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Re: [OM] N80 was Re: No, just the OM40 PC :)

Subject: Re: [OM] N80 was Re: No, just the OM40 PC :)
From: Moose <olymoose@xxxxxxxxxxxxx>
Date: Tue, 21 Jan 2003 16:56:11 -0800
Nothing to say about the F80, as the newest Nik*n I've used is an FG, which is ancient history.

About the OMPC (and other 'double digit' Olys) and exposures.:

In Auto mode, all TTL SLRs of all brands, including all Olys in auto mode, the shutter speed shown in the viewfinder is just an estimate of the actual shutter speed which will be measured during actual exposure. The cost saving measure of only showing whole speeds in the viewfinder in many cameras has no impact whatsoever on the accuracy of the final exposure. (The 4(T(i)) bodies in spot mode set a fixed shutter speed before exposure, but they have 1/2 stop speed increments in the viewfinder.) Thus, all this testing you are doing is entirely meaningless relative to Auto mode exposures.

There are several factors to consider in all measurement systems. The ones that particularly apply here are accuracy, resolution and repeatability

Resolution: A reading of 1/60 on a camera with resolution of one f-stop can mean a measured speed between 1/90 and 1/45 sec. If it is actually 1/45.001, rather than in the middle (something I can't know other than in a lab environment) and I close the lens down one stop, the new speed theoretically reported should be 1/120 sec with a range of 1/90 to 1/180 and an actual speed of 1/90.002. In this case, the linkage aperture 'reporting' pin on the lens can be off by less than 1% and result in the same 1/60 reading as the slower f-stop. Notice the theoretical ambiguity at this particular jump in the speed scale, where the theoretical 1/120 sec. 1 stop jump up from below differes from the 1/125 sec. 1 stop jump down from above. You know why nobody worries about that? Because of:

Accuracy: The electro-mechanical linkage that conveys the f-stop set on the lens to an electrical component is subject to manufacturing tolerances. The device that converts mechanical motion to electrical value is nover perfectly linear, so its tolerance may be variable over its range. Lenses vary from sample to sample in actual light transmittance wide open and then there are variations in the mechanical components that stop the lens down. All the mechanical tolerances are then subject to variations in wear, mechanical stress, lubrication, etc. But then, the sentsitivity of the film to light is significantly different over the range of tempertures over which we regularly use film. In fact, temperture is one of the factors everywhere in thesystem, affecting electronic components, lubrication/friction, etc. Even the size of the glass and aperture blades in a lens change size with temperture.The point is that there are hundreds of factors that go into determining the accuraccy of the final exposure and all have tolerances rather than exact values. The vast majority of the time, they all balance out to a correct exposure (i.e., density range within the tolerance for viewing or a good print).

Repeatability: This is the extent to which the same system gives the same results under the same circumstances at different times. Friction and the results lead to the most significant factors in poor repeatability accuracy. Although theoretically part of accuracy, so I have commented on them above, in practical terms, we tend to pay little attention to temperture except at the extremes, so it are a repeatability factor. In the whole system sense, film speed is a factor too, as actual speed varies from roll to roll and batch to batch due to manufacturing tolerances, age and storage temperture.

So, as Thomas, says, the old mechanical meters excel at resolution, particularly over the 1-stop resolution bodies. That says nothing about their accuracy and repeatability.

Assuming roughly equal accuracy and repeatability, the higher resolution of the single digit bodies is superior to the double digit bodies for Manual Mode, esp. for slide film.

Question. How much is the more accurate exposure measurement of ESP mode on the PC vs Average mode (on it or the other OMs) in many practical picture taking situations worth vs. more accuracy and resolution in an estimate of the actual speed to occur later?

Don't know why I wrote all this stuff, since I use Auto and negative film almost all the time, so it all hardly applies to my practical use. Guess I"m still bothered by discussions of distinctions that make no diference. Time for some meditation using my favorite mantra....OOOMMMM ;-)

Moose

Jim L'Hommedieu wrote:

Wow.  I love the OM-PC but I had forgotten this.  Today, I was making some
test exposures to try to calibrate the OM-PC's meter for use as a backup
during vacation.  Others have noted that their meter (on other cameras)
doesn't show a full stop's difference between f/1.4 and f/2.0.  Today the
same thing happened to me with the 28/f2.0 with the OM-PC in manual
metering.  Manual suggested the same shutter speed for wide open (f/2) as
stopped down one (f/2.8).

*THAT* was really alarming.  Tonight I'm gonna try out other lenses to see
if the aperture pin is being interpreted correctly by the camera.  It's
possible that the difference on my 28/2 between f/2 and f/2.8 is something
less than one full stop (in transmission) but the PC's meter display isn't
showing me those 1/3 stops.  Heck, as others have noted it doesn't even show
you 1/2 stops.

<sigh>  The worst part about this is while I was waiting for my prints, I
raised a Nikon N80 with a new dedicated, Nikon Speedlight (strobe) to my
eye.  Now I've been much impressed with this vixen before.  I mean 5 spot
meters, your choice of focus sensors.  Manual everything.  Programmed
everything.  Aperture priority.  Integral film advance without glitches.  IT
EVEN HAS AN ON/OFF SWITCH AND A FIXED HOT SHOE!  I could go on and on and
on.

But this strobe is new and they have thought of *EVERYTHING*.  You mount the
strobe and forget it.  When you turn the camera off, the strobe goes off.
When you turn the camera on and zoom back to 28mm, the strobe turns on and
power zooms to 28mm.  "Wow."

There's a flip up (non-detachable) wide angle diffuser.  Nice.  The salesman
showed me the strobe's tilt-down feature for close-up.

"Yeah," I said, "my Olympus T-32 will do that.  What's this second diffuser
do?"

He smile.  "Well!  If you're using the big strobe, you can point it up at
the ceiling, then popup the camera's own flash and flip down the strobe's
diffuser (over the camera's flash tube).  That way the front fill is
diffused."

"Ooooooh."

"Watch this."  He removed the flash and held it at arm's length, then fired
the camera.  The strobe has a built-in slave.  I think it does TTL at arm's
length but I'm not sure.  The room started spinning.

"Ooooooh."  Then he handed me the prints that showed my OM-PC needs an
overhaul.  "Uhhhhhhhhhhhhhn."

Pray for me, my brothers and sisters, for I have lain hands upon the
forbidden N80 and her siren sister Nikon Speedlight.

Lama

ps, I'm beginning to use Nikon-speak.  "Ooooooh."


From: <T.Clausen@xxxxxxxxxxxx>
Actually, IMO neither of the two-digit-bodies are really suitable for
manual work. The fact that it shows the shutter speed in the viewfinder,
not how "far off" ones exposure is from what the meter recommends, makes
the two-digit-bodies my last choise for manual exposure.


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