yellow filter for digital B&W

I want to shoot B&W film and scan the negatives.

When _printing_ the negatives the use of filters (yellow - orange - red)
is advised while shooting, is there any point in using a yellow filter
when I only want to scan the film and do corrections in Photoshop?

I think the use of a red filter in very bright weather (great skies and
clouds) will make a difference...

Views on this matter are appriciated - Rob

"Rob" wrote in message
...
I want to shoot B&W film and scan the negatives.

When _printing_ the negatives the use of filters (yellow - orange - red)
is advised while shooting, is there any point in using a yellow filter
when I only want to scan the film and do corrections in Photoshop?
When you shoot on B&W film, you are left with a negative that has black
bits, white bits and grey bits. There is no colour information in the black
and white negative at all, so you have no colour info to base your photoshop
corrections on. Using a colour filter at time of shooting alters which bits
of the image are black bits and which are white bits. Eg a red filter lets
only red light through, blocking green and blue. As a result, things that
are green and blue (sky, leaves) will appear dark. Things that contain a lot
of red in their colour (ie, reds, oranges, yellows, whites), will appear
light. Using a yellow filter will will let red and green light through, but
block blue light. So reds, oranges, yellows, and greens in the original
image will appear lighter in colour, while blues will appear darker. In
practice a yellow filter will also darken blue skies, but the effect isn't
as pronounced as a red filter.
Now lets say you take a photograph of three coloured crayons - red green and
blue. Lets assume these crayons are equal brightness [1]. If you take the
photo with no filter, all three crayons will appear the same shade of grey.
If you use a red filter, the green and blue crayons will be darker grey,
while with a yellow filter only the blue will be darker. An orange filter
would result in a slight darkening of the green crayon, and a darker grey
for the blue crayon.
Now it makes no difference whether you will be printing directly from your
negatives, or if you scan the neg and import it into photoshop, if you
didn't use a filter when you took the photo all 3 crayons would be the same
shade of grey. The only way you can change that in photoshop is to
selectively darken just the blue crayon - for a subject more complex than 3
crayons, this would be nigh on impossible.
The use of colour filters with B&W negs _always_ happens at the time of
taking the photo. The only time colour filters would be of any use in the
printing phase would be if the photo was originally taken on colour film,
and is then being printed onto B&W paper.
With a digital darkroom you can shoot in colour (either film or digital),
and then produce a good B&W result in post-processing with photoshop. While
this won't give quite the same result as shooting with B&W film, you can
simulate the effects of various colour filters in photoshop, and see how
they effect the final output. Because you are starting with full colour you
can see how the same photo would look with different coloured filters
applied.

I think the use of a red filter in very bright weather (great skies and
clouds) will make a difference...
yes a red filter makes a partially cloudy sky come to life. Personally I
prefer orange because it still gives great skies, but not quite as severe as
red, and it isn't as severe on the other colours in the photo.

Views on this matter are appriciated - Rob
[1] In practice the three crayons would have slightly different
brightnesses, and so would appear different shades of grey, but lets just
assume for the sake of this exercise that they are all exactly equal
brightness.