Pentax 6x7 Prism Problem

bigredrobotninja · Feb 27, 2015

Just picked up a Pentax 6x7 (actually my first film camera, really excited). While putting my first roll through it, I noticed some odd discoloration at the edges of the eyepiece of the TTL Prism. It's bronze and purple, and it blocks some of the view through the eyepiece. The attached photo is the best I could manage on my phone. Is this normal? Or should I send it back and get a replacement? Thanks.

AgX · Feb 27, 2015

To me it looks as if the front lens of the eyepice is chipped at the edge (chipped in the sense of crack).

You can screw-out the retaining ring (nothing will fall out), which gives you more sight at that eypiece.

Even if there is something broken it might not affect your sight through the finder, but it may worsen. And a chip falling off could be harmful too.

bigredrobotninja · Feb 28, 2015

Thanks, yeah after taking out the retaining ring, it does look like a chip. It really only affects my view through the viewfinder when there is a bright light behind me. Is this the kind of thing that you guys would accept from a BGN-rated prism from KEH? Or would you send it back?

AgX · Feb 28, 2015

If you mount a rubber cup (out of the rummage box) the problem of backlighting should be gone.

I wonder though how that chipping/fracturing may have happened, as that lens-element is located quite retracted. I got a similar propblem at a 35mm SLR, with less retracted eyepiece, where it turned out that camera seemingly had fallen on its back and the eyepiece frame, partially bending inwards the eyepiece. Resulting in uneven focusing on the screen. I have to re-mount the whole eyepiece assembly.

Thus that chipping as such might be something you can live with. But check for even focusing at the groundscreen.

I got your camera too and the retaining ring has a deep mark, but the eyepiece is intact.
Check for the front arrest pins of the prism too.

AgX · Feb 28, 2015

Not some idiot: to access that lens you have dismantle the prism housing first.

JW PHOTO · Feb 28, 2015

Could be optical cement separation. Same as with lens elements. Some of these high-end prisms have glass elements cemented together. A rubber eye-cup would solve the problem, but if you wear eyeglasses it might not. I have slight seperation in one of my old Pentax prisms, but it doesn't bother me. John W

AgX · Feb 28, 2015

JW PHOTO said:
Could be optical cement separation. Same as with lens elements. Some of these high-end prisms have glass elements cemented together. A rubber eye-cup would solve the problem, but if you wear eyeglasses it might not. I have slight seperation in one of my old Pentax prisms, but it doesn't bother me.

The issue is not with the prism as such but with the eyepiece. Though that might be a cemented group indedd and thus what we are seeing is not a fracture within glass, but between elements. I don't know.
Instead of using eyeglasses one can install a diopter lens in that ring.

bigredrobotninja · Feb 28, 2015

Hmm. Would cement separation cause focusing issues? I guess I will find out when I get that first roll back...

AgX · Mar 1, 2015

A focusing issue can happen if the eypiece is dislocated (and one's eyesight is critical as mine). But just element seperation typically only introduces a new reflective surface.

Pentax 6x7 Prism Problem

Attachments

Privacy & Transparency

Privacy & Transparency