Minolta Hi-Matic 7s - how does it work?

[johnbear]

I've posted this question on another forum, but am not getting any comments. I thought I'd try here. I have two questions.

1. Page 34 of the instruction manual includes a graph of the automatic exposure aperture and shutter speed selection profile. Assuming this is accurate, it suggests intermediate apertures and shutter speed values are invoked: there are only four EVs at which the profile intersects standard stop combinations:



• f/2 @ 1/30th for EV 8,

• f/5.6 @ 1/60th for EV 11,

•f/11 @ 1/125th for EV 14, and

• f/22 @ 1/250 for EV 17.



I'm not sure what to make of this - it seems an unlikely profile for a wholly mechanical camera? I think if the Hi-Matic was capable of setting intermediate values, this would have surely been something worth mentioning in the literature.





2. The camera has a CLC meter. According to Minolta's explanation of the CLC in the SR-T 101, the Contrast Light Compensator (CLC) circuit allows the identification of discrepancies between the two cell readings, and if there is little contrast, those readings are averaged. However, where there is more significant disagreement, then the CLC compensates to reduce underexposure of shadows, or other dark areas, and minimises the influence of particularly bright regions.

The problem is, the Hi-Matic has just one cell, so how can it possibly detect and compensate for contrast?

Thoughts and insights appreciated.

[John Farrell]

John - my thoughts......intermediate diaphragm openings are possible, but not shutter speeds. CLC may have become Minolta's marketing speak for their meter system, whatever its configuration.

John.

[johnbear]

John (the other John) 

It seems just you and I are interested in the mysteries of this camera.
I've been talking to one of the editors at Camera-Wiki, and he's located some patents for Minolta systems which suggest the Hi Matics (7s, 9, and 11) may have some form of step-less auto exposure, and a CLC type method of favouring metering of the foreground (via the cell being off the axis of the lens).
Rather than explain it here, I've put a link to the Hi-Matic page on my website.


Minolta Hi-Matic 7s

[julio1fer]

I have used the Himatic-9 and the AL-F. Both seemed to have a similar exposure system that worked very well in practice, although it is hard to be sure if you only shot C-41 or B&W. A better test would have been slide film.

Once, I took apart my AL-F to repair the autoexposure mechanism. It definitely had a single CdS cell; I even measured currents as I was not sure if the fault was mechanical (it was) or electrical.

I have heard that the Minolta CLC single cell system favored the lower part of the frame; this would be consistent with your patent research. The exposure system worked well in against-the-light situation, FWIW.

[John Farrell]

Nice website, John. You've mainly got cameras I don't have. I don't have any Minolta rangefinders, and there seems to be a lack of information on the Seiko LA shutter out there.

[johnbear]

Thank you for your kind comments. It's a way of keeping my brain alive ... and trying to immortalise knowledge which is disappearing rapidly.

[conan]

Mar 17, 2017 6:48:54 GMT -5 johnbear said:

Thank you for your kind comments. It's a way of keeping my brain alive ... and trying to immortalise knowledge which is disappearing rapidly.

I enjoyed reading your site but please tell me what metal polish did you use on those Silettes? I am not certain whether those metal fronts are pot metal or some form of aluminium. Whatever - these and the Braun Paxette’s tend to discolour, pit and look pretty poor when they have few years on them.


More by accident I have acquired yet another Silette with a working meter and everything worked except the front focusing which appeared to be locked up (I thought I would have to re-read John Farrell’s experiences on removing Agfa’s green superglue) luckily a little brute force freed it up – however the front area could do with a little clean up which mars a camera that is cosmetically and operatically 95%. Perhaps you are going to suggest Brasso?

[johnbear]

Conan - Yep, I used Brasso, and it took a lot of rubbing, but they eventually gleam and it feels like the effort was worth it. Fortunately it's the sort of mindless task that can be done while watching TV. I think the material is aluminium.

PS: kind comments appreciated.