The problem of filtration when using ultra wide-angle lenses with bulbous front elements has been a thorn in the side of photographers wishing to take advantage of these stellar optics. As a whole, these lenses are never threaded for filters as the front element's convex construction prohibits threads. The hoods for these lenses are usually fixed, as well, and given their unique nature, makes it impossible for a single holder system to work on all variations without significant modifications to the holder for each different lens.
I came across a DIY describing how an intrepid photographer was able to adapt a Lee Filters SW-150 150mm filter holder onto his Samyang 14mm ultra wide-angle lens. (Currently, the Lee SW-150 filter holder is made only for the Nikon 14-24mm f2.8.) The process, however, mangled the scarce and expensive filter holder and there was still the problem of there being no circular polarizer that was currently available for the 150mm system. (Some have adapted circular polarizers meant for other applications for use with the SW-150, however.)
Formatt-Hitech make a system for ultra wide-angle lenses that have several adapters for various lenses, including the popular Samyang 14mm. The Hitech LucrOit system looks to be a well though-out solution, but until recently it was very difficult to find the product in stock. After playing the Lee Filters stock game I wasn't looking to double down on that particular experience. The LucrOit system also does not allow you to mix square/rectangular filters and circular threaded filters. In fact, there are no threaded filters available for the system, period.
Enter Fotodiox. This American company, based out of Illinois, developed a near complete system for fixed hood, bulbous front element ultra wide-angle lenses called WonderPana 66. Reading the description, I became excited.
The WonderPana 66 uses a base kit specifically designed for a lens to mount circular, double-threaded filters which Fotodiox call the WonderPana 145 Core Unit . Onto this foundation one can optionally install a rail kit, called the WonderPana 66 Upgrade Bracket. This bracket allows you to install either two rectangular filters or one screw-in filter and one rectangular. It's made of aluminum and attaches via thumb screws so you don't need tools when you're out in the field.
Unfortunately, the thumbscrews that tension the rectangular filters in the Upgrade Bracket are of a different length than the thumbscrews that mount the bracket to the Core Unit. This has the potential to frustrate if you are looking for one type and pick up the other, which apart from slight length difference appear nearly identical. The longer filter tensioning screws will not work as bracket mounting screws. The tensioning itself is not unlike the way the Schneider/Century Optics variation of the Lee Foundation Kits secure slide-in filters and it works very well. (If only Lee would adopt something similar to their basic foundation kit, but I digress.)
The Core Unit is novel in both its method and construction. Other methods for attaching large filters to lenses not designed to accept filters might require the user to push on the foundation holder, similar to the way you push on a lens cap for slim filters that have no front threads. This method can be secure, to be sure, but the Wonderpana system uses threaded collar that slides over the back of the lens and screws into the front of the unit resulting in a very positively locked system, similar to Lee's SW-150 holder. All of the Wonderpana components, however, are made of aluminum.
Onto this core attaches the rail bracket with brass thumbscrews. In the above picture I used four total but there are holes for six. The small thumbscrews are fiddly to work and would be very difficult with gloves on. In fact, attaching the bracket is best done where you have a clear surface to work on. Out in the field this entire operation could prove nerve-wracking - balancing the lens and collar, lining up the holes, screwing in the thumbscrews while keeping the two pieces, lens collar and bracket, from moving. Once you get one thumbscrew in, however, the rest of that side is a piece of cake.
For scenes where you'd like to place the ND grad transition line at an angle, it is possible to rotate the bracket about the core unit but you're limited to rotating in 45° increments. This isn't ideal, but it sure is better than having to compromise your placement by only being able to work with perfectly horizontal transition placement. To rotate the rails you must unscrew them from the core unit and re-mount them in the angled configuration. There are another set of mounting holes for this.
The WonderPana's rectangular filters are HUGE. We're talking 168mm wide huge. In comparison, the Lee SW-150 filter holder accepts filters that are 150mm on the wide side. The estimable and popular 4x6 filter, above, looks like a Cokin P compared to the WonderPana.
Not only are the WonderPana filters large length and width-wise, but they are also thick. Hitech's Lucroit filters are 3mm thick and that's already pretty robust. WonderPana filters are 4mm thick and unless you hold it in your hands you might not have an appreciation for just how much filter that is. Lee's 150mm filters are like their 4x6 filters in this regard, half as thick at 2mm.
