Out of curiousity, I fired up the OM-3Ti last night and attempted to
focus on my targets at 4, 5 and 6 meters. Using the 50mm F1.4 lens, I
was able to individually select the focus using the ground-glass on
any of the three targets. The 2-13 screen has a nifty feature, though.
When in focus (or nearly so), it shimmers. I've used that function
many a time. Between the 5 and 6 meter targets, focusing wasn't overly
easy and in low light or when focusing on a low-contrast object I
would say that it requires a little back and forth tweaking to find
the sweet spot. But in normal light with normal contrast object, I
wouldn't hesitate to say that it wasn't a problem.
With the 24mm F2.8 lens, things are a different story. The 2-series
screen has an issue with wide-angle lenses and is extremely hard to
focus on the ground-glass portion of the screen. An older 1-series
screen is actually far easier to focus wide-angle lenses because the
"bokeh" as presented on the screen is real, not imaginary as the
2-series screen's matte area is actually a fine microprism. (Nikon
uses a deformed microprism which has the brightness advantage of the
2-series screen, but maintains both higher contrast and a more natural
bokeh rendition). The viewfinder screen in the E-system bodies is
similar to the 2-series screen and uses a fine microprism, but with
different angles to better handle the short focal lengths--probably at
the expense of the longer focal-lengths.
So....
To the split-image focusing aid I go. The question is can the human
eye, using a 2-13 screen and a 24mm lens be able to selectively focus
on targets 4, 5 and 6 meters away? Without question, this
photographer is able to do it! And, frankly, it wasn't even
difficult. The microprism collar is not quite up to the task, but the
split-image was quite simple.
Of course, I must acknowledge the elephant in the room. Calibration
accuracy of the focus system in the OM-3Ti is probably not that good
and you also run into the issue of film flatness. But those are issues
outside of the discussion regardling human abilities.
A side-note... A friend here has the E-3. I asked him to do the test
with his equipment. When using the 12-60 he says he is able to
differenciate between targets at 5 and 6 meters with either the
live-view (magnified) or with the viewfinder. When using the Leica 25
F1.4, he couldn't with the viewfinder until stopped down to F2, but
live-view was no problem. I personally didn't supervise the test nor
compared directly with my own eyes (yet), but was pretty stringent in
my requirements with him. Having used his lenses, I would completely
concur with his analysis. The 12-60 tends to have more of an image
snap when in focus. The E-3 has a far larger viewfinder image too,
which makes critical focusing easier.
AG
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