Question for split-screen owners

Clem Nichols · 12-31-2008, 07:34 AM

I recently purchased one of the e-bay split screen focusing screens for my K10D, and my initial impressions were very favorable. There is no question that it makes manual focusing in low-light conditions much more accurate. Further use has raised a couple of questions that hopefully someone can answer. First of all, does your camera seem to have slightly more difficulty auto-focusing with the split screen installed, and secondly, what about evaluative metering? I don't know about the Katz eye, but with the e-bay screen the prism and ground-glass central portions are considerably brighter than the periphery. I keep my camera set on the center focus spot and 16 zone multi-segment metering with AE tied to AF in the custon setting menu. Until recently this has worked just fine, but since installing the split screen my auto-exposure seems to function as if it were set to spot metering. I've taken several pictures recently which were very over-exposed, and this has never before been a problem. As a for-example, while experimenting yesterday, I took 2 back-to-back pictures of my golden retriever who was lying about 20 feet away from me in bright sunlight. These were taken with a Sigma 70-300 lens, and the dog's body made up probably 30% of the total picture area. When I put the center focus spot on a shaded portion of the dog's coat the picture was grossly over-exposed, and conversely when I focused on an area just a few inches away that was in direct sunlight the picture was slightly underexposed. As I said, the camera acts as if it's set to spot metering, and I can only assume that this is the result of changing focusing screens. I was wondering if anyone else had noticed this with either the e-bay or the Katz eye screens. Obviously with photography as well as with life in general we have to make a lot of compromises, but if better manual focusing in low-light conditions can only be obtained by a loss in accurate auto-exposing that's probably more of a compromise than I'm willing to make. Thanks for your response.

CN

Clem Nichols · 12-31-2008, 09:48 AM

Update

After some more experimentation this morning with various lenses and continuing to get a high proportion of over-exposed images I wound up replacing the e-bay split screen with the original Pentax screen, and voila, the problem was corrected. I think what was happening was that the peripheral (and slightly darker than the OEM) portion of the split-screen unit was allowing less light to pass through to the camera's sensor causing the over-exposure by about 1 and 1/2 stops. I've decided to leave the Pentax screen in place and discard the ebay item. I still would be interested in knowing if users of the Katz eye screen have noticed anything similar.

(What I have referred to as the ground glass portion of the viewfinder is what the folks at Katz eye call the microprism collar, and what I called the peripheral portion is what they call the matt portion of the screen. According to their web-site their Opti-brite treatment brightens the matt portion which leads me to believe that this would probably prevent the over-exposure I saw with the ebay screen. In fact they recommend their basic screen for fast primes and recommend the opti-brite screen for use with telephoto or slower lenses, and it was with the latter that I had problems. I never noticed any exposure problem when shooting with my Sigma 17-70. Considering that the basic Katz eye is over $100 and that the opti-brite treatment adds another $50 or so I think I'll stick with the original Pentax screen barring the unlikely possibility that I wind up with several manually focusing lenses. At least my experience with the ebay screen only set me back $27, and I have been able to verify that auto-focus in my K10D is spot on accurate.

CN

stevebrot · 12-31-2008, 10:32 AM

Sorry your purchase proved to be disappointing. There is partial documentation on the Katzeye Web site regarding the affect of their product on exposure. I would expect that the similar cautions would apply to any split image screen, though your experience seems to be more severe than what they describe. Thanks for sharing your findings. I am sure that your notes will be appreciated by other people considering a similar purchase.

Steve

BTW...The focus screen does not affect auto-focus. That system uses a completely different light path than the viewfinder and is actually located in the bottom of the mirror box.

Wheatfield · 12-31-2008, 11:10 AM

The Katz-Eye can ply havoc with spot metering (no surprise), but other than that, it is fine. If anything, I am getting more consistent exposures with the Katz-Eye than I did with the stock screen.
This is in a k20.

Clem Nichols · 12-31-2008, 11:49 AM

Wheatfield:

Did you get the basic Katz eye or spring for the opti-brite? I can't help but think that it would make a definite difference at least with multi-point metering.

