Hello Olympians,
there was an discussion about which compared silver based and CCD
images. Here some thoughts I have about it.
An Photo CD image (produced by an CCD) has an size of 3072x2048 pixels,
some people claim that this resolution represents the full quality an
silver based 35mm image has.
3072pixels / 36mm = 85 pixels per mm
A line needs at least a row of two pixel for his representation.
85 pixels/mm = 42 lines per mm
This looks not very impressiv, but wait it is worse.
Because it is unlikely that an (real life) grid of 42 lines/mm will be
projected in a way it fits exactly on the CCD array you need an higher
resolution to represent this or your usable resolution will be reduced
further.
I think this is a phenomenon, a man called Shanon (sp?) has discribed
(Shanons theorem). Acording to this theory you need at least double the
resolution (frequency) you want to represent.
So the practical resolution is further reduced to the half:
21 lines per mm
That´s a very poor resulotion compared what modern lenses and films can
capture.
But that´s still an very optimistic asumption, because it´s based on an
perfect CCD and does not take in acount their typical flaws as: not
perfect aligned color decals, interaction between the cells (blooming),
poor capturing of contrasty or dark objects, low sensitivity (comparable
ISO).
Another effect of resulotion should be considered, the influence on the
representation of fine color differences. You need a minimum of pixels
or silver/dye to produce an color gradient without banding or steps.
This is one reason why medium format (and bigger) is superior to 35mm
film (and of course by far CCDs). This advantage persists, even if you
compare an excelent (ultra sharp) 35mm lens with an mediocren MF lens.
I´m no engineer, so I might have made some mistakes, so you might
correct me.
I understand that companies developing electronic cameras spend a lot of
money, so they try to sell there intermediate results to the customer to
pay the developing expenses.
And yes, the market honors not always the best, but most of the time the
"good enough" solution. If this would be different, we would photograph
with LF stuff not with 35mm OMs.
But the euphorical supporter of new electronic toys and the confused by
the CCD camera hype should consider the obove before spending his hard
earned money on an
"plastic-throw-away-next-year-a-doorstopper-light-trap".
Regards
Richard
(steping down the soap box)
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