Scratch on Pentaprism

Lazaruscomeout · 04-07-2009, 05:12 AM

Okay, so it's official... I'm an idiot.

I am going to tell the whole story, so after you've read it, please feel free to ridicule me! I had annoying dust in my view finder that I couldn't get out with my rocket blower, so I decided to use a little more "horsepower". I removed the focus screen and plugged in my air compressor and started blowing...

It turns out that what I thought was an empty chamber above the focus screen was actually the pentaprism. I discovered this when the metal tipped nozzel of my air compressor blower smacked into it! After putting everything back together and looking through the view finder, I could see that the dust was gone. That was the good news. The bad news was that I replaced the dust with a small gouge on the top left of the pentaprism!

To add insult to injury I sent the focus screen skipping across the kitchen floor scratching it in three places. I used this as an excuse to buy a Katzeye, so I'm not too worried about the focus screen.

Sorry for the long post, but my question is whether or not there is a protective screen in front of the pentaprism that can be replaced, or did I actually damage the prism?

I know you're going to tell me that I shouldn't try to fix it myself based on how I have messed up so far, but I'm usually quite good at detailed work like this. I have to ask anyway - If there is a protective screen in front of the prism, is there any way to replace it myself? (I actually ducked after typing that question).

Have fun with your answers. I'm braced for them.

WerTicus · 04-07-2009, 07:45 AM

geezus an aircompressor is a no no with such things, your lucky you didn't do worse tbh.

octavmandru · 04-07-2009, 07:55 AM

Oh... I'm sorry to hear. you'll get used with it (the scratch I mean).
I doubt there is such thing as a protector screen between prism and matte.
you were lucky not to damage the shutter with that speedy flow of air.
I avoid using any blower inside the camera.

rburgoss · 04-07-2009, 08:00 AM

Hmmm,,, are you sure its a pentaprism or a pentamirror?

Diferences:

Pentaprism: Solid block of glass
Pentamirror: Hollow plastic with mirrored coatings on all sides except bottom where focus screen goes.

Bodies with Pentaprism: K20D, K10D, istD
With pentamirror: Al the others (digital)

If you are sure its a pentaprism, you probably smudged some debris onto the pentamirror surface (it is not easy to scratch) and it is most likely that can be cleaned away, with lots of care. If it is a true pentamirror, then you most likely scratched the surface and there is not much to do here.

Hope you can get it cleaned..

creampuff · 04-07-2009, 08:05 AM

Q: Is there is a protective screen in front of the prism?
A: No

Q: Is there any way to replace it myself?
A: Probably not as it requires dis-assembly of the upper body panel.

Suggest you send it in to Pentax for repair. Looking at the exploded view of the K20D, there are a LOT of parts that needs to be taken off to remove the pentaprism.
Suggest you leave the tinkering to the experts. You might not have the tools, schematic diagram, run the risk of having your warranty being void, introduce even more dust into the camera, lose small parts or fail to put it back correctly. Expect a costly repair job.

BCtoad · 04-07-2009, 09:21 AM

Thank you for a good laugh this morning. I visualize in my head what happened and the look on your face I am sorry to laugh but I just couldn't help myself. Only use hand-operated blowers good luck with any repair.

*OregonJim* · 04-07-2009, 09:47 AM

Originally Posted by Lazaruscomeout

Okay, so it's official... I'm an idiot.

I am going to tell the whole story, so after you've read it, please feel free to ridicule me! I had annoying dust in my view finder that I couldn't get out with my rocket blower, so I decided to use a little more "horsepower". I removed the focus screen and plugged in my air compressor and started blowing...

It turns out that what I thought was an empty chamber above the focus screen was actually the pentaprism. I discovered this when the metal tipped nozzel of my air compressor blower smacked into it! After putting everything back together and looking through the view finder, I could see that the dust was gone. That was the good news. The bad news was that I replaced the dust with a small gouge on the top left of the pentaprism!

To add insult to injury I sent the focus screen skipping across the kitchen floor scratching it in three places. I used this as an excuse to buy a Katzeye, so I'm not too worried about the focus screen.

[...]

Have fun with your answers. I'm braced for them.

Is your real name Tim Taylor?

MORE POWER! ARR ARR ARR!!!

aesch · 04-07-2009, 10:37 AM

In addition the *ist D, I believe the DS and DS2 also have the pentaprism. I think the DL started the pentamirror.

**Marc Sabatella** · 04-07-2009, 12:22 PM

Well, I always say that trying to clean dust from the viewfinder is more trouble than it's worth, and is as likely as not to make the problem worse. But you've definitely gone the extra mile here in demonstrating just how much it is possible to screw things up by not leaving well enough alone!

Lazaruscomeout · 04-07-2009, 01:24 PM

I'm glad I provided a laugh. I expected to be roasted over this one.

As I was doing it I knew that it was a stupid idea. The scratch isn't very big and it's on the top left so it won't be a major problem.

It's a k20D so definately a prism, but I am surprised that it scratched (it is a scratch, not dirt) because it's glass. Thats why I thought that maybe there was a plastic screen in front of it.

Perhaps I should try to buff it out with my rotary tool.

Thanks for the replies!

Gerry

**Marc Sabatella** · 04-07-2009, 05:31 PM

Originally Posted by Lazaruscomeout

Perhaps I should try to buff it out with my rotary tool.

Sure, we could all use *another* good laugh!

OK, seriously, I'm sorry you had to learn this the hard way, but I'm also glad things aren't actually as bad as they perhaps could be!

Lazaruscomeout · 04-07-2009, 05:43 PM

The scratch on the prism and the focus screen damage fiasco is a sacrifice I am willing to make seeing as it gave me the excuse to order a Katz Eye screen.

My wife couldn't really say I didn't need it you see.

*OregonJim* · 04-07-2009, 06:04 PM

Hmmm.... I wonder if the pentaprism is interchangable with any of the film bodies? Perhaps you could pick up a beater camera for a song and exchange prisms?

edit: oops, I forgot who I was talking to. Probably not the best idea....

Lazaruscomeout · 04-07-2009, 06:48 PM

Originally Posted by OregonJim

Hmmm.... I wonder if the pentaprism is interchangable with any of the film bodies? Perhaps you could pick up a beater camera for a song and exchange prisms?

edit: oops, I forgot who I was talking to. Probably not the best idea....

Okay, now that was funny!

**Damn Brit** · 04-07-2009, 06:58 PM

Perhaps when the next Pentax comes out you can find an innocent way to destroy your K20 completely so that your wife can't say that you don't need a new camera.

Oh and you're not an idiot, your the photographic equivalent of a crash test dummy. Thanks to you, no one will use a compressor to clean the inside of a camera. We appreciate your research.