Katz eye focusing screen.

In article , Michael Benveniste
writes
"Matt Clara" wrote:

My Nikon split prism for my F3HP blacks out on one side when
I try to do macro, particularly with the bellows, so does my
Mamiya RB67's. You can hold your eye back a little bit, and
regain use of the split screen, but then your head isn't
braced, and your a little farther from the "split" to see it
and line up the two halves.

That's likely because of the "bellows effect." At 1:1, an
f/2.8 lens is effectively an f/5.6 lens, and most split image
focus aids are only marginally usable at f/5.6 and unusable
by f/8. The Katz eye prism claims to be usable down to f/11,
but I've held off on buying/installing one since Nikon USA
considers it a warranty-voiding modification.

I would be more worried about the general problems an f/11 split image
prism introduces rather than the advantage it provides in limited unique
situations. An f/11 prism has no more than HALF the focus precision of
an f/5.6 prism, and should ONLY be used when required (ie. when the
f/5.6 prism does black out).

If you want to understand why f/11 is less appropriate for faster
lenses, read this description of HOW a split image viewfinder works.
http://doug.kerr.home.att.net/pumpkin/Split_Prism.pdf

The split image prism system is basically a rangefinder and at f/11 the
baseline of the rangefinder is half that of f/5.6, with consequential
effects on focus accuracy. In fact, in the not so old days, some
manufacturers offered both slow and fast split image screens for
precisely this reason.

Holding up to f/11 may be a benefit when using such slow optics, but it
certainly is NOT an "improvement" in general terms. If you plan to
shoot fairly wide then you would be much better to use a screen that
only operates to f/5.6 or even faster.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)

Paul Furman wrote in
:


Probably 10 years since I used my old Canon AE1. I never really
used the microprism collar on it through all those years either,
I just used the split prism.

I didn't get split prism focusing in an SLR until maybe my *third* one
(fourth serious camera, there was a Leica M3 in there too). My first
few were microprism only.

And I converted my FM2 to a matte screen, no focusing aid at all.

--
David Dyer-Bennet, ; http://dd-b.net/
Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/
Photos: http://dd-b.net/photography/gallery/
Dragaera: http://dragaera.info

Paul Furman wrote in
:

I got my Katz eye focusing screen in the mail yesterday and
installed it today.

I read their instructions for installing on a D200 (which they asked
me *not* to post, incidentally...), and got scared off of self-
installing. Which has kept me from getting one so far. It sounded
like there were little shims that set the position of the screen,
which if lost or misinstalled would cause manual focusing to be
inaccurate due to screen mis-positioning. How did your actual
installation go? Did it look like there were opportunities for that
level of disaster?

--
David Dyer-Bennet, ; http://dd-b.net/
Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/
Photos: http://dd-b.net/photography/gallery/
Dragaera: http://dragaera.info

"Floyd L. Davidson" wrote:

The Katz eye prism claims to be usable down to f/11,
but I've held off on buying/installing one since Nikon USA
considers it a warranty-voiding modification.

Really? That would be a bit silly of Nikon... and I
find it pretty hard to believe. It *is* a customer
replaceable component, no different than the carrying
strap, for example.

But I still don't see that as a problem anyway. If you
warranty need work done, just put the original screen
back in before handing it to Nikon.

Really. I asked Nikon USA this specific question in March of 2006.
The incident number was 060306-000163. As with all their replies,
the email includes a prohibition on quoting it here, but my
statement is consistent with their response. Unlike screens for other
Nikon cameras, they do not consider a D200 screen a customer
replaceable component.

While _you_ might be able to put back in the original screen, I'm
not so sure about my own abilities to do so without leaving some
evidence. When I get one of these screens, I will have it installed
by Katz-Eye or a local technician.

It's possible that Nikon USA's stand has changed since then, so you
may wish to ask them yourself.

--
Michael Benveniste --
Spam and UCE professionally evaluated for $250. Use this email
address only to submit mail for evaluation.

