If precise focus was as critical as we seem to be talking about here I
would use a DoF calculator to place the near and far focus points and
then focus on the point within that range that produces the precise
fore/aft positioning.
Dr. Focus
On 1/4/2012 4:26 PM, usher99@xxxxxxx wrote:
> 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
>>
>
--
_________________________________________________________________
Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
Archives: http://lists.thomasclausen.net/mailman/private/olympus/
Themed Olympus Photo Exhibition: http://www.tope.nl/
|