Simon, thanks for your explanations.
So, the Olympus 'clear' screens are truly that - clear? And therefore
do not offer any 'focus-ability'?
I'm trying to square this with the eSIF which, for screens 1-5, 1-6
and 1-7 says "Focusing is done on the central microprism spot." And,
"The lack of a matte surface means depth-of-field effects cannot be
ascertained."
1-9 and 1-12 have *no* focusing aids but can somehow be focused in
conjunction with an endoscope and microscope respectively - how the
heck does that work?
. . . think I'm missing something simple here . . .
Thanks!/Scott
On 5/3/05, Simon Worby <simon@xxxxxxxxxxxx> wrote:
>
> ScottGee1 asked:
>
> > From the archives my understanding is that one cannot focus with the
> clear
> > area, but rather the focusing aid is used to focus - correct?
>
> The focussing aid (split prism / microprism) is not *needed* to focus,
> but it can be helpful. However, without anything (ground glass or
> focussing aid), focussing is impossible.
>
> What you are doing when you focus, is to get the image on the focussing
> screen sharp and in focus. If it's clear glass you can't see the image
> on the focussing screen as there isn't one; hence it needs to be at
> least part ground glass with or without a focussing aid.
>
> The focussing screen is at the same distance from the subject as the
> film will be when it's exposed to the light. Hence you are making sure
> the image, when it's projected onto the film, will be in focus.
>
> To the eye, due to the various lenses, the focussing screen appears to
> the eye to be about 6 foot away, though in reality it is but an inch or
> so away. (It's not possible for normal humans to focus down to an inch!)
>
> > <snip> Also, how much brighter/clearer are the clear screens than a
> comparable
> > 1 series matte screen? 2 series?
>
> I think a stop or so. But, IMHO, they are almost impossible to use
> except for specific purposes. Unless you have a specific purpose in
> mind, I would recommend a ground glass screen of some description, with
> a focussing aid. Some photographers like not to have the focussing aid
> (as per 1-4 or 2-4) but personally I think they make life hard work.
>
> Regards,
>
> Simon
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