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DSLR Infrared

Exploring the World of Infrared Photography
With a Modified Canon 20D


Chart Courtesy MaxMax.com

I always admire well done landscape images shot in Infrared. It's a technology and technique that I have never explored myself until now. The main reason for my not investigating IR work sooner has been the hassles involved in working with Infrared materials. IR film needs special handling in the field as well as during processing. The use of IR filters means that one can not view through the camera lens with the filter in place, and manual focusing is "off", autofocus doesn't work, and the camera's built in metering can't be used either. Exposures can also be quite lengthy.

But now there's a solution, and all it requires is one of the popular DSLRs from Fuji, Nikon or Canon, and US $450. This plus shipping costs and a few days with your camera away from home will return you a modified camera that shoots in the Infrared with no reduction in its usual functionality. Except, of course, that it no longer can shoot normal colour images in visible light, and can't be changed back again if you decide that IR shooting isn't for you. Oh yes – and it voids your manufacturer's warranty.

Since I had a Canon 20D that had been sitting on the sidelines for some months, when I heard that there was a company that did conversions to Infrared, I decided that now was the time to see what the fun was all about.


Edwards Gardens. Toronto. January, 2006
Canon 20D (IR Modified) with 28-70mm f/2.8L lens @ ISO 400

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LDP & Max Max

The web site and company which can do this magic for you is MaxMax.com, and the company name is LDP LLC. But whatever you call it, it is a company that specializes in optical products covering the Infrared and Ultraviolet ends of the spectrum.

Of interest to photographers working in Infrared is their line of IR filters, and especially modified cameras. These include camcorders, digicams and DSLRs. My particular interest was in their digital SLR conversions. These can be done to a number of current cameras, including the Fuji S3 Pro, Nikon D50, D70 and D100, as well as the Canon 350D, 20D and 5D.

The modifications made can be done in two ways; IR + Visible Light, and IR-Only. This takes a bit of explaining.

If you want the camera modified so that it can shoot in both normal as well as Infrared light, then what the company does is to remove the Infrared blocking filter that all cameras have in front of their sensor, and supply you with filters for use in front of your shooting lens – the main one of which is an Infrared filter, and another to restore normal colour balance when shooting non-IR images.

The upside of this approach is that you can still use your camera for normal photography. The downside is that you need to put an IR filter on your shooting lens, which means that autofocus doesn't work in Infrared; autoexposure doesn't work in Infrared, and you can't look through the viewfinder because the IR filter blocks visible light. You'll also need filters in different sizes for different lenses.

The second approach, and the one which I opted for, is to have the camera modified so that it can only shoot in Infrared. This is accomplished by the company removing the camera's IR-blocking filter and then installing an Infrared filter (visible light blocking) right in front of the camera's sensor – inside the body of the camera. The camera will then function normally in almost every respect, with full autofocus, autoexposure and normal through-the-lens viewing.


Chart Courtesy maxmax.com

Note that if you are sending your camera to MaxMax for modification from outside the US, obtain a US Customs FCC form (from your courier service) and use it to declare that the camera is being sent for repair, and will be re-exported. This will expedite delivery to MaxMax. US Customs will otherwise stop the camera until it has information related to RF emissions certification. Also, this will help prove to your own customs service that the camera was exported for service, then reimported.

Note that MaxMax also sells these camera new, with modification, in case you want to take that route. Naturally, your camera will no longer be in warranty after the modification.

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Seeing Infrared

Of course we can't see into the Infrared part of the spectrum, anymore than we can see radio waves. But that doesn't mean that they're not there. And whereas the human eye's sensitivity drops off dramatically starting at about 600nm, and is extinguished by about 700nm, silicon sensors have sensitivity out to about 1100nm, well into the Infrared. That's why all imaging sensors have Infrared blocking filters built into their coverglass.

What LDP does when they perform a full Infrared conversion is to remove that coverglass and replace it with one of their proprietary X-Nite filters, which opens up the sensor's inherent Infrared sensitivity and also blocks most visible light.


A typical 3-colour histogram from an IR modified DSLR.
There is some IR data recorded in the green and blue channels,
but the majority of the image data is in the red channel.

So what does the world look like in Infrared? Well, that depends. Some things reflect Infrared better than others, and some things even emit Infrared on their own. Living things are rich in Infrared, such as plants and leaves. It can be very hard to anticipate what something will look like when rendered in IR. Green leaves typically become very white, and the sky (especially near the zenith) becomes very dark. So does still water. People's skin becomes an almost ghostly white, which can either be attractive or cadaverous, depending on the situation.


Bridal Party. Toronto. January, 2006
Canon 20D (IR Modified) with 28-70mm f/2.8L lens @ ISO 400

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Exposure Compensation Techniques

Normal as-metered exposures are good much of the time, but I have found that I need to dial in plus exposure compensation as often as minus. The reason for this is that Infrared exposure is more of an esthetic decision that a technical one. Different things in the shot absorb or reflect Infrared in varying amounts, and not always predictably.

Consequently I have found that the simplest approach is to set the camera to autobracket three exposures, at -1, 0, and +1 stops. With the 20D set to multi-shot mode, pressing the shutter release produces three bracketed frames in less than 1 second. This may seem wasteful of card space, and is to some extent since I always shoot RAW, but with large cards this isn't an issue, and one can always later delete in-camera the frames which are obviously not needed.

This technique turns out to be much more efficient than taking an exposure and then having to make another one with a fairly substantial adjustment – far more often than one would usually require when shooting with visible light.

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Working with IR Files & Lightroom Synergy

As can be seen in the screen shot above, IR files from such a modified camera are very red. They therefore need to be converted to grayscale. Most programs do this in quite a simplistic manner. For example desaturation in Camera Raw, or using Convert to Grayscale in Photoshop, really don't do justice to the rich monochrome tonalities hidden behind the strong red cast that JPGs or raw files fresh from the cameras show.

