IR Foto Guide
If you'd like to try Infrared photography on your digital camera, the three (blue) numbered options below show the main options. I have followed this up with a few brief paragraphs covering some other topics about Infrared (red bullet points):
1. Normal Camera + 720nm IR Filter (only)
Simply adding an infrared filter on your digital camera's lens can work. It's often a great place to start if you'd like to try out IR, but beware - this does not always work! For this reason I recommend borrowing an InfraRed filter (if you can) or finding a very cheap one if you would like to try this. The 720nm wavelength will give you the highest chance of success ere, anything lower or higher will likely not give you enough effect (or any at all).
Nikon D3 (Non-Converted) + 35mm f/2.0 AF-D + 830nm IR Filter
f/8, 4 minute exposure
The above image shows the Nikon D3 (2007) actually works with the more aggressive 830nm IR filter, albeit requiring an insanely long shutter speed. The up side is you can get some rather interesting clouds (depending on cloud cover and wind speed of course).
If simply adding an IR filter to your non-converted camera works you will almost certainly need a tripod due to the exposures being quite long and if using a DSLR you won't be able to see through the lens. DSLRs also require focus adjustments too. If you set the focus using the viewfinder, before putting on your filter, it will need to be focused a little closer. If your lens has IR focus offset markings (common on older lenses) that will help, but they are usually not accurate enough for shallow depth of field and are only set for one specific wavelength (luckily usually 720nm).
Pros
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Cheapest way to play with IR, if it works >
Cons
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** May not work (some cameras block all IR) **
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Long exposures require a tripod
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DSLRs Can't see through lens with IR filter on lens
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Focus offsets for each focal length / wavelength
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Colour separation in IR is not easily achieved
2. Converted 'Infrared' Camera
Converting your camera to IR means removing its "hot mirror" (which blocks IR) and replacing it with an "IR pass" filter. Allowing infrared light through and blocking some or all visible light. When DSLRs are converted the autofocus is usually calibrated to your favourite lens, although this will only be accurate for that specific one in that specific wavelength. This will allow the viewfinder to be used, but only in visible light of course. This can be done to mirrorless cameras too, although I personally feel like a full spectrum conversion makes more sense there.
Canon 40D (Converted to 720nm) + EF 24-105L + 830nm IR Filter
24mm f/5.6, 1/100th, iso 200
Conversion can be done in any wavelength you like. 720nm is the most popular option, but that seems like a legacy option from the film days. If colour IR is desirable to you I would recommend something more like 590nm. Higher wavelength filters can be added to the lens (as desired) which will still provide good exposures, you just won't be able to see through the optical viewfinder on a DSLR.
Pros
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Normal exposure values (easy hand-held)
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No external filters needed
Cons
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Stuck with a specific wavelength (mostly)
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Camera can no longer shoot visible light
3. Converted 'Full Spectrum' camera
Instead of replacing your camera's hot mirror with a set wavelength you can replace it with nothing (or glass, more on that later). This process is called a "Full Spectrum" conversion. It takes the camera's sensitivity from around 400-650nm up to 350-1100nm. It's important to note that whether the conversion process uses a glass layer or not is related to focusing and not protection.
Sony A7R (Converted to Full Spectrum) + ZA 55/1.8 + Various filters
A full spectrum conversion allows you to shoot visible light, Infrared, UV, or any combination of the three. The down side is that they will require different filters for each combination, which can be expensive and/or fiddly. The above image shows some of my favourite filters, but there are a lot more. I also have the 720nm (Hoya R72) and Ultraviolet filters available to test, as well as great cheaper alternatives to the Kolari IR Chrome and Hot Mirror filter, but I only had so many magnetic filter adaptors, more are o the way...
