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http://www.tipf.co.uk/forums/topic/46369-important~-the-forum-its-future-and-finances/

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 Clicker and Ryewolf  ...  Admin Team 

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https://www.tipf.co.uk/forums/topic/57184-202223-forum-finances-update-4th-july-2023/

 

Focus problem


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I do a lot of sports photography with a Canon 7D and a 70-200 L series USM lens. I am using a single autofocus point (dead centre of the frame) but even when I have it covering the subject the image is sometimes out of focus. Its not a shutter speed issue as I never use speeds below 1/1000th sec for this type of shot, aperture f2.8 and ISO usually 400 or 500 . I use the Canon DPP4 editing software which shows the focus point(s) on each photo. The out of focus shots have the subject covered by the focus point yet they are fuzzy. Should I have the camera / the lens checked over or is there something wrong with my technique? 

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Hello!

Any chance you could post an example image with exif?  If you could also give estimate to the distance of your subject and state where you focused I or another member may be able to offer some ideas? 😀 

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Whilst I've never used this Camera + Lens Combination (you don't mention if the lens has IS) I have used several Canon bodies with different lens (including 2 Canon IS L series) and each camera worked better with either a single point AF (100D), a group/zone (800D) or large zone (90D) depending on the subject. I mainly photograph birds, jetskis or trains using a burst/continuous shooting mode, I found my older 100D was far more accurate using 1 spot AF point particularly for birds but I never got 100% shots taken totally in focus. I don't think it's a problem with technique or Camera+Lens combination

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You are suffering from diffraction.  A wide aperture and a long focal length don't go well together.  Closing your aperture by a couple of stops will improve the sharpness.

Also bone up on hyper-focal distance, to cover all eventualities.

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Thanks everyone for your replies. I went for the max aperture to create the bokeh effect but I expect I will still get it to some extent by stepping down. The distance to the subject is usually between 10 and 50m. Covering a whole shinty pitch (180 X 80m) isn't doable with a 200m lens so i tend to stick to around a 50m max. I am noticing that even though the subject at the focus point shown by the editing software is actually out of focus, 30m further back is sharp. I wonder if I haven't given the camera enough time to find the focus before pressing the shutter all the way? Either that or I have pressed the shutter half way while swinging the camera to latch on to the moving subject and have actually focused on something else? You have certainly given me plenty to think about, thanks. Couldn't put any examples up as they seem to be too big. 

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At 200mm, focusing just 10m away is giving yourself a very small dof to work with, around 30cm. Great for bokeh, but on a moving target its gonna be near impossible to nail focus I'd say.

Check your focus mode and make sure your on Servo so the camera constantly adjusts the focus if the subject moves.  Back button focus may make it easier.

Stopping down will help.  Lenses down like being wide open and won't be at their sharpest.  Using a slightly shorter focal length will give you more dof to play with.  Less bokeh, but more room for error.

If you're not familiar with dof and what affects it, do a Google search for dof calculator and play with the options to see what I mean.

All that said...I'm no sports photographer so others may have better advice. 😀 

 

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6 minutes ago, MattGrey said:

Check your focus mode and make sure your on Servo so the camera constantly adjusts the focus if the subject moves.

That's a good point whenever I'm photographing fast moving objects I always use AI Servo Mode, it's not going to be perfect for every shot

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