I spent half of saturday photographing dead trees so you dont have to...
This lens test is unline the normal lens tests in that i am testing, not so much for sharpness and colour but for performance under long exposure
infra-red lighting conditions, I bought a 16-35 f2.8 mk1 lens a few months ago and after using it for infra-red started to notice the centre hotspots.
Research on the net hinted that out of the 2 lenses that i had considered, the 16-35 and the 17-40, i had chosen the wrong one.
but to what extreme were these lenses different, so i decided to find out.
For this test i printed out my testing conditions, borrowed a 17-40 lens and headed out to start my testing
Im using a Heliopan 715nm filter which allows light over the 715 nanometer spectru
m to enter the camera
all the tests were done at 17mm, there are further tests that i did at 35mm but these tests didnt prove anything further so ive not included these results
I concentrated on 3 trees and for a few hours passers by must have thought i was waiting for squirrels to fall out the tree or something...
the light conditions obviously change minute by minute so these arent exactly controlled tests, so dont take these tests too literally, there are variation in contrast and colour.
all of the images have had the same preset applied in LightRoom:
the first test
f13 at 13 seconds
A slight difference here between the 2 lenses, the 16-35 slightly brighter in the centre
Close-up you can see the 17-40 has slightly more detail and contrast
not much difference around the edges
f8 at 15 seconds
At f8 here you can see a markable difference between the centres of the image
the 16-35 has alot less clarity and contrast
the 17-40 looks slightly sharper here but this could be caused by the wind
again slight difference here but not that noticable
f16 at 15 seconds
Here at f13 you can see a defined hotspot on the 16-35 image
very noticable up close
not much difference around the edges
f9 at 25 seconds
At f9 here you can see the centre is brighter on the 16-35
Clarity looks sharper on the 17-40 again but this could be down to the time differences
f13 at 25 seconds
at f13 here you can see the hotspot clearly
My conclusions: Personally because i do alot of IR work, i have decided to get a 17-40 f4L because of the slight increase of clarity and the way it
deals with the internal reflections, whether i will get rid of the 16-35 yet, i dont know. The tests i did were supposed to give a wide range of results, i know you wouldnt normally shoot Infra Red at f16
but i wanted to show the extremes, also the length of shutter speed have a great deal to do with the outcome as well.
So dont take this test as gospel, im not drawing any dramatic conclusions, just adding to the research material available on the interweb.
