[LRflex] Re: Low light Digital Photography with close subjects
- From: Scott McLeod <scott.s.mcleod@xxxxxxxxx>
- To: leicareflex@xxxxxxxxxxxxx
- Date: Tue, 11 May 2010 02:46:35 +1000
Hi Walter,
I saw your post about shooting in low-light conditions. If you want to
stop motion, fast shutter speeds are the only way to go, which means
large apertures, high ISO, and preferably a larger-than APS-C sensor
i.e. "full frame" or 135-size. As others have pointed out, the problem
with ultra-fast apertures is the depth-of-field gets (possibly)
unusably small, perhaps defeating the original intent of you want
detail in more than one location.
On the other hand, if your subject/s are relatively stationary, there
is another (much less expensive) way: a good, recent APS-C camera and
a lens with VR/IS. This sort of setup has several advantages (besides
cost) over the full-frame/super-fast lens alternative: a stopped-down
lens (with VR/IS) will have a much greater depth-of-field for any
given field of view because a) it's stopped down, and b) the focal
length will be shorter, by 1.5-1.6x. You can hand-hold at *far* lower
shutter speeds with VR/IS, and the longer exposures mean you can keep
the ISO under control. Here are some examples I shot in a cave at
ISO800 with shutter speeds of 1/8 to 1/3s, handheld:
http://www.pbase.com/smcleod965/wombeyan_caves&page=all
The 16-85VR is an excellent lens, and a camera such as the D90 would
provide even cleaner results in terms of noise. To get the same
results in terms of depth-of-field with a full-frame camera and no VR,
using DSC_1131 as an example:
DSC_1131 1/3s f/5.6 72mm ISO800
"Full-frame": first the focal length would need to be at least 105mm
(actually 109mm). Luckily Nikon have fast 105mm lens, the 105/2DC. So
far so good. Then we look at depth-of-field - to get into the same
range you'd need to be stopped down to f/8. Now you have 2 choices:
drop the shutter speed to 2/3s (no chance of hand-holding a 105mm lens
there) or crank up the ISO. Even at ISO6400 the shutter speed will
still be an unusably low 1/12s. To get to (say) 1/50s would need
ISO25,600. I know that full-frame cameras are good at high-ISOs but
they are not *that* good (i.e. not 5 stops better). Opening the lens
up all the way to f/2 gets you 4 more stops of light, so if you stick
to a reasonable (for FF) ISO of, say, 3200, you can be 1 full stop
ahead of the APS-C setup, and have a choice of 1/200s, *or* stopping
down to f/2.8, *or* dropping the ISO to 1600 (which will probably look
cleaner than ISO800 on APS-C). Unfortunately you now only have 1/4 to
1/3 of the DOF, which may not be enough (and will certainly be
noticeable in a side-by-side comparison). In this particular case,
Nikon also make a stabilized 105mm lens, in which case you are in the
clear. But that is not true for all focal lengths...
In summary, for things that move, get a full-frame camera (even a
good, used Canon 5D) and the fastest lens you can afford. For things
that don't move (or move very slowly or intermittently) a good APS-C
camera with a stabilized lens is a better bet (IMO)
Hope this helps,
Scott McLeod
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