From: Peter Marshall (petermarshall@cix.co.uk)
Date: 07/01/03-03:59:48 AM Z
>
>
> On Fri, 27 Jun 2003, Peter Marshall wrote:
>
> > > And what's the situation concerning the blue meanies (blue edging on
> > > backlit objects)? I quit the upgrade cycle at the Nikon 950 because
> > > of
> > > this, now use it only for fairly simple illustration online, like
> > > for
> > > ebay and woodworking.
> >
> > Pam,
> >
> > It did worry me a few times when I first had the camera, very bad in
> > some
> > pictures. But I think I have it more or less solved by changing the
> > way I
> > expose. It is one of the reasons you need to shoot raw.
>
> Um, shooting "raw." I know it doesn't mean "in the buff," or ... ???
>
> J.
>
>
That's optional.
Personally I don't like to show my knobbly knees more than necessary:-)
Raw files represent the actual values from the sensor cells, usually as a
single 12bit value from each cell. Most cameras use rows of alternate
green and blue filtered cells and red and green filtered cells, so for
every 4 cells you get 2 green values and 1 red and 1 blue.
The camera then does some maths on these values to cook up a set of RGB
values for each cell, usually outputting 8 bits for each colour as either
a tiff or jpeg. In the process it adjusts, colour balance, sharpness etc
according to the values set in the camera.
The number of pixels in the file is sometimes but not always more or less
the same as the number of sensor cells in the chip. If it is the same, a
tiff file will contain twice the number of bits as the raw file, but have
lost half of the information. The advantage of using raw format is that
you can post-process the raw data, and adjust the characteristic curve,
the exposure, the colour temperature, the sharpness, digital noise etc
using the full data set rather than the pre-digested version you get in a
tiff.
It would also be possible to use 16bit tiffs, but these get rather large
and there are no advantages in storing these on camera. I usually output
from raw to 16bit tiff in Capture One, work on the 16 bit files in
Photoshop for final retouching, colour balance and any 'dodging and
burning', then finally output as 8bit.
A 6Mp camera will usually give a 9Mp raw file, which converts to 36Mb
16bit and then 18Mb 8bit file. I archive the raw files from most exposures
and those 18Mb output files from the selected images.
More on the Frank etc stuff, when Kertesz went to American they didn't
like his pictures partly because they didn't share the technical quality
of most US press work from 5x4s, but also because they "talked too much."
Having said that I walked round the current Walker Evans show in London on
Sunday and found myself thinking again and again 'I'd like to make a print
of that and get it right' particularly when looking at those labelled at
vintage prints (the best prints were those made in the 60s and 70s.) They
are better printed in some of the books. Frank's work is more expressive
the way it is printed, but Evans would probably have been better served by
Ansel at the easel.
Professional digital cameras have largish sensors with larger cells than
consumer ones. They also need to have a reasonable number of pixels, and
do something when you turn on and press the shutter, not 5 seconds later.
I think all those that qualify are interchangeable lens SLRs. I'd include
cameras such as the Nikon D100 which Nikon doesn't regard as a
professional model because you can't bang in nails with it, or at least
not when its raining.
Both Canon and Nikon make some good zoom lenses (as do Sigma, Tamron,
Tokina, Minolta etc) but there is a little problem with many digitals,
because most have sensors smaller than film. Put that Canon 35-135 on the
cheaper Canon DSLR and it works like a 50-200 because of the smaller than
film sensor. I have a 24-85 Nikon that works as a 36-130mm or so. For a
real wide-angle I'd need to buy the 12-24mm. But the 24-85 covers most
things at a pinch. The real answer long-term will be to design cameras and
lenses specifically for digital - like the Nikon 12-24mm and the
forthcoming Olympus E system.
> 6Mp may not seem much, but I'm putting work from the D100 in an online
> agency as 50Mb 24bit tiffs, alongside work from film at the same size.
I meant at 50Mb, but yes, scanned from 35mm film.
I've said on too many occasions that you can take great photographs with a
Diana, and there are plenty of good pictures taken with cheap digital
cameras. If like me, you want quality similar to 35mm film (and I think
some gum prints need this, though others don't), then the route I've
suggested will give it. If you want something to replace medium format,
then you need to get into a different league of expense.
Regards,
Peter Marshall
Photography Guide at About http://photography.about.com/
email: photography.guide@about.com
_________________________________________________________________
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and elsewhere......
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