Seeing things in a new light

This is an unashamedly technical post. For those of you turned off by nanometres and transmission filters, other blogs are available.

A couple of years ago  I took the plunge and invested in an infra red converted camera. Since then I’ve learnt to understand the best conditions and subject to apply infra red to, and I’ve experimented with post processing.  I had my Nikon D300 converted to record infra red images in 2013. I love the effect, particularly when post processed into black and white images. This post is about the basics and is based on a presentation I recently gave to my local camera club.

The nanometre bit

Infra red light is invisible to the naked eye and has wavelengths starting at around 590nm and stretching on to 1000nm and beyond.

 

Most digital camera sensors are so sensitive to ultra violet and infra red light that a special filter is placed in front of them to cut this light out. Converting a camera to take infra red photographs is simply a case of replacing this filter with one that blocks visible light and transmits infra red. That’s what I had done to my D300. It gets a little more complicated because there are different filters available to allow different wavelengths of light to pass through (in the same way that coloured filters allow different wavelengths of visible light through). My camera has a 720nm filter, (which blocks light of wavelength less than 720nm). Sensors to pick up heat energy are a completely different beast and are not dealt with here.

As a converted DSLR camera doesn’t need a transmission filer on the lens, you can compose and focus as normal. The image in the optical viewfinder remains bright and in visible light. To see the effect of the internal filter you will need to use live view. If you are using an unconverted camera with a transmission filter, you will need to compose and focus with the filter removed as by it’s very definition, the filter will block out visible light.

My D300 was calibrated for focusing and exposure by the company that converted it (Protech repairs). I still find that when faced with different subjects, I need to adjust the exposure from the indicated values and a degree of trial and error is sometimes required. You’ll always find me reviewing the image immediately after taking it.

Effects

The sun emits as much infra red light as it does visible light and so it is possible, with a converted camera, to use exposure times similar to normal. The classic infra red effect – white vegetation and dark skies – happens because green leaves reflect a lot of infra red light but blue skies do not. Scientists use infra red photography to spot growth and dead vegetation in the landscape. Contrast can be high in these photographs and you have to keep this in mind when taking the shot. Water also absorbs infra red.

Infra red light penetrates skin slightly and this results in a a soft, blemish free appearance in portraits. Eyes tend to appear black. The longer wavelength of infra red light is less affected by haze and pollution and so landscape photographs appear clearer and crisper.

Flare can be more of a problem as most lenses are designed to be used with visible light. The lens coatings and internal coatings that reduce reflections aren’t as effective with the longer wavelengths. Some lenses suffer from ‘hotspots’, a bright central portion which varies (and may disappear altogether) with a change in aperture. Of the collection of lenses I’ve gathered over the years, about half exhibit a hotspot with the D300.

Lenses that work with 720nm Infra red and a D300 camera:

• Nikkor 60mm macro
• Sigma 10-20mm D f/4-5.6
• Nikkor 50mm f/1.8
• Nikkor 85mm f/1.8 (manual focus)
• Nikkor 24mm f/2.8D
• Nikkor 70-300mm AFS f/4.5-5.6
• Tamron 90mm macro
• Tamron 18-270mm
• Vivitar 19mm (manual focus)
• Sigma 170-500mm

 

Results

below are a set of photos I took this morning. I’ve been experimenting with additional filters progressively the shorter wavelengths. This is very much a work in progress.

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Grey Days

Saturday

We knew it would be raining on Saturday morning and sure enough, when Rufus persuaded me to take him out into the garden for his pre-breakfast stroll, it was drizzly. After a brief discussion, we decided it didn’t matter. So we had breakfast and then off we went to Rhossili, up we went onto Rhossili Down, it rained, we got wet and some of us got muddy paws and heather tangled in their fur. We explored the old radar station, watched a huge flock of sheep depart en mass as we approached and made friends with several horses and a couple of foals.

