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Well Pete ages ago suggested I write an IR tutorial. I had the following prepared, but wasn't happy with the images I was getting to put my name to it. Thanks to Nik Silver EFEX Pro, I now have a few images I quite like so thought I would put this up in my blog area first.
I would appreciate comments +/-, suggestions, tips etc before i submit to Pete for full inclusion as a tutorial / article.
First of all infrared is not everyone's cup of tea, the images attainable can vary quite considerably from conventional photographic imagery.
When referring to infrared in terms of photography, we are really talking about near Infrared.
What is Infrared?
This is the science bit, don't worry I will try to keep it as simple as possible. Our eyes have evolved to see light in what we call the visible spectrum, this is light that falls roughly between 400 and 700 nm.
Ultraviolet, is wavelengths less than 400 nm and Infrared is wavelengths greater than 700 nm.
Cameras are designed just to record the visable spectrum, however modern sensors have the ability to record well into the infrared portion of the spectrum. With conventional photography recording infra red is undesirable, so cameras have an Infrared blocking filter added (this will be discussed in detail later). With the latest models this filter is exceptionally good. Differences between models is also one of the reasons some people have problems with colour castes with ND graduated filter.
What uses are there for Infared photography.
Infrared photography has been around since the early days of photography, with images going back to at leas1 1910.
Infrared is uses include the following:
i. Forensic Science
iii. Heat seeking devices (typically deeper into the IR)
iv. “Hot Spot” in cricket
v. Creative photography
How can I produce Infrared images ?
There are three options available:
1. Use an Infrared filter on your existing dSLR
2. Use a conventional film camera
3. Have a dSLR converted
1.Use an Infrared filter on your existing dSLR
This is the easiest and cheapest method. You can get a variety of filters from the likes of Lee, Cokin and Hoya. Lee & Cokin have slot in types, the problems with these is light leaks. Remember the camera is far more sensitive to visible light, so any leak will find its way to your cameras sensor. I chose a Hoya Screw filter calibrated to record Infrared greater than 720nm.
Relatively cheap and convenient.
Easy to Experiment
Acceptable images possible
If you buy a screw on filter, you are limited to lenses with the same filter thread.
Very difficult to focus you have to compose without the filter lock the focus, then reposition the filter. The viewfinder is completely opaque.
Extremely long exposures even in bright daylight exposures run to several minutes – even at high ISO's making a tripod is a necessity
Focal inaccuracies due to the focal point of the sensor been calibrated for visible light. To explain different wavelengths of light have a different focal point, its why in conventional photography you get chromatic aberrations, as blue light focuses at a different point to red light. This is exacerbated when you move further into the infrared spectrum. Its also why some lenses are better suited to Infrared. This can be overcome somewhat with hyperfocal focusing, but again lenses in infrared don't perform at their best at smaller apertures, some produce quite significant hot spots.
The viewfinder must remain covered at all times. Any light leaks find there way onto the sensor (see example). It is my belief that some examples you see of hotspots etc are leaks via the viewfinder. To explain, I would estimate that light entering via the lens is reduced by at least 10 stops. So of 1000 photons that would normally be registered on the sensor only 1 will be registered with a filter attached. So even minimal leaks from the viewfinder will be amplified.
2.Use a conventional film camera
Relatively cheap, even quite advanced film camera can be picked up cheap on eBay
Fun, quite refreshing to go back to the film era.
No filter required
Easy to compose and focus (note older lenses often have a red line for the focus inaccuracies for IR to the film plane).
Tripod not necessary
No instant review of the image
Extra processing costs
Need to load the camera in complete darkness.
Only Black and White possible – Agfa used to provide a colour emulsion, but this has long since been discontinued.
Film very scarce. I only found the following for sale:
i. Rollei Infrared IR400 135-36, ISO 400
ii. Ilford SFX200 120 Roll Film
The Ilford film is not true IR, but is best described as extended sensitivity into infrared.
I must stress my experience with film based IR was about 15 years ago. I never did manage to process a film without suffering from light contamination either in loading or in the dark room.
3.Have a dSLR converted
Just point and shoot
Best in terms of image quality
No Filter required
Don't need to cover viewfinder in most cases (still advised)
Choice of internal filter (see later)
Some lenses better than others
But Can't I get an IR effect in photoshop with conventional images ?
It is true there are a multitude of Photoshop actions / plugins and Lightroom presets that claim to do this. However they cant give you information that's not there, that is recorded in IR.
Where Can I get my Camera converted ?
There are two possibilities you can either do a DIY job, or you can use a specialist company. Lifepixel in the US provide comprehensive details on how to do this and provide the filter to block visable light.
The second option is to have the camera converted by a specialist company.
I opted to have a custom conversion by a specialist company, as I didn't have the time or inclination to do the conversion myself. In my research on IR conversions I only identified 2 companies in the UK who can provide conversions, there were very mixed reviews on one (out of fairness I won't say who they are as I did not have personal experience of this company). I opted to have my conversion done by ACS, and found them extremely helpful, I had several phone calls to them, and the service I had was first rate. I have included their details at the end of the article in the useful links / further reading section.
The cost of conversion for a Nikon D80 was £250 + VAT (End of 2010). This may seem steep, but each camera has to have the IR block filter removed, a new filter added, and calibrated to focus correctly for infra red. ACS also provide a 6 month guarantee, the service took 2 weeks from posting the camera to receiving it back, this can vary on how busy they are.
When considering your conversion to IR you will have to make a choice of filter. There are currently three available.
1. 720 nm Filter
The most frequently selected option. This records light at wavelengths greater than 720nm. This is the closest version to the old Kodak film favoured by many in times gone by (also the one I selected), this also has the ability to produce colour Infrared images as some colour information is recorded.
2. Enhanced Colour IR Filter 665 nm
To date this is not readily available in the UK, The light sensitivity is extended into the visible light Spectrum, enabling more vibrant colour Infrared imagery.
3. Super Colour IR Filter 590 nm
With the super Colour IR filter it's possible to extend the sensitivity even further into the visible spectrum than the 665 nm filter.
4. Deep Black and White IR Filter 830 nm
This is probably the filter of choice if you want to produce only Black and White images. No colour information is recorded, so it won't be possible to do colour Infrared nor the in vogue swap channel method.
In the review I won't go into great detail, however this may be the subject of subsequent tutorials. The main reason is that at this stage I'm still learning about Infrared processing.
RAW processing, like conventional images its preferable to record RAW. Although getting an acceptable white balance is extremely difficult, as most RAW converters don't go below 2000K as they are designed for use with visible light. Whilst for Black and White images accurate white balance isn't vital for colour IR it is. You can create custom profiles in Lightroom, but to date I haven't done this as my own preference is for Black and White IR Images.
Even with Black and White images, the white balance does have an effect, if you have Lightroom just open an image press the Black and white tab, and alter the White balance to see the difference.
….example black and white
…. colour IR
….. Swapped channel IR
Are all lenses suitable for Infrared images?
The simple answer is no, many lenses are very poor for IR, even expensive professoinal lenses. This is because they are designed for visible light. The expensive coatings applied to reduce flare increase contrast, can have a negative effect in the Infrared part of the spectrum. I have included links to some resources on lens compatibility in the links section.
Links / Further reading
Advanced Camera Services Limited
Unit 10 Linmore Court
Threxton Road Industrial Estate
Watton Norfolk IP25 6NG
T 01953 889 324
F 01953 880 086