Sand Dunes of the Namib-Naukluft Desert, Canon 1DsMkIII, 24-105mm, ISO 200, f5, 1/1600
Larger version here
Last night, I was having a brief look through my archives from Namibia last year and found this aerial shot from a microlight. Over the years I’ve unearthed a few gems through this process. It usually makes me sleepy so it’s an activity I reserve for just before bed. The image you see shows some of the wind-sculpted dunes of the Namib-Naukluft desert. Having had several experiences in aerial photography (microlight, Cessna and helicopters) over the past year, I thought I would share a few thoughts. The exposures are going to vary a bit depending on the speed you’re flying and distance from the ground but here are a few general comments.
The importance of getting the balance of speed versus depth of field is amplified once you’re in the air. Since landscape subjects are much further from the lens in aerial photography compared to when you’re on the ground, you can often obtain adequate DOF at wide apertures. My favourite lens in the air is Canon’s 24-105mm 4L IS. The focal length allows me to shoot wide landscapes and it’s also long enough to isolate structures for abstracts like the one above. The image stabilisation is irrelevant since I never shoot at a slow enough shutter speed for hand shake. Perhaps it may have some benefit given the vibrations you get from flying. In any case I leave it on. If I’m able to bring up a second lens and body, I use a 70-200mm 2.8L IS.
Wide open at f4, the 24-105mm, provides enough depth of field for most aerial images. However I usually prefer to stop down to f5-5.6 since the lens is sharper and less affected by vignetting. Occasionally, I’ll have a composition where there’s a definite foreground and background. In this case, a little bit more depth of field may be required to get everything in focus necessitating me to stop down further to 6.3-7.1.
Shutter speed is obviously critical in maintaining a sharp image while moving at fast speed. I’ve found 1/500 the absolute minimum exposure I can get away with using the 24-105mm. However I much prefer to use 1/1000 as a minimum and 1/1600 to be safer still. With a telephoto lens, I stick to the range 1/1600-1/3200.
I use whatever ISO is necessary to make the exposures as suggested above. This will obviously depend on the available lighting but usually I start off with ISO 200 or 400.
ND grad filters are just about impossible to use while flying so I don’t bother with them. My preference is to expose for the highlights even if that means a bit of under-exposure. I find that my ability to shoot at adequate shutter speeds takes too much of a hit from polarising filters so I don’t use them either.
Lastly, an important thing to do is to make time to occasionally quickly check the images on your LCD screen (chimping from CHeck IMage Preview) at 100% crop to make sure that the images are sharp enough and adapt if necessary.
On the Run. Canon 5DMkII, 70-200mm 2.8L IS, ISO 400, f5, 1/3200