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>>> I keep reading about rating the T400CN at 200
- why do you guys do this, what does it do for you? I have never
tried it, any problems you have to watch out for, i.e. camera
shake, over/under exposure etc. when you rate films different
than their stated ISO? Hopefully this isn't too dumb a question
- I'm self-taught, what can I say?! <<<
Kevin responds:
No question is dumb, questions are how we learn. Rating TCN
at 200 reduces the contrast slightly, gives a small improvement
in skin tone, and helps prevent underexposure (which can cause
grain and poor tonality). While I often rate this way myself,
I suspect that the reason some folks notice a big difference
is because they are using in camera metering, and not adjusting
that reading. For instance, if I use my in camera meter to read
the face of my subject, the exposure that will give me will produce
an 18% gray skin tone, so what I should be doing is opening up
at least one stop from that reading in order to get a pleasing
skin tone. So, if I am rating at 400, if I don't compensate for
my meter (which tries to render everything as 18% gray), I end
up with underexposed flesh tones. If I rate at 200 I am already
(whether or not I am conscious of it) compensating for this by
providing an extra stop of exposure.
That's not to say there aren't valid reasons to rate at 200 even
if you are metering correctly. It can still give you a slightly
nicer skin tone, because when overexposed, many C-41 films will
get "creamy" in the highlights. You will also get increased
shadow density, which can be helpful in rendering detail in dark
areas. This film also becomes slightly softer when overexposed,
and the grain structure becomes even tighter, giving a very smooth
look. The only real down side is that the negs will take longer
to print.
All that said, I have gotten good results with TCN at 400 as
well, as long as I meter properly.
As far as problems, overexposure is really not an issue with
this film - it can handle alot of it. Underexposure should not
be an issue (unless you grossly mis-expose) with this technique,
because you are giving the film an extra stop of exposure.
As far as camera shake, it depends how much light you have, and
what lens you are using. The rule of thumb when shooting hand
held is to use a shutter speed number that is at least as big
(inversely) as the focal length of your lens. In other words,
a 50mm lens means I must use a shutter speed of at least 1/60,
a 100mm lens means I must use a shutter speed of at least 1/125,
etc.
So, let's say I am shooting in the last light of the day as the
sun creeps below the horizon, I have been rating my TCN at 200,
and I am using a 100mm lens with a maximum aperture of f 2.8,
and let's say I have metered properly and come up with a reading
of f1.4 at 1/125. I now have a choice to make, because theoretically
I have one stop less light on hand than I need. I can do one
of several things:
1. I can switch to a lens with a wider maximum aperture if I
have one.
2. I can use a shorter lens, which will allow me to use a slower
shutter speed, but may not be ideal for portraiture.
3. I can use a tripod and a cable release, which will allow me
to drop the shutter speed, but may not be ideal for a moving
subject.
4. I can rate my TCN at 400 to get back the extra stop.
5. I can switch to a faster film.
Now, that is all a theoretical, but not uncommon situation. The
short answer is, If I have enough light I'll rate at 200. If
I don't, I'll either rate at 400 and meter carefully to avoid
underexposure, or I'll use a faster film.
One thing to keep in mind is that the principle of rating
your film at a slower speed GENERALLY only works with a) color
negative films, or b) C-41 B&W films (which include TCN,
Portra B&W, Kodak Select B&W, and Ilford XP2). Traditional
B&W films when overexposed (or rated below their standard
speed)become grainy, and the highlights can block up, UNLESS
you also underdevelop ("pull") them, which will decrease
their contrast, and some modern B&W films, such as Tmax,
don't even respond well to this technique. Color slide films
(which are not commonly used by portrait photographers) will
simply become too light and washed out if overexposed. The exceptions
to this are some B&W or slide films that have been found
to be slower than their advertised speed. One example would be
Fuji Neopan 1600. |
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