My Radioactive Spotmatic!

Pentax Spotmatic SPF

I have re-acquainted myself with the Pentax Spotmatic! I never actually owned one before, but I used one often in the 80’s, and when I spotted an un-loved one on eBay for just £6:99 plus a little for postage, I couldn’t resist.

The Top Plate

This is the Spotmatic F, or as it’s noted on the top plate of the camera, the SPF. As you can see from the photo, it offers shutter speeds from B-1000th. What you can’t see in the photo is how smooth it feels to operate. There is a quality to these cameras, when you wind on – so smooth, or rather it should be! In my case, the first couple of frames were lost as the rewind lever/pole was much stiffer than it should have been. I suspect a lack of use. So, I had to reload the film, and loose a few frames. Not an issue as I was once again using up my massively out of date stash of colour negative film that expired in 2000 in this case! By the end of the film, it had already slackened off quite a bit!

I’m happy to report that all the shutter speeds seem to be fine, and there is no sign of light leak. The film didn’t behave quite so well this time and the scans had an “embedded” cyan cast that was difficult to remove. However, it’s 20-year-old film, and I could still test the shutter and light seal, so it did its job.

As for the title of this post, well as anyone who’s been around cameras for a while will know full well, some lenses of this age from Pentax (and others) are radioactive. If you have not heard this before – don’t panic! Thorium was used in the glass production as it has properties of low dispersion, helps to keep optical aberrations to a minimum. The radioactive level though is very low and is difficult to detect above background levels**, in most cases, or put another way, not much more than granite or bananas! It is in the glass and not the coatings as some people would have you believe – the problem these days is that it tends to “decay” to a brown/yellow. Not good for colour but might even help b/w, depends on the effect you like. The problem can be partially reversed by exposing the lens to UV light, but care is needed with this, don’t just leave it in the sun!! Lenses and sun make fire people! These days the same optical properties can be obtained by fluorite, most notably from Canon. It seems that people who mention the radioactive issue, often think it was a “Pentax” thing, in fact, most manufacturers of the day used it. Kodak Pony for example – but also some Canon, and many others.

** If you have a Pentax  Takumar SMC 50mm f1.4 (7 element version) you might want to do a little research.. that’s the lens that seems to be the “hot one”!

Anyway, after a long digress, below are a few photo’s made with my latest acquisition, it’s certainly a keeper for me, and I’m thinking I might just have it serviced, hopefully it will give another 50 years service!

St Peters, Dorchester
Statue to William Barnes, Dorset Poet
The Bike Rack
A View down the main street, Dorchester.

2 thoughts on “My Radioactive Spotmatic!

    1. Hi Mike, I used one back in the 80’s quite a lot. A friend used to make historical AV programmes, and I’d shoot endless rolls of Ektachrome for him on a copy stand! Never owned one until now – I’m looking forward to doing some “proper” photography with it! All the best Andy


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