|
Post by Peter S. on Mar 16, 2010 14:58:09 GMT -5
We have first results from a MC W.Rokkor 2.5/28. I haven't seen the raw data, but the guy, who took the measurement said it, the gamma spectrum proved that Thorium and its decay products had been found.
This is in line with my expectations, as I could not believe, that unwanted impurities could come into the glass in a percentage enough to have such an massive effect. We will measure two of my lenses, two 2.5/28 and one 1.2/58, and I will report the findings, too.
Furthermore I will test whether a 365nm UV LED is capable to clear that yellowish 1.2/58, which is a very nice short grip Rokkor (Berg&Tal), that was a pity if not used, at least occasionally.
Best regards Peter
|
|
|
Post by Peter S. on Jan 19, 2010 16:03:19 GMT -5
Hi there,
haven't read through the whole thread, and don't have enough time to visit often... but anyway - this is what I found out so far:
- for the more mundane lenses we typically use here (e.g. the F/1.4 early pentax lenses and some Rokkors, 2.5/28, early 1.2/58 and early 1.7/85) it still isn't clear whether some amount of unclean rare earth (i.e. undesired radioactivity) or thorium oxyde (i.e. planned radio activity) is the source of the radioactivity. For a thorium containing lens (e.g. the Kodak Aero-Ektars) one would expect a lot of radioactivity, while for some rare earth ingredients that contain a fraction of active isotops a lower amount of activity can be expected. I still think by myself that the usage of Thorium might have been to promising for the designers to resist...
- there are two major ways to cure the damaged structure of the glass: exposing to UV (sunlight, UV-curing lamps, exact wavelength and intensity still not exactly known) or heat. Heating will require to use at least 150 .. 200°C for several hours. Exposure to sunlight will require a few weeks up to a few month. I have cured two MD W. Rokkor 2.5/28 with an over-weekend exposure to an UV curing lamp, which took place in a locked lab, as the UV radiation is pretty hazardous.
- in the German Minolta Forum we currently discuss to measure some of the mentioned lenses most probably at the univerity of Ulm, Germany. I am _very_ curious on the outcomes, and I agreed to supply my two 2.5/28 and a yellow 1.2/58. But the test hasn't started yet. Forgot to mention, that any isotope got a unique finger print when measuring the gamma spectrum of the radiation. So we can be sure to find out what's inside the lenses.
Best regards Peter
|
|
|
Post by Peter S. on Jan 12, 2009 12:12:23 GMT -5
Hi there,
as a pretty big Minolta enthusiast I can assure, that the capacitor issue is over estimated. I bought about ten X-cameras over the time (sold some of them later), and only two or three of them went defective. I did exchange the capacitors for all of them - to find that the capacitor wasn't the cause of the trouble. Apart from the exchange of the capacitors (two of them are in a X-700) is straightforeward - if You got the correct size of the caps (pretty small ones are required).
Somewhere over the net there are series numbers, which are said to be susceptible to the capacitor problem. Both the latest and the most early ones seem to be OK. I would vouch for the older cameras here, as the seem offer better craftsmanship.
In the end it is a long time however that I loaded a film in an X-camera, as the XD-7 is soo sweet.
Best regards Peter
PS: incredible bargains can be made in buying Rokkor glass. As there is no serious digital option, even excellent lenses go away for ridiculously low prices.
|
|
|
Post by Peter S. on Jan 10, 2009 12:18:30 GMT -5
Hi Wayne,
I'd never put my real friend into the trunk of my car. ;-)
P
|
|
|
Post by Peter S. on Sept 18, 2008 10:43:06 GMT -5
Dear Wayne, dear Bob,
er, this is from the new location*). So, yes, it did hurt very much to lose the job. But after all I think I don't got too much reason to complain. My new accommodation is about 70km south of Munich just at the edge of the Alps.
Thank You for Your empathy!
Best regards Peter
*) both places are great to live at. I just prefer living out there in the countryside. Even if this means having to drive a lot.
|
|
|
Post by Peter S. on Sept 18, 2008 7:38:17 GMT -5
Oly C8080WZ from my window. Dear fellow camera collectors, I went through a tough time as I had been laid off after the development department I worked at had been shut down a few month ago. I found a new job (though with less salary - but that seems to be a minor issue, as it still is not that bad...), but have to find new accomodation since the new job is in Munich, way to far away from the Lake of Constance to commute (over 200km). I established a small home office, where I sit now. And this is exactly the view from my window.... Best regards Peter
|
|
|
Post by Peter S. on Sept 18, 2008 7:33:09 GMT -5
Hi Drako,
the light in the first one is exceptional! I like it very much! Otherwise I think I like green meadows more than deserts... ;-)
Best regards Peter
|
|
|
Post by Peter S. on Aug 6, 2008 12:16:47 GMT -5
Hi Tommy,
Thank You for showing these images! It is a dream of mine to once visit both the Inka trail, i.e. Machu Picchu and the upper Amazonas valley and then take a personal look on the place of "Touching the void" in the Cordillera Huayhuash. I think I will do this as my first encounter when retiring. Er, in about 15..20 years from now... But no need to hurry with both. ;-)
Best regards Peter
PS: I think a two month period is more suited for that than just two weeks...
|
|
|
Post by Peter S. on Jul 29, 2008 4:55:47 GMT -5
Beautiful! And another proof that carrying the tripod is well worth the effort. ;-)
Best regards Peter
|
|
|
Post by Peter S. on Jul 19, 2008 12:54:28 GMT -5
Well, what is now the state of the project?? I am pretty curious what to do in such a bad situation.
Best regards Peter
|
|
|
Post by Peter S. on Jul 19, 2008 12:50:42 GMT -5
Hi T.,
You should try to expose a roll of slight film (Fuji Sensia would do fine, Kodak Elitechrome is also OK) using Your camera in manual mode. In fact a hand meter would even be better. My idea is this: had the color cast being introduced by underexposed film?
There is no better way in checking colors than using slight film as the lab typically is less prone to failure.
Best regards Peter
|
|
|
Post by Peter S. on May 29, 2008 4:29:25 GMT -5
Hi Bob,
what's the state of the issue? Is it resting in the shelf or has it wandered into the waste bin??
P
|
|
|
Post by Peter S. on May 23, 2008 14:02:54 GMT -5
Hi Reiska,
I never heared something on the 37mm lens. The 37-A however got an excellent reputation. Most likey both are good performers.
Best regards Peter
|
|
|
Post by Peter S. on May 22, 2008 13:16:47 GMT -5
Dear Gene, dear Michael,
Thank You for Your kind comments. I am pretty happy with it.
Best regards Peter
|
|
|
Post by Peter S. on May 22, 2008 13:15:29 GMT -5
Hi JMI,
I think You're right with Your enthusiasm. I got one here - which is a heritage from a pro pg - and as such I don't have access to it. The pg used to work 18x24cm and owned the Mamiya for the fast snaps. He did prefer it over the Hasselblad (he could have bought both of them). He never used a lens different from a normal, btw.
Maybe I will ask for permission to use it at some time in future. I will need a replacement screen. I am also pretty curious how the near square format as opposed to 36x24mm and 6x6cm.
Best regards Peter
|
|