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tedwhite
Guest
Is there anyone out there who does CLA's who might be able to remove the faint polishing marks on a front element?
Faint Polishing Marks on Lens
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Roger Hicks
Veteran
http://www.optil.co.uk/
The lens will of course need to be recoated and they only do single coating -- hardly a major problem on a front element.
Cheers,
R.
The lens will of course need to be recoated and they only do single coating -- hardly a major problem on a front element.
Cheers,
R.
F
former member
Guest
You will create more problems by polishing the marks out. The focal length of the element will change ever-so-slightly. Unless the lens is unusable, best to leave it alone.
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tedwhite
Guest
Thanks Roger and Brian. I will provide this information to my friend.
The lens is an Auto-Takumar 85/1.8 in M42. Somewhat rare.
The lens is an Auto-Takumar 85/1.8 in M42. Somewhat rare.
F
former member
Guest
Someday I'll do some 2-D Fourier Transforms of images taken with lenses with cleaning marks and with those that are perfect. My wife used to make me do stuff like that. "Honey, I need a 2-D Fourier transform of this image. Can you write me a program to do one?"
I could put a scratched filter over the lens to simulate the marks. Would be better- same lens, and photo's before and after scratching the filter.
I could put a scratched filter over the lens to simulate the marks. Would be better- same lens, and photo's before and after scratching the filter.
jan normandale
Film is the other way
some heavy hitters here... I'm sitting on the fence watching ;- )
F
former member
Guest
I'll probably use the DCS200 for this. It is an N8008s with a monochrome digital back. I already have a FORTRAN program that reads in the raw files, and a mixed-radix FFT in FORTRAN. The CCD is "raw" without an AA filter that kills the high-resolution of modern digital cameras. The E3 has reduction optics, and the D1 has an AA filter.
The question is the degree that small marks on the lens effects images. To quote an optical engineer on small scratches, "There's a Fourier transform involved, so it will not have much of an effect". So it's a good test. The high-frequency content should change as the glass is scratched. The question is, by how much.
I have a Summicron that had an opaque front element. Bought for $60 to get the inner elements for a lens with a good front and poor inner elements. I made a best of the best and worst of the worst. Polished the front element using polishing sheets for fiber connectors and recoated it using an eye-glass repair kit. It produces an amazingly good image.
The question is the degree that small marks on the lens effects images. To quote an optical engineer on small scratches, "There's a Fourier transform involved, so it will not have much of an effect". So it's a good test. The high-frequency content should change as the glass is scratched. The question is, by how much.
I have a Summicron that had an opaque front element. Bought for $60 to get the inner elements for a lens with a good front and poor inner elements. I made a best of the best and worst of the worst. Polished the front element using polishing sheets for fiber connectors and recoated it using an eye-glass repair kit. It produces an amazingly good image.
Roger Hicks
Veteran
Dear Brian,
On a closely related topic, Ilford did some research a few years ago on the detrimental effects of scratched below-lens contrast filters. They were not expecting all that much degradation but they were surprised that it was even less -- a great deal less -- than they had expected. Most of the degradation could be negated with a harder grade of paper...
Cheers,
R.
T
tedwhite
Guest
Jan:
I'm hiding behind your fence.
Ted
I'm hiding behind your fence.
Ted
