Hmmm,
Dr. Focus has had a busy day. Thanks for posting your observations. Would
have thought the Ee-s screen would be too dark with slower glass.
I wonder if a custom diopter with astigmatism correction wouldn't be useful.
Perhaps I'll need to try to twist the arm of the optometrist whose
office is next to mine and check if this is possible. (May as well make 2
or 3.) I'm not sure why Canyon
even sells diopters with a +0 power.
The bright screen is $$$ more and always worried that the downside might be
trouble with fast Zuikos. Below is
a note from Rachel at Katz Eye. I can't imagine she would mind. They no
longer have any technical hurtles that held
them up before but they have not deemed it economical to sell anything for
the 5D yet. Arrgh.
Mike
"Regarding the brightness and focusing of fast glass, that is a legitimate
concern and loss of focusing ability is commonly the case with brightness
enhancement techniques that apply a coating to the screen. Essentially,
what those coating techniques do is cut down on the diffusion (and by
extension, the focusing contrast or 'snap') by smoothing over the surface.
I don't want to single anyone out by name, but that general idea is the
traditional brightness enhancing technique that's been around for a while
and is used by most of the other companies you can find offering brighter
screens. Our process is significantly different, however. We do not coat
the screen and we do not simply smooth over the surface. The details of our
OptiBrite treatment are of course proprietary, but we actually change the
structure of the plastic at the microscopic level in a very controlled way
to modify the scattering profile for a specific result. What this allows us
to do is maintain the overall level of diffusion so that the focusing
contrast remains high and focusing of fast glass is still optimal. But
within the overall diffusion profile, we can preferentially augment specific
scattering angles to increase the amount of light that reaches the eye. So,
to make a long story short, the OptiBrite treatment we offer on the Katz Eye
screens does not have a negative impact on the focusing of fast glass as is
the case with other brightness enhancement processes."
I did some tests today which only left me confused. I used the 85/2
manually focused at f/2, 2.8, 4, 5.6 and 8 but all shot at f/2. Was the
best shot focused at f/2. No, the best one was focused at f/8. The f/4
shot was grossly out of focus and the others were pretty close to being
in focus as judged by using the Tokina 28-80 at 2.8 in autofocus mode.
But I didn't feel really bad since even one of the autofocus shots was
as bad as my worst. Not sure what happened there.
All of this caused me to question my shooting without glasses. I use
only the built-in dioptric adjustment which does not correct for my
astigmatism which is maybe worse than I realize. So I tried another
test using the Tokina in both auto and manual focus modes but this time
I changed the dioptric adjustment so that all was correct using my
reading specs. Then I was able to take the sharpest shot of the day by
focusing the Tokina (using the DOF preview) at f/5.6 and (without
thinking) shooting at f/5.6 instead of wide open at 2.8. Focus or DOF.
I don't know. I'm tired of testing and going to quit for the day.
Anyhow, I don't really believe the Ee-s screen is an impediment to
manually focusing above f/2.8.
Chuck Norcutt
Chuck Norcutt wrote:
> For those not in the know, the Canyon Ee-s focusing screen is designed
> to assist manual focus for lenses of f/2.8 or larger apertures. If I
> get a chance today I'll try a comparison test with the standard and Ee-s
> screens with the Zuiko 135/3.5. I did try a couple shots with it
> yesterday which seem to be fine but I didn't compare. I did notice that
> metering was quite accurate at f/8. The Ee-s screen works fine with the
> Tokina 80-200/2.8 on auto but, with my eyes, I haven't even tried
> manual. That lens has a minimum focusing distance of 1.8 meters and I
> don't have a Canyon mount extension tube so it doesn't get used with
> anything even approaching macro which is where I'd probably choose
> manual focus.
>
> Chuck Norcutt
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