If possible i would take both as no sunset is equal to the next one :D
In sunsets the lighting conditions vary a lot, depending on the height of the sun above the horizon. You may need a wider range of ND grads to deal with it.
If you like to go for quality and get a more expensive filter, start with a 2 stop soft gradient, as you can always use the lighter part if you don't need more. You can buy a 1 stop later. If a cheaper brand is OK for you, simply get both.
Good thing about having two is that you can move one in from the bottom, to reduce reflections off a water surface.
I bought a new Cokin filter holder for my 72 mm lens - you know, thinking I could actually use it. When I got home I found that my old Cokin square filters were too small. I had always assumed that Cokin filters were universal - I mean unless you are using those honking big teles. As far as I know Cokin only made one size filter...........anyone know if there are larger filters or if I can buy an adaptor so I can use them?
Maybe I'm still old school but these skies over Seattle really need some graduated filter help and its just too hard to hold the filter and shoot at the same time. Id much rather do it in camera than with PS, just not the same is it?
Sorry, can't help you myself Tor - lost myself - but really interested in what answers you get.
Post Edited (18:04h)
What you should have is the P series.
They are available with ajustment rings from 48 untill 82mm
so larger then the old A series.
Most of the short to medium zoom lenses use the P series
I use myself the P121S = soft Gradual Neutral grey and the P121F = full Gradual Neutral grey
Hope this helpes !!
P series are good for most SLR's, unless you have larger than 82mm filter size lenses or very wide angles that would otherwise "see" the filter holder.
Quite some color correction filters or filters for B&W photography can be simulated in PS. Still I find it more convenient to start with the right filters in the first place.
I have a handful of Cokin filters for different situations. A few ND grads (neutral - gray - graduated) are always handy to get a better balance in brightness in a picture when the sky is too bright (clouds), but also for creative effects like add vignetting, darken foreground,... This is a filter that is also important in digital photography, because there is little possibility to correct for an over exposed sky if all pixels clipped to full white.
I have several warmup filters for landscape photography (P027,P035) to accentuate clouds in the sky (not as strong as a polarizer) or add some warmth in general (ie. to skin tones in outdoor portraiture)
A light blue to add coolness (tranquility) to a scene.
And a few more...
A description of what each Cokin filter does (with example pics) can be found here: http://www.geocities.com/cokinfiltersystem/
This is not an official Cokin site but maintained by an enthousiast.
If you like to know a bit more about filters, get in touch (Skype...)
Couple of examples:
I really needed a graduated filter for this shot. When I got it home and processed it I found that in order to get the contrast I wanted I lost what little detail I had in the sky. It's a standard problem that photographers seem to have here. It comes out better in color because the sky had lovely colors, but in black and white they vanish.
This one was with my little Kodak. I had a 1 or maybe 2 filter on it.
Post Edited (22:17h)
When you say the sky had nice colors; could you have played with the channel mixer for a better translation between color and B&W??
Kind of a cool place for a nude though. Had all kinds of ideas for it.
by reading through your desciptions of the cokin filter systems I got very eager to learn more about it, and looked up the websites you listed above. but i couldn't find a pricelist or a shop selling this system on the internet. do you know one, or do you have a lokal fotodealer at home, and don't go on internetshopping? is it very expensive to start a new collection of those cokin filters or are they at a moderate price level?