Something like "AI-Servo" or "Continuos Focus" or at least release priority? - Feature Requests - CHDK Forum
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Something like "AI-Servo" or "Continuos Focus" or at least release priority?

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Offline m3nt0r

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Something like "AI-Servo" or "Continuos Focus" or at least release priority?
« on: 14 / May / 2008, 07:04:54 »
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Hi folks,

a feature I miss badly on my S5IS is "AI-Servo" for the autofocus, especially while taking sports pictures (mainly beach-volleyball). The dilemma is: if you prefocus an object (player) and it moves then, it's in most cases out of focus; if you don't prefocus, the shot is delayed too much due to the autofocus... :(

The camera DOES try to focus all the time, whether you press the release button halfway or not. If you then press the button halfway, it refocuses the object that is mostly in focus already. Maybe this continuos focusing is not as accurate as the "explicit" focusing on half-pressing the release button, but sometimes it would be enough - "to capture the moment" is more important.

Is it possible to implement such thing? Or at least to disable autofocus "ON_RELEASE_BUTTON_PRESS", thus letting the camera shoot immediately?

I am not sure if it is only an autofocus problem, because in the M-mode with manual focus there is still an obvious delay between pressing the release button fully and the camera actually taking the picture, while there is no noticeable delay if you shoot after half-pressing the release button. I wonder, why the delay? I mean, there is no nead for the cam to calculate something (M-mode), neither it has to focus an object (manual focus). What it really does (I can see and hear it) is openinig and closing the diaphragm (aperture) before shooting. Why that? In full manual mode with manual focus??? Is it possible to lock the diaphragm in the chosen state in M and AV modes and would this cause the camera to release faster?

I am sorry, if I am missing something and therefore asking stupid questions...  ??? Maybe someone can show me the wood behind the trees  ;)

Greets,

-Eugene
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Offline PhyrePhoX

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Re: Something like "AI-Servo" or "Continuos Focus" or at least release priority?
« Reply #1 on: 14 / May / 2008, 09:05:37 »
hm, i never attended any beach volleyball games, and i'm not really a photograpgher. yet yesterday i was visiting a buddy who was playing beachvolleyball at that time. i was about 10 meters away from the field and used the long zoom and a really fast shutter (i think it was too fast, because i had to up the iso too much, which i greatly regret, shutter was between 1/1250 and 1/2000).
i made about 300 shots, of which about 10% weren't in focus.
attached is one sample picture, which isnt really a good sports photo, but that was the first somehow decent one i could come up with so fast.
as i understand sports photography, it is all about anticipating when to shoot. i mostly focused on the net, because there it was where i expected the most action to be. if i had more photographers skills AND the knowledge of the sport itself i think i would have made a ton of great photos (light conditions were excellent!).
what i'm trying to say is that my s3is is sufficient, i wasnt even using sports mode, i used TV mode in burst mode. as soon as i saw the ball advancing to the net i hit the shutter, usually getting one good shot out of three.
i guess it also is having to do with me being so far away from the subjects, as i understand it the focus is set to infinity then? i guess you are much closer (baseline?). if this is the case, well, consider my post obsolete, yet the part about the anticipation remains.
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Offline m3nt0r

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Re: Something like "AI-Servo" or "Continuos Focus" or at least release priority?
« Reply #2 on: 14 / May / 2008, 12:05:08 »
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as i understand sports photography, it is all about anticipating when to shoot. i mostly focused on the net, because there it was where i expected the most action to be.

you're right, anticipation is very important while both playing AND photographing volleyball! focusing on the net is a good idea if you want to take attack/block pictures, that's what i do in such cases, too (see attached pics). however it fails if you want to photograph some defence action, which is often more interesting (spectacular digs). you cannot really anticipate where such a dig takes place, the other pics attached are really lucky shots...

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i guess it also is having to do with me being so far away from the subjects, as i understand it the focus is set to infinity then? i guess you are much closer (baseline?). if this is the case, well, consider my post obsolete, yet the part about the anticipation remains.

i am, let's say, 3-5 meters away from the sideline, so the distance to the object varies from 3 to 12 meters. i prefer to shoot with open diaphragm to blur the background, although the depth-of-field is still to great to my taste. so infinity focus doesn't do...
« Last Edit: 14 / May / 2008, 12:08:08 by m3nt0r »
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Offline wontolla

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Re: Something like "AI-Servo" or "Continuos Focus" or at least release priority?
« Reply #3 on: 14 / May / 2008, 12:54:21 »
Did you try the CHDK's DOF calculator?

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distance to the object varies from 3 to 12 meters

Maybe if you set Av to 4.0 you can keep 3 to 12 meters in focus and still maintain some background blur.

They also say that the "sweet spot" of the S3/S5 is 4.0. (Whatever that means).
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Offline jeff666

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Re: Something like "AI-Servo" or "Continuos Focus" or at least release priority?
« Reply #4 on: 14 / May / 2008, 12:59:58 »
Quote from: m3nt0r on 14 / May / 2008, 07:04:54
I am not sure if it is only an autofocus problem, because in the M-mode with manual focus there is still an obvious delay between pressing the release button fully and the camera actually taking the picture, while there is no noticeable delay if you shoot after half-pressing the release button. I wonder, why the delay?

My A720 has a feature called "Safety MF" that does "auto focus in a close range around the manually set focus area". If I enable "Safety MF" the shoot-delay is about 3 to 4 times as long as without.

There is still a very small delay having "Safety MF" off and fully pressing the shoot button.

GrAnd, ewavr, DataGhost: any idea what the camera does when half-pressing the shoot button?

Cheers.
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Offline DataGhost

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Re: Something like "AI-Servo" or "Continuos Focus" or at least release priority?
« Reply #5 on: 15 / May / 2008, 03:20:58 »
Even in manual mode with manual everything, it'll measure the light and display the EV (-2..2 in 1/3 steps) in the top-left corner of the screen. That's what's causing the short half-press delay. I guess it's possible to disable it, it's on my 'to investigate' list.
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Offline m3nt0r

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Re: Something like "AI-Servo" or "Continuos Focus" or at least release priority?
« Reply #6 on: 15 / May / 2008, 04:54:46 »
Quote from: DataGhost on 15 / May / 2008, 03:20:58
Even in manual mode with manual everything, it'll measure the light and display the EV (-2..2 in 1/3 steps) in the top-left corner of the screen. That's what's causing the short half-press delay. I guess it's possible to disable it, it's on my 'to investigate' list.

This would be VERY COOL! Just an option in CHDK that says to the cam: shoot immediately the frame "as it is" without measuring/focusing/whatever...

The finest thing would be real AI-Servo focus, but that's beyond possibilities of CHDK, isn't it? On the other hand, who could imagine motion detection before?  ::)
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