Nikon D4s: Bayer processing breakthru?

Started Jun 4, 2014 | Discussions thread
Truman Prevatt
Truman Prevatt Veteran Member • Posts: 7,243
Re: Thanks to all: Nikon D4s: Bayer processing breakthru?

DMillier wrote:

I guess we are talking about acutance again. Similar to the effect of developing in rodinal compared to a fine grain developer. It makes the end result look crunchy. It wouldn't surprise me if luminance aliasing also contributes to that look.

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"...while I am tempted to bludgeon you, I would rather have you come away with an improved understanding of how these sensors work" ---- Eric Fossum
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Acutance would be my guess. However, the way that non-silver solvent developers such as high dilute Rodinal or techniques such as water bath developer or stand development generated the illusion of "acutance" was to actually cause a "very slight under development" one one side of a sharp line (the least exposed side) and a "very slight over development" on the other side. This only took place at the boundary of the line.  This produced an "outline" in the images at the boundary between the areas.

This happened because the exhaustion of the developer was different on the two sides of which would cause a little natural diffusion across locally the line of developer from the least exposed side to the more exposed side where just at the boundary of more exposed side more development occurs only at the boundary of the more exposed side . When you agitated - you delivered fresh developer everywhere. By letting such developers as dilute Rodinal stand for long times between agitation or by water development where the developer was removed from the sheet of film and put in water and then replenished periodically this exhaustion on the more exposed side would occur and the edge effect will be produced.  However, the same process accentuated the edges of grain - calling attention to the grain of the film.

The Callier effect in which the highly collimated light source of a condenser enlarger would also produce a scattering patter that had the effect of an artificial "outlining" of sharp boundaries. Neither the development trick or the Callier effect produced sharper images, they called visible attention to the sharp boundaries in the image which went by the term acutance.

Personally as soon as I found out about the wonders of a cold light enlarger head at a Fred Picker Zone VI clinic, I got one and never printed another print by an enlarger that used used a point source light bulb - either with or without a diffusion screen. The cold light head produced wonderful smooth images with out the artificial scattering lines that accentuate both grain and edges. People like Ansel Adams, Minor White - masters known for smooth prints with sharp focus used cold light heads produced by Aristo. Some papers (Oriental Seagull and Ilford for example) formulated papers for cold light heads.  Even today the official reprints of Adams'  images are done the same way using an Aristo cold light head.  The Zone VI Cold Light head, sold through Picker's Zone VI Studios was based on an Aristo light source tube.

I expect it is acutance or the illusion of acutance to be the reasons many people are drawn to the Foven. However, there is something similar could be going on with the Foveon to what produced the visible illusion of acutance in prints. It takes an infinite spatial frequency response to reproduce a sharp boundary between areas. On the Foveon, at that boundary the spatial frequency energy of all the colors have the same Nyquist cutoff and will be aliased at the boundary in the same way which may very well produce a subtle perception of acutance outline.  Since the Nyquist cutoff is different for each color in a CFA (the "red" and "blue" 1/2 of that of the "green"), the effect my not be as pronounced to the same extent to the extent that there is any visual effect in the image.  This is one thing I am looking forward to seeing when the Q sensor is released which will not unlike the CFA will have two different Nyquist cutoffs - the lower 1/4 of the higher. How will this change the perception of acutance?  We'll soon know.

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