1. What M42 lenses do you already have or are you planning to use?
-- Are they very old (no automatic diaphragm)? Then you have to be very careful e.g. if the camera's mirror is very large.
-- Do they have some open aperture metering feature or pin? (Carl Zeiss Jena electric, some Fuji, some Pentax, etc.) Then only the matching camera is a good advice, IMHO.
2. Does your camera need
-- exchangeable finders? Then there are some Praktica, Miranda/Soligor (and to an extent one very cumbersome Ricoh), AFAIK.
-- TTL metering? Electronically timed shutter? Brett (Sarcophilus Harrisii) already addressed the battery problem.
-- open aperture metering? See above.
-- average metering plus spot metering? I guess there's a Mamiya having that feature.
-- Mirror Lock Up? I would know of one Yashica having that feature.
So, there is really no *best*, it depends... 🙂
Some good points above. Permit me to add to them please.
Interchangeable finders:
The Zeiss Ikon Icarex 35 offers interchangeable viewfinders also. In both the proprietary bayonet mount version and the "TM" or thread mount (M42) model. A waist level finder, un-metered pentaprism finder and uncoupled CdS pentaprism finder was offered, and these are all still to be found on Eg. eBay with a little looking. I have thread mount versions of the Icarex 35 and Icarex 35S (with fixed, integral pentaprism) and although the internal build quality is not as good as older model Voigtländers (it was a Voigtländer project originally, picked up and marketed as a Zeiss Ikon as part of the Zeiss Ikon/Voigtländer merger, I believe), they are beautifully finished externally, solid, and a delight to photograph with.
Mirror Lock Up:
People frequently conflate the terms "mirror lock up" with "mirror pre-fire" or "pre-release". The latter two can be helpful to minimise vibration when, for example, doing macrophotography or when using very long lenses, (particularly with a tripod that may not be as heavy duty as you might prefer). It's usually activated with a 35mm camera that features it by releasing the shutter via the self timer (although certain cameras such as some early Prakticas, the KW Praktina, and some ALPA SLRs, to name a few, may also let you pre-fire the mirror simply by gently, and slowly depressing the shutter release part way). But pre-release is
not the same as mirror lock up.
This was a feature traditionally fitted to some professional or better quality 35mm SLRs, when the use of retrofocus-type wide angle lenses in conjunction with SLRs was still uncommon. Yashica, Zeiss, Nikon and several other manufacturers produced wide angle lenses in their SLR mounts which protruded so far into the mirror boxes of their cameras that mirror damage would occur when these were fitted, unless the reflex mirror was first retracted and locked up mechanically. The mirror was locked in the raised position, and would then remain so, regardless of film advance status, rewinding exposed film, or even releasing the self timer (if fitted). "Lock up" meant precisely that--the mirror would not descend at any time, for any reason, until it was unlocked. Obviously, these cameras were incapable of reflex focusing when used with such lenses, which were generally supplied with accessory viewfinders. (Essentially the SLR involved became a scale focus camera in this condition, however with the substantial depth of field offered by these short focal lengths this was not usually an issue.)
There are certain M42 cameras that will pre-release the reflex mirror when the self timer is utilised. The Chinon Memotron is, I believe, one such, and is sometimes cited as having a mirror lock up (it doesn't), as is the Yashica TL Electro X (which does, more on that in a moment).
The M42 bodies that I am aware of which definitely do have a mirror lock up are:
Yashica TL Super;
Yashica TL Electro X (which will also pre release the mirror, via its self timer when this is set); and
Pentax Spotmatic with Honeywell MLU conversion.
The latter is somewhat rare, and uses an additional switch similar to the standard stop down/metering switch that is fitted to the front wind side of the mirror box. They can command a substantial price premium over standard unmodified versions, although, occasionally, if a seller does not know what they have, one might go cheaply online if the listing images don't encourage the extra switch to be noticed. I'm still looking for a cheap one of my own...
Cheers,
Brett
