Re: [OM] Moderate Contrast Lenses

Subject: Re: [OM] Moderate Contrast Lenses
From: John Hudson <xyyc@xxxxxxxx>
Date: Mon, 13 Nov 2000 00:04:48 -0800
Ray Moth wrote:
> John Lind wrote:
> I believe it's much easier to reduce the contrast of a lens than
> increase it.  Someone correct me if I'm wrong:  doesn't a ND filter
> also reduce contrast in addition to the light reduction (one could use
> a polarizer for this too)?  Soft focus, fog, or diffusion filters
> typically reduce contrast, but they also reduce resolution.
> =======================================================================
> I agree, there are many ways to reduce contrast. To me, the ND filter
> approach makes sense, because the less light there is the lower the
> contrast. In a totally dark room, everything looks black, whatever its
> colour or shade. There is no contrast. If the light level is increased,
> light coloured objects brighten while dark objects are still dark, i.e.
> contrast is also increased. Use of an ND filter (or polarizer) will
> simulate the effect of a dark room, reducing contrast.

To me this is not logical. Contrast is a consequence of the light,
whether natural or otherwise or a combination of both, prevailing in and
about the scene that is to be photographed. An ND filter serves to
lengthen the time it takes for that light to register on the film but
does not in and of itself affect the quality of the light in question.
Use of the filter necessitates a slower shutter speed and / or a larger
aperture but other than that the quality of the light is not affected by
the ND filter. All the filter does is to extend the time it takes for a
given volume of light to register on the film as compared to the time it
would otherwise have taken without the filter in place. If these
assumptions of mine are correct, how might an ND filter affect contrast?
As the name implies does not an ND filter just serve to slow the rate at
which the prevailing light passes through the camera's lens system?

> Another way to achieve low contrast could be to under-expose negative
> film, thereby depleting the emulsion. The overall brightness can be
> corrected in the printing stage but contrast will be lower.

Doesn't under exposure in the camera coupled with normal film
development result in near normal negative contrast but lower negative
density? Extended film development would result in higher negative
contrast and near normal negative density. Lower negative contrast and
very low negative density would result from underexposure in the camera
coupled with shortened film development. 


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