Problem w/Nikon K3 focusing screen on K30

elliott · 04-14-2014, 01:18 PM

I believe that is right.

What kind of target are you using for testing front or back focus?

gmiyamoto · 04-14-2014, 03:59 PM

I followed the instructions contained at GhettoCAL DIY Lens Calibration DSLR Micro Adjust Fine Tune
Thank you for your continued help.

stevebrot · 04-14-2014, 04:12 PM

Originally posted by gmiyamoto

I installed the focusing screen with the "rough side" facing up toward the pentaprism.
The smooth, shiny side is facing down toward the mirror.l

Hmmmm...tab to the left? The instruction photos on focusingscreen.com show a K10 which installs opposite of the one for your camera. The scribed circle on your K3 screen should be facing ~~down~~ up towards the pentaprism.

Steve

elliott · 04-14-2014, 07:17 PM

Just to be sure we're actually talking about the same thing. When you say front focused you mean the actual image is focused further forward than it appears in the viewfinder, correct?

gmiyamoto · 04-14-2014, 08:25 PM

By front focus, I mean that the point of sharpest focus appears to be in front of rather than on or behind the target.
Based on the target that I'm using, it appears that the focus point is a slightly more than 1" in front of the target.
I have to apply a slight adjustment when focusing thru the viewfinder to match the focus arrived at in Live View.

pavpen · 04-14-2014, 09:10 PM

Originally posted by gmiyamoto

I installed the focusing screen with the "rough side" facing up toward the pentaprism.
The smooth, shiny side is facing down toward the mirror.l

I would check with vendor of your focusing screen about the correct side of screen installation. According to instruction i have to install screen mated side to mirror - but this was for old tlr camera.

Cheers.

gmiyamoto · 04-14-2014, 09:56 PM

Thank you for all the responses.
Tomorrow, I'll try flipping the focusing screen so that the matted side faces the mirror and the tab is on the right rather than on the left side.

stevebrot · 04-14-2014, 11:43 PM

Originally posted by gmiyamoto

Thank you for all the responses.
Tomorrow, I'll try flipping the focusing screen so that the matted side faces the mirror and the tab is on the right rather than on the left side.

Tab is supposed to be on the left.

Are you sure you have your terms straight? Front focus is when the viewfinder focus aid indicates that the subject is further away than it actually is. The distance from the lens to the focus screen when in true focus is less than the distance from the lens to the sensor. A front focusing screen will not be able to discern infinity or even moderately distant objects before running up against the infinity stop on the lens.

Steve

gmiyamoto · 04-15-2014, 09:08 PM

I tried to flip the focusing screen so that the tab would be on the right side. The tray that the focusing screen sits on has a raised lip at the front. There is an opening on the left side of the lip that allows the focusing screen tab to protrude. However, there is no corresponding opening on the right side. Therefore, it's not possible to mount the focusing screen with the tab on the right. I think at this point I'll re-install the stock focusing screen & shim.
I appreciate everyone's suggestions.

gmiyamoto · 04-17-2014, 05:49 PM

After removing the focusing screen & shim I found the problem.
The thin aluminum frame that sits between the shim and pentaprism was not seated properly.
I aligned the frame and tried different combinations of shims again.
I found that using only one of the thin plastic shims results in accurate focus.
It is a big improvement over the stock matte screen.
I hope that this will help other K30 owners if they decide to replace the stock focusing screen.
Thank you everyone for your suggestions.

04-14-2014, 11:43 PM	#23
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by gmiyamoto Thank you for all the responses. Tomorrow, I'll try flipping the focusing screen so that the matted side faces the mirror and the tab is on the right rather than on the left side. Tab is supposed to be on the left. Are you sure you have your terms straight? Front focus is when the viewfinder focus aid indicates that the subject is further away than it actually is. The distance from the lens to the focus screen when in true focus is less than the distance from the lens to the sensor. A front focusing screen will not be able to discern infinity or even moderately distant objects before running up against the infinity stop on the lens. Steve Last edited by stevebrot; 04-15-2014 at 05:53 AM.

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04-14-2014, 01:18 PM	#16
elliott Inactive Account Join Date: Dec 2008 Location: North Carolina Photos: Albums Posts: 1,720	I believe that is right. What kind of target are you using for testing front or back focus?

04-14-2014, 03:59 PM	#17
gmiyamoto Junior Member Join Date: Jan 2014 Location: Maui, Hawaii Posts: 46 Original Poster	I followed the instructions contained at GhettoCAL DIY Lens Calibration DSLR Micro Adjust Fine Tune Thank you for your continued help.

04-14-2014, 04:12 PM	#18
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by gmiyamoto I installed the focusing screen with the "rough side" facing up toward the pentaprism. The smooth, shiny side is facing down toward the mirror.l Hmmmm...tab to the left? The instruction photos on focusingscreen.com show a K10 which installs opposite of the one for your camera. The scribed circle on your K3 screen should be facing ~~down~~ up towards the pentaprism. Steve

04-14-2014, 07:17 PM	#19
elliott Inactive Account Join Date: Dec 2008 Location: North Carolina Photos: Albums Posts: 1,720	Just to be sure we're actually talking about the same thing. When you say front focused you mean the actual image is focused further forward than it appears in the viewfinder, correct?

04-14-2014, 08:25 PM	#20
gmiyamoto Junior Member Join Date: Jan 2014 Location: Maui, Hawaii Posts: 46 Original Poster	By front focus, I mean that the point of sharpest focus appears to be in front of rather than on or behind the target. Based on the target that I'm using, it appears that the focus point is a slightly more than 1" in front of the target. I have to apply a slight adjustment when focusing thru the viewfinder to match the focus arrived at in Live View.

04-14-2014, 09:10 PM	#21
pavpen Veteran Member Join Date: Sep 2012 Location: US Photos: Albums Posts: 381	Originally posted by gmiyamoto I installed the focusing screen with the "rough side" facing up toward the pentaprism. The smooth, shiny side is facing down toward the mirror.l I would check with vendor of your focusing screen about the correct side of screen installation. According to instruction i have to install screen mated side to mirror - but this was for old tlr camera. Cheers.

04-14-2014, 09:56 PM	#22
gmiyamoto Junior Member Join Date: Jan 2014 Location: Maui, Hawaii Posts: 46 Original Poster	Thank you for all the responses. Tomorrow, I'll try flipping the focusing screen so that the matted side faces the mirror and the tab is on the right rather than on the left side.

04-15-2014, 09:08 PM	#24
gmiyamoto Junior Member Join Date: Jan 2014 Location: Maui, Hawaii Posts: 46 Original Poster	I tried to flip the focusing screen so that the tab would be on the right side. The tray that the focusing screen sits on has a raised lip at the front. There is an opening on the left side of the lip that allows the focusing screen tab to protrude. However, there is no corresponding opening on the right side. Therefore, it's not possible to mount the focusing screen with the tab on the right. I think at this point I'll re-install the stock focusing screen & shim. I appreciate everyone's suggestions.

04-17-2014, 05:49 PM	#25
gmiyamoto Junior Member Join Date: Jan 2014 Location: Maui, Hawaii Posts: 46 Original Poster	After removing the focusing screen & shim I found the problem. The thin aluminum frame that sits between the shim and pentaprism was not seated properly. I aligned the frame and tried different combinations of shims again. I found that using only one of the thin plastic shims results in accurate focus. It is a big improvement over the stock matte screen. I hope that this will help other K30 owners if they decide to replace the stock focusing screen. Thank you everyone for your suggestions.