Or you can just have the raw converter (or jpeg creation) extract
something less contrasty and apply curves to that to put the contrast
where it's desired... but even then, I sometimes have to do multiple raw
conversions to recover blown highlights.

Not a filter, it would add its own 1-2% reduction (assuming quality
coating on all lens groups). A well configured lens hood *will*
increase Dynamic range, especially if the lens isn't spotless clean.

Bart

There are filters which in some circumstances make a picture less contrasty.
That would mean that in those circumstances you actually can record a
scene with more dynamic range. Later on you can use part of the dynamic
range
to get the picture you actualy want, or you can stretch the dynamic range to
obtain a dynamic range which represents the reality a bit more.
I do not now how to make such dynamic range visible though. (Not on screen,
not on paper).
And I don't think that filters which reduce the contrast will improve the
picture.

ben brugman

SNIP

They can/could extend to the full 12-bit (4095:1) range that the
DSLR's ADC provides, give or take half a bit quantization error.
Boosting that to the 32767:1 or 65535:1 working space range will help
to allow for post-processing rounding errors, before reducing that to
the 126:1 printing range.

Bart

You mean a non-linear luminance response?  I've never heard of anything.
The filter would have to be able to distinguish light passing through it
at different angles; at any point on the surface, light can be coming
from different source points with different destinations, so even if
there was a way to make photon sweaken sensitivity to further photons,
it would have to distinguish between different directions, and it would
not work in front of the lens.

Maybe on the sensor itself?

Usually, the compromise with such things is increased noise, defeating
the purpose.  That's probably why the cameras aren't creating
gamma-adjusted RAW files on the fly; the circuitry might be very noisy
to do so (and harder to calibrate).

That depends on the standard of DR.  I can read large black and white
text on a box with my 20D under-exposed by 11 stops at ISO 1600 (pushed
to ISO 3,200,000, and binned), so by some standard, highlights 15 stops
below the sensor maximum are usable against blackness ("banding" really
competes with the signal at this level).  As far as individual pixels
are concerned, as measuring instruments, DR is limited by the bit-depth,
if not further by noise, which seems to be what Roger Clark is testing
with his DR experiments.  Some people say they are 5 to 6 stops, but
that would be a very high standard; they might be talking about exposure
latitude of a 5 to 6 stop DR image and mistakenly calling it the DR of
the camera.

Whatever the standard, though, I would think that the cameras will rank
pretty much in the same order, but issues like banding vs random noise
could cause relative shifts in ranking.

I don't know about a filter but I know when using camera raw in
photoshop to open a raw image, you can alter the contrast which results
in more detail in shadows and (provided it is there in the first place)
highlights. It makes for a very flat looking picture but one which can
have it's attenuation increased with other tools to liven up the image.

My experience has been that under exposing when bright objects are
present by up to 2 stops allows you to use Photoshop tools the lighten
the dark areas while keeping the highlights under control. This also
results in flat looking pictures.

I think that until the sensors can capture a wider range of detail -
maybe closer to human vision - no digital camera and no filter will
produce a pleasant looking picture with the full range of such scenes
as would normally have blown highlights and blacked shadows.

Maddy

Just as an aside, I often hear how cameras (film or digital) don't
capture anywhere near the dynamic range of the eye.  But I have an
objection to that simplistic criticism..  The eye cheats!!!  The eye
builds up it's image from scanning about, and it adjusts its pupil
(aperture) as required.  The final image you are 'seeing' is more of a
composite than a single snapshot!  This happens very quickly, but it is
not unlike the way a video camera adjusts it's aperture as it pans
acroos light and dark scenes.

Once the eye has gathered that information, it does a very creditable
job of handing over the best bits to the brain to collate it into a
usable image.  It's not unlike Photoshop's HDR or whatever it's called.
And would be very hard to measure...

If you don't believe me, allow me to repeat a small party trick similar
to one I use in my digital imaging classes....
Look intently at a word in the middle of a paragraph.. (in a paragraph
you *haven't* read!)  Now, while you hold your eyesight aiming steadily
and  *directly* at that word (no cheating!!), try to 'read' the
sentences that are 4 or 5 lines above or below it.  You will notice two
things:

1. You can't do it!  If you can, you are very unusual!

2. Somehow, even though that nearby text is illegible, it somehow seems
'sharp'.

Think about this - how can it seem sharp, and yet you can't read it?
The answer is simple, your brain *knows* that the stuff is sharp, and
so it 'is'.  But in reality, anything outside that centre few degrees
of sharp vision is in fact quite blurred.  So what you are seeing is
not actually the truth.  The 'sharpness' is built up from the rapid
scanning it has done, or in some cases it is simply because you know
from experience that the unresolved area is sharp.