Since it's necessary to turn all files into grayscale, wouldn't it be nice to be able to do them all at once, and with optimized tonalities. (It's very hard to judge these ruby-red thumbnails within a browser. They must be converted to monochrome for evaluation).

Well, there is a Santa Claus after all. Adobe's new Lightroom can do just what's needed. The program has a very sophisticated monochrome conversion capability, and an even more sophisticated "Auto" function built into it that optimizes tonal distribution during grayscale conversion. (Lightroom Beta One is currently only available for Mac computers, but a Windows version will be along soon).

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Down the Road

I have just started scratching the surface of what can be done with an Infrared modified DSLR, such as my Canon 20D. The modified camera has only been in-hand for a short while, and since I live in Canada, and it's now mid-winter, the nearest flowers and trees that aren't dormant are at least 1,000 miles away.

But, I will be spending some time in Florida in February (as all good Canadians do), California in March, and then several weeks in Namibia and South Africa in April. I'm greatly looking forward to doing a lot of Infrared landscape shooting on those trips, and any worthwhile results will subsequently be found on these pages, along with an update on any new operational insights.

February, 2006

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Update:

During the first few hours after this piece was published a few readers wrote to say that even with the IR filter behind the lens it was still important that correction be made due to the fact that Infrared light focuses at a different point than visible light.

My knee-jerk response was to assume that since the modified 20D was still able to autofocus, and since none of my (admittedly limited) tests had shown a focus issue, that there wasn't one.

Well, I was wrong (partially). I wasn't thinking the issue though carefully. A few minutes shooting a receeding ruler with the lens with the most limited depth of field that I own, the Canon 85mm f/1.2L, (one that has an IR focusing position noted on the barrel) showed that indeed a focus adjustment may need to be made when shooting IR. (But, see below).

But, having said that, at moderate apertures, and with anything other than long lenses, this isn't than big a concern. Outdoors, for landscape work, just remember to either stop down a bit more than usual, or if your lens has an IR focusing correction mark, try and remember to use it.

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False Colour

One aspect of working with IR that I neglected to touch on in the first version of this article was that of false colour. In other words, rather than simply doing a monochrome conversion, adjusting the colour to try and neutralize the heavy red cast and then achieve an aesthetically pleasing, though obviously false colour image.

David Burren has written an informative piece on this that can be found near the bottom of this page on his web site. It involves choosing a white balance point and then running a Photoshop Action which he kindly provides as a free download.

Above is an example IR image processed with David's Action and the colours adjusted to a palette that I found appealing. Note that David also does IR conversions of DSLRs. You can contact him about this on his site, or directly.

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More on Infrared Focusing

Sometimes (all the time?) there is more than meets the eye when it comes to topics photographic. My empirical tests showed that my converted 20D focused fine. But, then when called into question by some readers, my ruler test showed that focus was indeed off, at least on an extreme close-up and with an unforgiving f/1.2 lens, wide open.

I now have received some email correspondance for Dan Llewellyn, the President of the company that IR converted my camera. Here is what Dan had to say (reproduced here with his permission)...

Just a quick note. I got a few questions from people asking about the focusing on the converted cameras after reading your article. On my conversions, I recalibrate the AF to focus in the infrared. On my earlier SLR cameras, the AF would focus in the IR and the visible focus would be slightly off. Thus, what you would see through the lens in AF on an IR-Only camera would be a little off, but the actual picture would be sharp. I have since been doing new things that allow the visual focus through the lens and infrared focus to the CMOS to work simultaneously on most, but not all, cameras.

On the IR+Visible cameras, I don't alter the AF, so the camera focuses in the visible range. If you take IR pictures with the IR+Visible camera, you do need to compensate for the focal shift or shoot at a high enough F-Stop to compensate.

The Canon 10D, 20D, 300D and 350D, Nikon D100, D50, D70 and D200, and Fuji S3 Pro can be converted to IR-Only, picture AF and viewfinder AF. The Canon 5D can be converted to IR-Only, picture AF at the moment. I will probably be able to convert the 5D to AF AF in about 6 weeks. Once I get time to do more calculations, experiments and order the optics, I will get the 5D done as well. Please note that some others that convert cameras don't do any AF modifications forcing the user to shoot at high f-stops to maintain focus. We also use custom double coated filters and a class 100 clean bench.

So, at the end of the day, it appears that cameras converted by MaxMax do indeed focus properlyin the Infrared, without user intervention. But, my own tests show that at the extremes, either with very long focal lengths or very wide apertures, an extra stop of two of stopping down doesn't hurt to provide a depth of field safety margin.

 


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Concepts: Digital single-lens reflex camera, Nikon, Camera, Single-lens reflex camera, Visible spectrum, Infrared, Infrared photography, Photographic lens

Entities: Canon, Nikon, MaxMax, LDP LLC, Adobe, AF, FCC, DSLRs, Photoshop, US, Canada, Namibia, South Africa, David Burren, David, Dan Llewellyn, Dan, CMOS, JPGs, Windows, D50, D100, California, Florida

Tags: cameras, infrared, visible light, ir filter, modified camera, image, Infrared filter, Fuji S3 Pro, false colour, company, sensor, IR filter blocks, shooting lens, normal colour, Canon 20D, picture af, IR shooting, IR focusing correction, IR focusing position, colour image, ir+visible camera, camera lens, autofocus, monochrome conversion, IR film, web site, example ir image, Infrared conversion, IR work, red cast, IR data, IR conversions, IR files, IR pictures, grayscale, IR-Only camera, normal colour images, Camera Raw, Normal as-metered exposures, typical 3-colour histogram