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01-14-2009, 01:14 PM   #1
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Focusing manual lens with OEM focusing screen, is a split screen really needed?

I was playing around with a Pentax-M 80-200mm lens on my *istD the other day, I noticed that when focus was achieved, the green focus indicator light came on, so I thought, why does one need a split prism focusing screen if the focus indicator still works with a manual lens?

Maybe just because it's faster? With a split focus screen you are looking at your composed subject rather than the sidebar of your viewfinder so I could it being more convenient and faster, but maybe not a necessity.

Thoughts?

01-14-2009, 01:17 PM   #2
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1- Better low light focusing.
2- There is actually some slack in the green focus light activating. It can be a tad out of focus, but the green light is on.
01-14-2009, 03:06 PM   #3
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How many threads do we currently have active on this very topic?

It has been discussed to death in this one, for example.

Got another one going here.

It may be time that split-prisms be given their own subforum.
01-14-2009, 03:09 PM   #4
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Yes, I saw those, I wanted input on the focus indicator, not which screen to buy.

Thanks!


QuoteOriginally posted by Mike Cash Quote
How many threads do we currently have active on this very topic?

It has been discussed to death in this one, for example.

Got another one going here.

It may be time that split-prisms be given their own subforum.


01-14-2009, 03:26 PM - 1 Like   #5
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Pentax - take a note - put a split prism screen in the next Pentax DSLR.
01-14-2009, 04:11 PM   #6
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QuoteOriginally posted by mithrandir Quote
Pentax - take a note - put a split prism screen in the next Pentax DSLR.
Yes Pentax, pls do so.

If this is done, there would be a compelling differentiator with the competition.

hmmm, I wonder what the reasons are why the current DSLRs by Nikon & Pentax (I've never looked at Canons and Sony's) don't have a split prism? I mean don't they tout the ability to use manual focus?
01-14-2009, 04:13 PM   #7
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QuoteOriginally posted by skid2964 Quote
Yes, I saw those, I wanted input on the focus indicator, not which screen to buy.

Thanks!
The matter of the focus indicator has also been discussed in depth. As with many things; however, it is often hard to find the pertinent posts. Sooo...

The focus indicator is not very precise and suffers from the same issues as the autofocus sensor that drives it. Low contrast and low light yield may yield a failure to lock. When the AF sensor fails to lock, you are thrown back to the matte surface of the stock screen which has greater apparent depth-of-field than is actually present wide open with your average fast prime. The result is less-precise focus all-around with manual focus lenses.

Adding a split-image and/or microprism allows for much greater focus accuracy and precision than is available with the AF system.

The general consensus among those of us with prior film camera experience with some of the best viewfinders ever developed, is that the current viewfinders and stock screens are extremely lacking. If you are confused as to what I am talking about, simply look through the viewfinder of a Pentax ME, ME Super, or MX the next time you are in the used camera department of your friendly neighborhood camera store. As stated by another forum user..."It is like looking out a window...".

Steve


Last edited by stevebrot; 01-14-2009 at 04:18 PM.
01-14-2009, 04:17 PM   #8
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QuoteOriginally posted by PentHassyKon Quote
Yes Pentax, pls do so.

If this is done, there would be a compelling differentiator with the competition.

hmmm, I wonder what the reasons are why the current DSLRs by Nikon & Pentax (I've never looked at Canons and Sony's) don't have a split prism? I mean don't they tout the ability to use manual focus?
No they don't tout the ability to MF. In fact, most modern AF lenses are d*** hard to manually focus due to short focus throw and crummy MF controls.

As to why no split-image?...That is an easy one. If the AF is off, the split-image will tattle on the system. There is also the issue of split-image black out with today's slowish zoom lenses.

Steve
01-14-2009, 04:23 PM   #9
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QuoteOriginally posted by stevebrot Quote
The focus indicator is not very precise and suffers from the same issues as the autofocus sensor that drives it.

Adding a split-image and/or microprism allows for much greater focus accuracy and precision than is available with the AF system.

Steve
Could the 1st point be why they don't want to put a microprism or split image in? I mean, then we would be griping why the focus indicator or rather the autofocus is imprecise.
01-14-2009, 05:40 PM   #10
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QuoteOriginally posted by PentHassyKon Quote
Could the 1st point be why they don't want to put a microprism or split image in? I mean, then we would be griping why the focus indicator or rather the autofocus is imprecise.
Imprecise and inaccurate

However, I have the Katzeye screen and the AF is usually pretty accurate with my two AF lenses (18-55 kit and FA 35/2). Still though, people would complain. It is our nature...

Steve
09-03-2010, 02:01 AM   #11
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QuoteOriginally posted by skid2964 Quote
I was playing around with a Pentax-M 80-200mm lens on my *istD the other day, I noticed that when focus was achieved, the green focus indicator light came on, so I thought, why does one need a split prism focusing screen if the focus indicator still works with a manual lens?

Maybe just because it's faster? With a split focus screen you are looking at your composed subject rather than the sidebar of your viewfinder so I could it being more convenient and faster, but maybe not a necessity.

