Meet the K-iR – or is that K-Ir? Whatever.

As promised, I took the plunge and bought a digital SLR camera, with the express purpose of converting it to infrared-only photography.
I settled on a Pentax K-r, mainly because the price was right, and I realized that my Nikon lenses were better suited to full-frame photography and I didn’t have the budget to go cannibalizing one of those.
My widest lens in the Nikon system is my 20mm, which isn’t all that wide on a 1.5x APS-C format body – and for some weird reason it’s not all that sharp on those bodies. For the Pentax crop format, I’ve got the sharp 21mm. Just about as wide, and maybe I need an excuse to buy something wider anyway.
Another bonus to using the K-r is it does have live view for more precise focusing of the infrared image, in case I can’t trust the focusing screen or AF. There’s also in-body stabilization – something we never dreamed of in Kodak infrared days gone by.
For the conversion filter, I decided on cutting down a spare Hoya R72 (720 nanometer) filter I already had on hand. There’s always the possibility I might go to the more colourful 665nm type at a later date.

This was the guinea pig for my latest infrared plans

This was the guinea pig for my latest infrared plans

Converting the Pentax is definitely more of a challenge than what I’ve tried before, as Pentax for some reason uses more soldered connections to its main circuit board than is typical. It’s not a problem doing it once, but since I ended up adjusting the focus three times, it got to be a bit of a chore.
After first installing the filter, I moved the sensor backwards on its spring-tensioned adjusters a precise amount, hoping to get in the ballpark for focus accuracy with AF and the finder. This is necessary because the combination of longer wavelength light and the thicker filter require the sensor to be slightly behind its stock position.
Sure enough, I fell short and needed to move it back further. In fact, it was way out – focusing on a target 2m away showed decent sharpness at about 4m. Whoa. I tried to get clever and carefully calculated the exact adjustment required and dialed it in on the second try. Nope, for some reason I was closer, but still short. On the third disassembly and reassembly I found I had perfect focus for my 21mm lens. The 40mm works well too.
The black thingy replaces the rainbow coloured one

The black thingy replaces the rainbow coloured one

The next challenge to converted infrared is colour. If all you want is black and white imagery with near black skies and white trees, you can simply switch the camera to B&W and have at it. With normal white balances you’re dealing with a red-and-white image.
But part of the fun of converted cameras is the delicate colours you can achieve by isolating the subtle tones between the sky and foliage. The trick is to get the right white balance. But since you’re essentially shooting through a near-black deep, deep red filter, that balance is way weirder and well outside the usual daylight-to-tungsten spectrum.
A custom pre-set balance is the easiest way to go, when you take a reading off green grass in sunlight. Unfortunately, the Nikons I converted refuse to read that far down the colour spectrum. But the K-r obliged and loading the raw files into Photoshop showed a colour temperature of 2000k, and a “tint” of -90. At this point, the sky looks deep sepia brown, and the trees light grey. I also found that raising the tint to around -75 puts a bit more colour in the foliage, if you want it.
Then you do a “channel swap” – I use Photoshop’s channel mixer for this to make the red channel 0% red and 100% blue, and the blue channel 100% red and 0% blue. I save it as an “action” to speed things up with multiple files. Now you’ve hopefully got a deep blue sky and ghostly trees. Monkeying with hue and saturation can also get you closer to your heart’s desire.
White balance and channel swapping makes a big difference

White balance and channel swapping makes a big difference

Now I can go snap happy in the world of infrared, just in time to see the leaves fall off the trees this season. Without foliage, infrared doesn’t have as much to say. I’ve still got time.
While the finder is perfectly normal, the sensor sees only in infrared

While the finder is perfectly normal, the sensor sees only in infrared

Gotta love those dramatic skies

Gotta love those dramatic skies

If pink trees aren't to your taste...

If pink trees aren’t to your taste…

Maybe this was the way infrared was meant to be done. No temperamental films or filters. I don’t even need a tripod as the camera’s effective ISO is just about the same as visible light, maybe even a tad more sensitive. And the images are much, much sharper than I’ve ever managed with any other IR material. So my old apologies for softness or grain are gone (“well, I shot it in infrared, so that’s what you get”). Where was this 20 years ago?
Since I’ve still got more than half a Hoya R72 filter left, and maybe you’ve got an older DSLR that could use a new lease on life … well, let’s talk.


~ by windsorphotooutfitters on October 10, 2015.

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