On Tuesday I took an objective lens to pieces to find out why the pictures were milky. The problem was a deposit on the glass -- condensed grease. Its a bad idea to allow lenses that have lubricated helices to get hot. This one has a small diaphragm and rather small elements --one is about 2mm in diameter. It was quite difficult to clean them. Now the picture is fine.
I did a couple of plan (focussing) eyepieces at the same time -- they were easier since the smallest element is about 15 mm in diameter. Again the problem was condensed lubricant to which dust and small particles were adhering; probably including small cellulose fibres from tissue used to clean (wipe) the exposed surfaces -- it gets down the barrel very easily during this process. But getting the four pieces of glass and the spacers back into the barrel and screwing it up without getting more crap in was difficult. These were all part of a large donation of 'redundant' equipment from the University; old perfectly good stuff no one uses any more. For examples of this 'close to focus' rubbish showing up on pictures look at: http://kotisivu.mtv3.fi/edfw/wild03/index.htm The same minute pieces of dirt on the eyepiece show up on almost every picture. It does not detract from the result, but makes the images look crappy. I hope that after my careful cleaning things will be slightly better. The human eye can cope with extraneous garbage in an image and 'process' the noise out, film cannot, and so the optics must be very clean. The nature of the imaging geometry is such that anything on the first transfer lens (eyepiece) is close to being in focus on the film. The human brain is one of the best (analogue) image processors that exist. I have another objective that looks like it has become delaminated. Delamination of cemented elements can sometimes look like a crack in the glass. When I can find some really clean Canada Balsam I'll do the repair. But I'll need to have a jig made that will hold the glass in line while the cement hardens. Don _______________ Dr E D F Williams http://personal.inet.fi/cool/don.williams Author's Web Site and Photo Gallery See New Pages 'The Cement Company from HELL!' Updated: August 15, 2003 "Oh my God! They've killed Teddy!" ----- Original Message ----- From: "David Madsen" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Saturday, November 29, 2003 12:17 PM Subject: RE: More lens problems > That's a tough one. If it's a hair it's removable. A crack is not. Too > bad it will probably cost money to find out for sure. Good luck. > > David Madsen > mailto:[EMAIL PROTECTED] > http://www.davidmadsen.com > > >