I am certain the brain does something similar with contrast, but how
would you measure it?  And of what significance is it, anyway?  I
dunno, but it's interesting to think about..  (O:

Anyway, we already have light sensitive plastics that darken on
exposure to sunlight...ok, maybe not applicable.. but why not an
electronically driven polariser/lcd that sat in front of the sensor and
had adjustable darkness per pixel?  (O:  Who knows what the future will
bring, maybe sensor technology will improve along the lines suggested
before, ie the sensor simply shuts itself down as much as it needs to,
and more importantly, records the amount of 'compensation' so that the
light level is still recorded accurately..

No.

The camera sensor can record each pixel from blackpoint to max.

You cannot lower the blackpoint, not with a filter, you cannot
get a higher value than a filled electron well provides, not with
a filter.

The response of each pixel is (nearly) linear.  Again a filter
cannot change that, unless it was *directly* on the sensor itself
and acted somewhat like a self-toning sunglass.

You could, however, build a sensor that had such a filter, or
used sensitive and less sensitive wells, or had a sensor well
coupled with a timestamp when full (and use the 'when was it full'
timestamp to estimate how mny times it would have been filled ---
although that will play hell when combining flash with longer
exposures and not act like film at all) or have a sensor dump
itself when full (and continuing to collect data) with a counter
telling you how often that happened, or try if huge electron
wells will give you more dynamic range (though noise can be a
problem there!) ...

Or you simply use multiple exposures with different exposure data
and combine that data with DRI.  Unfortunately, that is not an
indicated technique with moving objects.

Or you simply use the usual methods (reflectors, fill flash,
etc.) to ensure the objects to be photographed are all within the
dynamic range of your camera.  The added bonus there is that this
technique also works with slide and print film.


-Wolfgang

With film there is a way to use a double exposure to do this.  First shoot a
gray card (not 18% I think, but I don't know the details and don't have time
to look it up), then second exposure you expose for the highlights.  This
pre-exposure is supposed to affect the film somehow that gives the shaddows
some help.  I first read about this in one of Ansel Adams' books.  I have no
idea if there is some trick that could simulate this, although I read some
blending techniques that work pretty well at Luminous Landscapes.

A few things:

If dynamic range is your primary concern in photography, even more than
resolution, then you should look into Fuji's Nikon-mount S3 Pro. Each
pixel location is actually a large pixel and a small pixel, capturing
shadows and highlights. The camera has a relatively low resoluion at
around 6 megapixels, but it apparently has tremendous dynamic range.

Barring that, you could get Adobe Camera Raw, which has tremendous
highlight recovery capabilities. Check out "Camera Raw with Adobe
Photoshop CS2" by Bruce Fraser for some wonderful insights. You'll
start to convert RAW files in a quarter of the time and get 500% better
results. In any case, that's how I estimate my improvement after
reading that book.

Long story short, when exposing for RAW, you always want to do the
following two things:
1.) Expose low enough that nothing blows out that shouldn't be blowing
out (obviously, if you've got a light source in the shot, you might not
mind that it blows out; it would on even the best films if exposed
properly for the whole scene.

2.) Expose as high as you can with regards to (1.). Basically, you
don't want any blowout, but you want to be knocking on the door of
absolute white.

The reason for this is better explained in the book (and in the "Expose
Right" article on Luminous Landscape), but basically, a chip records
light in a linear fashion and this means that your hottest stop
contains half of your picture information, and your second hottest stop
contains one quarter (which makes perfect sense if you understand our
logarithmic perception of light). Adobe Camera Raw *basically* allows
you to distribute these bits more evenly throughout the image and
results in better conversions. Doing this, you'll find that most
cameras have terrific dynamic range.

As for specific DR ratings for cameras, Imaging Resource has started to
collect data on this. A recent example of their stats can be found on
the review page for the Canon EOS 1Ds MkII:

http://www.imaging-resource.com/PRODS/EOS1DS2/1DS2IMATEST.HTM

The methodology leaves plenty to be desired, so take it with some salt,
but they conclude that, independent of RAW conversion, the following
make the top 5 DSLRs in terms of DR:

1. Fuji S3 Pro : 7.94 stops at "high" quality
2. Nikon D50 : 7.36 stops at "high" quality
3. Canon 20D : 7.29 stops at "high" quality
4. Canon Rebel XT : 7.11 stops at "high" quality
5. Olympus E-VOLT : 7.07 stops at "high" quality

They only test RAW conversion on two cameras: the S3 and the 1Ds2, and
these both see an increase of a little over a stop because of it. So
you can conclude that alot of DSLRs, even cheap ones, can get 8 stops
with RAW conversion. That's nothing to shake a stick at.

Anyone know what the typical range of luminance is in natural settings
around the world? If we trust the "Sunny 16" rule, then you have
ambient light of around 6826 footcandles in bright sunlight. Which
suggests to me that the 14-stop difference between 1 footcandle and
8192 footcandles would get you nearly everything you want, if exposed
properly. Surely, then, a 16-stop range from 1 footcandle to 32,768
footcandles would be enough, right? And even then, that's if you wanted
full seperation between 1 and 2 footcandles. How long until we have
sensors that can give us that kind of range? At that point, do you even
rationalize exposure in the same way?

Food for thought,

Will