The more light you have hitting the metering sensor the more accurately
it is measured. That's pretty much true with any meter. Pentax makes a
number of over optimistic assumptions I think, but the calculations
preformed from a wide open reading of the existing light, seem to be
much better than the readings I get stopping down.
I've tested it with the FA 43mm limited. Using the lens in dim light,
set at f4-5.6 (on A), I get pretty good exposures. Stop down metering
in the same situation with the same aperture yields wildly varying
shutter speeds, usually running to under exposure due to much shorter
shutter speeds*, but sometimes to much longer shutter speeds.
The reason I tested it at all was that I noticed that the M 85mm in dim
light was often giving extremely under exposed images, (sometimes
extremely over exposed, but not as often). The diaphragm doesn't seem
to be sticky, it doesn't seem to have problems in bright light. However
when using the 43mm limited and A 24 f2.8 I had fewer metering problems.
*I've been experiencing this since the *ist-D days. The K20D was a
little better, the K-5II a little better than that, but open aperture
metering still gives better, more consistent exposures in dim light.
On 2/24/2016 3:25 PM, Larry Colen wrote:
P.J. Alling wrote:
Bottom line is the only reason that makes any real sense.
The rational has variously been that it was inaccurate, but it isn't as
inaccurate as stop down metering can be.
OK, this really confuses me, because when you meter wide open, you are
assuming perfect linearity from wide open to the projected aperture,
and I seem to recall reading an article that explains wu this
assumption tends to be overly optimistic, without even considering the
difference between t-stops and f-stops. I believe that the problem is
also exacerbated on digital sensors which are also particularly
sensitive to the direction at which light hits the sensor (though
less so now). I've got a few brain cells that are tickled thinking
that this might be related to why split prism (and microprism)
viewfinders look so much darker at smaller apertures than at larger ones.
Also, while things seem to have improved in the past few years, I have
found Pentax metering so unpredictably inaccurate that if I don't want
my highlights blown out, in the vast majority of cases I use the green
button (or other exposure estimation), a test exposure and the
histogram (or at least bracketing) for the vast majority of my shots
anyways, so my workflow with K and M lenses, even without an aperture
simulator, to usually be identical to using A and AF lenses.
Since every moving part increases complexity, cost, and opportunities
for the camera to break, the ability to use unreliable auto exposure
on a few $40 used lenses falls somewhere between un-needed and
undesirable to me.
Features that I would like to see, which would cost Ricoh nothing but
a little bit of programming (which I'd probably do for them for free
given the source code):
Having the RAW/Fx button not only put the camera into on occasionally
used mode, but take it out of that mode with a simple press. As it is,
if I press the button accidentally, it will change the mode of my
camera, and then I have to go through the menus to undo what I
accidentally did.
Having the histogram read raw files, rather than the jpegs so I can
tell what my sensor is really doing.
Having astrotracer read the lens focal length from the manual settings
so I can use it with manual focus lenses (or telescopes).
Restore the ability to set astrotracer to times less than 10 seconds.
Often, when shooting the full moon, I'll want astrotracer to stop the
blur, but only want a 1 second exposure. Honestly, I'd rather it went
down further than that.
While we're at it having a lunar astrotracer mode, because the moon
moves differently than the stars relative to the ground.
Having astrotracer work like every other exposure mode so that I don't
have to go through all of the menu rigamarole everytime I want to
review a frame or change the shutter time.
Have bracketing work on astrotracer.
Have astrotracer/non-astrotracer bracketing so that when you are
shooting night landscapes you can get clear shots of both the
foreground and the stars to recomposite later.
(come on guys, astrotracer is cool, you advertise it, polish it up so
that it's not just a kludgey parlor trick).
Being able to set exposure times longer than 30 seconds, with the mode
of being able to easily take dark field frames at the times of my own
choosing without having to fiddle with a lens cap.
Have a metering mode that takes a sample picture (or several) and get
set the exposure (or exposure and bracketing) to capture all of the
data, rather than taking a guess and having to guess based upon the
inaccurate jpeg based histogram. While we're at it, have the info
display report percentage of blown out pixels, and noise levels based
on analysis of the data.
When shooting for HDR, being able to bracket more than two stops
between exposures. When I've got 14 stops of latitude, adding two or
four stops doesn't really gain me a lot in the cases where I need the
added latitude, and I don't want to have to shoot five exposures to
get the latitude I want.
Being able to choose bracketing independently of what the auto
exposure value is.
Being able to bracket the focus (when shooting macros with an
autofocus lens).
Recording the shutter press time stamps more accurately than the
nearest round second, and by when the shutter is activated rather than
when the file is written. I'm not sure which of these cause bracketed
photos to show up in lightroom in some bizarre, semi random order.
Wifi based flash control (now theoretically possible with the K-1).
The only one that makes sense is Pentax thought that they could get away
with orphaning all those K mount lenses prior to the A series and add a
few bucks per unit to the bottom line. The Shit Storm that hit them was
a huge surprise, (which shows how tone deaf a company can be), so they
got some software engineers to institute the green button kludge.
The other explanation is that to the vast majority of their customers
an aperture simulator is about as useful as being able to use a hand
crank to start their car if the battery is dead.
--
I don't want to achieve immortality through my work; I want to achieve
immortality through not dying.
-- Woody Allen
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