Hmm,
You could always ask your in house consultant Dr. Focus, but suspect
stopping down would likely just dim the VF a tad.
The injuneers seem to design the DSLR focusing screen to be bright as
it is primarily for framing as they
assume most will be using AF anyhow. The scattering to improve
brightness results in loss of OOF information thus the
F4 depth of focus accuracy. I suppose one could try and find the
midpoint in the near and far limits of the depth of focus and place
the desired plane of focus at the center to moderately improve the
accuracy of course.
I see Dawid statements referred to using the matte section not the
prism area and thus the different findings. I would be the 1-13 (vs
2-13) may be a bit better at nailing the desired plane of focus at
F1.2, but have not found evidence that anyone had done the experiment.
It would burn a bunch of film to properly perform the experiment.
Mike
Does that mean for most reliable focus to close down to f/4 and hold in
the DoF preview button since DoF indications will be unreliable anyhow?
Chuck Norcutt
On 1/4/2012 9:52 AM, usher99@xxxxxxx wrote:
> Yes, per Rachel at Katzeye the increased brightness always comes at
the
> cost of
> "focusing contrast." It is always a compromise. I had thought the 1-13
> and 2-13 enable reliable focus at f1.4 and was a bit surprised by
> Dawid's observation.
> Perhaps itis because I was comparing performance with the Z. 50/1.4?
> I could not find any experiments on this in the archives. Perhaps John
> would know if the 2-series have consistent trouble at f1.2.
> The stock Canyon OM 5DII screen seems to be about F4 for reliable
focus
> (against mag LV) as far as I can tell. (no surprise)
> I recall some mention of one Nykon model that enabled one to flip
> focusing screens that were pre-installed. Changing OM's FS is
> not very fussy, but is still not something one wants to do while out
> and about. (I use sterile powderless surgical gloves which really
> makes it fast.)
>
> Clean Screen, Mike
>
>
http://olympus.dementix.org/eSIF/om-sif/findergroup/focusingscreens.htm
>
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