[TheForge] Mastermyr photo question...

Sun Feb 8 11:20:01 2004

If one is planning to photograph black ironwork, I recommend exposing at a
setting which is the lowest setting (i.e. least exposure) which is near black,
but still shows all the detail you are trying to show.
Shoot a series of exposures starting at the reading off an 18% gray card, then
bracket above and below that setting three exposure settings in 1/3 steps. Keep
notes when you do this.
Then select the one which shows the iron the darkest, but still retaining the
level of detail you want.
Different films will have different contrast levels, and this is the best way
to calibrate your camera meter to the film you are shooting.
Same thing will work for a digital camera, except the film is no longer part of
the equation.

My preference is to set my camera meter to spot metering.
I then take a reading of the darkest area where I want to retain detail, then
underexpose by the appropriate amount from the camera reading. You can do that
manually, you can set the camera to underexpose by a specific EV (exposure
value) amount, or you can set the camera to an appropriate higher film setting.
I'm in the habit of usually doing it manually because sometimes I go the other
way and expose an area where I want the lightest value which still retains
detail, and have forgotten I've modified the exposure value setting.

It's true that the film response curve is an S-curve, but you only run into the
non-linear portions of the curve at very long (several seconds) or very short
exposures (shorter than most typical cameras will shoot).

A worse problem is color cross-over, where one of the color layers responds to
exposure differently than do the other two color layers. For example, if the
green layer is more sensitive to the other two color layers in the dark range,
but less sensitive to them in the brighter range, a graduated gray background
will have a green tinge in the darker areas, but will have a magenta tinge in
the brighter areas. You can't remove the color bias with color-correction
filters when this happens, because in the process of correcting the bias in one
area you'll make it worse in the other. That's the primary thing pro
photographers are checking for when they test a roll of film from a batch
before buying a large quantity of it. No batch of film is perfect, but small
deviations from the rated film speed or slight (but consistent) color biases
were (are) no problem, as they're easy to correct.

That's one thing I have yet to test my digital camera for, as I'm curious to
find out if its color response is consistent across the exposure range.

Bob

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Mike McKim
Sent: Sunday, February 08, 2004 10:02 AM
To: [email protected]
Subject: Re: [TheForge] Mastermyr photo question...

I think it is important to point out that film, and particularly color film
is non-linear in its response to light and colors in somewhat of an S shaped
curve. The 18% gray is a reference only, and it happens to work great in the
center of this S curve.which works well for "typical shots" and it is good
to have one as a check on your metering systems. Photographing dark metal
tools happen to be in the dark end of the S curve and will tend to have to
be overexposed to obtain maximum detail/information.

Generally films and cameras are optimized for "typical shots" indoor
family/party activities and outdoor activities. And further, film and
cameras are optimized to capture the human face accurately, this is the most
highly recognized item our tiny brains are tuned to interrupt.

Well documented test shots of the items to be photographed, and using a pro
shop as Terry points out will give the best results.

Mike McKim