CN

**Kerrowdown** · 12-31-2008, 12:12 PM

I'm using the Katzeye with opitbrite, but only with manual fast glass ( in the range of f1:1.2 up f1:2.8).

So for me I have not had any exposure problems and my focus accuracy has gone up in leaps and bounds.

Katzeye rules for old manual buggers like me.

Wheatfield · 12-31-2008, 12:59 PM

Originally posted by Clem Nichols

Wheatfield:

Did you get the basic Katz eye or spring for the opti-brite? I can't help but think that it would make a definite difference at least with multi-point metering.

CN

I went with the Opti-Brite treatment. I figured that with my ever more fading vision, anything that gave me an edge would help. As I haven't used a non treated screen, I don't really know if it makes a visible difference or not though.

Finn · 12-31-2008, 09:03 PM

Funny, I had the opposite problem with a katz eye knock off on a K100D. It consistently underexposed by about 3 stops...but only on M lenses. And on variable-aperture zooms, exposure was fine at the wide end but way underexposed at the long end. And the screen would darken a lot to boot. I finally got tired of constantly fiddling with the exposure and stuck the original screen back in.

Wheatfield · 12-31-2008, 09:42 PM

Originally posted by Finn

Funny, I had the opposite problem with a katz eye knock off on a K100D. It consistently underexposed by about 3 stops...but only on M lenses. And on variable-aperture zooms, exposure was fine at the wide end but way underexposed at the long end. And the screen would darken a lot to boot. I finally got tired of constantly fiddling with the exposure and stuck the original screen back in.

This is the problem with knock offs sometimes. I could make a focusing screen out of some thin plastic and Scotch Magic tape for the ground glass if I wanted to, but I wouldn't expect accuracy from it.
Don't be surprised, BTW, if some or all of your problem was caused by your meter being out of range.

12-31-2008, 07:34 AM	#1
Clem Nichols Veteran Member Join Date: Mar 2007 Location: Munfordville, Ky. Photos: Gallery Posts: 370	Question for split-screen owners I recently purchased one of the e-bay split screen focusing screens for my K10D, and my initial impressions were very favorable. There is no question that it makes manual focusing in low-light conditions much more accurate. Further use has raised a couple of questions that hopefully someone can answer. First of all, does your camera seem to have slightly more difficulty auto-focusing with the split screen installed, and secondly, what about evaluative metering? I don't know about the Katz eye, but with the e-bay screen the prism and ground-glass central portions are considerably brighter than the periphery. I keep my camera set on the center focus spot and 16 zone multi-segment metering with AE tied to AF in the custon setting menu. Until recently this has worked just fine, but since installing the split screen my auto-exposure seems to function as if it were set to spot metering. I've taken several pictures recently which were very over-exposed, and this has never before been a problem. As a for-example, while experimenting yesterday, I took 2 back-to-back pictures of my golden retriever who was lying about 20 feet away from me in bright sunlight. These were taken with a Sigma 70-300 lens, and the dog's body made up probably 30% of the total picture area. When I put the center focus spot on a shaded portion of the dog's coat the picture was grossly over-exposed, and conversely when I focused on an area just a few inches away that was in direct sunlight the picture was slightly underexposed. As I said, the camera acts as if it's set to spot metering, and I can only assume that this is the result of changing focusing screens. I was wondering if anyone else had noticed this with either the e-bay or the Katz eye screens. Obviously with photography as well as with life in general we have to make a lot of compromises, but if better manual focusing in low-light conditions can only be obtained by a loss in accurate auto-exposing that's probably more of a compromise than I'm willing to make. Thanks for your response. CN