"Paul Furman" wrote in message ...
David Ruether wrote:
Paul Furman wrote

I got my Katz eye focusing screen in the mail yesterday and installed it today. Installation instructions (slow loading PDF):
http://www.katzeyeoptics.com/files/D200.PDF

The split prism center aid does indeed help with manual focusing, in particular I had a heck of a time without it focusing the
old 28mm f/2 at medium distances and even where I thought it was easy like closeups, the focusing aid gives me a little better
confirmation.

Funny - back in the "good old days" with really sharp Nikon
viewfinders (before the N7007 and the N90, and before the
center of my focus eye went soft), the first thing I did when
I got a new body (which came with that %$#& split-image
rangefinder and useless microprism, that just spoiled the view
and didn't help at all with focusing [the center of the split needs
to be on what? perpendicular edge how's that for
handy? for accuracy, assuming 1/2 doesn't go dark - and
I never could get Nikon's microprism to look different with
the lens in or out of focus] - and it all just slowed me down)
was to yank it out and replace it with the matte plus Fresnel
screen

Is that maybe what comes in the D200? The OOF does have a granular look to it. Still, it's cropped frame and not 100% either, even
if it is a heck of a lot better than my D70 viewfinder was.

Yes, the D80 and similar come with the basic matte plus outer
area Fresnel (for edge brightening) screen. The "grind" in the
matte screen gives the eye something to "stop" on for focus.
Otherwise, as with clear screens, you would see no point of
correct focus at all - though you could still use paralax focusing
(tedious, and you need a reference mark in the finder). When
you stop a lens down with the DOF preview, you see more
clearly on the darker screen its texture. BTW, the smoother
and brighter the screen is (achieved by reducing the level
of texture), the harder it is to focus with the screen - so a
compromise must be found. The same is true for the Fresnel
at the edges - one optimized for some lenses will likely not
work as well for others, and since the Fresnel offers a
second (and different) layer in the optical path for the eye
to "catch", it can reduce focus accuracy. Darn! ;-)

that was so sharp that I could beat any AF system for
accuracy and focus speed (until the F100/F5 came along,
as well as my eye problem...). Fortunately, Nikon has again
returned to making sharp matte screens (with diopter
adjustment, too!), making an N80 almost as easy to focus as
the F3/F2/F or the FE/FM/FA/8008. These matte screens
give a better idea of what the texture and "feel" of OOF
areas will I look like, also. I think I will not be paying extra
for a screen type I have many of on my shelves since I didn't
like them much when they came with the cameras...;-)

There are trade-offs but like I said, lenses like the 28mm f/2 & fast 50mm are really hard to focus at distances more than a few
feet away and it does help with that. --
Paul Furman Photography

Are these lenses sharp wide open? Also, some lenses (or
lens speeds) just do not mate well with the optics of some
viewfinders. My guess is that your camera's stock VF is not
designed to match speed lenses, since most DX lenses are
f2.8 or even slower...
--
David Ruether

http://www.donferrario.com/ruether

Kennedy McEwen wrote:

In article , Michael Benveniste
writes

"Matt Clara" wrote:

My Nikon split prism for my F3HP blacks out on one side when
I try to do macro, particularly with the bellows, so does my
Mamiya RB67's. You can hold your eye back a little bit, and
regain use of the split screen, but then your head isn't
braced, and your a little farther from the "split" to see it
and line up the two halves.


That's likely because of the "bellows effect." At 1:1, an
f/2.8 lens is effectively an f/5.6 lens, and most split image
focus aids are only marginally usable at f/5.6 and unusable
by f/8. The Katz eye prism claims to be usable down to f/11,
but I've held off on buying/installing one since Nikon USA
considers it a warranty-voiding modification.

I would be more worried about the general problems an f/11 split image
prism introduces rather than the advantage it provides in limited unique
situations. An f/11 prism has no more than HALF the focus precision of
an f/5.6 prism, and should ONLY be used when required (ie. when the
f/5.6 prism does black out).