Pros
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Can shoot normal colour (w/Hot Mirror)
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Can shoot any Infrared wavelength
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Can shoot UltraViolet
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Can shot any combination of wavelengths
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Normal exposure values in IR & Colour
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Removable internal clip-in filters are common
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Allows for filters like "IR Chrome"
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Magnetic filter swaps are a great experience
Cons
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Filter options for many lenses can get expensive
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External filters can cause slight IQ issues
Cameras Types - For Conversion
DSLRs - Barely Functional
Converting a DSLR to a specific wavelength allows the optical viewfinder and exposure values to function normally, which is great, but there are still some pretty big down sides. This makes the cost of conversion rather difficult to justify IMO. Each lens requires different focus offsets and zooms change throughout their range. The camera can be calibrated for one lens, but even if done well it can only guarantee accuracy for a single focal length at a specific wavelength. Metering is problematic too, since it's not calculated on the sensor. It will bypass the IR filter and thus won't be accurate or consistent. A full spectrum conversion will be even more problematic as filters used on the lens will block the viewfinder, metering and AF system. "Live-View" will help a lot, but even a good implementation of it will be a poor version of a mirrorless camera with an EVF. Focusing with Live View will actually be accurate, but very slow. General camera functionality will be clunky and viewing your scene on a fixed LCD in sunlight won't be pleasant.
Mirrorless - Game Changer
Whether converting to InfraRed or Full Spectrum, every single issue that DSLRs have don't occur on mirrorless. Switching between an EVF and the LCD is instantaneous and doesn't change the focus system. The viewfinder not only works, but shows you the correct colours, with whatever custom white balance you need. Focusing works accurately, for every lens, focal length and wavelength, no mater how shallow your depth of field (no calibration needed). Metering works much more accurately and if there is any artistic requirement you have, it's much easier to capture when the camera is showing you the exact exposure you're capturing in real-time.
Various Filters For Full Spectrum Camera
Pros
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On sensor AF just works in any wavelength
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On Sensor exposure is much more accurate
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Viewfinder works with opaque filters (IR)
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WB preset shows correct colours live
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EVF & LCD show true exposure
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EVF & LCD use proper PD AF speed
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No light leaking through the viewfinder
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Live histogram, focus peaking, hightlights etc.
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No colour cast when using external hot mirror
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Review images on the EVF in strong sunlight
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Zoom in on EVF to focus check manual lenses
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Access to cheap vintage lenses
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Old manual lenses are often superior for IR
Cons
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Nothing
This pros and cons list can be reversed for DSLRs, which hopefully demonstrates why mirrorless cameras are so much better for conversions. So, are mirrorless full spectrum conversions always the best option? Well, mirrorless? Mostly yes, but full spectrum? maybe not every time... As awesome as they are, they can also easily add a lot to your costs and complexity due to requiring more filters, so I still recommend making this choice carefully.
Lenses
Many modern lenses are sharper than older ones and this is especially true for colour infrared. However, sharpness is likely less important than getting a clean image and a lot of modern lenses have quite bad light contamination issues in infrared (see "Hotspot" section below). Your chances of finding a good lens for IR go way up when using older & cheaper manual SLR lenses. Usually the older the better. Mirrorless cameras provide another huge benefit here as they're able to adapt pretty much any of them (with cheap, simple adaptors) and manual focus is much more easily and reliably achieved using mirrorless focus assistance.
There are some lenses specially made for infrared, but if searching for them online just make sure they're not for thermal cameras (that's a different kind of infrared). Zeiss made a set of primes with special coatings for infrared (25mm, 50mm & 85mm), one of which you will see the results from in the Hotspot image below, but unfortunately these were discontinued in 2015 (only a couple years after they were introduced), so finding these now is difficult and/or expensive).
Hotspots - IR Lens Database
No, that's not the sun in the Sigma image below, it's Infrared light contamination. Often referred to as: "Hotspot". Bright areas around the edges of the frame make it worse and dark, flat areas towards the centre show the issue more clearly. This can subtly unbalance general contrast or cause an obvious blemish, but it's not always a circle / spot. Light bouncing off the sensor and getting trapped in the lens element coatings seems to be the main cause (note the exposure times for each lens / wavelength). The Zeiss lens is a rare version with special infrared coatings and thus is about as good / clean as you can reasonably expect.
It's a bit of a myth that lower wavelengths can fix hotspot issues. Although the issue is more intense with higher wavelengths (like 830nm), any infrared effect is going to show its issues. Lower wavelengths, like 590nm (on the left, above) tend to have colour separation and the issues will be concentrated in the blue channel. Poor performance here will make proper colour separation nearly impossible, despite the stray light being less contrasty. Digital Aerochrome filters (see below) are the best way to minimize Hotspot if you're looking to shoot colour infrared, due to them passing very little Infrared light.
I have dedicated a lot of time to designing reliable tests for lenses that show the "Hotspot" issue clearly, using a scoring system. Many other Hotspot tests online go largely on anecdotal results and are counter-productive for purchase decisions. When you don't fully understand what causes the issue it's easy overlook it. It's too easy to find sample images that looks fine when in fact the lens can be far from good. To see which lenses I've tested and how I do that testing, Click here.
Filters
There are a lot of filters that produce interesting results on a full spectrum camera. It is easy to get carried away with buying lots of filters and in various sizes (for each filter thread size). It can get expensive and complicated really quickly. Fortunately there are some tricks to reducing the amount of filters you "need" to buy / carry however. Click the image below to read more about these options...
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Limit your lenses to one filter size (see below)
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Stick to your favourite wavelengths (see below)
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Internal Clip-In filters
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Mirrorless to SLR lens adapters with slot-in filters
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Just get the largest filter size you need + step-up adapters
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Filter holder systems
Digital Aerochrome
Kodak Aerochrome has a bit of a dark history, it was a colour infrared film that was developed to see camouflaged people in foliage. However it was also used by photographers to get a unique pink/red foliage look that could also show non-IR reflective materials in somewhat normal colours.
Colour infrared wavelengths (like 590nm / red filter) usually require swapping channels in post to get the classic look (blue sky with yellow foliage), but if you want to see the classic Kodak Aerochrome look directly in your Electronic Viewfinder (EVF), or rear LCD, the IR Chrome (Kolari) or Crimson (True Color Infrared) are two great options. Note that these filters only work on Full Spectrum, or Two Spectrum conversions. Click the image below to see my full review of the IR Chrome...
Processing
With black and white infrared it's fine to get the white balance as close as you can and then just desaturate the colours before playing with brightness & contrast. For the latter I usually use curves in Photoshop (mostly ACR).
Dealing with colour infrared is much more complicated. The below example shows a 590nm image, taken through various stages. The second image shows that Photoshop requires a bit of a hack to get the colour channels into a usable range, before the channel swap can be applied. To do this requires converting an image to .DNG, running it through the DNG Profile Editor and making a custom profile (for each camera). Once you get the blue foliage and brown sky the red and blue channels can be swapped to get you closer to the desired look (blue sky, yellow foliage) and from there you can tweak the colours more easily.
Faking InfraRed (In Post)
Below demonstrates a colour image (left) put through the infrared preset of the 'Black and White' adjustment in Photoshop. Compared to the actual infrared image on the right. I have further tweaked the colour sliders to better match the infrared shot . Bringing the blues down to darken the water and sky more, while taking the edge off the green boost to avoid clipping. As weak as the sky effect is here it still caused some nasty postarization artefacts and generally doesn't have any of the "magic" you get from a real filter IMO. The dark sky against bright foliage effect isn't here, neither is the way the light bounces around foliage, but judge the results for yourself.
UltraViolet (UV)
Although it's possible to shoot UV with a full spectrum conversion, it's a lot more difficult than infrared. The filters are very expensive, available light is problematic and finding a good lens is tough. Infrared is far more friendly, so I have focused on that.
Infrared Photo Notes
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Which of these (progressively more versatile but expensive) options is right for you will depend on your level of interest.
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All digital sensors are sensitive to infrared light, but it's getting increasingly common that conversion is required to shoot IR.
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Converting cameras is pricey, but modifying the camera should be a big consideration too as it won't act the same as before.
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Some cameras block so little InfraRed light they don't need to be converted to shoot infrared hand-held.
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Some cameras have easily removable Hot Mirrors (usually old / weird ones).
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Second hand converted cameras are usually your best bet on a budget.
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Converting a camera yourself is possible, but not advised.