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03-16-2009, 02:21 PM   #1
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Focus Screen - diag or horiz? What do u think?

Hi all!

I'm soliciting opinions from people that have used a diagonal split screen. I searched the forums for "diagonal split" and read pages and pages in the various threads on the inexpensive and related SPLIT focus screen discussions. Unfortunately I didn't find anyone mentioning the relative merits of diagonal or horizontal split.

I have shot view finder, twin lens reflex, view camera....all sorts of stuff over the years. My film camera of choice is still my Nikon F3HP. I have some different split screens for the F3 but have never used a diagonal in anything. I understand for the 45* orientation.

The price of the Chinese split screens is so good, that it's not a show stopper if I don't like the diagonal, but I'm curios what your opinions are on the 45* split vs the more common horizontal split.

Anyone want to voice their opinions and experiences using the 45* split over a horizontal split?

Thanks!

Tom

03-16-2009, 03:12 PM   #2
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I used horizontal split image screens for so long that I found the 45 split to be quite odd, but I liked it once I got used to it.
I think it's pretty much a toss up as to whether one is better than the other.
03-16-2009, 04:27 PM   #3
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I have used both over the years and still have no particular preference. A few months ago there was a post where a forum member stated that Rachel Katz (Katz Eye Optics) told him that there was some loss of focus precision with the diagonal split.

Steve
03-16-2009, 09:02 PM   #4
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I have the cheap Chinese diagonal split. Haven't noticed any problems, and like the fact that I can easily focus on horizontal and vertical lines without having to jig the camera here and there.

QuoteOriginally posted by stevebrot Quote
... there was a post where a forum member stated that Rachel Katz (Katz Eye Optics) told him that there was some loss of focus precision with the diagonal split.
Interesting. What element of physics would cause that, I wonder?

03-16-2009, 09:53 PM   #5
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QuoteOriginally posted by marcdsgn Quote
Interesting. What element of physics would cause that, I wonder?
You got me...The poster had called Katz Eye asking why they did not offer the diagonal split. While the post included the Ms. Katz's plausible sounding technical explanation, I can't remember the details.

Steve
03-16-2009, 11:12 PM   #6
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QuoteQuote:
You got me...The poster had called Katz Eye asking why they did not offer the diagonal split. While the post included the Ms. Katz's plausible sounding technical explanation, I can't remember the details.

Steve

One of the things about my Chinese Prism that I preferred over the Katz eye is the diagonal split. I prefer it because it allows me to use both vertical and horizontal lines to obtain focus. The horizontal split is nice, but, unfortunately, is limited to vertical lines, unless of course you like turning your camera sideways to obtain focus.

Anyway, I liked the Katz eye screen--it made manual focusing much easier than my stock Pentax screen. But, I like my Chinese screen too--here is a manually focused shot with the Tamron 90mm, done by my diagonal split prism. BTW, Rachael never mentioned to me any "loss of precision" from using a diagonal split screen. no PPing, jpg cropped and resampled for forum EXIF: Handheld--400 ISO--spot metered--1/800th--f 4--manual mode--manual focusing

Last edited by Jewelltrail; 09-25-2009 at 09:04 AM.
03-17-2009, 08:55 AM   #7
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Thanks for all the replies! I think that I'll go with the diagonal split & give it a try. I think the biggest concern I had was the perception of feel of the diagonal split - would it make me feel like I wanted to jig my head to set it right?! I think like Wheatfield said, I'll get used to it.

Stevebrot, I knew there would be a relative loss of precision. Trigonometry...loss of precision by a factor of 0.707. The "projection" of the split image or a perfectly vertical line on the diagonal will result in a smaller offset. But, even though the offset of a vertical or horizontal line will be smaller by that factor, I don't think this will grossly affect real focus speed or precision. If its not a shot that has to be made quickly & I'm worried about absolute focus acuity I'll pass the point of apparent focus to reach an split image offset on the other side and then return to the relative center focus (manual focus hunting!) So, Katz were technically correct but I have to say that I feel when the rubber hits the road (photons hit the receptor?) it is almost moot.

The real advantage that Marcdsgn and Jewelltrail pointed out is that it is possible to use both vertical and horizontal lines/edges to confirm focus w/o having to shift the camera.

Thanks again all! Now to run out and spend a wee bit of $ on a diagonal & then try to be patient while waiting for it to arrive!

Cheers,
Tom
03-17-2009, 08:59 AM   #8
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Editorial Correction:

The "projection" of a perfectly vertical line onto the diagonal split image will result in a smaller offset.

03-17-2009, 11:52 AM   #9
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I think you're making a good choice by giving the diagonal split a try. I've used one in a Ricoh XR-10 for 20 years and I've found it more convenient than the horizontal split screen in other cameras I've used. When using my Nikon FE, I find that the microprism collar nearly makes up for the split direction difference. In fact, I think that not having a microprism collar in addition to the split is a bigger deal to me than the direction of the split.

I don't feel like a horizontal split would be a dealbreaker in any event, so if the chinese screen has other issues I wouldn't keep it just for the diagonal. But that's just my preference.
03-17-2009, 12:40 PM   #10
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QuoteOriginally posted by Popeye.Tom Quote
...Stevebrot, I knew there would be a relative loss of precision. Trigonometry...loss of precision by a factor of 0.707. The "projection" of the split image or a perfectly vertical line on the diagonal will result in a smaller offset. But, even though the offset of a vertical or horizontal line will be smaller by that factor, I don't think this will grossly affect real focus speed or precision. If its not a shot that has to be made quickly & I'm worried about absolute focus acuity I'll pass the point of apparent focus to reach an split image offset on the other side and then return to the relative center focus (manual focus hunting!) So, Katz were technically correct but I have to say that I feel when the rubber hits the road (photons hit the receptor?) it is almost moot.

The real advantage that Marcdsgn and Jewelltrail pointed out is that it is possible to use both vertical and horizontal lines/edges to confirm focus w/o having to shift the camera.

Thanks again all! Now to run out and spend a wee bit of $ on a diagonal & then try to be patient while waiting for it to arrive!

Cheers,
Tom
Thanks for the explanation. I could visualize the "why" for this one, but was having trouble coming up with the words. As for the vert/horiz advantage of the diagonal split...I have been shooting with a Ricoh XR7 since the early 1980s and have always been comfortable with the diagonal split on that camera. My K10D has a horizontal KatzEye and to be honest, I don't often feel the need for a diagonal. It may have more to do with style of shooting than with the practicality of design.

Steve
03-17-2009, 09:12 PM   #11
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QuoteQuote:
ytax
I think you're making a good choice by giving the diagonal split a try. I've used one in a Ricoh XR-10 for 20 years and I've found it more convenient than the horizontal split screen in other cameras I've used. When using my Nikon FE, I find that the microprism collar nearly makes up for the split direction difference. In fact, I think that not having a microprism collar in addition to the split is a bigger deal to me than the direction of the split.

I don't feel like a horizontal split would be a dealbreaker in any event, so if the chinese screen has other issues I wouldn't keep it just for the diagonal. But that's just my preference.
My less than $30 Chinese screen has both a diagonal split and a micro prism collar--both of these tools have their merits.
03-18-2009, 08:29 AM   #12
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Picture of Chinese Split Prism

It is not perfect, I was rushed for time, but here is a shot of the Chinese prism, in focus, through the K20 viewfinder--taken with a P & S piggybacked on the K20 with tripod.


edit: The Diagonal split runs right through the center of the letter "O" It is not as obvious, mostly because it is in focus--when out of focus the split is more obvious.

Last edited by Jewelltrail; 09-25-2009 at 09:05 AM.
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