Cokin P-sized versus the Larger Lee-sized Graduated ND Filters
While there are some outliers such as Cokin's tiny "A" and gigantic "X-Pro" sizes, in the world of rectangular graduated neutral density filters, it generally comes down to the pervasive Cokin "P" size and the somewhat larger and somewhat less common Lee size. But while Cokin may have invented the 84mm-wide "P" size, Singh-Ray has played perhaps an even bigger role in popularizing it by creating their high-quality Galen Rowell line of compatible filters. Now that Singh-Ray has also started offering their own version of the larger "Lee" sized grad ND, it's worth a look at the pros and cons of each size.
I've long been a user of Singh-Ray "P" sized graduated filters. They've represented a good compromise between being large enough to cover the 77mm filter diameter Nikon seems so fond of, yet not so large as to be inconvenient to carry. True, they require the use of a single-slot holder to prevent vignetting on extreme wide-angle lenses, but this has rarely been inconvenient. The most common other filter for nature photography is a polarizer, and using one on lenses with such a large angle of view would cause uneven coloration across the frame anyway so I rarely feel a need to use both when going wide.
| Filter Brand and Series
|| Filter Width
|Lee "4 x 6" and Cokin "Z-Pro"
Apart from removing the limitation on stacking filters on wide angle lenses, the argument most often heard for using larger filters is that one can hand hold them, dispensing with the holder and adapter ring completely. The lure of being able to work more quickly in this way resulted in my recently getting a new Singh-Ray Lee-sized filter for testing and comparison. As my first foray into the larger size, I ended up with a 3-stop hard-edged grad. I find that while I like the larger size, at the same time I'm not ready to give up my existing "P" sized grads either.
I like the precision inherent in being able to position a graduated filter exactly where I want it in the holder. In order to minimize the probability of the filter transition showing, I tend to spend a reasonable amount of time moving filters up and down until I have them just where I want them. And once I do, I want them to stay where I put them. While hand-holding a filter is definitely convenient, I have yet found no way to get the same ability to accurately position them when doing so. Some subject matter though lends itself to one technique more than the other. For quickly changing lighting, it may be acceptable to trade accuracy for rapid response. Switching from horizontal to vertical aspect ratio takes me time since I have to reposition any filters. Doing so when the light is quickly changing has I know cost me shots. At such times, I now reach for my Lee-sized grad ND instead.
I've found that with hand-holding, I can intentionally move the filter around during the exposure to simulate the effects of a softer edged filter. This makes my one hard-edged Lee do double duty as a variable soft-edged filter, something completely out of the question with smaller filters. With an 84mm-wide "P" filter hand held, you'd never be able to keep it safely over the front of most modern lenses, and with it in a Cokin holder, any attempt to move it would obviously induce camera vibration. The 97mm-wide Lee-sized filter is big enough to keep fully over the front of a lens while still allowing freedom of movement if desired.
Hand-holding also makes it easier for me to use more than one filter at the same time. I can accurately position the most critical filter in a "P" holder and hand hold a second one, even at a different angle, in front of it. This works great on wide-angle lenses too, so I can now use more than one filter even with the Nikon 12-24mm DX zoomed all the way out. Pretty cool.
Some may wonder whether there is still a need for graduated neutral density filters at all in this modern digital age. While there are now numerous ways to digitally adjust the exposure of part of an image after the fact, it still seems prudent to get it right in field to the extent possible. Merging multiple exposures in Photoshop requires that nothing moves between when the constituent shots were made. If the wind is blowing and anything does move, it will register as a blur in the composite result. This is not to suggest that you can't use multiple techniques when appropriate of course. Graduated ND filters may be used only to get you in the ballpark and avoid burned out highlights, allowing you to adjust levels from a single shot later in Photoshop, giving you an option for those subjects that defy easily hiding the filter transition zome. Extensive Photoshop work can also require extensive amounts of time. If grad filters can mean I can get the results I want more quickly, they remain an excellent investment.
Of course, larger filters do cost more than smaller ones. Bigger filters mean more acrylic needed to manufacture them, and more potential quality control issues. So I think the decision of which size best fits their needs must fall to each photographer. In my case, rather than trading one size for another, I now carry both with me in the field. I don't regret it, since I can now have accuracy or flexibility on demand, as each situation warrants. I get to have my cake and eat it too I suppose.