Rufus had to have a shower when we got home. He doesn’t like the shower but I think it’s more about dignity than dislike. I make sure the water isn’t too hot and the spray isn’t too strong. He made a show of trying to escape; he understands the word shower and I spent 5 minutes rounding him up. In the end, he curled up on his bed and pretended to be asleep. But once in the shower, he wasn’t too bad. He tends to grunt and huff a lot, but if he really wanted to get out he could. Instead he allows me to wash under his paws and under his chin. The water was brown running off him, and I probably could have planted a small heather patch in the garden with all the bits that came off him. I don’t have a selection of hair care products, so he had to use the same Head&Shoulders Itchy Scalp hair shampoo that I do. Other shampoos are available and Rufus doesn’t endorse any particular products.

Sunday

Back in the day, I went to the Polytechnic of Central London. As soon as I left, they changed the name to the University of Westminster in the hope that I wouldn’t return and that they could purge all records of my existence there. In fact, I did pop back in December, but that’s another story.

I enjoyed my three years in London. I liked being self sufficient, I liked being in a place that really didn’t seem to stop, day or night. I was fortunate enough to live for the first year in halls of residence just off Oxford Street. It was fantastic. The course I took – Photographic Sciences – was an eye opener and confirmed my interest in all things photographic. Although I did become a little jaded at the end and took a break from photography (ironically, just as I started working as a photographic technician in the local further education college).

The things that held my attention most on the course were the experimental and technical photographic techniques. Some of the most interesting techniques for me were macro, high speed photography and filming, and infrared photography. This was a long time ago and everything we did was on film and we developed everything by hand. I remember right at the end of the course being shown a new little chip that was one of the first image recording sensors – the forerunner of today’s digital camera innards.

Since I left college, I’ve carried on with some of those techniques as best I could. While I was still using film, I used to use Ilford’s SFX emulsion. It had an extended red sensitivity that, with the right filters, could give some infrared effects. It took some handling though (you couldn’t load it in daylight) and gave grainy results. It was great! I got back into macro photography a couple of years ago, and I bought an infrared enabled Fuji S3 just over a year ago. I’ve used it a lot since, experimenting with the effect and finding the best combination of lens, exposure and subjects. I love the effect and have posted some results here int he past.

Last week, after some weeks of trying, I realised that no one wanted to buy my old D300 body. So after some research, I contacted Protech in Uckfield who quoted me a good price to convert the D300 for infrared photography. The company was great. I had a conversation with Jo, who gave me some advice about what lenses could and couldn’t be used. I sent the cameraq off at midday on Thursday and around 11am on Saturday it was back with me. A combination of a fast turnaround at Protech and great service from Royal Mail made that possible. Thank you both.

So for the rest of the weekend, apart from last night’s gig, I’ve been playing with the D300. There are a couple of immediate differences between it and the S3. The main one is that the infrared filter is different. GEEK ALERT – Do not read further unless you can handle nanometres without any side effects.

The filter on the S3 blocks light with wavelengths shorter than around 665 nanometres, that is, light in the visible part of the spectrum. In practical terms, (because filters aren’t perfect) this means that some visible light is recorded and the recorded image before processing appears a deep red colour. The filter in the D300 blocks light from about 720 nanometres, which means much less visible light is recorded. The recorded image takes on a more purple hue. The D300 allows for a custom white balance to be applied, which means that the review image on screen is very close to the black and white final image I would be looking to get. The D300 is a more advanced camera, it has better resolution and low light capability and is a more robust camera. The metering and focussing is better, too.

GEEK ALERT OVER. It is safe to continue reading.

So I’ve been trying lenses and subjects and all sorts of combinations to make sure it’s all working well. And it is! Bearing in mind that it’s been raining non-stop for the last two days, I think I’ve got some interesting shots. I’m certainly happy with the camera’s performance. The only think I haven’t been able to test properly is a sunlight landscape. Below are a few of the test shots. They’re not meant to be works of art.

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