The WonderPana rectangular filters are multi-coated (!), which makes them unique among this large class of filter, and made from organic glass called CR-39 or "optical resin." If you wear corrective lenses, optical resin is the material the lenses are probably made of. Plexiglass is also a type of organic glass. CR-39 is a high quality transmissive material that's cheaper and lighter than glass but won't (read: shouldn't) shatter when dropped.
The system comes with a complete line of standard neutral density filters, 4ND, 8ND, 16ND, and 32ND in 145mm screw-in configuration, and four graduated neutral density filters, 2 and 4-stop versions of both hard and soft graduation. There is also a clear protective UV filter and a circular polarizer in 145mm available. To top it off, Fotodiox include a 145mm lens cap to protect that precious front element when the system is attached without filters. All of the components come very well appointed. The rectangular filters come in large foam-reinforced nylon zippered pouches that are plush on the inside. For some reason there is also a mesh pocket on the inside of these pouches. I suppose you can keep a microfiber cloth in the pocket, but a microfiber cloth doesn't need a pocket to be stowed. I find that the pocket catches the filter when the filter is slid in more times than not. The internal pocket annoyance is one quick scissor procedure away from being corrected. The screw-in filters ship with nylon pouches similar to the blue B+W pouches that Velcro close. The hardware components, the core unit and bracket, ship in zippered hard clamshell pouches with flocked foam fitted inserts.
Looking at the 145mm ND filters one notices that the reflected color of the filter themselves changes rather dramatically from the 2-stop to the 4-stop. The color of the 2-stop is bronze while the 4-stop is greenish.
It's not clear if Fotodiox make these filters in-house or outsources some or all of them. Interestingly, the 145mm circular polarizer is labeled "XS-Pro" on the ring. XS-Pro is B+W's designation for their slim form digital filters that are thin for ultra wide lens use yet retain front threads for filter stacking or a lens cap. Do B+W make at least the 145mm circular polarizer for Fotodiox?
Regardless, there is a reassuring physical quality to both the 145mm screw-ins and the 168mm rectangular filters. There is no play between the glass and the filter ring that I could detect. The ring of the circular polarizer rotates independently and does so smoothly but not loosely - it stays where you rotate it - similar to high quality rings from B+W and Singh-Ray.
But how do they perform?
Using a Canon 24-70mm Mark II mounted on a Canon 5d Mark III, here is the scene without filtration or processing of any kind. (Was it too difficult to get some clouds?)
Here's the same scene with a Singh-Ray 2-stop soft graduated neutral density filter. In attempts to create as level a playing as practical using two such different sized filters, I slid the Singh-Ray down into the scene until the meter went from 1/1250th of a second, which is where the baseline image was taken, down to 1/640th of a second and immediately stopped and took the picture.
Using the same method, I slid the Wonderpana 2-stop soft graduated neutral density filter into the scene and stopped when the meter hit 1/640th of a second. It's not scientific but it is illustrative for our purposes.
The scene is remarkably similarly rendered.
After a predictable corralling of the blues in the skies you can see that the filters were slid down enough to affect the greens in the trees, too. The Singh-Ray brought more into the midtone region, note the green channel, than did the WonderPana. Both affected the highs in much the same way if they are not nearly identical.
Here's a more chaotic baseline scene. The scene has a smattering of detail, a great area for testing the polarizer, and it blows out through the trees. The should give us some convenient examples for comparison.
This is the same scene with the WonderPana 145mm circular polarizer installed. Notice the reflection on the siding of the house in the upper left corner.
I was concerned that a multi-coated 145mm circular polarizer that costs $120 would create some problems with resolution and sharpness. After all, quality multi-coated circular polarizers in 82mm can cost over $250! We're talking 63mm more filter for $130 less.
Mind you, this area of the image was outside of the polarized band that affected the siding reflection. (On extremely wide angle images, polarizers cannot affect the entire image. This usually creates a noticeable band of polarization over just a portion of the image.) However, the lines of the leaves are well maintained with no noticeable amount of resolution lost.
This is significant because in this area of the image light has to travel at an angle through the filter that is most extreme, so light goes through more filter glass at the edges than anywhere else in the image, if only very slightly so. If there are going to be imperfections, they should be most pronounced in this area.
