Tuesday, April 21, 2009

Filters, holders and vignetting: building a filter system that works with your lenses


When outdoor photographer and author
Darwin Wiggett writes about filters, he's speaking from his own years of successful experience. His series of stories featured on this blog have become a trusted reference source for many visitors. Now Darwin reviews the complicated topic of filter holders and vignetting, and offers us his personal perspective based on his own methods, experience and equipment.

"I hear from a lot of photographers wanting to know which filter system and filter holders to buy for their lenses. The answer of course is: 'It depends.' No one system will work best for everyone, and I can only speak from my own experience. Let’s start with the basics.

Ring-mounted Filters vs Sprocket Ring Filters
"There are two main ways to attach a filter onto your lens. The simplest way is to use a threaded ring-mounted filter which screws onto the filter threads on the front of your lens. The big advantage to buying ring-mount filters is that you need no special holders or gadgets to hold them in place; they simply screw onto the lens. For my photography, however, there are two disadvantages to ring-mount filters. First, my lenses don't all have the same size filter ring on the front element. I would need to either buy a different size filter for each lens or I could buy a filter to fit my largest lens and then use step-up rings to fit that same filter onto the front of my smaller lenses. Secondly, whenever I change lenses, I would have to switch the filter from lens to lens which takes valuable time and usually occurs just when the light is at its best and fleeting quickly! And the colder it is outside, the more difficult it is to unscrew a filter from my lens. Many times I have had a threaded filter stuck on my lens from the cold. I'm guessing that having to switch ring-mount filters from lens to lens leads many photographers to just give up on filters, or end up buying a filter for every lens they own. I know several landscape photographers, in fact, who keep polarizers on each of their lenses, just to avoid the need to switch from lens to lens.

"So, instead of ring-mount filters, I have for some time used the slim, rectangular, optical-resin filters that fit easily into slots in my Cokin P-size filter holder. This popular filter holder has become the 'industry standard' for serious outdoor photographers, and several filter companies make the flat 84 x 120-mm 'P-size' filters for this holder. This system offers me a wide choice of graduated neutral density, solid ND, and even polarizing filters -- the polarizers are mounted into special 'sprocket' rings that slide into the very back slot of the holder and can be easily rotated with the tip of my finger. Cokin also makes a bigger Z-Pro holder for larger lenses (more about that later). Photographers shooting with digital SLR cameras generally use a P-size or Z-Pro-size (4x6-inch) holder.

"By having a holder mounted on each lens, I'm able to swap filters from one lens to another very quickly -- even under frigid conditions. For me, that's the main advantages of filter holders -- I only need to buy one set of filters that can be swapped from lens to lens. Swapping filters is very fast if each lens has its own holder. Graduated Neutral Density filters (ND grads) can be precisely placed and firmly held in the filter holder, and best of all the holders have three slots to allow me to easily 'stack' several filters together. What's more, I only need to handle and adjust one of each type of filter -- such as my polarizer -- as I change lenses. I use a holder on each of my lenses to hold my various P-sized filters from Singh-Ray. These include the sprocket-mount LB Warming Polarizer and Gold-N-Blue Polarizer, plus a number of rectangular ND Grads and the 5-stop Solid ND filter. If you do not know the benefits of using multiple filters see this link. And if you're not clear about what polarizers and ND Grad filters do and which ones you should consider buying, there are numerous articles on this blog discussing the advantages of these and other types of filters.

"To mount filter holders on each of your lenses, you will need an adapter ring of the correct size to fit the filter thread on the front of each lens (photo 3-A). Once you have threaded the adapter ring onto the lens, slide the filter holder onto the front flange of the adapter ring (photo 3-B).

"Then you can slide in your ND grads or other filters of your choosing. Photo 3-C shows my Singh-Ray sprocket mount LB Warming Polarizer being placed into the rear slot of the P-holder.

"In spite of the many advantages to using filter holders, there are some drawbacks to consider. First, to make switching filters fast and easy, you need to outfit each lens with a holder like those shown in Photo 2 above (note, the holders are shown with a lens cover in place). Having holders on each lens means some added expense for the holders and adapter rings, but this option is still less costly than buying a filter to fit each lens.

"Also having a holder permanently on a lens means that it takes up more space in the camera bag, and you can’t use the lens hood that comes with each lens (lens hoods can help reduce lens flare in many back-lit situations).

"The other main drawback to filter holders is the possibility of vignetting. When a filter holder is attached to a wide-angle zoom lens, chances are good that the lens might 'see' the holder at the edges of the image frame. I will cover some ways to overcome this vignetting problem shortly.

To Use a Filter Holder or Not?
"If the only filter you ever use is a polarizer, then I think there would be no real benefit to using a filter holder. Just buy a polarizer in the sizes you need for your lenses. As a landscape photographer, I believe polarizers are the most important filters I own, and I use one on almost every shot I take. Whether you leave a polarizer on the front of your lens all the time or not is a personal choice, but I think it makes more sense to have a polarizer on each lens for ‘protection’ than a UV filter that offers no optical benefits!

"If you use or plan to use several filters at the same time, then you need to consider whether to use a filter holder or not. I regularly combine a polarizer and an ND grad filter for my photography. For example, the Photo 4-A shows a scene captured without the benefit of any filters.

"Photo 4-B shows the benefit of using a Singh-Ray LB Warming Polarizer to saturate colours and reduce contrast in the bright sky while photo 4-C shows the combined effect of using both a polarizer and a Singh-Ray 2-stop hard-step ND Grad over the sky and mountains to further reduce contrast and control exposure across the frame. The benefits of combining the two filters are obvious. (Click image to enlarge.)

Hand-holding ND Grads
"Some photographers hate filter holders because they take up space and add extra weight in their camera bag and often cause vignetting with wide-angle lenses. These photographers most often use screw-on polarizers and when they need to add a Graduated ND filter, they just hand-hold the filter in front of the lens. Some popular landscape photographers who hand-hold their grads are Kah-Kit Yoong, Marc Adamus and Art Wolfe. Most photographers who hand-hold their ND Grads opt for the larger 4x6-inch (100 x 150mm) rectangular filters because there is less chance their fingers or the edges of the filter will show up in the photo.

"Personally, I rarely hand-hold my ND Grads for several reasons. First, whenever I do, I almost invariably bump the camera lens during exposure, or knock the filter on the front of the lens, or drop the filter because my hands got cold, or fog up the filter from the heat of my hand, or get sore arms holding the filter for a 4-minute exposure. In short, I suck at hand-holding! So that's why I much prefer to use my filter holders.

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.

Editor's Note: With so many possible combinations of cameras, lenses, filters, holders, and other factors, it's virtually impossible to predict exactly when vignetting will occur, and to what extent, without actual testing. Also, when selecting a filter, it is important to weigh the benefits the filter offers against using a lens at its widest angle setting. It may be possible to compensate for potential vignetting by modifying camera position, focal length, composition, or other adjustments. Click here for more information.

2 comments:

A. Dean Lynn said...

Finally, an explanation that actually makes sense and that I understand. Thank you for clarifying this issue

T.E. said...

Indeed great presentation, as my earlier colleague said, thank you for that, a few "convictions" have changed though, but it's better than learning the hard way :)