Monobrow Bob wrote:
Interesting. I tend to prefer the monochrome conversions from RAW
files.
The in-camera stuff just doesn’t quite get there. For me. <g>
Where I slightly beg to differ would be in regards to the DMC-L1 and
the
E-3. I've always liked the in-camera E-3 B&Ws and the DMC-L1 was
certainly
influenced by both Olympus and Leica in the programming of the
algorithm.
There is just something "right" about those files--when it comes to
getting
people pictures.
The thing that seems to make the biggest difference that I've found is
using a lens-filter to match the general color sensitivity of B&W
film.
Most B&W films tend to be more blue-sensitive that color films AND
digital
sensors. In otherwords, B&W films are more like tungsten color films
in
that they are more blue sensitive and therefore look better in indoor
artificial lighting.
You see that with Tri-X film, which looks great indoors with no
filters,
but the moment you step outside, you want to put a yellow filter on
the
lens. This is to counteract that unnatural blue-sensitivity of the
film.
If you change a digital camera's white-balance to tungsten you'll
come a
lot closer to how B&W films see the color spectrum. Should you do
that with
a filter or with a conversion setting in Lightroom? Good question. It
depends a lot on the sensor and how the three sets of color sensels
of the
sensor respond to light and their spectral response and noise
patterns.
Take the blue sensels as an example. They are usually the most noisy
of the
lot. You would think that adjusting white-balance in your raw
converter
diminishes the blue-sensel "volume" in the mix. It actually does
not. The
raw converter is typically doing a 3-pixel merge. Not four, but
three--the
two greens for every one blue and red have to do with how the matrix
is
merged, not any particular advantage to having twice the number of
green
sensels--except Olympus and Fuji will sometimes use two greens of
different
responses, which forces a 4-pixel merge which is not nearly as
inherently
sharp or well behaved as a 3-pixel merge.
(some converters actually do let you deep-dive into altering the
ratio of
how the pixels are merged, but the Olympus and Adobe converters do
not).
So, we have a situation where the blue sensels are overly noisy for
a given
picture. The noisy blue sensels are merged in with the green and red
and
then the white balance is applied. Unfortunately, the noise addition
of the
blue sensels has already been added to the merged calculation and the
derived pixel value has this noise built-in.
What if, you can balance the blue, red and green pixels at time of
shooting? Instead of the scene being overly yellow cast (interior
lighting), you can put a tungston correction filter on the lens and
adjust
your exposure to compensate. Ten years ago, the sensors were still
noisy
enough that the increased exposure usually offset the improvement
you got
off of the blue sensels, but with this method of color correcting
BEFORE
the light hits the sensor, you are essentially mapping the noise floor
evenly across all three color sensels. The primary benefit isn't so
much
with noise improvement, but with far better behavior in Zones I-II,
IIV-IV.
You don't have one color clipping before the rest and you can
actually do
extensive shadow and highlight recovery without strange color casts or
out-of-gamut conditions.
So... To a picture destined for B&W conversion, either in-camera or in
Lightroom, if you put a cyan or blue filter on the lens you'll
better match
"Tri-X" in how it sees. If it's for outdoor shooting, you can
usually just
forgo the filter entirely as a bare lens will give you a basic Tri-X
with
yellow look. But indoor picturs will be way off and the look is just
wrong.
A tungsten correction filter or a light cyan or blue filter will
generally
be all that is required to alter the spectral response curves enough
(without screwing up metering too much) to give more "proper"
digital B&Ws.
The DMC-L1 and E-3 in-camera B&W converter is actually doing this to
some
extent which is why they do better than the average bear at in-camera
indoor B&W pictures, but kinda stink up the show with outdoor shots.
So, for indoor color digital photography, if you do some lens-filter
color-correction, you absolutely will end up with a greater usable
dynamic
range and better uniformity in color response across the brightness
spectrum.
Sorry for the mixed topics of color and B&W, but you really can't talk
about one without talking about the other.
--
Ken Norton
ken@xxxxxxxxxxx
http://www.zone-10.com
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