If you want to understand why f/11 is less appropriate for faster
lenses, read this description of HOW a split image viewfinder works.
http://doug.kerr.home.att.net/pumpkin/Split_Prism.pdf

Page 11:
"There are special modifications to the prisms (not involving a change
in angle) that can mitigate this “blackout” effect down to smaller
apertures than usual while still maintaining a desirable large baseline
distance (in the interest of retaining greater “sensitivity” when a
large aperture lens is in place). These modifications are used in some
split prism focusing screens available today. The principle involved is
proprietary, and is beyond the scope of this article."

The split image prism system is basically a rangefinder and at f/11 the
baseline of the rangefinder is half that of f/5.6, with consequential
effects on focus accuracy. In fact, in the not so old days, some
manufacturers offered both slow and fast split image screens for
precisely this reason.

Holding up to f/11 may be a benefit when using such slow optics, but it
certainly is NOT an "improvement" in general terms. If you plan to
shoot fairly wide then you would be much better to use a screen that
only operates to f/5.6 or even faster.


--
Paul Furman Photography
http://edgehill.net
Bay Natives Nursery
http://www.baynatives.com

David Ruether wrote:

"Paul Furman" wrote in message ...

David Ruether wrote:

Paul Furman wrote


I got my Katz eye focusing screen in the mail yesterday and installed it today. Installation instructions (slow loading PDF):
http://www.katzeyeoptics.com/files/D200.PDF

The split prism center aid does indeed help with manual focusing, in particular I had a heck of a time without it focusing the
old 28mm f/2 at medium distances and even where I thought it was easy like closeups, the focusing aid gives me a little better
confirmation.


Funny - back in the "good old days" with really sharp Nikon
viewfinders (before the N7007 and the N90, and before the
center of my focus eye went soft), the first thing I did when
I got a new body (which came with that %$#& split-image
rangefinder and useless microprism, that just spoiled the view
and didn't help at all with focusing [the center of the split needs
to be on what? perpendicular edge how's that for
handy? for accuracy, assuming 1/2 doesn't go dark - and
I never could get Nikon's microprism to look different with
the lens in or out of focus] - and it all just slowed me down)
was to yank it out and replace it with the matte plus Fresnel
screen


Is that maybe what comes in the D200? The OOF does have a granular look to it. Still, it's cropped frame and not 100% either, even
if it is a heck of a lot better than my D70 viewfinder was.


Yes, the D80 and similar come with the basic matte plus outer
area Fresnel (for edge brightening) screen. The "grind" in the
matte screen gives the eye something to "stop" on for focus.
Otherwise, as with clear screens, you would see no point of
correct focus at all - though you could still use paralax focusing
(tedious, and you need a reference mark in the finder). When
you stop a lens down with the DOF preview, you see more
clearly on the darker screen its texture. BTW, the smoother
and brighter the screen is (achieved by reducing the level
of texture), the harder it is to focus with the screen - so a
compromise must be found. The same is true for the Fresnel
at the edges - one optimized for some lenses will likely not
work as well for others, and since the Fresnel offers a
second (and different) layer in the optical path for the eye
to "catch", it can reduce focus accuracy. Darn! ;-)


that was so sharp that I could beat any AF system for
accuracy and focus speed (until the F100/F5 came along,
as well as my eye problem...). Fortunately, Nikon has again
returned to making sharp matte screens (with diopter
adjustment, too!), making an N80 almost as easy to focus as
the F3/F2/F or the FE/FM/FA/8008. These matte screens
give a better idea of what the texture and "feel" of OOF
areas will I look like, also. I think I will not be paying extra
for a screen type I have many of on my shelves since I didn't
like them much when they came with the cameras...;-)

There are trade-offs but like I said, lenses like the 28mm f/2 & fast 50mm are really hard to focus at distances more than a few
feet away and it does help with that. --
Paul Furman Photography

Are these lenses sharp wide open?

