Thanks for that. It explains a lot including why CH and I had different
views of the effectiveness of the Canon fast glass focusing screen. The
reason I've never seen the difference is that I was still shooting at
small apertures and DOF has probably been covering my errors. I'll have
to watch out in the future. Recommended reading.
Chuck Norcutt
usher99@xxxxxxx wrote:
> Thanks Bob, chuck, CH and all. I found the original reference, but had
> to go to the way back machine ---it takes quite a bit to load.
>
> http://tinyurl.com/cvl29s
>
>
> I had excerpted Rachel's comments from Katzeye as well in a previous
> post:
>
>
> I then quieried Rachel at Katzeye on how they achieve both a brighter
> screen
> yet retain the ability to accurately manually focus fast glass:
> I think some have tried Brightscreen screens on the 5D/5DMkII which
> have helped some
> in this regard but was not a total solution.?
>
>
>
>
> Rachel replied:
>
> "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."
>
> After a few more emails she admitted that some focus contrast is ALWAYS
> lost with any brightening process.
> They worked it out for FF Canyon but have to waste a bunch of screens
> as it is tough to get it right consistently.
> She said the the EG-S is btter with fast glass though is way toooo dark
> with slower lenses. They are unlikely to market them from what she was
> saying due to the economics. There is a maxwell treatment. Hmmm
>
> Sooo,
> I'd bet lunch that if one takes 10 shots with the OM-4(t) with a 1-13
> screen with Velvia? compared to 10 shots with a 2-series and look at
> them with a loop
> using a Z. 50 1.2 wide open that the focus will be nailed at a better
> rate with the 1-series.
> Notice that I would not bet my 4T (John has it anyways)
>
> Mike
> Arrgh, back to work
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