Spotmatic F meter question

<p>I recently acquired a Pentax Spotmatic F which is in good shape. Only (minor) problem is that the mirror does not always return properly when using slow speeds since the second curtain sometimes does not travel all the way - pushing the second curtain to its final position usually helps.<br>

The lightmeter is approx. 1 stop off but this is not really annoying since the ASA dial goes up to 1600. But there is a strange issue with the light meter. Even if the light meter is switched off (button at the lower position), the needle shows some reaction to light (of course the needle position changes drastically), it is moved when turning the speed dial and also moves in bright light conditions. Is this normal?</p>

 

<p>Yes, it is normal that the meter needle would move; on these types of cameras, any time the lens cap is off, the meter is reading incoming light.</p>

<p>How is it that the light meter would be switched off otherwise? What button at the lower position? Is this the FP/X synch switch? That would adjust the synch timing for flashbulbs or strobe.</p>

<p>Here's a link to a manual for that camera: http://www.cameramanuals.org/pentax_pdf/pentax_spotmatic_f.pdf</p>

<p>If that mirror is not returning right, or the curtain not traveling right, it probably just needs a CLA. The mirror return is based on a spring synch inside the bottom plate of the camera. Another set of springs and gears moves the shutter. Those two mechanical paths are linked up through the behavior of a notched lever that rides in the bottom plate. By the time you get a Spotmatic these days, they are still great cameras, but they will need a little maintenance. I bet your synch problems could be cleared up with a light drop of oil, and some exercise. [You will want to be careful with oiling the camera interior, as some parts are incompatible with oils; may contaminate the optics or the film if you are too sloppy or apply too much.]</p>

<p>That type of light meter will be most reactive to changes in the speed dial; shutter or ASA, that is normal. For most accurate use of that type of meter, remember to make your CWA judgments at the aperture that is the square root of your film speed. For example, 100 speed film, square root would be 10, the closest f/stop would be f/11. Meter at f/11 to determine average acceptable shutter speed, and then extrapolate your changes from there.</p>

<p>I went over to KYPhoto.com (camera repair site) and over to pentax-manuals.com, had a look at the schematic for that Spotmatic's light meter; I think the only switch in that circuit has to do with routing electricity over to the synch. I could be wrong, but I am confident from tinkering with several Spotmatics that there is no on/off switch for that meter at all. I have not used a Spotmatic F in particular, but I am confident that what you need is a lens cap.</p>

<p>It's kind of unusual, but on Spotmatics, the lens cap still has a practical function.</p>

<p>You're right, the Spotmatic F's meter is on as long as the lens cap is off (to preserve your batteries, keep it on unless you're actually shooting).</p>

<p>This was the 1st Spotty to use open aperture metering so possibly the lens is set to manual rather than auto which would produce the erratic metering you've described. You can check it by removing the lens. Hold it w/the glass away from you & look along the top back ridge of the lens. If you see man. in red letters, then look on the back of the outer rim of the lens for a small pin almost flush w/the surface. Depress this pin & push the knurled lever on top near the back until auto is visible in white letters. Manual will then be covered. Camera uses a 3rd cds cell above the eyepiece as an on/off sw. When the light falls below ev2, then the meter is switched off. The stopdown sw. on the side of the lensmt is for the older lenses used on previous models.</p>

<p>Thank you all for your answers - in the meantime I found one or two older very similar questions and figured out what's going on.<br>

I forgot to mention that I use the camera with standard M42 lenses, NOT the SMC Super Takumar with "extra" pins for open aperture metering (but I just learned that they exist...). So probably the readings with the light meter set to "open aperture metering" (lower position) will be erratic with a non-Super Takumar lens - I found that the reading is quite different from what I get with an f/2.8 lens wide open with "stop down metering" (and this just puzzled me).<br>

Concerning the mirror problem, it occurs with slow speeds (1/15 sec and slower) only, and actually it seems to get better - now the mirror hangs once or twice out of ten cycles, when I received the camera this was much worse. Thanks for the hints to get to the mirror sync mechanism. As some of you might know, I have some experience in camera tinkering and know about over-lubrication problems with cameras. From my experience, most problems with moving parts in cameras are rather due to dirt and/or sticky oil/grease and can be cured with some drops of lighter fluid, adding VERY little oil can be helpful to avoid future problems. For parts made from plastics, I rather use silicon grease or oil which does not affect plastics.</p>

 

<p>Re: the slow mirror. Check the foam @ the front top of the mirror cage. Maybe its rotted & needs replacing. If you see "gook" along the front edge of the mirror then its a pretty good bet this is part of the problem. If the 2nd curtain is a bit slow & doesnt have enuf "oomph" to return the mirror @ the end of the cycle then the travel times need adjusting. Its not hard to adjust the curtain tension & its acessable by removing the bottom plate. Easier to have a test instrument for accuracy. You have to loosen a small grub screw (dont remove it) thats usually sealed w/red lacquer & then turn the setscrew cw to add tension. 2nd curtain adj. is the 1 closest to the front. W/o a tester, you might have some luck turning the screw in 1/2 turn increments & see if that helps.</p>