IR filter

<p>Hi<br>

I am wondering if anyone knows what IR filter from B&W is equivalent lense to Hoya R72?<br>

Thanks<br>

Ehsan</p>

<p>B+W 092 is equivalent to Hoya R72 and Wratten 89B</p>

<p>None are, but if you're shooting film, you can use the 092 and not notice the difference. If you're shooting digital, you probably want to forget B+W, unless you have a modified camera.</p>

<p>B+W makes 3 IR filters, the 092, 093, and 094</p>

<ul>

<li>092 is erroneously listed in some catalogs as equivalent to a Hoya R72 or Wratten 89B. Its 50% pass point is at 695nm (that's why the Schott glass used in it is called RG695) while the Hoya R-72 and Wratten 89B are 50% at 720nm. That doesn't sound like much, and as I said, the difference is hardly noticeable on real (Kodak or Maco) IR film. But it's a big problem on digital, because the camera's build in IR blocker is a sharp-cut dichroic filter at about 700nm. With the 092, you get a picture dominated by BVR (barely visible red) light from 680-700nm, with essentially no IR content. With the Hoya or Wratten, you get a "false color" image, with IR in the green channel and BVR in the red channel.</li>

<li>093 is a deeper IR, 50% at 850nm, it will give you an essentially monochrome IR picture on an "old" no-dichroic filter DSLR like a Nikon D100, or on a newer one that's had the dichroic filter removed. It's between a Wratten 87 and 87C.</li>

<li>094 is a hard-to-find filter that is 50% at 1050nm. It requires a camera with the dichroic filter removed, and the IR is so deep that it hardly registers on IR film. But it's very dramatic. It's "stronger" than the (also hard to find) Hoya RM-90.</li>

</ul>

<p> </p>

<p>And see, while I was typing my post, someone chimed in with the incorrect info about the B+W 092.</p>

<p>Sorry, Curt, it's not even close.</p>

<p>As Joe points out, the difference between the Hoya R72 and the B+W 092 is practically imperceptable for IR film use and that is why I use the B+W 092 with the Maco Aura - type film. The tables he refers to probably all pre-date the digital era. So, if the OP's question dealt with film as I assumed, this is a good answer for an "equivalent" even if it is not exactly equal. If the subject is digital, then I don't recommend trying to use any external IR filter on an unmodified camera because of the very efficient cutoff filters on recent sensors, as Joe pointed out. Even my D200 was not particularly useful this way, so I had the cutoff filter replaced with a 720nm filter and I am quite pleased with the results even if I still prefer the medium format film approach with the B+W 092; but that doesn't work very well for moving subjects.</p>

<p>i have a question, not about infrared film but is it possible to use the r72 filter with regular black and white film instead of infrared? will the effect of this just be just like the 25a filter except stronger? examples maybe? thanks</p>

<p>Nope. The average B&W film has essentially no sensitivity to near IR. Most B&W films need a 12 stop (4000x) exposure increase to make a properly exposed shot with a 695nm filter, and will not register at all with a 720nm (and yes, I have tried this).</p>

<ul>

<li>The datasheet for T-MAX shows a "bumpy" plateau of about D 1.6 from 450nm to 630nm, then a plunge to D -2.0 (a drop in sensitivity of D 3.7 or 12 full stops) by the time the graph cuts off at 700nm. You'd get something if you shot it at EI (can't call it ISO when you're doing this) 0.02 with the 695mn B+W filter, but eh "sunny 16" rule says you should start the experiment at f16 and a 50 second (not 1/50 sec) exposure.</li>

<li>The datasheets for Tri-X, for example, show it being 1.5 D (4.5 stops) down at 670nm, where the chart cuts off. You might get some response with a 695nm filter, but you won't get a thing at 720.</li>

</ul>

<p>The only non-IR Kodak film that could work with a 720nm filter was the long-discontinued Tech Pan. It could actually make a decent shot with just a 500x exposure increase, as opposed to films like Tri-X and T-MAX that needed a 5000x increase to work with a 695nm filter. The results were gorgeous, but "unconventional" looking. Back in the film IR days, most of the "IR look" came from Kodak HIE not having an anti-halation layer (which made anything bright "glow", whether it was visible light "bright" or IR), being insanely grainy, having really screwed up developing procedures, and all the guesswork that went into exposing it, along with the weird characteristics of many popular lenses when used with IR.</p>

<p>Tech Pan IR had fine grain and no glow, and I used to use it with a select few lenses that performed well with IR (20mm f3.5, 45mm f2.8, etc). So my IR results looked more like Ilford 820 on a 4x5.</p>