Camera meter exposure test question (70's rangefinder)

[peter_kim2]

Now this is wierd. I have a Minolta Hi-matic F. Its a fully

automatic 70's era range finder with ASA settings from 25 to an

oddball 500.

 

So anyways I am using 1.4 volt zinc-air hearing aid batteries and

did an exposure test to see how it would work out. Sensia 100 with

consecutive shots set at the following:

 

160, 125, 100, 80, 60, 50, 40, 30.

 

This is the weird part. The first 3 exposures (at 160, 125 and 100)

were virtually identical. I cant tell any difference. And the

exposure 'seemed' perfectly on, but none of the shots were

overexposed so I coulnt compare.

 

The next 3 (80, 60, 50) are also almost identical but ever so

slightly darker than the first set of three.,

 

Heres the wierd part the last 2 at 40 and 30 are really, really

dark, definitly underexposed with almost no detail.

 

Now, if I down rate the ASA from the film's rated 100 to 40 or 30

(effectivily puposely overexposing the film) Shouldnt the ones at 40

and 30 be bright and blown out instead of dark? This is really

wired...I even tore out the slide holders to make sure the lab didnt

mess up the order of the frames but they didnt...

 

Any ideas on this wierd situation? Maybe my first mistake was using

a film with such a wide exposure latitude...But this is normally the

only slide film I shoot when I do shoot slides.

[jim_gifford]

The good news is this part...

 

<<The first 3 exposures (at 160, 125 and 100) were virtually identical. I cant tell any difference. And the exposure 'seemed' perfectly on, but none of the shots were overexposed so I coulnt compare.>>

 

The little Keebler elves who determine shutter speed and aperture settings inside yout Hi-Matic F are sworn to secrecy, and will not reveal their settings no matter how you beg and plead with them. But at least they are giving you proper exposures when you give them reasonably good info about your chosen film.

 

You are right of course that setting the camera's ISO dial to 40 or 30 should have given overexposures on 100-speed film. And rating that same film at 160 should have underexposed things.

 

I think your test is teaching you more about the film's exposure latitude than it is about your camera's exposure meter.

 

I bought a Hi-Matic F back in the 1970s and somehow lost it (or perhaps someone with thin ethics helped me lose it?)... and I've pined for it once in a while. It's so small, and light, and cute you just want to pinch its little metal cheeks. So I found a nice one on E-bay last month, with flash, and for about $30 including shipping I have my old buddy back.

 

Be well,

[grahams]

Peter - I would guess that the film speed setting dial is a potentiometer (variable resistor) and the contact between the moving slider and the base has deteriorated to the extent that good contact is only made in that area where ISO 100 is set. At all other settings, either the same, or the incorrect voltage is being sent to the meter circuit. Turning the dial back and forth may clean the contacts somewhat, otherwise a CLA may be the only way out.

[jason hopper]

On the Hi-Matic F, the ASA dial is actually a disk where the ASA number reads in the lower window and this disk's concentric slotted mask rides between the upper metercell lens and the cell itself. This disk rotates so that the mask's slot is full open at higher ASA's, and tapers in width when the disk is rotated to lower ASA's. When rotating towards lower ASA's, this slot mechanically limits the light reaching the metercell, and the metercell then sets longer autoexposures at lower ASA's (for the same scenes like you shot). The mask's slot seems to change taper at ASA 100 and at ASA 50 becomes a silvered slit mask.

 

With this simple mechanical connection between the ASA settings and metercell readings, my guess is that the ASA dial itself isn't the cause of your Hi-Matic's underexposure. Your Hi-Matic should automatically adjust for longer/more open exposures at lower ASA's (for the same scenes): have you checked the larger lens diaphram openings and for shutter speeds beyond 1 second to its full 4 second shutter speed? Your camera maybe isn't responding to the decreased light getting to the metercell, maybe not responding with longer shutter speeds or larger diaphram openings.