Glenn said:I frequently use a graduated mauve
together with a rotary polarising filter with my 50E (slide film) and
wondered if this is still necessary if I move over to digital. Did
you used to use filters (and still do?)
Yes I used to use filters, skylight and 81B for sunny and overcast days,
graduated greys for darkening overly bright skies (or lightening overly
dark land) and a polariser.
Nowadays I no longer bother with the skylight and 81B (I can easily
adjust colour balance digitally, or in Photoshop afterwareds) and nor do
I bother with the grads anymore.
I can now get essentially the same effect as the grads in Photoshop,
using either contrast masking, layer masking or the new shadow/highlight
control. This does require a little time spent post processing, but
produces far better results than grads IMO, because you can create masks
which fit the shape of the horizon, rather than being limited to a
straight line. You can also adjust the strength of the effect to get it
exactly how you want it, it's far more versatile than grads.
But of course, you do have to learn how to do it, there's no magic
button to press. Some argue that using a filter is easier, and it
probably is, but when I'm out shooting I don't like to spend a lot of
time faffing about with filters. I'd rather spend 10 minutes on the
computer than waste 5 minutes out in the field.
It's also far more practical because digital cameras have a much wider
dynamic range than film (contrary to what most people mistakenly
believe). It's not immediately obvious, but if you shoot in RAW mode
and convert to 16 bit per channel, it's amazing how much detail and
colour you can get out of the shadows. For this reason you simply
expose for the highlights and worry about the shadows later. The
shadows may look black on the LCD, but they're not. The histogram will
confirm that you haven't underexposed the image, even if it looks like
you have.
Some have also argued that using a grad gives better quality results,
since digital shadow detail is of lower quality. This is a valid point,
but there are two things to consider. Firstly, if you use a grad when
you take the shot, it's very difficult to "undo" the effect later, it's
much easier to work on an unfiltered image.
Secondly, regarding quality, the big question is how much contrast there
is in the scene and how much you want to brighten the shadows. If it's
extremely contrasty and you want to brighten them a lot, then shadow
quality will suffer. However, in most situations the contrast isn't
that great, and you don't brighten the shadows too much, so the results
look fine.
If you really do have a high contrast problem and you want the best
quality, the simple solution is to take two shots, one exposed for the
highlights, one for the shadows (on a tripod of course for identical
framing). These two shots can later be blended using layer masking for
excellent quality results.
As for the polariser, that's one filter that you can't simulate in
software. Certainly you can darken blue skies and so on, but it's not
the same and it's not as good. You obviously can't remove glare from
the surface of water and see what's underneath. So a good old polariser
is still a very useful filter, that can't be replaced with software.
There's one more filter than I now use which you may be interested in,
an infrared filter. Many digital cameras are sensitive to infrared
light, so if you use a filter to block out all visual light, only
infrared light will be recorded. These require very long exposures
(usually 8-30 seconds) and are difficult to take because the viewfinder
is black (so you have to set up the shot on a tripod before you attach
the filter), but can produce very interesting effects. Fortunately
auto-focus works through the filter (you can't focus manually because
infrared focuses in a different plane).
Hope this helps.
Paul
--
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