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Chuck
Doswell's Outdoor Photography Advice
NOTE: This information
has been reproduced to the World Wide Web for general use.
If it is to be reproduced, in whole or in part, in any commercial
medium, please contact the author first.
These notes are
the outcome of having been asked in an Internet newsgroup
about the clarity of my images on my photography page. First
of all, I often use a polarizing filter, but not always.
I am now almost always using a "Skylight" or "UV"
filter when not using a polarizer ... having damaged lenses
in various ways in the past (usually by dropping them during
a lens change), plus I have noted how much clarity my vision
gets from the UV filter (the so-called "blue blocker")
in my prescription sunglasses.
Image clarity depends
on many factors and, of course, I am not scanning and posting
images I have taken that do not have clarity! That is, I
do not show off my failures. Having been asked about factors
that produce images with high clarity ... I offer the following
thoughts:
- Use good quality lenses. For
many of us using Canon (me!) or Nikon equipment, this
means we tend to stick with Canon or Nikon lenses, as
opposed to buying "third-party" lenses (e.g.,
Sigma, Spiratone, Cambron, etc.). It's not that those
lenses are necessarily inferior, but I like to stick with
the lenses made by my camera's manufacturer.
- Use good quality filters, but use them sparingly. A filter
is another optical device between the subject and the
film (the lens is one). The more devices in the chain,the
more likely you are to introduce distortion.
- Use a tripod for virtually every
shot. If you must shoot hand-held, stick as closely as
possible to the rule that you don't hand hold any shot
at a speed slower than one over the focal length. Thus,
if you are using a 50 mm lens, put anything slower than
1/30th - 1/60th of a second on a tripod. For a 24 mm lens,
you can hand-hold down to about 1/15th - 1/30th of a second.
For a 200 mm lens, the break point is in the range 1/125th
to 1/250th of a second. And so on.
- Always stop and ensure that your
lens is focused, usually on infinity for skyscapes. With
some zoom lenses, the focus at infinity can be tricky
because it is not always at the end of the focusing range.
- In cases where your shutter speed
is between about 1/30th and 1/4 second, it is advisable
to lock up your mirror (in an SLR 35 mm) before you expose.
In this range, the image is likely to be affected by the
vibrations caused as the mirror flips up during the exposure.
- Long lenses used to bring distant objects up close typically
will create a contrast loss, due to the intervening distance.
It's better to get closer and use a shorter lens, if possible.
Although zoom lenses have improved greatly in the last
10 years, a fixed focal length lens is almost always sharper
than a zoom lens, and usually has fewer elements inside
(see #2).
- All else being equal, use f-stops
near the upper middle of the range: f /8 or f /11. Most
lenses perform best in this range in terms of sharpness
and contrast. It is best to avoid the extremes of the
aperture range at either end, but especially so at the
larger apertures (smaller f-numbers). A wide-open lens
typically has substantially inferior sharpness and contrast
to one that is stopped down. Thus, I assign high priority
to the aperture and normally don't care much about shutter
speed. Only when dealing with high speed movement (e.g.,
tornadoes) is shutter speed a high priority. Thus, a lot
of images have to be shot with slow shutter speeds ...
with the slow film I am using. This reinforces the need
for a tripod!
- Depth of field for sky shots
is not really an issue most of the time. However, if I
am trying to get a certain object in the foreground along
with a dramatic sky, then the depth of field becomes very
important ... this also reinforces my concerns about aperture
priority.
For most slide film, a slight underexposure (on the order
of a half-stop) produces the best, most saturated color.
I use Fuji Velvia for most of my daylight shots and Velvia
tends to be a bit intolerant of underexposure, so I usually
stick to a "normal" exposure for Velvia. I use
Kodachrome 64 for lightning shots at night .. see my lightning
photo page for more discussion. Using slow film (ISO 100
or less) means fine grain, which translates into image
clarity. Since I do not use print film for anything besides
snapshots, I have nothing to recommend along that line.
- Be aware of the sorts of situations
that produce the best images. There is no way to describe
how generally to do this ... practice, practice, practice!
If you can train your brain to SEE and not just to "look"
then it can help you in this directly.
The weather influences clarity a lot! In the relatively
dry, clean air of the Great Plains, High Plains, and Rocky
Mountains, you are more likely to get the right sort of
conditions for image clarity than in the hazy, polluted
air of the Eastern third of the country.
I can offer little or no advice to users of cameras that
do exposure and/or focus automatically. I am so old-fashioned,
my cameras have a mechanical shutter! If you are using
an automatic exposure camera, as far as I'm concerned,
you're on your own ... sorry. I have said some things
that are relevant for those with auto cameras operating
in AE mode, and that's about as much as I can say.
Perhaps the best advice I can give is for you to experiment
until you achieve what you want. But you've probably heard
that before. Happy shooting!
More tips:
Outdoor
Photography Advice
Some Basic Elements of
Photography
Some More Advanced Photgraphic
Skills
Lightning Photography
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