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10-20-2014, 08:00 AM   #1
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Finger print visible in viewfinder new K-50

Hi I have a fingerprint mark that becomes visible when looking through the viewer that comes and goes depending on the light and focus . It is normal according to the dealer ? I have a new K50

10-20-2014, 08:24 AM   #2
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Normal It won't be noticeable which a fast/bright lens.
10-20-2014, 08:38 AM   #3
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I can't be sure without seeing your VF but all vfs have a pattern to them. It looks just like a finger print. It's from when they grind them. It's much more visible with certain lenses than with others.
10-20-2014, 10:08 AM   #4
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QuoteOriginally posted by Another dyemention Quote
It looks just like a finger print. It's from when they grind them. It's much more visible with certain lenses than with others.
The focus screen incorporates a Fresnel lens on its lower surface to focus and concentrate light to the viewfinder*. The pattern of concentric grooves looks a bit like a finger print to some users while other users complain about a grainy/smeary look. The grooves are particularly apparent at narrower maximum apertures when looking at the blank sky. The are less apparent when shooting with faster (wider maximum aperture) lenses.


Steve

* Fresnel lens focus screens have been the norm for SLR cameras for a long time. I remember the first time I looked into a SLR viewfinder in the late 1960s. I immediately asked the camera's owner, "What are those funny lines?"

10-20-2014, 10:23 AM   #5
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I think there are fingers inside your camera....

10-20-2014, 10:50 AM   #6
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I thought I knew what it is but I can't put my finger on it right now.
10-20-2014, 10:54 AM   #7
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QuoteOriginally posted by stevebrot Quote
The focus screen incorporates a Fresnel lens on its lower surface to focus and concentrate light to the viewfinder*. The pattern of concentric grooves looks a bit like a finger print to some users while other users complain about a grainy/smeary look. The grooves are particularly apparent at narrower maximum apertures when looking at the blank sky. The are less apparent when shooting with faster (wider maximum aperture) lenses.


Steve

* Fresnel lens focus screens have been the norm for SLR cameras for a long time. I remember the first time I looked into a SLR viewfinder in the late 1960s. I immediately asked the camera's owner, "What are those funny lines?"
Hi Steve Thanks for that excellent reply You are spot-on and have made my day


Wolfgang

10-20-2014, 11:14 AM   #8
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QuoteOriginally posted by LOBO RSA Quote
Hi I have a fingerprint mark that becomes visible when looking through the viewer that comes and goes depending on the light and focus .
It could be the fresnel screen built into the focus screen. or it could indeed actually be a dirty fingerprint. It happens. Check it out carefully with a bright LED torch to make sure you understand what it really is..

I remember when I go my new K-5, there was a clear dirty thumb-print on the focus screen straight out of the box. it looked like whoever had installed the focus screen forgot to wear gloves, or something. I took the camera back to the dealer, and they exchanged it for a new camera on the spot. I checked the new body with a LED torch before accepting it though. Luckily all was clean.
10-20-2014, 12:27 PM   #9
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There are nice problems When I used a SLR...it was not just dirty but I could see the wires to the "metering" sensor in the middle (Praktica MTL3)

It's OT but ..This will never happen again (not my photo, neither camera)

10-20-2014, 06:37 PM   #10
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QuoteOriginally posted by LOBO RSA Quote
Hi I have a fingerprint mark that becomes visible when looking through the viewer that comes and goes depending on the light and focus . It is normal according to the dealer ? I have a new K50

Oh good, it wasn't just me thinking the same thing.
A few weeks back I was very curious about why it seemed covered in prints. Was delighted to find it was just the viewing screen too.
10-20-2014, 09:36 PM   #11
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QuoteOriginally posted by LOBO RSA Quote
Hi Steve Thanks for that excellent reply You are spot-on and have made my day
It is my pleasure and the same for the other helpful people on this site.


Steve
01-09-2015, 03:23 PM   #12
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Just to note, that focus screen is removable for those who didn't notice. Mine had a legit fingerprint on it... not the ridges in the nylon that make the Fresnel lens (if we're talking about the same piece). You could see the crooked fingerprint in the viewfinder. I ended up carefully unhinging the retaining bracket and letting the nylon focus screen fall out into my hand. Then I gently cleaned it with sensor cleaner and using a pair of tweezers replaced it back into the retaining bracket, and locked it back down. It actually has a little tiny plastic tab that I suspect serves no other purpose than to handle it with tweezers.


But it is nylon (or looks to be) so I'd be careful not to scratch it. I wonder how much a replacement costs. Replacing takes seconds.
01-09-2015, 05:09 PM   #13
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QuoteOriginally posted by Suleeto Quote
It actually has a little tiny plastic tab that I suspect serves no other purpose than to handle it with tweezers.
That is one of the tab's functions. The other is to serve as an index for correct placement. If the tab is on the wrong side, the screen will be upside-down and manual focus will not be possible. The tab should be oriented to the left (towards the grip-side of the camera).

I would use caution if you are planning on cleaning it again in the future. I am not sure what is in sensor cleaner, but what is safe for sensors may not be safe for a focus screen. Solvent erosion of the Fresnel surface will result in a dimmer view and may also shift the plane of focus such that accurate focus may not be possible. KatzEye has included a cleaning tutorial with the information on their Web site detailing how they clean screens:

cleaning - KatzEye Optics


Steve
01-10-2015, 12:36 AM   #14
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I have no experience with this =[
02-01-2015, 06:58 AM   #15
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QuoteOriginally posted by Suleeto Quote
Then I gently cleaned it with sensor cleaner
Did that work? Focusing screens seem to get damaged by *anything*...
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