Well, the latest report thread really criticizes the Katz Eye screens. The
current consensus (at least for those speaking the loudest lately) is that
the focus aids are great for focusing, but that the effect on exposure is
deleterious (very inconsistent exposures, generally overexposing by
unpredictable amounts). However, I have one, and I'm not about to give it
up yet - it is ~so~ good for manual focusing (and it seems to cause no
autofocus problems) that I'm willing (so far, anyhoo) to put up with less
than ideal exposures. I still have to experiment a bit, but I'm hoping
that the "unpredictability" of the exposure accuracy can become more
predictable with practice (I am hoping that each lens, fast versus slow,
say, will have a corresponding exposure compensation factor). We'll see...
I would just like to add that after playing with mine a bit
more, there are a few variables that need to be taken into account:
- A/AF lenses vs. M lenses
- Stop-down lenses (S/T)
- Maximum aperture of lenses (slow vs. fast)
- Individual lens differences.
- Shooting RAW
Basically, the stop-down nature of either S/T lenses or K/M lenses
with the "green-button" trick tend to be the most inaccurate. My own
playing with S/K/M lenses show blackout around f/5.6 on the focus
screen... and that's when exposure may change by as much as a stop or so.
If the lens is A/F/FA and at least f/4 or faster, it will likely not be an
issue at all, since metering is done at f/4 or faster. If slower than
that (or stopped-down to be slower), the results are more unpredictable.
Also, the focal length and construction type of the lens appears to make a
bit of difference as well.
Finally, I barely tell a difference between the errors while
shooting RAW. The auto-expose tends to normalize out differences in
exposure between different shots, with the only perceiveable difference
being the shadow noise. Since I tend to evaluate the histogram after
shots with the majority of my lenses (K/M/S) and exposing to the right,
the focus aid is definately worth the trouble.
If you tend to use auto-everything on slow glass shooting jpegs,
you'll have the hardest time dealing with it. Of course the AF is
probably fine in those circumstances anyway... :)
-Cory
--
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* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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