[rollei_list] Re: xenotar 2.8f vs planar 2.8f

  • From: Don Williams <dwilli10@xxxxxxxxxxxxx>
  • To: rollei_list@xxxxxxxxxxxxx
  • Date: Tue, 16 May 2006 16:14:41 -0700

At 02:56 PM 5/11/2006 -0700, Jeffery
you wrote:

I must point out that a lens hood will not make much difference if the lens is scratched up. The scratches act to diffuse light from the image. They will, of course, also have an effect on extra-image light, which is the only light affected by a lens hood. Scratches affect mostly the contrast of the lens, reducing it significantly. If bad enough they can also affect the sharpness. I think its a good rule to avoid scratched lenses. As I pointed out in an previous post "cleaning marks" are scratches and often very fine ones. These are quite effective in scattering light and reducing lens contrast. The term is a euphemism for scratching. Again, a single large scratch or gough may have minimal effect on the image where a number of fine scratches will destroy image contrast.

Richard Knoppow
Los Angeles, CA, USA

There is always one option, when you are far away from civilization and have just scratched the front surface of a lens. Just paint the scratch with anything which is opaque, black paint, shoe polish, whatever. You will lose some light, and depending on the lens design, you may or may not see some artifact on the image, but you at least won't have a lot of scattered light which decreases the image contrast.

Just a thought.


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