Full Spectrum Conversion
To convert a digital camera to Full Spectrum involves removing the UV/IR Cut Filter [ Hot Mirror ] that covers the CMOS sensor, this allows all wavelengths of light to hit the sensor. However with no filtration the image will be very soft as no lens can focus UV, Visible and Infra Red light to the same point, but by simply adding a blocking filter to the front of the lens in use, will allow photos to be taken in whatever type of light is desired.
Infra Red Conversion
To convert a digital camera to Infra Red involves removing the UV/IR Cut Filter [ Hot Mirror ] that covers the CMOS sensor, then a IR Passing [Visible Blocking ] filter is added where the UV/IR Cut Filter was removed. This filter is permanent and the camera will only be able to “see” light that the filter passes.
Converted Cameras and Bespoke Camera Conversions
590nm, 680nm,720nm or 850nm Internal Filter – Which is the Best Conversion?
There is no definitive answer, but which is best for you depends on your own specific requirements. If you are having a camera converted to IR with an internal filter, which wavelength to go for depends on whether you like the false colour effects, where foliage looks yellowy gold and skies look blue. This is not an effect that can be seen in the viewfinder or on the raw or jpg file. It is obtained by swapping the Red and Blue Channels in Photoshop, see the tutorials page for more details.
The example shown on the left is a typical example of the “Goldie” look, certainly interesting, but some people love it and some hate it. You can only get that sort of result with a deep red filter, that allows some Visible Red as well as IR light through, something in the region of 565nm to 680nm filter, the photo on the left was taken with a 590nm converted Sony Nex 6. A 720nm filter, the most popular IR filter, would only have very muted colours even after swapping channels. With wavelengths longer than about 700nm, there is very little colour information, the R,G and B channels are all practically the same, so these are more suited to Black and White effects. The longer the wavelength of filter though the greater the contrast between blue skies and foliage, so a more dramatic Black and White effect is obtained with something like 850nm filter, although exposures will have to be longer as these filters are blocking all visible light and quite a lot of Near Infra Red that the camera is sensitive to.
The simple answer is if you want to do Black and White only, then go for the 720nm or 850nm, if you want to keep the option to do False Colour then go for a 590nm or 680nm. The 590nm and 680nm conversions can do Black and White, with very slightly less contrast as they stand.
If you have a 590nm conversion, for example, you can always add an external R72 IR filter to the lens to get the same effect as an internal 720nm conversion, with very slightly longer exposures, approx 1 stop at most. Likewise if you have a 720nm conversion you can add an 850nm filter to the lens to get slightly more contrast in landscapes, you cannot however put a 590nm or deep red filter on and get false colour effects. It won’t work that way round as the internal 720nm filter will block any red light that the red lens filter is letting through!
Full Spectrum or Specific Internal Filter Conversion?
In Full Spectrum Conversions, the internal UV/IR Cut Filter is completely removed, whereas in a Specific Filter Conversion [ IR Conversion, normally ] the UV/Cut Filter is replaced by a filter that blocks most or all UV and Visible light, such as a 590nm or 720nm filter. In the Full Spectrum Conversion a similar filter has to be placed in front of the lens in use, such as a Deep Red or R72 Ir Filter. The results are the same if a similar filter is used, so what are the Pros and Cons of each type of conversion and each wavelength.