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08-16-2014, 06:59 PM   #1
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Smudges?

I have a Pentax K-50 with the 18-55 WR kit lens. Lately I have noticed smudges when looking through the viewfinder, and it's more pronounced at bigger zoom levels. When the zoom is at 55 I can clearly see what appears to be fingerprints smudges all over the viewfinder.

Honestly this doesn't seem to be affecting the pictures when looking at them on the computer but it does bother me a lot when taking them.

Also I wonder where these smudges are because they are not in the front of the lens (as I clean this very often), so this baffles me a lot? Do I have to remove the lens and clean the back-end of the lens?

As you can probably tell I'm new to a camera with removable lens etc.

Thanks!

08-16-2014, 07:02 PM   #2
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The smudges are probably due to dirt, oil, or hair on the focusing screen and/or mirror.

Adam
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08-16-2014, 08:09 PM   #3
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QuoteOriginally posted by Adam Quote
The smudges are probably due to dirt, oil, or hair on the focusing screen and/or mirror.
Protective UV filter? Eyepiece glass?


Steve
08-16-2014, 09:03 PM   #4
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Also clean the back element of the lens. Don't be afraid to take it out. But don't try to clean the focusing screen or mirror by yourself. It's a very different job than cleaning a lens.

For cleaning the lens, use microfiber cloth, and cleaning solution dedicated for optical glass.


Last edited by JimmyDranox; 08-16-2014 at 09:20 PM.
08-16-2014, 09:39 PM   #5
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Check the front and rear of the lens. You can do this best by shining a flashlight through the lens. Every bit of haze, dust, and oil will glow. Don't let it freak you out though. Gently clean off what you can. Leave what you can't. You also look at the lens at an angle to a lamp. If your lens is clean and your images are clean then it's your viewfinder and mirror. The concern there is that any loose dirt can make it's way into your sensor. As others have said, cleaning the mirror is a whole different game compared to a lens. Be careful! Cleaning your viewfinder and focusing screen is simple in comparison.

I'd only worry about the lens unless the mirror and viewfinder are so dirty that it impedes your ability to compose and frame a shot.
08-16-2014, 11:13 PM   #6
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Is it the grainy fingerprint-like structure of the focusing screen you see? It looks like some kind of circular grainy pattern and will be more noticable the lower the light entering through the viewfinder (hence the longer zoom range).
08-17-2014, 04:16 AM   #7
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Remember before you start wiping, you should remove the large bits by blowing for example with a rocket blower or what your lungs bring up. That way you dont scratch the glass with possibly hart particles/sand. A blower has the advandtage of having dry air and is usually stronger.
08-17-2014, 05:41 AM   #8
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QuoteOriginally posted by VisualDarkness Quote
Is it the grainy fingerprint-like structure of the focusing screen you see? It looks like some kind of circular grainy pattern and will be more noticable the lower the light entering through the viewfinder (hence the longer zoom range).

That's what I was thinking as well since it's not showing up in his photos.

08-17-2014, 06:31 PM   #9
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Thanks for the responses.

I have only cleaned the front-end of the lens but never the back. I dont know what the focusing screen and the mirror are. So I wouldnt know how to check if it is those components?

The viewfinder's outside glass I maintain clean but I dont know if there is some other cleanable inside structure of the viewfinder.

I only have this lens so its not like I'm constantly switching lens for it to get dirty inside. I have literally dismounted my lens only 2-3 times since I bought the camera a year ago so its kind of weird for some inside component to be dirty. So maybe it is the grainy structure on the focusing screen? I dont know.

Could someone tell me how I can check each component (focusing screen, mirror, viewfinder etc) to see if indeed they are dirty?

Thanks!
08-17-2014, 07:49 PM   #10
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The mirror is what you'll see when you take the lens off and look into the camera, the focus screen is just above that, mounted horizontally. If it's a "smudge", it's likely on your mirror, since you're new to this, I wouldn't try to clean it or the focus screen yourself, either learn to live with it or go to a camera shop for cleaning. If it just looks like a "fingerprint", then it's likely the lines etched on the focus screen, that's the part you see with the bracket lines when you look through the viewfinder. That is perfectly normal, and there's nothing you can do about it. A lot of newcomers "suddenly" start seeing it, eventually, you'll stop noticing it.


Hope this helps!

Last edited by Al_Kahollick; 08-17-2014 at 08:13 PM.
08-18-2014, 06:08 AM   #11
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Does it look like a fingerprint texture?
08-18-2014, 07:00 AM   #12
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I have taken a look back through this thread and have also done a little remembering regarding a similar issue a few months back where the user complained of "smeared/smudged" viewfinder image. To review:
  • Problem is worse at 55mm with kit lens
  • Looks like fingerprint across entire frame
  • Not present on photos, just in viewfinder
Possible causes:
  • Gunge on filter
  • Gunge on rear of lens
  • Gunge on mirror (unlikely given second symptom above)
  • Gunge on focus screen (also unlikely)
  • Normal Fresnel pattern of focus screen
In the previous thread with similar symptoms, it was finally narrowed down to the pattern of the Fresnel screen. It is generally more visible with slower maximum aperture or when the lens is stopped down as when using vintage lenses. To test:
  • Make sure the viewfinder diopter is set properly to your eyes (manual p56)
  • Camera in Av or M mode
  • Set aperture to f/11
  • Point camera to sky and trigger the optical DOF preview (manual p114)
  • Notice the fine concentric circular lines of the Fresnel lens.
Use of a Fresnel lens on the focusing screen is a feature of almost all SLR cameras made since the late 1950s and is generally not an issue except with slower lenses. The reason why it is visible with the kit lens at 55mm is that the maximum aperture is narrowest at that focal length.

I hope this helps.


Steve

Last edited by stevebrot; 08-18-2014 at 07:42 AM.
08-30-2014, 11:22 AM   #13
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Hello everyone,

I did a road trip and felt limited with the zoom of the 18-55 and so decided to buy the 18-135. (I wanted a walk-around WR lens so I don't have to change lens etc, according to what I read that was my only option).

In this new 18-135 lens I don't see the "smudges" when zoomed in at 135. And yes I agree with above concensus that it's probably that fresnel pattern you all spoke about. Thinking about it those "smudges" looked too uniform to be an actual smudge etc.

But I'm glad I don't see that anymore. Even if I knew it was nothing wrong it would still bother me.

By the way, why don't I see that pattern with my new lens?

Thanks.

Last edited by Moropo; 08-30-2014 at 11:37 AM.
08-30-2014, 04:27 PM   #14
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Whatever you do, DO NOT touch the mirror...
09-13-2014, 07:31 AM   #15
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Sorry to come back to this thread but what I said before that in my new 18-135 lens I do not see the smudges was wrong.

When I looked I was in my poorly lit apartment and didn't notice but in a well lit situation you can always see the "smudges". By the way, I only use the viewfinder to shoot. When I'm composing the picture it looks like the picture will come out all grainy because of this. Yet it doesn't.

I'm so bothered by this...
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