Starting with Infra-Red Photography Part 7 – Testing modern lenses

I am aware that modern lenses are not necessarily suitable for infra-red photography as they often produce hotspots – I have read that this is due to the type of glass used in modern lenses. So, before I get my camera converted, I thought I would undertake some testing of my lenses.

First up is my 10-24mm wide-angle zoom. The presence and intensity of the hotspot varies with the wavelength passed by the filter:

10mm focal length, 720nm filter, no discernible hotspot
10mm focal length, 760nm filter, visible hotspot
10mm focal length, 850nm filter, definite hotspot

Other tests of this lens with different apertures showed the same problem. A similar result is for the 18-55mm lens:

18mm focal length, 720nm filter no discernible hotspot
18mm focal length, 760nm filter, visible hotspot
18mm focal length, 850nm filter, strong hotspot

The best lens proved to be the 55-200 telephoto zoom:

200mm focal length, 720nm filter, no discernable hotspot
200mm focal length, 850nm filter, no discernable hotspot
200mm focal length, 950nm filter, there might just be signs of a hotspot

At least I have some idea what to expect from my modern lenses…

Author: Paul L.G. Morris

I am an amateur photographer whose photography is mostly of gardens, nature and the rural environment. My specialities are close-ups, panoramic views, or a combination of both that I call 'Nearscapes'. I work mostly for my own interest having closed my business PM Studios Ltd.