How do they do that?

Dear All, It is completely beyond me how an old rangefinder camera

like the Kodak Retina Automatic III can mechanically block the

shutter release button and make a 'STOP' flag pop up in the

viewfinder when for example the light is too low. There are of course

no batteries and no motors in this camera, so there must be some sort

of mechanical linkage between the meter needle and the shutter button

but I can't figure out how such a tiny meter needle can lock the

release button or make anything else happen for that matter. I am

sure there are other examples of 'automated' functions in non-powered

cameras. Can someone please explain how they link things up inside?

Thank you in advance.

I was amazed about the same thing, but with a canonet28. The meter needle has a balancing side, oposite to the one that shows the value on the scale. That is fitted between two plates, and it walks in a very tight hole. Whenever it's out of the "enough light" range, it blocks a lever that is connected to the shutter release button. True that the needle is very thin, but the space where it moves is also very tight (i.e. it is supported by two strong metal pieces that are very close to each other) so it can strongly block that small lever.

It's not unbreakable, of course.

 

If you open up such an old mechanic or semi-mechanic camera, you will find tons of very clever ideas executed with a mindblowing precision.

i had a zeiss contessamat, that while it didnt do anything like youve stated, just looking through the viewfinder and seeing the f stop and shutter speed by a series of tiny little mirrors amazed me.

I believe that in the automatic Retinas, the photocell drives a small wheel. This, in turn, moves a piece of string (really string) which provides the mechanical linkage to other parts of the camera.

Out of curiosity I would have taken off the top cover of my camera, but since it was in an as good as new condition I preferred not to. I had already decided to resell it because I was not too impressed with the results. I also sold on a Retinette IIb for the same reason. Now I regret the Automatic III since the auto feature was really admirable and fun in its own way.

The old Voigtlander cameras are crawling with clever little mechanical arrangements. Fascinating.

In most cameras of that type, your finger on the shutter release is what provides the power; the needle moves within a sort of gate that closes as you press the button, and the gate's stopping position depends on where the needle happens to be. A given position corresponds (typically) to an aperture, and if the needle position allows it to go beyond the available aperture range it locks up.

 

The gate looks sort of like a guillotine blade with a serrated edge, and the needle operation is from left to right across the bottom bar (where Marie Antoinette's head would have been). As the leading edge of the blade is angled, if the needle is to the left the blade will go farther before hitting it than if it is to the right, and the vertical position of the blade determines the aperture setting (or shutter lock). The serrations keep the needle from slipping along the blade edge, and your trigger finger is what presses the blade downward against the needle.

 

Don't know if this makes sense but it's the best analogy i can come up with short of a sketch or photo.

 

rick :)=<div></div>

It does make sense, richard:) at least, it's the same idea in the canonet, with the serrated guillotine. Looks a bit different though...

Thank you Rick and Csab' (and the others) for a clear explanation. So I guess that also explains why the needle appears to 'freeze' in place when you start depressing the shutter button...

Fascinating indeed. Damn... gonna have to get me another Automatic III !

Just a side note to the mechanical precision of these old beasts. I assume that making all those delicate, yet effective mechanisms was expensive to design, and produce. Even on cameras that were moderately priced.

The advent of miniature electronics to perform the same control functions as those marvelous levers and fulcrums must have saved camera companies collective millions.

That's probably why we have cameras today, with a dizzying array of bells and whistles, yet they cost a fraction of what the precision instrument would have.

They do a tremendous amount of things, but just don't feel the same.

That's also the "trap needle" operation of the auto aperture in the half-frame Olympus Pen EES-2 (and presumably other Olympus models with a selenium auto aperture) -- I just finished fixing one this past Sunday, which had gotten oil on the blades and was locked as tight as if superglued. There's not much leverage, and springs in the release linkage prevent applying enough pressure to damage the aperture blades (at least on that camera); after all, you're working against a milliammeter movement.

 

With the EES-2, there's a secondary mechanism that switches the shutter from fast (1/200) to slow (1/30) at about f/5.6 to f/4, giving a range of exposure from 1/200 at f/22 down to 1/30 at f/2.8 -- pretty decent for a camera without even a battery! In practice, the selenium meter isn't very accurate in low light with ISO 400, as one might expect, and has an extremely wide acceptance angle that makes it susceptible to side light fooling the exposure system -- but for a consumer camera made in the 1960s, it's not bad, and the lens is quite nice.

 

A few auto aperture cameras were even simpler; I had a Keystone 126 cartridge camera in the mid-70s that had an aperture mask simply attached to the meter movement, and it would continuously move with changing light, going from a round opening of about f/5.6 to a slit probably equivalent to f/11 or f/16.

aperture as a slit? That should have a funny "bokeh" :)

You're right, Csab', it "should" but I don't recall seeing a problem. Of course, it was an Instamatic, fixed focus, and out of focus would mean anything within about four feet of the camera -- which I avoided. I mostly had fun with the built-in strobe freezing motion; eventually even installed an external slave jack wired to the test button to use the camera as a strobe for a 127 Brownie of some sort (to which I wired an external sync socket, connected the two with a cord and mounted them on a bracket -- after also hacking in tripod mounts for both). All of this when I was fourteen...

Hey Rick, that's the first time I've ever heard Marie Antoinette used in a discussion about classic cameras -- good one!