Sharp enough for a tiny viewfinder perspective.

Also, some lenses (or
lens speeds) just do not mate well with the optics of some
viewfinders. My guess is that your camera's stock VF is not
designed to match speed lenses, since most DX lenses are
f2.8 or even slower...

Unfortunately you cannot see the improvement of lenses faster than f/2
or f/2.8 in the viewfinder. This has been discussed here and no
authorative explanation discovered. My best guess is some obstruction in
light path due to smaller mirror perhaps in a less than 100% viewfinder.
The diameter of OOF circles above f/2 or so does not increase in the
viewfinder compared to what pops up on the LCD after shooting the actual
image.

--
Paul Furman Photography
http://edgehill.net
Bay Natives Nursery
http://www.baynatives.com

David Dyer-Bennet wrote:

Paul Furman wrote in

I got my Katz eye focusing screen in the mail yesterday and
installed it today.

I read their instructions for installing on a D200 (which they asked
me *not* to post, incidentally...), and got scared off of self-
installing.

They provide the public web link in the package.

Which has kept me from getting one so far. It sounded
like there were little shims that set the position of the screen,
which if lost or misinstalled would cause manual focusing to be
inaccurate due to screen mis-positioning. How did your actual
installation go? Did it look like there were opportunities for that
level of disaster?

I read that too but nothing fell out. There isn't any diagram or photo
showing what those shims look like.

--
Paul Furman Photography
http://edgehill.net
Bay Natives Nursery
http://www.baynatives.com

"Michael Benveniste" wrote:
"Floyd L. Davidson" wrote:

The Katz eye prism claims to be usable down to f/11,
but I've held off on buying/installing one since Nikon USA
considers it a warranty-voiding modification.

Really? That would be a bit silly of Nikon... and I
find it pretty hard to believe. It *is* a customer
replaceable component, no different than the carrying
strap, for example.

But I still don't see that as a problem anyway. If you
warranty need work done, just put the original screen
back in before handing it to Nikon.

Really. I asked Nikon USA this specific question in March of 2006.
The incident number was 060306-000163. As with all their replies,
the email includes a prohibition on quoting it here, but my
statement is consistent with their response. Unlike screens for other
Nikon cameras, they do not consider a D200 screen a customer
replaceable component.

Okay. If the D200 is different, it might well be exactly as
you are describing. I was assuming, and might be totally wrong,
that it was similar to the D2 series.


While _you_ might be able to put back in the original screen, I'm
not so sure about my own abilities to do so without leaving some
evidence. When I get one of these screens, I will have it installed
by Katz-Eye or a local technician.

It's possible that Nikon USA's stand has changed since then, so you
may wish to ask them yourself.

--
Michael Benveniste --
Spam and UCE professionally evaluated for $250. Use this email
address only to submit mail for evaluation.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

Kennedy McEwen wrote:

I would be more worried about the general problems an f/11 split image
prism introduces rather than the advantage it provides in limited unique
situations. An f/11 prism has no more than HALF the focus precision of
an f/5.6 prism, and should ONLY be used when required (ie. when the
f/5.6 prism does black out).

If you want to understand why f/11 is less appropriate for faster
lenses, read this description of HOW a split image viewfinder works.
http://doug.kerr.home.att.net/pumpkin/Split_Prism.pdf

This (quite interesting) source does _not_ say that an f/11
prism must have a reduced baseline, to the contrary!
| There are special modifications to the prisms (not involving a change
| in angle) that can mitigate this "blackout" effect down to smaller
| apertures than usual while still maintaining a desirable large
| baseline distance (in the interest of retaining greater "sensitivity"
| when a large aperture lens is in place). These modifications are used
| in some split prism focusing screens available today. The principle
| involved is proprietary, and is beyond the scope of this article.
(Page 11, last paragraph, of above URL)

-Wolfgang