Mike,
I wouldn't call it "consistent trouble at f/1.4" at all, just that
more appears to be in focus than what really is (and the lens looks
sharper and with stronger contrast than what it really is wide open).
It still accurately shows the actual plane of focus, but with the
depth of field as at f/2.8, instead of at f/1.4 (i.e. stopping down
with DOF preview, f/2 and f/2.8 looks *identical* in terms of
brightness and DOF).
Like Ken remarked, this means you are not accurately seeing the scene
as it would be recorded (you have to, like with a rangefinder,
visualise the shallower DOF in your mind). And your eyes need to be
pretty good to judge focus that accurately, especially with the faster
wide angle lenses. Of course, we're talking about the matte area of
the screen here - the split-prism variant is extremely accurate,
showing me focus differences with my 21mm lens - such as focusing
between 4m and 6m - which wouldn't even really show up on the film.
As somebody who came from Canon DSLRs, this is still better than their
standard focusing screens (I switched to the Ec-S very quickly) which
look pretty much the same even at f/4.0 to f.5.6. In fact, it's the
Nikon F with it's amazing DOF-accurate viewfinder (1950s technology,
ha...) that started all this nonsense - I became "visually aware" of it.
Dawid
On 04 Jan 2012, at 4:52 PM, <usher99@xxxxxxx> <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.)
--
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