Yes Paul it's a nice lens to convert. I can't wait to finish it up. Here's something I want to discuss with you.
As an improvisation I'm trying to utilise the lever inside to show DoF preview, maybe tie a string around it and lead it outside through the 1 of the 2 screw holes on the breechlock ring. Operation wise, we would stop down normally, but pull that string and the lever inside will engage and open up fully, release the string (since it's spring loaded), it will go back to the selected aperture.
I don't know, it could be helpful when you leave the lens at say f5.6 for desired DoF, then pull the string to WO the lens and focus easier (brighter VF), then release the string and depress the shutter.
What do you think?
PhotoMaximum: I agree, I got this lens because my Rokkor 58 is a bit long sometimes, I think I'm going to like this focal length as a street shooter.
It is an interesting idea, Leon. Some very thin, but strong, braided cabling might do the trick. Maybe put a loop in the end to hook your finger into. Although, any resistance in cable movement may slow down or even halt the blades from stopping down, upon release. A stronger spring might be in order.
I'll fiddle with mine and see if I have any revelations.
Inhaling depleted uranium U-238 which emits only alpha particles is now believed to be the cause of Gulf War syndrome. I wouldn't grind my radioactive lens up and smoke it; however, I also wouldn't worry about the radiation.
TWoK wrote:
Inhaling depleted uranium U-238 which emits only alpha particles is now believed to be the cause of Gulf War syndrome. I wouldn't grind my radioactive lens up and smoke it.
Thanks! I will keep that in mind. Its good to know these things...
cogitech wrote:
Well I'm not uptight
Not unattracted
Turn me on tonight
Cause I'm radioactive
Radioactive
I think I'll quit (casually) smoking after reading that article, but there's no way I'm letting go of my rare earth glass.
Thanks Aham!
Haha! Yeah the point about serious radioactive elements in cigarette smoke is quite shocking. Maybe especially because of this:
Polonium and lead volatilises in lighted cigarettes. Ten per cent of Pb-210 and 20 per cent of Po-210 contained in cigarettes enter the smoker's lung through the main smoke stream; remaining ninety percent of Pb-210 and 80 per cent of Po-210 float in the ambient air for the passive neighbours to inhale! Source.
I don't have rare earth lenses, but simply because using them means added exposure to radiation (mainly to the eye, when looking through the viewfinder), I find it sensible not to buy them.
PhotoMaximum wrote:
Hmmm,
I think its OK to use this lens. I mean, has anyone ever heard of a rare earth photography lens actually harming anyone?
Is it necessary that someone gets hurt before we start avoiding potentially harmful things? You agree that it wouldn't be smart to sleep with a radioactive lens tucked in your undies , but I take it one step further and prefer not to put such a lens to my eye. Because of the potential harm, I think it's just not worth using these lenses.
Anyway, this is my perspective on it - don't want to make a rant here.
Please correct me if I'm wrong, but I don't believe alpha radiation, which is stopped by so little as a sheet of paper or even low levels of beta radiation will pass through a thick brass camera body. If I had a Geiger counter I'd measure it at the finder, but really this isn't something to even consider in my mind.
Because of the short range of absorption, alphas are not generally dangerous to life unless the source is ingested or inhaled, but then they become extremely dangerous. - http://en.wikipedia.org/wiki/Alpha_particle
@TWoK: Quote from the article: The Wikipedia link above states that this is alpha radiation, but it is not stopped by paper (which I confirmed with the Gieger counter). I therefore think that at least some of the radiation is beta radiation, which can go out a bit further. The radiation drops off very quickly, and is not readable about four inches away from the lens. But if you think about it, every second that my eye is at the camera to take the photo, I'm receiving about 150 ionizations. These add up in a hurry.
Note the real problem with inhaling U-238 has nothing to do with the radiation and everything to do with heavy metal poisoning. If you've inhaled enough to have radiation poisoning the heavy metal poisoning will already be in the process of killing you.
Rare Earth glass doesn't emit enough radiation to significantly alter the level of background radiation you're already receiving just by being outside. Even held up to the eye.
The gulf war vets who inhaled a lot of depleted uranium dust from the burnt out wreckage of Iraqi armor suffered from the effects of Alpha radiation causing chromosomal abnormalities in their DNA. It was not heavy metal poisoning from what I've read.
Benjamin--I enjoyed your use of ALARA, as I thought that was only known in a few circles.
Alpha particles (being very large) have a difficult time penetrating the dead parts of one's epidermis due to scattering whereas Beta particles are much more likely to succeed. Photon based radiation will fly right through you with aplomb.
That said, once an alpha does enter the skin, it tends to do a lot more cellular damage than a beta due to its mass and ability to transfer momentum.
All in all, I wouldn't be too worried about old radioactive lenses, but am curious if anyone has taken a geiger counter to one to see how active they still are. Most thorium isotopes are pretty stable so their counts should remain quite low. Typically the distance between you and the lens element should be enough considering the material between you and the elements. A metal cap would not be a bad idea.
Well, I'm considering sacrificing my Novoflex M42-EOS adapter as a donor mount for my FD 35/2 conversion. Currently it is a semi-permanent fixture on my Zenitar Fish, but I am eager to get using the 35/2. It is a nice matte black colour, which is a bonus. Just having trouble convincing myself to butcher this beautiful adapter, which is worth 2x the price I paid for the lens
I took the lens completely apart, I mean completely . So when I put it back together I misaligned the helicoil and it ended up being a macro lens way short of infinity. But this produced a very special swirly bokeh effect we used to see in zuiko 55/1.2. Well, now I got it back to normal and fine tuning for infinity as we speak. It was a fun accident and experience regardless, the effect was so pronounced it was almost showing 3D hologram in the VF.
I played with mine last night and was trying to decide how to tune infinity. Took it apart partially and found that there is a bit of wiggle room in the focusing helicoid. I adjusted the focus stop "bracket" so that the helicoid now focuses as far as it can before it's first ridge binds against the barrel. This gains me a bit, but not quite infinity. It seems I'll have to reduce the mount base itself in order to get infinity (which I really want with this lens).
There's no buffer ring to shave off to reduce that 0.5mm, so I also adjusted the stopper a bit, but it wasn't enough also. You can always take 0.5mm off the m42 adapter, it's easier I think.
I dremeled off the mount base about 2mm and now the thing is past infinity. Doh!
Oh well if I don't want it to hit the mirror I may have to do something about the rear element shroud as well. Too much work!
Yeah, I pretty much figured I'd be Dremeling that mount base as well. Trick is doing it nicely. I fully expect to have to file the rear element shroud too. Oh well, at least there's a lot of space there so little danger of f&cking up the rear element. Did you Dremel the mount base with it all together? If so, did you just mask it all off with tape, or what?
If you don't want to contaminate the lens with debris, I strongly recommend taking it apart, with a good memory (or just document it) you can easily put it back together .
Masking tape wouldn't help because you cannot shield all the inner parts of the lens, fine metal dust would be all over the place and get into the grooves of the helicoil, which is a mess to clean up.
Thanks. I'm not a fan of taking lenses apart so completely. The one time I did it, the lens never performed well again. Threw it in the garbage eventually.
I can't wait to finish it up. Here's something I want to discuss with you.
