Hmm… maybe it isn’t obvious, perhaps an unprocessed image will help…
Yes, I had the camera modified for infrared photography. And, yes, I’m going to have a lot of fun with it…
If you don’t know this, digital sensors are highly sensitive to the near infrared spectrum. All digital cameras contain a “hot mirror” that reflects infrared on top of the sensor. In the early days, these hot mirrors were weak, allowing some infrared leakage, but now they are extremely strong.
This explains a lot of things:
- Why people buy older digicams for infrared photography.
- Why the Nikon D70 tested noiser than the Canon 300D Digital Rebel and why color contrast improves when a 486 UV+IR filter (hot mirror) is placed on the Nikon D70.
- Why Canon has a reputation of having “fire truck” reds.
- Why the Leica M8 has a “magenta problem.”
Basically what has gone on is that cameras with a stronger hot mirror, have less susceptibility for exhibiting luminance noise when shooting a dark scene lit with any black body (incandescent) light . In some cases, they’re just recording infrared spectrum that is there, but not necessarily visible, and over time this has resulted in reviewers lauding cameras with extremely strong hot mirrors and consumers purchasing those cameras.
Canon was the first company to figure this out by adding a very strong infrared mirror to their digital cameras and bodies. Because electronics were primitive back then, to preserve color accuracy, the red channel (which is partially blocked by such a strong mirror) is boosted, resulting in its reputation for “fire truck” reds and more saturation on skintones. The “truer colors” of the Nikons at the time were a selling point, but I never quite understood it—after all, the landmark color film of the 90’s, Fuji Velvia, was a contrasty film with exaggerated sensitivity to the red channel.
Still sometimes you can turn that IR sensitivity to your advantage…
By the introduction of the Leica M8 in 2007, super strong hot-mirrors had be so commonplace that when it was announced that the anti-alias and infrared mirror had to be thinner and weaker than usual to accommodate the rangefinder design, people instantly caught on that this would be a problem with synthetic black clothing reflecting as magenta.
Infrared contaminates digital in much the same way ultraviolet does film. For the same reason we use UV filters for film photography, we use infrared filters for digital. The only difference is, that filter is placed on the sensor instead of the lens—unless you own a Leica M8.
I’ve been interested in infrared photography ever since I read an old article about someone who used my old Olympus C-2500L for infrared photography.
What attracts people to infrared landscapes is blue sky and water turns to black giving clouds a lot of contrast—even more than using a red filter for black and white film, and foliage green becomes snow white, creating an ethereal look. In portraits, skin blemishes disappear and becomes silky smooth and you can see the actual detail in black fabrics. If you avoid the freakish look of the eyes in near infrared—you can understand why infrared cameras are a sometimes favorite for outdoor wedding photographers.
(I have heard that IR can “see through” light clothing, and sometimes IR conversions are sold this way—a la “nightshot” mode in Sony videocameras. I haven’t tried this, but it sounds rather pathetic. Maybe if you’re really lucky and lecherous, you can a really blurry nipple. Good for you!)
When I read Sportshooter’s article on infrared basketball photography, it got me thinking that the infrared spectrum is an interesting way at looking at the world. Since good photography is about seeing differently, I resolved a few years back to turn my Nikon D70 into an infrared camera when I upgraded to a Nikon D200.
But then I got lazy.
(At least, in the meantime, I managed to convince my friend George to get a Nikon D200, on a lark that his old D100 would have new life as an infrared camera.)
With the move this year, I’ve been going through my photography gear and repairing and upgrading things as needed. As I was unpacking my D70, I realized the last time I lent this camera out was over two years ago. Time to do something about that.
How to get an infrared camera
Basically how this is done is you open the camera and remove the hot mirror and replace it with a filter that blocks visible light or just a piece of glass. If you don’t replace the filter, it can shoot in both visible and infrared—if you want to do infrared photography, you’ll have to put a filter on your lenses.
Why have a infrared photography glass put on the sensor? Since these filters are opaque to visible light, you have to do all the focusing and such before you screw in the filter or you can’t use the viewfinder at all. Not only that, but since infrared is a different frequency, it actually focuses at a different distance than what visible light meters at. (If you have an old lens, you will see a red line on the scale focus, which represents that infrared shift.) When you replace the hot mirror, you could go in and shift the focusing distance slightly to adjust for this—it’s not perfect because every lens shifts a different amount, but it’ll help.
(I have heard that some people have gone in and put an IR glass over the autofocus sensor area so that it’ll correctly autofocus infrared for all cameras. This sounds like a terrible amount of work to get to that part of the camera.)
I used LifePixel in Washington which took about two weeks total. Here was my schedule at the cheapest shipping rate:
- July 9: ordered it
- July 10: shipped it
- July 14: they received it
- July 28: they shipped it back
- July 30: I received it
- July 31: I picked it up and started shooting
Apparently you can use my name and address and I get some referral money which will probably go into buying a elePHPant to give to people who claim they actually read this blog. 😀
Other vendors I’ve heard about are Jim Chen, LDP LLC, and Hanson Fong. I didn’t try them, but since they’ve been around even longer than LifePixel, I’d bet it’s just as good and at a cheaper price if you are on a budget. In some cases they’ll sell you a camera already modified, and I’ve seen similar things offered on photography forums.
