Hi Ken
Thanks for the info. Very interesting!
Jens
-----Oprindelig meddelelse-----
Fra: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]På; vegne af K.Takeshita
Sendt: 23. marts 2001 02:27
Til: Pentax Discuss
Emne: Focussing ability of z-1p
Hello folks,
Sometime ago, I mentioned a test conducted by one of the Japanese camera
magazines on the ability of AF system of various cameras. I received the
initial info from somebody in Japan but lost it when I switched the mail
program.
Recently, he found the article and kindly scanned the page again and emailed
me.
Here's the rundown of what the test indicated;
1. Firstly, he scanned the test chart using the lowest resolution this time
so that the smooth gray is now shown as scattered dots. So, it does not
make much sense to email the charts or upload them to a web site. Besides,
it is in Japanese. But it is essentially simple test targets and I will
attempt to describe it orally.
2. ASA100 film, 50mm lens (aperture not known) and 2 meter distance to
target
3. 7 target charts from A to G
A-left side white and right side black
B-1mm black vertical stripe in the centre of white background
C-1mm white vertical stripe in the centre of gray background
D-1mm black vertical stripe in the centre of darker gray background
E-low contrast step (left side gray, right side black)
F-low contrast step (left side dark gray, right side black)
G-stepless transition (dark gray from the left end to black at the right
end, changing steplessly)
EV was plotted in 7 steps, varying from 6 through 0 to -1
4. Z-1p locked focus on all charts under all EVs except it required a focus
assist light under -1EV on charts B through G
5. On G chart, SFX locks down to 1EV while Z-1 down to 0EV.
6. MZ-3 and MZ-7 will not lock on G chart regardless of the EV. Recent
models are tuned more toward the chart A but under lower EV.
The camera magazine admired the Z-1p for its focussing capability which is
far less sensitive to the pattern of object or the lighting conditions than
any other cameras.
7. Recent cameras, regardless of makes, won't focus on the G chart at all.
In the past, only Nikon and Pentax valued the focusing accuracy and
sensitivity, being able to focus any of these charts, but no longer (except
z-1p).
For further details, I was referred to a back number of this magazine which
I am getting, when I could report more.
This confirms my observation that z-1p, in spite of its criticism on the
single sensor, almost always focusses on most everything even under very
poor lighting conditions. Single sensor issue does not bother me as I am a
"focus lock" guy :-) Difficulty to focus on horizontally oriented object
can be easily overcome and the problem is very infrequent. I rather value
the low light. low contrast focussing capability.
I am no AF expert but I saw an article somewhere about the trade off between
various elements of AF design vs. its sensitivity and focusing ability such
as the distance between adjacent sensor etc which greatly affect on the
focus sensitivity, for example.
But I always wondered this. It has been obvious that if z-1p's AF system
was brought up to at least MZ level with multi AF point, it would have been
a great update (so people say :-). I did not think it was not that
difficult for Pentax to do that, and I am sure they were keenly aware of it.
There may have been reasons why they so stubbornly stuck to the present AF
system. There may be a certain segment of the market who appreciates more
about the ability to focus on low contrast objects in darker lighting
condition, willingly trading it off with the single sensor arrangement. I
do not know if this could be true, but I certainly appreciate the Z-1p for
its focussing ability.
It is indeed a great camera but I parted it recently to get a MedF set and
am now wondering if it was a wise decision. It seems to me that every time
I sell off something, I suddenly realize the value of them :-)
Oh well, I hope the Z-1p price will come down even further soon so that I
can re-acquire it.
Cheers,
Ken
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