on the prism. The camera works perfectly except for the little window. I have a 50/2 SMC Tak on it now and can't see the fstops in the viewfinder.

Thanks folks.

Rick.