12-31-2008, 09:48 AM	#2
Clem Nichols Veteran Member Join Date: Mar 2007 Location: Munfordville, Ky. Photos: Gallery Posts: 370 Original Poster	Update After some more experimentation this morning with various lenses and continuing to get a high proportion of over-exposed images I wound up replacing the e-bay split screen with the original Pentax screen, and voila, the problem was corrected. I think what was happening was that the peripheral (and slightly darker than the OEM) portion of the split-screen unit was allowing less light to pass through to the camera's sensor causing the over-exposure by about 1 and 1/2 stops. I've decided to leave the Pentax screen in place and discard the ebay item. I still would be interested in knowing if users of the Katz eye screen have noticed anything similar. (What I have referred to as the ground glass portion of the viewfinder is what the folks at Katz eye call the microprism collar, and what I called the peripheral portion is what they call the matt portion of the screen. According to their web-site their Opti-brite treatment brightens the matt portion which leads me to believe that this would probably prevent the over-exposure I saw with the ebay screen. In fact they recommend their basic screen for fast primes and recommend the opti-brite screen for use with telephoto or slower lenses, and it was with the latter that I had problems. I never noticed any exposure problem when shooting with my Sigma 17-70. Considering that the basic Katz eye is over $100 and that the opti-brite treatment adds another $50 or so I think I'll stick with the original Pentax screen barring the unlikely possibility that I wind up with several manually focusing lenses. At least my experience with the ebay screen only set me back $27, and I have been able to verify that auto-focus in my K10D is spot on accurate. CN Last edited by Clem Nichols; 12-31-2008 at 10:30 AM. Reason: Clarification

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12-31-2008, 10:32 AM	#3
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Sorry your purchase proved to be disappointing. There is partial documentation on the Katzeye Web site regarding the affect of their product on exposure. I would expect that the similar cautions would apply to any split image screen, though your experience seems to be more severe than what they describe. Thanks for sharing your findings. I am sure that your notes will be appreciated by other people considering a similar purchase. Steve BTW...The focus screen does not affect auto-focus. That system uses a completely different light path than the viewfinder and is actually located in the bottom of the mirror box.

12-31-2008, 11:10 AM	#4
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,981	The Katz-Eye can ply havoc with spot metering (no surprise), but other than that, it is fine. If anything, I am getting more consistent exposures with the Katz-Eye than I did with the stock screen. This is in a k20.

12-31-2008, 11:49 AM	#5
Clem Nichols Veteran Member Join Date: Mar 2007 Location: Munfordville, Ky. Photos: Gallery Posts: 370 Original Poster	Wheatfield: Did you get the basic Katz eye or spring for the opti-brite? I can't help but think that it would make a definite difference at least with multi-point metering. CN

12-31-2008, 12:12 PM	#6
Kerrowdown PEG Moderator Join Date: Aug 2008 Location: Highlands of Scotland... "Hold Infinity in the palm of your hand" - William Blake Photos: Gallery Posts: 57,821	I'm using the Katzeye with opitbrite, but only with manual fast glass ( in the range of f1:1.2 up f1:2.8). So for me I have not had any exposure problems and my focus accuracy has gone up in leaps and bounds. Katzeye rules for old manual buggers like me.

12-31-2008, 12:59 PM	#7
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,981	Originally posted by Clem Nichols Wheatfield: Did you get the basic Katz eye or spring for the opti-brite? I can't help but think that it would make a definite difference at least with multi-point metering. CN I went with the Opti-Brite treatment. I figured that with my ever more fading vision, anything that gave me an edge would help. As I haven't used a non treated screen, I don't really know if it makes a visible difference or not though.

12-31-2008, 09:03 PM	#8
Finn Veteran Member Join Date: Feb 2007 Location: Phoenix Photos: Gallery Posts: 1,056	Funny, I had the opposite problem with a katz eye knock off on a K100D. It consistently underexposed by about 3 stops...but only on M lenses. And on variable-aperture zooms, exposure was fine at the wide end but way underexposed at the long end. And the screen would darken a lot to boot. I finally got tired of constantly fiddling with the exposure and stuck the original screen back in.

12-31-2008, 09:42 PM	#9
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,981	Originally posted by Finn Funny, I had the opposite problem with a katz eye knock off on a K100D. It consistently underexposed by about 3 stops...but only on M lenses. And on variable-aperture zooms, exposure was fine at the wide end but way underexposed at the long end. And the screen would darken a lot to boot. I finally got tired of constantly fiddling with the exposure and stuck the original screen back in. This is the problem with knock offs sometimes. I could make a focusing screen out of some thin plastic and Scotch Magic tape for the ground glass if I wanted to, but I wouldn't expect accuracy from it. Don't be surprised, BTW, if some or all of your problem was caused by your meter being out of range.