I was on my way to an old windmill for this project when I noticed a new wind turbine by the road side; what goes around comes around. I decided to use this to experiment with the effects of different shutter speeds on representing movement. The weather was changeable and the best images were when there was some blue sky behind the white turbine. The camera was set on shutter priority so that the aperture changed automatically to match the speed I chose. I used a 17-70 zoom lens and the camera was mounted on a tripod. To get as slow a speed as possible, the ISO setting was 100 but this still did not allow me to go as slow as I wanted. I, therefore used a neutral density (x8) filter when I got down to 1/15th second and less. The windmill didn't miss out; I used it instead for the project on fitting the subject to the frame.
1/500th sec. at f7.1. This and faster shutter speeds 'froze' the movement. There is no evidence at all that the propellors were rotating quite rapidly. The form of the turbine is emphasised.
1/250th sec. at f10. No discernable difference to the shot taken at 1/500th
1/125th sec. at f13. The first signs that the shutter speed was not freezing the action; there is some slight blurring at the ends of the propellors, but it doesn't show motion convincingly. This is, therefore, not a speed I would choose for this type of subject, unless I wanted fuzzy edges instead of form or motion.
1/60th sec. at f18. There is slightly more motion blur here but it still does not strongly convey the speed of the propellors.
1/30th sec. at f25. This shutter speed conveys the first impression of something other than lack of sharp focus; there is a slight stretching of the propellors, beginning to give the idea that they are travelling from one point to another.
1/15th sec. and I ran out of aperture settings therefore I held a cokin neutral density (ND) x8 filter in front of the lens. This allowed me to shoot at f20 without affecting the colours too much. The greater incidence of blue sky is more the result of the weather changing than the filter. The sense of the propellors travelling is increased as the ends are beginning to 'split'.
1/8th sec. at f25 with ND x8 filter. The sense of movement in the propellors is greatly increased and this is a much more convincing representation of the work of the turbine, rather than just its form.
1/5th sec. at f32 with ND x8 filter. This is the shot I prefer for conveying the action of the propellors and this shutter speed would probably be my starting point if shooting this subject again. The effect, of course, is as much a result of the propellor speed as the shutter speed, therefore there will always be an element of trial and error, which is helped enormously by using a digital camera. I had now run out of both aperture settings and ND filters so I decided to try another approach for conveying movement.
This image was taken using multiple exposure. I tried various numbers of exposures on one frame and three seemed to work best. This is three exposures at 1/125th sec. I couldn't really see the full impact on the camera screen, but when I looked at it on the computer, the main effect has been to reduce the 'solidity' of the propellors. It looks more like a turbine with 6 still, transluscent propellors than three moving ones.
3 exposures at 1/60th. There is a little more blurring of the propellors and the bunching probably helps slightly with the sense of movement. If there had been more speed blur this could have been quite effective.
Three exposures at 1/30th sec. The propellors are spread out again. I'm not sure if the spreading of the propellors is a result of the shutter speed, the starting position of the propellors or are just random. This was taken while the sky was cloudy so the contrast was reduced and it's difficult to see any motion in the propellors.
Two exposures at 1/15th sec. Again, the impact is lost due to the cloudy conditions, but there is clearly more movement here. This was as far as I got at the location. Having seen the results on the computer screen I will return, on a clear day, and try multiple exposures at around 1/5th sec.
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