Half stop meter error on Minolta and Olympus manual focus cameras

Leigh B said:

As I stated earlier, ASA is the reciprocal of film speed when exposing film at f/16. That's the definition of ASA speed.

Click to expand...

The next thing you'll be telling us is that the Sunny 16 rule of thumb used to be Sunny 11 between 1943 and 1954, at which time film manufacturers removed the safety margins against under exposure, resulting in an automatic doubling of ASA speed, and corresponding change in the Sunny aperture.

If you get a chance, please post the ISO standard for "sunny".

faberryman said:

If you get a chance, please post the ISO standard for "sunny".

Click to expand...

It's the opposite of "moony", which I'll gladly demonstrate for your edification.

"Sunny 16" is a consumer convenience since it matches the speed definition that I stated previously.
It's an American invention, as were many things back in the day.

Since Europe uses the same sun we do, I would expect their luminance standard to be the same.

- Leigh

But in some of the higher latitudes, for example in northern Europe, it works better as Sunny 11.

thuggins said:

It is hard to tell what you're trying to show there as your example changes both shutter speed and aperture, creating essentially the same three exposure with very different meter indications. And while one may be able to infer 1/3 stops on an OM 1 or 2, Olympus' intention was for these meters to indicate half stop increments.

View attachment 169360

Click to expand...

My point was that although Oly documentation showed 1/2EV needle positions, in reality one could SEE 1/3 EV changes of needle position. If the needle split the end of the 'tab' it was 1/2 EV and if the needle just barely touched the same 'tab' it was 1/3 EV.
And going from f/2.8 to f/1.8 was NEITHER full or half EV nor 2/3EV differences. As I said earlier, "displacement from f/2.8 to f/1.8 left a visible gap in the window. "...not full EV, not 2/3EV, but something 'in between 2/3 and full'

As for Olympus giving 1/2 EV needle position information, since neither lenses nor shutter speeds had fractional detents, it was somewhat pointless to show anything finer than a single value 'in between' the whole f/stops, although the needle position was sensitive enough to indicate finer gradations.

thuggins said:

This would indicate that you don't shoot transparency film. The difference between 100 and 125 is 1/3 of a stop and 1/3 stop is certainly noticeable on a slide. Light meter manufacturers didn't consider the difference trivial either, as meters from the era when speeds were undergoing the transition show both sets of shutter speeds. +/- 30% is essentially a full stop of error, which would make the camera useless for slide film. None of my Oly's have that kind of error.

Click to expand...

The actual marked top speed of a mechanical shutter may be off by 50%. I have seen higher errors quoted. Slower speeds are more accurate. This means that if you are shooting slide film that you really need to bracket!

Sirius Glass said:

But in some of the higher latitudes, for example in northern Europe, it works better as Sunny 11.

Click to expand...

Logic would lead one to make this assumption, but interestingly enough, I have found the opposite to be true. In both Alaska and northern Scotland during the summer the light was 1/2 to 1 stop brighter than what I was used to in Texas at the same time of year. It has to do with the angle of the sun. Being lower at mid-day it shines more directly on the subject. During summer time in Texas the sun is nearly at 90 degrees to any subject, unless you're shooting the ground at your feet. At this time of year (around the Birthday of the Unconquered Sun) the light actually meters brighter than in midsummer.

Gerald C Koch said:

The actual marked top speed of a mechanical shutter may be off by 50%. I have seen higher errors quoted. Slower speeds are more accurate. This means that if you are shooting slide film that you really need to bracket!

Click to expand...

I have never bracketed; it is a waste of film. None of my Oly's has ever produced an improperly exposed shot unless I screwed something up (like forgetting to reset the exposure compensation dial after setting the film speed on the OM-4). That includes shooting Provia 400 pushed a stop or two for hand holding with a long lens.