Thoughts?
The green focus-light works on your *istD and also on my K200D, but on the Z-1 it does so only with K-mount lenses, not with screw-mount-lenses.
(I used to have and use 80/2.0, 35/2.0 and 20/2.8 in screw mount next to the SMC-A 24/2.8, SMC-A 35-105/3.5 and SMC-F 50/1.7 where the first two were primarly meant for low-light and the last for the extreme wide-angle. At the time I bought the 20/2.8 (Aus Jena Flektogon) a new version of the SMC-A 20/2.8 went for more than 5 times the price, increasing to tenfold shortly thereafter. Secondhand I have never seen this lens offered. The same goes for the 80/2.0 (Jupiter-9) where a new Pentax 85/1.4 would cost 20-fold and secondhand more than tenfold in the rare occasions it is offered. The 35/2.0 I have neer seen offered secondhand either, and when the FA 35/2.0 came out it was not only five times as expensive but since then I've also had more urge for other lenses. With an APS-C sized sensor I see little use of a 35mm for my photography, I would now prefer a fast 24 and 40mm lenses, e.g. FA24/20 and FA43/1.9ltd.

This is an extra reason to want a split-field/microprism-screen
09-03-2010, 06:35 AM   #12
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QuoteOriginally posted by skid2964 Quote
I was playing around with a Pentax-M 80-200mm lens on my *istD the other day, I noticed that when focus was achieved, the green focus indicator light came on, so I thought, why does one need a split prism focusing screen if the focus indicator still works with a manual lens?

Maybe just because it's faster? With a split focus screen you are looking at your composed subject rather than the sidebar of your viewfinder so I could it being more convenient and faster, but maybe not a necessity.

Thoughts?
Note that while focus indication works on K mount lenses, it does not work for M42 lenses, or for lenses with non conducting lens mounts. (Anodized or Painted black)

Some people use tinfoil to short pin 7 of the lens mount to get focus confirmation.,

Also, split images are very useful to get close, and if you are using only the image in the viewfinder as focus confirmation note that the DOF of the viewfinder is greater than the lens.

I also find that for really wide angle lenses achieving precise focus is difficult without a split image
09-03-2010, 06:37 AM   #13
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QuoteOriginally posted by PentHassyKon Quote
hmmm, I wonder what the reasons are why the current DSLRs by Nikon & Pentax (I've never looked at Canons and Sony's) don't have a split prism? I mean don't they tout the ability to use manual focus?
most DSLRs offer spot metering, split image finders interfere with spot metering.

Additionally split image finders and microprism collars have limitations with slow lenses, and most kit lenses sold are F4-5.6 (I.e. SLOW)

As a result, to offer the slow lenses, and spot metering the split image had to go, and on an AF body, why not?
09-03-2010, 07:18 AM   #14
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QuoteOriginally posted by Lowell Goudge Quote
most DSLRs offer spot metering, split image finders interfere with spot metering.
It never did interfere with the spot-metering inside the Olympus OM4/OM4ti, OM2sp and OM3/OM3ti, nor with the one in Ricoh XR-X to mention just a few. Also for the Minolta 9000 which also had spotmetering Minolta offered a screen with a split-image-field.

Camera's where the ligh metering is not taken from the screen are generally not affected by the type of matte-screen installed (From Pentax this includes the LX). They do often need circular polarization-filers instead of regular ones.

QuoteOriginally posted by Lowell Goudge Quote
Additionally split image finders and microprism collars have limitations with slow lenses, and most kit lenses sold are F4-5.6 (I.e. SLOW)
Absolutely true
QuoteOriginally posted by Lowell Goudge Quote
As a result, to offer the slow lenses, and spot metering the split image had to go, and on an AF body, why not?
This is probably the true reason, but many people still prefer to manually focus, especially Pentax and Nikon users which can still use their MF lenses on their AF and digital camera's.
09-03-2010, 10:21 AM   #15
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QuoteOriginally posted by KX-Digital Quote
It never did interfere with the spot-metering inside the Olympus OM4/OM4ti, OM2sp and OM3/OM3ti, nor with the one in Ricoh XR-X to mention just a few. Also for the Minolta 9000 which also had spotmetering Minolta offered a screen with a split-image-field.
But regardless of how specific cameras coped with split image and spot metering, current production cameras, which do not have light path separators built into the mirror for metering, but measure light on the focusing screen, including ALL current pentax cameras, do have this problem
QuoteQuote:
Camera's where the ligh metering is not taken from the screen are generally not affected by the type of matte-screen installed (From Pentax this includes the LX). They do often need circular polarization-filers instead of regular ones.
note the LX was not a spot meter with perhaps 1% of the image in the metering, but from memory about 5% of the image, this would help.
QuoteQuote:

Absolutely true
yes regarding darkening, this is why even 20 years ago when I wanted a camera for use primairly with a long tele, I went for a ground glass vfocusing screen, the split image was useless
QuoteQuote:
This is probably the true reason, but many people still prefer to manually focus, especially Pentax and Nikon users which can still use their MF lenses on their AF and digital camera's.
The point is, other than pentax, no other manufacturer offers full metering capability across all models. the canikon users that can, are purchasing pro level cameras. It is curious they spend all that money oh the hiogh end camera with good AF and put a 30 year old lens on the camera.
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