There are no painful shifts in color. Many circular polarizers like to cool scenes down. Not so much here. The blues are nearly cemented in place. Corrected for light lost, there is a general midtone drift as you might expect.
Back to the baseline image.
To bring the 2-stop ND back in line with the baseline image required just +1.07 exposure adjustment, not 2 stops.
By the time we get to the 4-stop ND there is a very noticeable color cast. Correcting out magenta can sometimes be quite a pain compared to, say, a blue shift. If one has to deal with a color, pray it's of the blue variety. Other color shifts, like bronze and magenta, can lead to hours in post, fiddling with sliders and pulling hair.
You can see the red channel breaking away from the rest in the ND32's histogram. For its part, the ND4 holds up well where this is concerned. The adjusted ND4 image is a good facsimile of the baseline image, if only slightly more red. Then again, it's not a significant deviation, requiring only +1.07 stops to compensate for.
Thinking back on the reflected color change of the physical filters themselves, going from bronze to green, perhaps whatever change to the formula that is used to create the stronger density resulting in the green reflection is the culprit in the drastically more reddish example image. Who knows but the wizards concocting the density formulas.
Here again the sharpness seems nearly unaffected. Contrast is subtly affected and now there's a visitor on the flamingo, but apart from that there is little different between the two images. The slight red that was hinted at in the histogram can best be seen in the brickwork here.
Back to the baseline...
After the predictable midtone drift, the WonderPana 2-stop soft grad does well with color. Again, we have a slight reddening of the affected area, which is now the upper half of the image.
This close-up of the corner is really only a test of the quality of the resin used in the WonderPana system. As mentioned earlier, this area, and indeed all the corners, represent where the filter is at its thickest with regards to light travel. The CR-39 shows how little quality resin affects the resolution of an image even at 4mm thick! That impresses me.
After having used just about every piece currently available in the WonderPana 66 system, I feel the quality is overall better than I expected. I was, however, disappointed with the fiddly nature of the optional bracket, but considering the all-aluminum design I'm not sure there is a practical alternative that keeps the design tool-less, which I'm sure was a major goal of the Fotodiox engineers. The color cast of the amittedly low intensity ND filters is not without precedent, even by filters from highly reputed manufacturers, like Formatt-Hitech and Cokin, but it's unfortunate that the cast wasn't blue. At least it's not bronze. /shudder
Also, I would have liked to see a more convenient way to rotate the rectangular filter rails for scenes where you'd like the transition line for the grad filters to be at an angle. A clip-on rail bracket, similar to what's employed by the Lee Filters Foundation Kit would have been preferred. This design change might also alleviate the need for the user to juggle two different length thumbscrews. This, of course, could have made the bracket more cumbersome in packing and carrying, but the trade-offs, at least on the face of it, seem to be worth it. Unlimited angle choices isn't a minor thing. For some, though, angle options at 45° intervals might be just fine.
Attached to the lens, the system seems bulletproof. It's going to last quite a while if you take care of it, so as a long term investment the WonderPana should satisfy there. And since Fotodiox include high quality pouches for all the pieces, protecting the components shouldn't be a problem.
Best of all, the system is nearly complete. Hitech's LucrOit system may have more slide-in options, like alternate colors or the very popular reverse grad ND, but LucrOit doesn't have a convenient polarizer, nor can you use screw-ins, which don't have a habit of falling off when you're moving about. Were Fotodiox to come out with a reverse grad and a 10-stop ND there wouldn't be much reason you'd ever have to leave the WonderPana system.
Speaking of completeness, Fotodiox now make a series of step-up rings that allow you to attach the 145mm screw-in filters onto conventionally threaded lenses. It's possible that you could take to the field and only have to carry one set of filters! You cannot, at this time, connect the Optional Bracket for the slide-in rectangular filters to the step-up rings, however. (This would be another limitation that could potentially be avoided with the aforementioned clip-on style bracket design.)
The Fotodiox WonderPana 66 system cures just about everything that ails the ultra-wide angle landscape photographer.
EDIT (9/24/13): Fotodiox have upgraded the WonderPana Core so that it now allows the Upgrade Bracket to rotate. You can now set the graduated NDs at any angle you need. That's great! The new Core Unit is now branded FreeArc, but is currently only available for the Nikon 14-24mm. Hopefully, Fotodiox won't waste time getting FreeArc support for the other UWA lenses like the ubiquitous Samyang 14mm.