Infrared lenses need to be carefully chosen as some lens/camera combinations which work fine for regular photography create a ‘hotspot’ when used for infrared photography.
These hotspots show up a brighter area – usually a circle – in the centre of the frame. The effect can vary from very mild – which just looks like lens vignetting, to severe where a small bright area appears right in the middle of your image. If a particular lens is prone to hotspots, the problem gets worse as you stop down so that at very small apertures (eg f22) the hotspot is at its most obvious. I suspect that different infrared conversion filters also affect the way the problem shows up.
Sometimes you can correct for hotspot effects in Photoshop/Lightroom/ACR etc but I’ve found this process hard to automate, takes extra time and occasionally the problem just plain cannot be fixed. Its a much better strategy to find lenses that perform well in the infrared spectrum.
Ironically, the lenses which perform worst seem to be modern, multi-coated (and expensive) ones, while older, simpler lenses seem to do better. However, there are no hard and fast rules, its down to trial and error.
There is an extensive list of lenses on the Kolari Vision website
For what its worth – here is my infrared lens “Good hotspot” lens lists. These lists are based on personal experience of making images – rather than any kind of scientific or rigorous testing. Most of the time I shoot infrared images at f8. So, for me, if f8 is clear – then its a good IR lens.
Used either with a modified Sony a6000, 720nm filter with Kolari Vision anti-glare option and/or Sony a7Rii, 665 filter with Kolari Vision anti-glare option:
Sony 10-18 f4 – a versatile wide angle zoom for APS sensor cameras. Very small and full autofocus. This one is listed as “Poor” on the Kolari Vision list – but I’ve shot thousands of images with it in infrared – mostly at f8 with no problem.
Canon 24-105 f4 L – Sharp across the zoom range with no hotspots at any f stop. (Please note I have the mark I version which is now superceded by the mark II version and which I have not tested for IR.) Used on both a Fotodiox Pro EF-Sny(E) Smart AF Adaptor and a Metabones V.
Sony 16-35 f4 – good for infrared up to f11 or so. At the wide end does flare easily.
Sony 24-70 f4 – widley criticised as being soft in regular light – but one of my favourites for infrared shooting where razor sharp corners just dont matter.
Lensbaby Velvet 56mm f1.6 – love this lens both for infrared and regular colour work. Its an old school, heavy, glass manual lens and its party trick is to become progressivley soft-focussed from around f4 until at f1.6 its creates a very soft image with a tiny sharp plane of focus. This effect works really welll in infrared.
Sony 16-70 f4 – OK performance – depending on the light intensity I often noticed a mild large lighter area in the frame – more like reverse vignetting than a defined hotspot. Nice range for APS camera (24-105 equivalent) but not my favourite for infrared.
Sony 16-50 f3.5-5.6 – the aps kit lens – unusable for infrared – major hotspots throughout.
Sony FE 28-70mm f/3.5-5.6 – the full frame kit lens – significant hotspots from f4.