Pentax Takumar Lens Radiation for Pentax 6x7 Lenses

[cuthbert]

Anyway it would be interesting to see if a film roll in a camera with thorium lens starts fogging with time..

http://petapixel.com/2012/10/11/a-look-at-the-radioactivity-of-old-manual-lenses/

https://www.youtube.com/watch?v=3ozOMssiP2E

An interesting video. Makes my eye hurt.

According to the links:

This puts the “6hrs/day for a month” usage at about the same as getting a chest X-ray

So theoretically speaking if you leave a film inside your Spotmatic with the 50mm f1.4 for one week you'll get it exposed.

I think I've done it and no, the film wasn't fogged.

 

[DannL.]

I saw a sample somewhere where a takumar was left setting on a piece of photo paper for a bit. The paper was developed, showing a noticeable trace where the lens sat. I can't recall if an intensifying screen was used or not. I gave all my lenses away, else I would have liked to have tried that myself. I have no qualms with other people using these lenses. In fact, I recommend it. Except for the yellowing. I de-yellowed my 1.4. But it took a lot of sessions.

 

[macfred]

Did you hear about a technique named `Vorbelichtung´ (don't know the exact english term - maybe `pre-exposure´ or `flashing´), like the elders did with their b/w - negative film ?
The radiation coming from the old f/1.4 S_M_C Takumar creates the same effect. That's the only reason for the stellar results and high reputations of this lens … :wizard:

 

[DREW WILEY]

Then there's the ozone hole in the atmosphere. So in one way or another, we've all been pre-flashed anyway.