dante stella stories photographs technical guestbook
|Half of one, six dozen of the other?|
|The plastic fantastic|
Men reach a certain argumentative age where discourse inevitably turns to one of The Hobbies (fishing, cars, photography, guns). And it is difficult to understand how some internet rhetoric passes for legitimate argument. Take a tiny subset of the camera Hobby: the subject of plastic filters sold by Cokin, Lee, Hi-Tech, and Singh-Ray, among others. Cokin filters are denigrated; Singh-Ray are exalted. But is there much to this?
The first question is whether these are even differentiable as products. All of these manufacturers use eyeglass-grade materials to make their filters. All such filters depend on an eyeglass-type dyeing process (you know the process that gave you gradient-pink eyeglasses in the early 1980s? Voila!) All manufacturers omit to put optical antireflection coatings on that material. All such filters fit into lens-front mounts that are difficult to combine with glare protection. All such filters are easy to scratch. All such filters are standardized to Cokin P, 75mm width or 100mm width.
So that brings us to the $100 question - why buy a Singh-Ray, Lee, Hi-Tech, Hoyarex, or other expensive filter over a cheapo Cokin? This is actually a lot harder question to answer than you might think. Here are some of the answers you will see and some of the counter-questions those answers should trigger.
"Brand B is more consistent." Absolute consistency was a bugbear when everyone used transparency film and needed to be able to replicate the same type of shot, again and again, in a studio environment, on a testy film that served as the final product. But this was a conceit because you had to test and calibrate every batch of film (different emulsion number). And if you were careful, you did the same with every change of light bulbs. So "wearing out" a filter and recalibrating for a new one a couple of CCs or hundredths of a density unit off was no more of a problem than buying a new case of film. Of course, all of this depended on your process's being consistent enough for a filter's consistency even to matter. Today, studio transparency work is all but dead. And with color negative film and digital photography, you make your one-time adjustment and just shoot until the photos wear out your filter. This is a very negligible issue.
"Brand C is more neutral." This may also be an internet myth, but the conditions under which it can be tested may call into question the sanity of the tester. There are claims that certain brands of plastic filters have a "color cast," but in the case of the use of a single filter at a time, no one has ever pointed to densitometric (or colormetric) data demonstrating that one brand is better than another. The one almost-good case for this is where you stack multiple neutral-density filters and get some color cast (i.e., the tolerances are adding up). But then you have to question why, if you need 64x the exposure across the entire field, you aren't using a dyed-in-the-mass B+W solid glass filter (which would actually be a lot cheaper than buying and stacking any brand of ND). And on the plastic filters, a uniform cast in the substrate is easily corrected out the same way you white-balance a scene.
"Brand D is optically better." This is interesting theoretically, and it might be the one reason you might think about buying on the expensive end. People talk about stuff like this, but most users aren't sitting around with interferometers checking the flatness of their filters. The chances seem pretty high that all plastic filters are made of the same material - possibly from the same manufacturer. That might be why there is a decided reluctance of manufacturers to talk about their materials except in the vaguest terms like "resin" and "mineral glass."
We know that lowly Cokin uses CR39 (a material that has almost identical refractive index and Abbe numbers to crown glass used for lenses). And we can probably surmise that every higher-end company uses it too (since Plexiglas and polycarbonate - Lexan - are inferior optically and mechanically). In fact, given the relative performance of available plastics, any company that claims it is using a plastic other than CR39 should probably be avoided.
So is everyone buying CR39 sheets from plastics manufacturers, dyeing them, and cutting them down? That may well be the case - since glass filter manufacturers with far greater volume (like B+W and the Tokina, which makes Hoya filters) do not make their own glass (Lee says it "casts" its own filters but does not otherwise describe its processes). And with plastic, unless manufacturers are also polishing them and planing them to tighter tolerances than the commodity, there will be virtually no appreciable optical difference from one brand of filter to the next. The one differentiator might be dyeing solid-color correction filters in the plastic itself, but for these, like the NDs, it's questionable why you wouldn't just go to a solid glass item.
"Brand E is glass." Oh yes, the trick question. Some manufacturers make glass filters that fit the holders for plastic filters. Don't be distracted by the fact that these are glass; most are two sheets of glass bonded to a central sheet of polyester or gelatin film with the coloring. You can even make these from "water white" glass (which has very, very tight tolerances), but unless the finished product is controlled with as much precision, it may be optically inferior to a single thin piece of plastic. The one advantage of these is that being made from Wratten and similar filter sheets, they are consistent. These filters by and large are not coated, either. Glass is, however, more scratch-resistant.
At the end of all of this, the question still remains what really separates the "high end" from the "low end."
Otherwise, for the casual user, going expensive may just be paying more for the same thing. So the bottom line to all of this might just be to buy the cheapest version of a filter that does what you want it do.
The Cokin question
Among the most despised filter makers of all time, Cokin has tried - a bit belatedly - to rebadge its over-the-top effects filters as ironic. It has also dumbed-down its catalog, both in selection of filters and in the replacement of endless pictures of bare breasts on beaches with anodyne and provincial pictures of the French countryside (and some significantly less attractive models). Cokin does note that it is a supplier to NASA's Space Shuttle program, for what that is worth.
Is there any value to Cokin filters? Aside from the conventional color correction and gradient filters, there is a certain entertainment factor to the Cokin Creative Filter System. Following the transition to digital, very few effects filters survived, and if you are out to humiliate your children with 1970s-style effects, are you really going to pick up a 300-page book on Photoshop to learn to simulate some of them? No way- you are going to go to Ebay, buy some Cokins by the pound, keep your expectations low, and have some fun. Here are some highlights:
Most of these have been discontinued, so if you are looking for one (minus the scratches), you should step on it.
And really, who is going to laugh at you? Today, people are buying terrible Holgas, Dianas, and Lubitels for their analog badness. Are you really going to tell me that anyone is going to ridicule you for using a fog filter? Who? The nerdy guys with the fishing vests and the Leicas? The soccer moms? The dad still using a Canon AE-1? That gentleman with the Linhof?