So, before the return from Faizabad a week ago (the images from the flight up were all ruined), I did some online research and the advice for aerial photography was as follows.
- Switch off AF (as reflections can supposedly distract AF and glass can be polarised).
- Apply your hood (to cut down flare).
- Get as close to the glass as you can, without touching it (which I was doing).
I pondered this and then I added my own observations with respect to what might have changed since the successful flights:
- My last few flights were on a different airline with different aircraft.
- We were generally flying at higher altitude, which required the camera to often be angled downwards, often quite steeply.
- The greater altitude meant more atmospheric haze due to moisture and dust. The landscape was therefore also further away.
- I saw that the windows had some curvature in the glass towards the edges that took some noticing, but I wondered if the windows were somehow acting like a second lens. More on this later….
- In some cases it just looked like the AF had plain missed, despite the camera thinking it was in focus. This was very strange: camera locks on and gives green light, but frame out of focus. Odd. About as odd as the Eos 3 body I had that will not focus any 85mm canon lenses. The image in the viewfinder snapped into focus, but the negs were MILES out. This happened with three 85mm lenses (85mm f1.8 EF x2 and 85mm f1.2 L II) and no other focal lengths. I never did solve the problem and had to buy a Eos 1n to shoot with my 85mm f1.2 L II…..
I then decided I would take the following measures to ‘blitz’ the problem. I had a feeling quite a few factors were involved (1 – missed focus with AF, 2 – soft edges, 3 – soft ‘patches’):
- Use MF only.
- Set f5.6 wherever possible.
- Try to shoot as perpendicular to the glass as possible and avoid including the far edges in the frame.
- Allow shutter speed to creep down a bit if it allowed a smaller aperture.
- Inspect the windows more closely to see if I could identify the cause of the soft patches.
And it worked, although I did not encounter plain sailing at all – I had to work for it! I decided to forego the take-off frames for greater certainty of bagging shots once properly airborne and in the ascent. I Therefore set the focus manually to about 500m on both cameras just before take off. This is only a hair shy of infinity and so I figured depth of field would absorb any fractional error, should I be a bit closer or further away. However, I noticed quite quickly that the frames were not sharp and, when looking though the glass of the plane, I needed to twist the electronic ‘fly by wire’ focus considerably further away to get focus on terra firma no more than 500 to 800m away. I should not have been able to significantly change focus, seeing as how close I was to infinity already, but I could. Once I had confirmed focus through the viewfinder in magnified view, I settled back into composing on the rear LCD screen (much easier in the cramped seats and difficult angles required up close to the glass.
At this point, everything seemed to be going well, until I noticed that there was a very subtle band of ‘flaws’ running vertically down the centre of the window I was shooting through. It was hardly noticeable to the naked eye but it was completely throwing the focus out of frames that were shot through this band (remember you are up close, so even if the band is only an inch across, that’s most of the frame if your front element is only an inch away!!
I promptly changed seats, as the positioning of this flaw was almost impossible to work around. I did, however, kick myself knowing I had shot many frames that would now be ruined. A quick inspection of files on the rear LCD showed this to be the case L With my ‘new window’ I was able to shoot more freely, but I still took care to avoid the edges and minimised deviation from shooting trough the glass ‘straight on’. Severe tilting from the perpendicular was definitely having an affect.
So what was the outcome? It was not a perfect hit rate. I have frames that still have some soft zones, but these are mostly towards the edges where the edge of the window glass came into effect, but there are still some in random places. I suspect this is just a product of the type of glass in this particular model of plane. In contrast, the helicopter I flew on to Bamyan might have had dirty scratched windows, but it appeared to have uniform resolving power.
Ice crystals forming on the glass also robbed some frames of their contrast and increased flare, but overall I am very pleased and now know that shooting at lower altitude will be much easier. In summary, however, here are my recommendations:
- Use manual focus. The glass on some aircraft can play tricks with your autofocus. If you have the chance to do some test shots with AF on and check file quality, then its well worthwhile. Certainly when flying lower and the distance to the terrain can change significantly, AF is useful, but you cannot rely on it. It all seems to be down to possible polarising coatings on windows and other stuff you cannot determine without testing first.
- Focus through the glass using magnified view. Do not be surprised or worried if the distance shown is not what it should be!
- Try to stop down as best you can. This seems to minimise some of the issues caused by the window acting as another lens.
- Check your window in detail for flaws/distortions in the glass and inner plastic (where present). Flaws can have a massive affect on your images – far more so than scratches – and they can be extremely hard to spot.
- Select a high enough shutter speed. The right speed selection takes experience and, naturally, the lower you are, the higher the relative speed across the terrain. To give you an idea, at altitude, I try to ensure keep the speed at least 4 x 1/FL i.e. a 55mm lens should be shot at 1/500th I am more comfortable at 1/1000 or higher. When getting close to the ground, if you want sharp frames expect to ramp this up as far as it will go, but motion blur can be used to good effect too.
- Recognise that turbulence and vibration will have a very real affect on sharpness. Do not press your lens against the glass to steady the camera, as vibrations will transfer to your camera. Try instead to act as a ‘physical stabiliser’.
- Consider shooting in consecutive/high speed mode, as this helps ensure that you get frames during periods of relative stability between bumps through the air. This is much more important on small planes that can really bounce around.
- Do experiment with subtly panning with the passing landscape just as you release the shutter. This can be really important when the closing speed increases. It can result in some funky artefacts too….
- For reasons I cannot fathom, my 55mm lens seemed to be more affected by distortion and soft edges than my 35mm. The 35mm seemed to punch out better results more consistently, despite the fact that the 55mm is actually a touch sharper around the periphery in ordinary use. Its something to do with those darned windows….
- If you are in a small plane, in a cramped seat and the window is not in a convenient place, be prepared for some sore muscles! Try to select a seat, where the windows is more in front than slightly behind!
- Don’t worry too much about imperfections. Some of the flare, obstructions, reflections, smears and gunk on the glass can be put to good effect in the final image processing. If you don’t have a perfect window, for goodness sake don’t give up. Look at it as a vision and post-processing challenge. It’s all part of the process. I have a few soft frames I have decided to keep, because I have made them work.
So, without further ado, here are a couple of frames that worked, technically speaking. All are draft in terms of processing, but it will give you a rough idea. In shooting this last leg, I have also finally resolved how I am going to present this body of work and how I will sequence the images. That I will keep under my hat, but I will show a few more images in a future piece, for sure!
*Depending on the size of your screen, you can command + click (or whatever one does with windows) any image to see it larger in a new tab*