Advice for a newbie - razor sharp focusing on a moving subject.

[evelynlen]

Happy New Year all.

Hoping some experienced people could please help?

I'm on the SPI Foundation in Digital Photography course and tackling an exercise to learn more about shutter speed.

We have to photograph a moving subject, keeping the camera still and waiting for the subject to move into view at 1/1000s, one at 1/60s and then the final photo to track the subject as it moves.

I'm having problems with the moving subject against a stationery background. The background is sharp but the subject is soft, even though the focus point is on it. I've attached a link to an example image.

Obviously I want the subject to be sharp and I'm not sure what I'm doing wrong. Can any offer any advice or suggestions? Or is this a case of 'it comes with practise?'

I have a Nikon D5000 and used a tripod. The camera settings were:
Focal length: 55mm
Focus mode: AF-C
AF-area mode: Dynamic

This exposure was f5.6 at 1/1000s. I ramped up the ISO to 1250 because of the poor light - is this part of the problem?

I read that using Continuous AF can make sharp focusing difficult; it this the problem and if so do you suggest using AF-S or AF-Auto?

I'd appreciate help/ tips.

Thanks, Eve

http://www.flickr.com/photos/serenitysaint/4241422811/

[Malcolm_Stewart]

Looks to me that your cyclist in the example is a few feet from your camera, so why not use manual focus with it set to the appropriate distance? Or have your cyclist on the other side of the road.

HTH

[JohnHallett]

It depends what you want the background to look like. If you want both the cyclist and the background in focus then change the aperture setting to f16 (for example) to increase the depth of field (but you will then need to increase your ISO even higher to keep your shutter speed at 1/1000s). Ideally you want to have the background slightly out of focus so you need to turn off auto-focusing and manually pre-focus on the area of pavement that the cyclist is going to travel over (as mentioned above). Please bear in mind that with the subject this close to you and travelling at any speed then with a fixed camera position the cyclist is always going to be slightly blurred - but I guess this is the whole point of this project

[evelynlen]

Hi both,

Thanks for the advice. I have a 70mm to 300mm lense so I will try that. The idea is that we learn more about the effects of different shutter speeds and their creative applications etc.

I get the impression that for the first picture at 1/1000s both foreground and background are in focus and at 1/60s, the background is in focus but the subject is a big blur.

I have 11 point focus so would it be better to focus off - centre, say at 180 degrees?

Thanks, Eve

[PeteRob]

If the camera is static (on tripod and fixed) you will need to manually focus the camera to a distance same as cyclist will be and previsualise when to fire the shutter. I think there is a discussion of this in an old John Hedgecoe book - local library may well have a copy. memory says 1/500th or faster will freeze cyclist going across (slowly) frame with 50 mm lens and 1/4 frame filled with bike and rider, 1/250th if cyclist approaching. You can help get "focus" as opposed to motion blur by making cyclist go between markers not too far apart and where you choose a f stop to render both sharp. Can do this with a digital camera as can change ISO with shutter speed. Have fun. The other way of doing this is panning - then you can use autofocus - probably this is the next lesson!

[JohnHallett]

I get the impression that for the first picture at 1/1000s both foreground and background are in focus and at 1/60s, the background is in focus but the subject is a big blur.

I have 11 point focus so would it be better to focus off - centre, say at 180 degrees?

I think your 'impression' is spot-on - and a very useful project. When the cyclist is out-of-shot the auto-focus on your camera makes the background houses sharp. Suddenly the cyclist appears and the poor old auto-focus motors have to rapidly change the configuration of the glass in your lens to focus on something that is only there for a split second. Hardly suprising if it fails. Help your poor old auto-focus and either get the cyclist to go really, really slowly or get him to ride on the opposite side of the road so that the focusing plane doesn't have to change so much from the background in such a short time

[evelynlen]

Thanks John and Pete.

Much appreciated!

I started playing about last night with manual focus and focus lock. Just need lots of practise and some nice weather!

Eve x