Buying split and graduated neutral density filters

[Warren]

I am just a hobbiest looking to extend what I can do taking landscapes.
I've read about the marvels of using split and graduated neutral density
filters to avoid over or under exposure and want to try it, but I haven't
found a local source and don't know enough about what I really need to buy
intelligently on line. I shoot both film (Nikon equipment with Velvia and
E100S mainly) and digital, and as a result am potentially looking at several
lenses in the range of 55-82 I want to try filters on. So, here are some
questions:


Can/should I buy these kinds of filters as screw ons or do I really need a
holder system like the Cokin one I saw in a store once.


If I need a holder system, how do these things work and what do I need to
buy? The one store that carried this kind of stuff didn't have much of it
(virtually no filters of any use to me) and nobody there knew much about it
(almost like this was leftover junk from old inventory).


Any suggestions on where to buy this kind of stuff?

[Alan]

You want a system taking square filters, so you can shift the filter to
suit your composition. Cokin P and Lee are your choices.

Lee system consist of 3 parts (purchased separately of course):
adaptor ring, holder and filters. The ring screws into your lens. Ring
and holder are held together with a spring loaded pin which makes it
easy to mount and unmount the holder. The holder has 3 tension slots
for filters. All filters go in the same direction (there is Pro model
that allows you to rotate 2 sets of filters; I never had that need).

Lee is metal, larger and more expensive both for the system and the 100
mm filters.

Never used Cokin P, but it is cheaper, made of plastic and takes 84 mm
filters. You may have to chop off the last 1 or 2 slots if want to use
filters on wide angle lenses.

nd 3 stop hard and nd 2 stop soft is the two filters that I have. I
like the control you have with hard filters, and should probably get a 2
stop hard filter as well. Soft filters can be used when your scene does
not have a clear line you can align the hard filter with, and the result
is a long gradual light fall-off.

My advise would be to start with 2 stop hard grad and see how that goes
(if your scene has more lattitude than your film + 2 stop, then get a 3
stop). Negative film has 7-8 stops latitude, and slides 4-5
(http://www.nelsontan.com/articles/filmdyn.html).

My two filters are from http://singh-ray.com/ and have made a big
difference with my landscape photos (mostly good :-) ). You did not say
where you were located. B&H (www.bhphotovideo.com/) may be an option
for mail order.