Some thermographers are surprised to learn that many wide angle lenses can be used for high magnification work. After all, the wide angle lenses have a larger IFOV and IFOV footprint, so how can they be used for small targets effectively?
Here is a typical example for a FLIR E60 camera (320 x 240 resolution):
|Lens FOV||IFOV (mrad)||IFOV footprint at 19.7” Working Distance|
|25° x 19°||1.36||0.03”|
|45° × 33.8°||2.59||0.05”|
The specs above don’t indicate that a wide angle lens is any better, in fact it has a larger footprint. So what gives?
Take a look at the thermograms below:
Does a wide angle lens work as well as a dedicated close up lens? No, of course not. You might notice that the sharpest areas are in the middle of the image. A dedicated optic for close up work would be designed to reduce this effect while achieving higher magnification.
But as a dual purpose optic, when you need to do some close up work, a wide angle lens is pretty handy.
Here are some images from a FLIR P640 for comparison.