(One thing I found is that since my camera is old and only has a luminance histogram that is actually really just a green channel histogram, it is impossible to histogram meter the scene with it. That is because most of the light is coming in the red spectrum which the Nikon D70 just refuses to show. We hatesssess this, my precious! I eventually just gave up and left my D70 on bracketed exposure mode, +/-1 if you want to expose correctly +/-2 if you are going to merge the stuff in Photomatrix HDR.)
If you clicked on the last link or the LifePixel one, you’ll realize that there are actually three different types of filters that can be put on:
- Ones that block 830nm less – “Deep BW IR” because you can only do black and white photography with this camera since the visible spectrum is entirely blocked.
- Ones that block 720nm or less – “Standard IR” because this is the most standard portion. You can do color infrared photography with this because a little of the light gets through the red channel of the sensor.
- Ones that block 665nm or less – “Enhanced color IR” because this allows a little more visible light to leak through.
As you get more color, you lose contrast in the infrared spectrum. My camera is the last version. It’s a little weird, because as you see above, instead of foliage coming out snow white, it comes out with a greenish tint… that can be exaggerated:
One thing to be aware of is that you can measure this frequency differently: the frequency at which the light just starts to be blocked, or the frequency at which the light is 50% blocked, so don’t trust the numbers unless you know what they mean—the best way to know is to ask what IR filter the glass is equivalent to.
(For some excellent enhanced color infrared photographs, check out John Swanda’s work.)
The way that last image is done is using a pretty common digital IR technique known as “channel swapping.” It’s a pretty fancy term for a very simple thing: go into Photoshop and make the red channel blue and the blue channel red. And while you are there, you might as well mess with the saturations and levels.
Some more reading:
- Phil Malpas tutorial– a classic
- Luminous Landscape review– very easy read even if it had errors
- creative.tjhole.com tutorial– recent and complete
Seeing the world differently
The camera is an instrument to see. When we shoot, we try to see the world differently and capture that difference for others to see. We may do this with lens choice, timing, exposure, focus, postprocessing or in the dark room, or even in the print, but is a different way of seeing we express nonetheless. Infrared cameras capture what we literally can’t see.
It doesn’t matter if the processing is designed it seem like a standard black and white photograph, the tonality we get is just different enough:
Or maybe it’s just what we’ve always seen… emphasized:
Sometimes what the camera sees seem strange to us, like realizing that “to see a world in a grain of sand” might cause you to see the whole universe in a sidewalk:
Shot to Finish: San Francisco at sunset
Going back to the photo at the start of this article, I thought I might mention how it came from start to finish.
The fog fucked our attempt to get a panoramic view from Skyline College in the south, and Google Maps messed our attempt to get to the East Peak before sundown, so I opted for Hawk Hill in Marin, a place I used to visit twice a month on my bicycle, alas—sans camera (other than an iPhone)
Since I was here, I figured I should take a couple photos with my D3. When I swapped out the 14-24 for the 70-200, I noticed that I had put my Nikon D70 body in the bag, just in case I ran across some interesting foliage. I wonder what this scene looks like in infrared? I quickly put the 14-24 on it and mounted it on the tripod. It was cold, and I was tired so I didn’t even bother trying to figure out where the horizon was, nor did I notice I left the camera at ISO 500. No point in using a tripod for this, but I did. The cold must have gotten to my brain, but I didn’t really care as the sun was setting and Mt. Tam was casting a long shadow.
Since the horizon is wrong, that needs to be corrected for in Aperture—it provides the best tool I know for that sort of thing. I know you can’t see it, but my Nikon D70 has a defective blue hot pixel in the upper right middle part of the frame that appears at high ISO. Because it is a CCD and not a CMOS sensor, the linear readout contaminates all the charge data down a vertical line across the frame. When this is processed to RAW and the contrast is manipulated this is horribly noticeable—that’s the only reason I did a little retouching in Aperture also.
The high ISO means injecting a nik Dfine step to get rid of the noise and then a presharpen step since I know I’m not going to add much grain in the final black and white. I normally can skip those two steps. (Rule of thumb: don’t add film grain and sharpen at the same time, they do the same thing and interfere with each other when done as a finishing step.)
You may be wondering why I use a color filter (nik Color Efex Pro brilliance/warmth) for a black and white photo. The answer is that black and white imagesare actually best on low contrast but high saturation images. Higher saturation images make it easy to use color filters and control points to select dodge and burn points in Silver Efex Pro…and there is no such thing as too much saturation in a black and white photo. I attribute this realization to Kevin Kubota who likes to desaturate and warm skin tones just before black and white processing of wedding portraits—this makes the skin creamer when a black and white action Photoshop action is added. 🙂
The photo is completed in the black and white processing tool du juor: in this case, nik Silver Efex Pro. Structure and contrast are pulled up, a blue filter is used (to accentuate the red structure even more), some curves are manipulated and some dodging is done on the Marin side which is deep in shadow. If there is grain, it’s because of a bug in Silver Efex Pro where the only way to get at the curves tool is to use the film effects layer which adds in grain—I tried to make that grain as small and as soft as possible.
And just when I’m done, I realize that the blue filter has wiped the contrast on the sky so I burned the top for good measure to keep the eye from running off the picture.
By the way, here is a false-color channel-swapped HDR photo from the same place: