types of infrared filters

 

The CMOS sensors in our cameras naturally have a larger range than this, from about 300nm through 1000nm. That’s twice the range of human vision! To make our images look normal, manufacturers put filters in front of the sensors that limit the camera to only the spectrum that we can see.

 

Infrared photography takes things in a less realistic but fascinating direction: what if you shoot beyond what we can see, into deeper wavelengths of light? There are a number of infrared filters available that you can convert your camera to, by replacing the sensor filters than let through a different portion of the light spectrum. The images in this exactly were taken with a Lumix GX85 that I had converted to full-spectrum photography which allows for the use of screw-in filters on the front of a lens to choose the desired spectrum. Common options are as follows:

 

590nm (also called Super Colour):

Very colourful but hard to use the full amount of colour, since most of the time it becomes a wash of blue. It’s important to note that this wavelength cut-off includes a sizeable portion of the visible spectrum including orange and red. Because of this, the high-contrast details often found in skies and foliage are more muted.

 

665nm (Also called Enhanced Colour):

Adding the reds of the visible spectrum into the full infrared mix, this can add additional colour if you’re in a heavily urban area. With careful massaging, you can increase the contrast and have more vibrant colours, but a lot of post-processing work is required if you want to get the right colours.

 

720nm (also called Standard):

This is my personal favourite. Pure infrared light with glowing foliage, darker skies, contrasty clouds and deeper water. You can still play with false colour here at 720nm even without visible spectrum, since the RGB photosite colour dyes on the camera sensor don’t equally become transparent to IR light until about 820nm. This allows for a conversion to blue skies and a slight hint of colour in the trees if you want it. If you want to make it black & white, you’ll immediately already have good infrared contrast without any extra efforts.

 

850nm (also called Deep B&W):

Deeper into the infrared spectrum, there is no colour information to be found. Usually higher contrast and the easiest to deal with in editing since there is no colour to fuss with (processing for false colour is a can of worms).

 

1000nm:

Infrared filters are available down to 1000nm, but since the camera loses sensitivity to light around this point, you’ll need very long exposures (effectively making it function like an infrared ND filter). The contrast is roughly the same as 850nm but you can see a bit farther into scenes without any haze building up. Very few people consider these filters more than a novelty for very niche scenarios (long exposure IR).

 
Remember that any infrared filter with a number less than 700nm will include a portion of the visible spectrum, limiting the IR contrast effects in favour of added colour that is often times not needed. Beyond 820nm, no colour information exists so 850nm filters are primarily monochrome. Dyes used by different manufacturers may behave differently, but this is the standard behaviour. My favourite wavelength continues to be 720nm for its combination of high-contrast and the ability to process for false colour. There’s a reason why it’s considered the “standard”, which is not with “basic” vs. some other “premium” option!