wrote:

Let's say that you're shooting a black subject against a middle-grey
background with a 100mm lens on a full-frame DSLR, at a distance, and
you want the DOF that is had at f8. The camera's metering tells you
that at ISO 100 and 1/100 and f/8, you are "under-exposed" (or, in my
suggested terms, "under-digitized") by one stop. Common wisdom would
dictate to most people that they need to move to ISO 200. The fact is,
you could move to ISO 800, maybe even 1600, with cleaner, more detailed
results, with the same aperture and shutter speed (for 1600 you might
need to decrease the absolute exposure just a tad to avoid blowing out
the green channel).

Anyone who thinks that what I just wrote is outrageous is clearly
operating in an inefficent exposure/digitization paradigm.

It's not outrageous at all -- it just bears no resemblance to any way
I've ever approached photography. I guess it makes sense in the above
situation if you actually believed the camera's light meter, which
was wildly incorrect; if the better exposure was at ISO 800, then the
meter was two full stops off in its judgement, because you weren't
underexposing by one stop at ISO 100, you were underexposing by three
stops. So you're still comparing a proper exposure at ISO 800 to a
two-stops-under exposure at ISO 200, and the moral of the story is
still that it's better to boost ISO than to underexpose.

Too bad this couldn't be done in finer increments than one stop, on most
cameras. You have to vary f-stop and shutter speed by 1/2 or 1/3 stop
to get the in-between levels of digitization.

Do the Canons really make you use full-stop increments??

--
Jeremy |