hoya hd polarizer

While I'm waiting for U.S. online retailers to stock Hoya's new HD UV and Circular Polarization filters (typically, my local B&M hasn't even heard of it yet), I thought I'd go over what's groundbreaking about these new filters.

Apparently, "HD" refers to the new hardened glass used in these filters. To be blunt, I don't see why they bothered. The reputed benefit is impact resistance, but keeping in mind that the glass is protected by the metal ring, you'd have to be jabbing it with something very hard, not just dropping it. I suppose some war-zone journalists will appreciate the extra durability, but I doubt it will make a difference to the vast majority of photographers, professional or otherwise.

More useful, the coatings on these new filters are scratch- and stain-resistant and waterproof. I have no idea if this translates to any real-world advantage (I mean, are other coatings not waterproof?), but I welcome any improvements in these areas.

And that's it for the differences between this and Hoya's previously top-of-the-line Pro1 Digital UV filters. And that's not even close to worth replacing my existing Hoya Super HMC UV filters. The polarizer is something special though.

The headline feature of the new Hoya HD Circular Polarizer is a new polarizing film. Actually, it's not new at all, according to THK Photo, the U.S. Hoya distributor: this is the polarizing film used to reduce glare on LCD HDTVs. Hoya claims "25% higher light transmission" over current photographic polarizing films, which presumably refers to the light transmitted when the polarizer is set for minimum effect. This sounds pretty good, but according to their chart, it's even better than Hoya's poor grasp of English would indicate. What's really going on is, at least over the middle part of the visible spectrum (the greens and yellows), the new film transmits ~86% of the incident light, compared to ~61% for standard polarizing film.
That's 41% more light than standard film transmits. In photographic terms, the new film lets through half a stop more light than previous polarizers. Not earthshattering, but could be enough of an advantage to make polarizers practical indoors.

I spoke to representatives of THK Photo and my normal filter supplier, The Filter Connection, and I gathered from their vague descriptions that this filter should be just as flare-resistant and color-neutral as previous Hoya efforts.

I'm willing to take this at face value until proved otherwise, but looking back at Hoya's light transmission chart has me a bit concerned about color neutrality. The line for the standard polarizing film is flat between 400nm (violet) and 650nm (red). By contrast, the new HD film is only flat in the narrow range of about 500 to 600nm. In the reds, light transmission gradually rises, but less so than for normal film, so this doesn't seem to be a problem. The problem is in the blues and violets. The downward slope steepens at 500nm, until, at about 425nm, transmission takes a nose dive, touching 0% at 380nm. While this is a marked improvement in terms of UV filtering (380nm is about the lower limit of what the human eye can see), DSLR sensors are very insensitive to UV light anyway. The really bad thing is that most of the far violet light is being thrown out with the bathwater. Perhaps worse, the drop in the 425-500nm range means a sizable attenuation in the blues as well—and the most common use for a polarizer has to be generating deep blue sky. In other words, this new polarizer, even when not polarizing, should be something of a UV/Warming filter.

How much this can be seen in practice is anyone's guess until they start showing up in stores and being used to take pictures. Despite my poor success rate with new camera equipment to date, I'm willing to take a chance.