Little help with focus issue.. Canon 450D - examples..

ottor

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Canon 450D - 3.5fps - I always shoot in 'One shot' because I'm primararily a landscape photographer, however, today had an opportunity to shoot my dog... :lol:

Used 1/800, f/4.0, 200mm, iso 400 (very overcast) ...... using Sigma 70-200 f/2.8 OS lens....

For this series I switched to AI Servo ...... I used the image stabilazition and laid on the grass supporting the camera with my elbows on the ground.. Can someone
help me understand what happened with these pictures ??? I thought I had held the camera fairly still..... these look as though I was doing jumpin jacks during the shoot !! :blushing:

thanks,

r


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rexbobcat

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IS only works with stationary objects.

It looks to me like maybe your camera AI Servo was not precise/fast enough to capture the action before it was gone.
 

EIngerson

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The IS issue mentioned above, plus, What AF point? I recommend Spot AF, and make sure to track the subject properly or it will pick the wrong focus point. It appears that you're missing the subject because you can see the grass in focus where the camera picked it up.
 
P

punch

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servo has problems with objects travelling directly towards you.

try setting your focus and shooting her right as she enters that plane... or moving your focus ring as she runs.
 

KmH

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I don't shoot Canon, but I'll venture that AI Servo, by necessity invokes, shutter priority release mode. In other words the camera will release the shutter even if focus has not been achieved. In single focus mode the camera is in focus priority mode, and will not release the shutter until focus has been achieved.

Two other factors are also at issue in that the dog and the grass are virtually the same color, offering little contrast, and the grass itself has many, many edges, both situations any phase-detection auto focus system will have difficultly dealing with accurately. Autofocus - Wikipedia, the free encyclopedia

WTF is a Canon 450D in American Canon Lingo? Ok. I found it. Here in the US it's a EOS Rebel XSi, in Japan it's a EOS Kiss X2, and in the rest of the world it's a EOS 450D.
See page 162 of the XSi user's manual - When Auto Focus Fails. http://gdlp01.c-wss.com/gds/3/0300000933/01/EOSRXSi-EOS450D_EN.pdf
 

enzodm

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Plus, at 200mm and f/4, DoF is relatively shallow.
 

Overread

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Subjects moving toward/away from the camera are some of the most tricky to focus upon - and often if you don't nail the first shot the others will fail to lock as well (since whilst the camera tries to refocus between shots it does not get the time to). The point regarding light has also been made, dimmer lighting and flatter contrast makes it all the harder for the AF to lock on

Also were you using the single middle point? In the 450D its the most accurate point you have access to and using a single point helps to define what you want in focus (ie the dog) as opposed to expanded points which might grab other nearer points.
 

Joey_Ricard

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Quoted from another source and adapted from Wiki

>>>However, image stabilization does not prevent motion blur caused by the movement of the subject or by extreme movements of the camera. Image stabilization is only designed for and capable of reducing blur that results from normal, minute shaking of a lens due to hand-held shooting.>>
 

Overread

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Also IS does not work at higher shutter speeds normally above 1/250

This point gets a little bit debatable. IS won't be helping remove your handshake from the photos (unless you've more extreme shake than average), but IS will continue to smooth the viewfinder image for you. I find this helps a lot with heavier, longer lenses at removing small amounts of shake from the viewfinder image and thus making framing easier
 

gsgary

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Also IS does not work at higher shutter speeds normally above 1/250

This point gets a little bit debatable. IS won't be helping remove your handshake from the photos (unless you've more extreme shake than average), but IS will continue to smooth the viewfinder image for you. I find this helps a lot with heavier, longer lenses at removing small amounts of shake from the viewfinder image and thus making framing easier

And slow down focus
 

Overread

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Aye, but its easier to pin your focus on the subject part you want if its not jumping around in the viewfinder ;)
Of course the best answer (with a long lens) is a gimbal tripod head and no IS - or a monopod.
 

gsgary

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Aye, but its easier to pin your focus on the subject part you want if its not jumping around in the viewfinder ;)
Of course the best answer (with a long lens) is a gimbal tripod head and no IS - or a monopod.

300f2.8 works a treat :sexywink: never noticed subject jumping around in veiwfinder because i use a smooth action
 

Derrel

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It looks to me as if the IS system "might be" the culprit. I'm usually able to discern different types of camera shake or camera movement by eye, but these images look WEIRD. Very,very weird. One part of your question makes me think it is a problem caused by IS--the fact that you were shooting prone...perhaps THE most-stable hand-triggered shooting position...the way the grass blades are rendered is simply ODD...as if the lens's IS system is caught in a feedback loop, and the shutter speed is just the right duration to record the lens elements' shifting...I have seen similar ruined photos shot with the Nikkor 80-400 VR lens and a tripod (which is a No-No with that lens!!!).
 

KmH

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Aye, but its easier to pin your focus on the subject part you want if its not jumping around in the viewfinder ;)
If you have a camera system that puts the image stabilizing (IS) system in the lens.

Cameras that have the IS in the camera body, like Sony and Olympus, don't stabilize the viewfinder view.
 

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