I actually came across this
blog from award-winning Darwin Wiggett and have inserted the portion dealing with this issue here:
" Vignetting – A Super-wide Reality?
"Speaking of vignetting, I have found -- based on numerous tests -- that when wide-angle zoom lenses are used at their widest angles, the edges of the photos will 'see' the edge of the filter holder and cause every image to have darkened edges. I also have found that -- with full-frame-sensor cameras -- the P-size filter holder and/or the sprocket-mount polarizer will cause vignetting on lenses wider than a 24mm fixed focal length lens or wider than 28mm on wide-angle zoom lenses. For example, I see no vignetting with my Canon 24mm TSE (version 1) tilt-shift lens, but I do see serious vignetting at 24mm on my 24-70mm zoom when I'm using my sprocket polarizer and a P-size holder. And you will likely get vignetting with a P-size holder and/or a sprocket slide-in polarizer on any full-frame camera with a 17-40 or 16-35mm zoom lens unless you limit your shooting to focal lengths of 28mm or longer. (See editor's note below.)
"The smaller size of APS sensors, however, enables the use of zoom lenses as short as 17 or 18mm without vignetting. That means many popular lenses such as a 17-40, 17-55, or 18-200mm work well with a P-holder on such cameras. If you do not own or plan to own lenses wider than 17mm with your APS camera, it's safe to use a P-size holder without running into vignetting issues. Some lenses like the 10-20mm, 10-24mm or 12-24mm -- which are designed specifically for APS cameras -- will vignette with the P-size holder if used at focal lengths of 13mm or shorter (unfortunately the polarizers that fit into the P-holder cause further vignetting with these lenses up to about the 14-16mm settings). None of the tilt-shift lenses I use (the 24, 45, or 90mm TSE lenses) or either of my longer lenses (the 70-200mm f4L or 300mm f4L lens) vignette on my full-frame camera with the P-size holder.
"Some photographers have come up with ingenious ways to overcome their vignetting issues with wide-angle lenses and P-sized filters. Many successful photographers just use a thin-ring polarizer on the lens and then hand-hold their grads in front of it (as already discussed). Others use P-size holders that have only one main filter slot (but this option limits the use of multiple filters). Others use rubber bands, clamps, tape and other devices to hold their filters over the lens – for example, see Kevin McNeal’s solution here.
"For a number of photographers, however, the frustration of vignetted edges really makes the P-size holder an unusable option. What is their solution?
Going Big!
"The 'really big' solution for using multiple filters on wide angle zooms -- such as the 16-35, 17-40, or 24-105mm when they're used on a full frame camera or the 10-20 or 12-24mm on an APS-sized sensor -- is simply to get a bigger filter holder with bigger filters so they do not intrude into the angle-of-view of the lens.
"The Z-Pro holder holds 4x6-inch grads (100 x 150mm) and the Z-series polarizers. In my tests, none of the wide-angle zooms I tested (10-20, 10-24, 17-40, or 24-70mm) vignetted with the Z-Pro holder. Using the bigger holder, I can still use Cokin's Z-series polarizers (not currently available from Singh-Ray) plus Singh-Ray ND grads and a solid ND filter to get the same beneficial effects I get when using the smaller P-sized filters and holders.
"The problem with the 4x6 sized holders is that they are much bigger (see Photo 6) and more expensive compared to the P-holder. The higher cost makes it hard to justify a holder on each lens and it is also very hard to fit lenses with an attached 4x6-inch holder into a camera bag or vest. If you do go with the bigger holder, it will mean more time spent attaching and removing the holder whenever you switch lenses or put the camera away. However, the benefit of the larger holder is that you avoid most vignetting issues and you'll have a filter system that works on all the lenses you own.
"When I backpack, I will often take my 17-40mm or 24-70 mm lens with my full-frame camera or my 10-24mm on my APS-sized camera. Whenever I use these lenses, I always take my Z-pro holder and my 4x6-inch filters so I do not have to worry about vignetting. The reason I do not hand-hold grads in front of my lens is mostly because I like long exposures (from 4 seconds to 4 minutes) and holding filters that long is problematic. I also like using a holder to mount multiple filters and the 4x6-sized holder solves the problems I get when using these wide-angle zooms. For example, Photo 1 at the beginning of this story was taken using my 24-70mm lens at 24mm on my full-frame camera. I used the Cokin Z-Pro polarizer, a 4x6-inch Singh-Ray 2-stop hard-step ND Grad over the sky and sunlit peak and a Singh-Ray 5-stop Solid ND filter to lengthen the exposure for more cloud movement and color build-up. The total exposure time was 118 seconds -– I could not hand-hold three filters for that long! The Z-Pro holder allowed me to stack all three filters with no vignetting to get the final effect I envisioned.
"So... as you're building your own filter system and deciding what size filter holder to buy, it will help to keep all these various questions and issues in mind. As I said before, it all depends... Happy filtering!"
You will want to visit Darwin's newly 'overhauled' website and blog -- it's truly impressive."
