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Will the real infrared photography please stand up?

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The strange thing about infrared photography is that it represents a very small piece of photography in general, but there is apparently no space in photography so small that it can’t support some form of snobbery. And in infrared photography, it is the idea that there is “near” infrared versus “true” infrared. Not only does this convey a false sense of exclusiveness to people who shoot 850nm and up, it’s also not accurate.

When you shoot a normal camera in daylight, there is a small amount of infrared contamination – it’s about 10 stops less than daylight, or coming in at 1/10 of a percent or 1/1024. Tiny, even on something with big infrared contamination like a Leica M8. So any particular shot is overwhelmingly lit by visible light.

A dark red filter (RG630, 091, 8x, #29, etc.) flips the equation: the average blockage of visible light is 3 stops, or 75%.The reality is that most skylight scenes are predominantly blue, and this filter cuts a lot more than three stops. Even if you are shooting objects that are middle grey, these filters reject 75% of all light – meaning that when you shoot them on a camera with no other IR rejection, deep red and infrared light make up 75%+ of the light. The false color you are obtaining is infrared light that is still being blocked in part by green and blue squares on the Bayer filter on the sensor.

The case for the “near” classification is even weaker with the 695-720nm filter (RG695, 092, R720). First, consider that wavelength ratings on filters are at the 50% mark. So a 720nm filter really starts passing 100% of its light around 750nm. On a short exposure, which you will see is commensurate with a normal visible-light exposure, infrared light is providing almost all of the illumination.

Going the other way, “true” infrared is not that advantageous – and may not be something to commit to in an IR conversion. First, even though the Bayer filter does not affect 830nm+ light, the decoding algorithm in your camera still compensates for it. So if you dump the RAW file into DCRAW, what comes out still has something of a checkerboard pattern. Second, the false color effects generated by mid-band IR actually allow for more contrast control because there are multiple channels of useful information (and with 850nm+, you really need this, since everything likes to come out bright white in sunlight, especially around dusk). Eliminating this effect means that you have less ability to rebalance the tones in a scene.

None of this is to say that it’s good to meet one form of snobbery with another technical one. But let’s just keep the infrared world big, okay?

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Twelve filters for digital: what’s hot and what’s not

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B+W 491 redhancer

Hot

  1. B+W 010 MRC – pretty much the highest-quality protective filter that exists, the B+W MRC resists flare, dust, liquids, and fingerprints. This can be swapped out for a KR1.5, though the tone difference is so small as to be negligible. The newer Nano versions repel water even better, but probably not as much as their 40% premium would suggest. If your primary goal is killing UV haze in the mountains, the fabulously expensive B+W 415 is a better choice. It has only a single coating and no water repellent characteristics, but it has pretty much the highest UV blocking power you can get without a color cast.
  2. B+W 491 Redhancer (2x) – as far as red enhancing filters go, this is the real deal. Using the same Corning glass as Howard Ross did when he invented the enhancing filter, this one selectively cuts alternative colors, which makes reds, yellows and oranges stand out from each other. It has a flat suppressive effect elsewhere. This is not a filter whose effect can readily be replicated using Photoshop, but sadly, it is becoming extinct. You can still get the less impressive versions from Hoya, Marumi, or Tiffen. A couple of cautions that might make you think twice about making this “the new UV.” One is that rare-earth glass often suffers from humidity damage (corrosion). The other is that it does not block very much UV light.
  3. 80A/KB15 (2.2x) – automatic white balance has not rendered the tungsten correction filter obsolete – because incandescent light is deficient in blue – and blue is the noisiest channel when amplified. If you are shooting this filter in room light and balancing with a flash, be sure the gel the flash with an 85 to make it the same color as the room lights.

Warm

  1. Infrared filters (720nm) (~1,024x) – Infrared was a real pain back in the day. But most digital cameras have so much infrared contamination that when a 720nm filter is screwed on, they expose just like old-school infrared film (as in barely shootable without a tripod on a bright day). These filters work the best on contrast-detect AF cameras that automatically compensate for focus shift. You can get a 560 or 650nm filter for “false color,” but they focus less precisely – and the result may be mistaken for a Japan Air Lines travel poster featuring cherry blossoms. An 800nm+ is an option for true monochrome IR, but it is difficult to focus.
  2. B+W 486 UV/IR cut (1x) – this oddball interference filter is most often associated with the Leica M8. It has coatings that  cleanly kill UV (at least as well as a UV filter) and IR.  “Infrared,” you ask, “isn’t that filtration built into the camera?” Yes and no. Digital cameras attentuate IR light but do not completely eliminate it. That’s why you can screw a 720nm filter onto an unconverted camera and (barely) shoot a daylight picture with it. Further, camera AF systems are not aided by IR contamination in the red channel. The catch? You can’t use it on lenses wider than 35mm field-of-view.
  3. FL-D  – the rise of compact fluorescents is reason to revisit these filters that kill the sickly greenish glow. If only they made a version for LED light bulbs. Soon, my children, soon.
  4. Cokin these filters can be uncontrollably cheesy. But for an average price of five bucks apiece on the used market, you can have a lot of fun without cracking open your post-processing software or doing the same retrofilters as the fauxtographers you look down on. Mirrorless cameras are quite easy to use with them. If your taste is more conservative, Cokin has a decent selection of good grad filters, two-color polarizers, and other landscape staples.

Cold

  1. ND8x – unless you are shooting an f/2.8 lens, most modern cameras that go as low as 200 ISO can shoot wide-open in sunlight. Some cameras now have ND filters built-in (c.f. Fuji X100/X100s).
  2. Circular Polarizers – circular polarizers are needed only when you are metering through a semitransparent mirror. If you don’t have a DSLR, you can get away with a linear polarizer from the junk bin at your local camera store. That said, the need for any type of polarizer is usually exaggerated. If you want to experiment with polarizers, start with the junk bin at your camera store.
  3. Diffusers – soft-focused pictures are good for the 1980s, but that was 30 years ago. But they’re still perfectly good for nudes with perms.
  4. Round graduated ND filters – grad filters are already endangered by Lightroom. Use them if you don’t like computers. But if you don’t like computers, why shoot digital? And round graduated filters are inflexible (you can’t move the “horizon,” which can be pretty critical).
  5. Clear digital filters – why do these exist? Why not just an UV and get something out of that extra flare?