Motion in a Windmill

[jonjdoe]

I have a question about focus for a shot like this. The windmill was running intermittently. When the blades stopped, or almost stopped, I used spot focus on the blades. A mistake? There must be some lateral motion in those blades when they start to turn, so focus on the edges is almost impossible. Where should the focus be? 70mm-200mm lens @ 70mm, TV to get the motion (1/30 sec), F22, ISO 100. Thanks for any comments.

[Geoff F]

That is about all you can do, John. Focusing on the superstructure near the blades might work OK. But the danger is that auto focus will prefer the trees instead.

Probably a case for manually focusing, preferably on a tripod.

If autofocusing, I would certainly use just the centre focusing point, to avoid false focus confusion, and recompose if necessary.

[jonjdoe]

Thanks Geoff. That is helpful!!

[Dave Humphries]

Hi John,

I'd suggest aiming for the central hub, that isn't moving too much

I would query the f/22 though, it has made the trees almost sharp too - perhaps it was necessary due to the brightness of the scene (even at iso 100), in order to get the 1/30s to show the blade's movement?

If you have a polarising filter available (many people do), in lieu of an ND filter (many people don't), that would 'lose' a couple of stops of light and allow a wider aperture for less DoF - just be careful of any unwanted darkening of sky or blades it causes, you may want to rotate for least darkening in this instance.

HTH,

[jonjdoe]

I would query the f/22 though, it has made the trees almost sharp too - perhaps it was necessary due to the brightness of the scene (even at iso 100), in order to get the 1/30s to show the blade's movement?

Thanks, Dave. Yes, the f/22 was set for the shutter speed (Tv). I do have a polarizer and will try that. Thanks for the help!

[elfbob]

Several considerations:1) were you constrained to this view of the windmill or did you perhaps move to other angular aspects to check if one might have had less tree branches behind it? 2) Tv is great for getting the motion effect you desire; have you ever ventured into the mysterious M realm where you can also set a f/ that could possibly also isolate the windmill from the adjacent trees by controlling dof; sometimes i get stumped in M when i've exhausted the factors i can control to limit ambient illumination & still get the image i've previsualized; sometimes, like was stated earlier, you can use a circular polarizer as a light limiting filter, you just need to rotate it to see what suits you best;3) ND filters not only limit ambient light but can be used creatively in the f/ : shutter speed "tango" ; 4)when the windmill slowed down were you able to see anything near adjacent to the blade section you wanted as your focal point that you could have prefocused on, then having focus lock recomposed & shot.

[jonjdoe]

Thanks for your reply, Robert. #1 there was some constraint. The windmill is in a botanical garden; my choices were this one, or some fake barns, or power lines. My purpose was to show motion and still see some blade. #2 M was my next consideration. By this time the battery had gone out in the remote shutter trigger, I'm mad (because I let this happen with no spares in the bag), and packing up . #3 I have no experience with ND filters; am interested, but need advice on the proper adapter and rectangular shaped filters vs screw-in filters. My next "expense" I think. #4 this was not one that came to mind, but in retrospect seemed like a good idea. I actually would like to have seen the apparent "edge" of the whirling blade in focus, but this might have been asking too much (I doubt if the spindle is precision enough to prevent some vibration during the spin ). Focus-lock and recompose is a technique I'm working on anyway, but again see #2 above . Thanks again for your help.

[jonjdoe]

Okay. Here is another whack at the windmill. I think this one is in focus, at the hub.