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07/21/2005 06:35:11 PM · #1 |
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07/21/2005 06:36:32 PM · #2 |
Good question..... anyone?
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07/21/2005 06:38:28 PM · #3 |
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07/21/2005 06:40:54 PM · #4 |
Can't be arsed to read all that, in a nutshell please? |
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07/21/2005 06:42:21 PM · #5 |
well there are a few different types of Autofocus, so your best bet is to read it if you want a good answer
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07/21/2005 06:53:59 PM · #6 |
Originally posted by longlivenyhc:
well there are a few different types of Autofocus, so your best bet is to read it if you want a good answer |
Well, I did read it - very informative - thanks!!
Nutshell - active autofocus will emit a signal and calculate distance based on reflected signals (like sonar & radar). Passive autofocus takes a section of the image and alters focus to maximize contrast between adjacent pixels.
Message edited by author 2005-07-21 18:55:53. |
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07/21/2005 07:04:52 PM · #7 |
| Ok, so autofocus is like the bat's sonar system, it sends out a signal , detect the bounce and deduce the distance and move the lens to get the subject in focus. No wonder it's slow on my cam...Now, I'd like to know, how fast can a dslr lens autofocus? I can't get any picture of my 1 and 1/2 year old son cos he moves too fast and my cam can't focus fast enough... I think I need a 350D, would it be faster to focus than my A80 ? |
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07/21/2005 07:32:01 PM · #8 |
Originally posted by tazza:
Ok, so autofocus is like the bat's sonar system, it sends out a signal , detect the bounce and deduce the distance and move the lens to get the subject in focus. No wonder it's slow on my cam...Now, I'd like to know, how fast can a dslr lens autofocus? I can't get any picture of my 1 and 1/2 year old son cos he moves too fast and my cam can't focus fast enough... I think I need a 350D, would it be faster to focus than my A80 ? |
The AF systems on DSLRs are very different from those on non-SLRs. In an SLR, the focussing is done by sensors designed to do exactly that. In a non-SLR, the focussing is done with the same sensor as the imaging. That implies much slower performance, and a time delay when pressing the shutter button to take the shot.
Pro level DSLrs with some specific lenses can track objects moving toward or away from them at high speeds, close to 100mph. They can typically lock focus in well under one second. Even entry-level DSLRs are much faster than P&S cams.
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07/21/2005 07:37:33 PM · #9 |
there is a link somewhere among the canon websites that shows how the digital camera works it shows how the AF works via animated diagram, been looking for abut an hour now
cant find it
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07/21/2005 07:58:02 PM · #10 |
Originally posted by tazza:
Can't be arsed to read all that, in a nutshell please? |
just plain old magic :)
James |
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07/21/2005 08:22:29 PM · #11 |
| Canon AF uses a special technologie using small gnomes that turn a series of knobs... L lenses uses the best of the gnomes will the school dropouts are used for the regular lenses....and the ones that fail remedial get sent to sigma. |
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07/21/2005 08:31:41 PM · #12 |
Originally posted by Gil P:
Canon AF uses a special technologie using small gnomes that turn a series of knobs... L lenses uses the best of the gnomes will the school dropouts are used for the regular lenses....and the ones that fail remedial get sent to sigma. |
ROFLMAO :D |
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07/21/2005 09:43:35 PM · #13 |
Canon's SLRs use several different vatiations on focusing. The better the camera, the better (more complex and comprehensive) the focusing mechanism.
THe 300D has fewer sensors and less sensitive ones than the 20D. So the 20D is more accurate under difficult conditions, can work in darker environments, etc.
canon has 2 lens focusing systems - regular and USM (ultrasonic motor), The USM is much faster.
While not on any of their digital SLRs, canon has an Eye Focus system on some of the film SLRs - the camera focuses where your eyeball is looking. How it works
Canon's SLRs have more than one focus mode as well. One Shot and AI and AI Servo.
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07/22/2005 08:33:23 AM · #14 |
| so what are you saying? the Canon rep lied to me? no Gnomes? |
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07/22/2005 08:54:19 AM · #15 |
Originally posted by Gil P:
so what are you saying? the Canon rep lied to me? no Gnomes? |
the gnomes hide in the sensors i guess.
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07/22/2005 09:02:26 AM · #16 |
Originally posted by Prof_Fate:
THe 300D has fewer sensors and less sensitive ones than the 20D. So the 20D is more accurate under difficult conditions, can work in darker environments, etc. |
Read on SportsShooter - a number of people are having problems with the 20D focusing..
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07/22/2005 11:50:05 AM · #17 |
The A80 uses the seek back and forth until it finds the most contrast method.
Actually, it scans for horizontally adjacent pixels for this contrast, so you will have better luck if there is a verticle line somewhere in your image.
Also, since you mention that your 1.5 yr old is too fast, but don't mention anything about your experience, procedure, camera settings, or environment a couple of things to mention just in case....
If using "Auto", mode, the camera will try and figure out what the subject is (where is there more contrast/brightest area). Sometimes this works, sometimes not. If you switch out of Auto mode, you can use the camera settings and turn off AiAF, and have the focus spot be the center always. If you're in a dimly lit environment, it could be the camera is having trouble focusing, or just a slower shutter speed. If that is the case, add more light. One last thing, again, since you didn't mention your methods or experience, be sure you are pressing the shutter button half way and allow the camera to focus, then when you finish pressing the shutter release, it will be much quicker.
HTH |
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07/22/2005 12:00:12 PM · #18 |
You might find this helpful.
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07/22/2005 12:00:36 PM · #19 |
| If I read your question correctly you are asking "Please tell me I NEED a 350D - give me an excuse to buy one". Yes, it is impossible to take photos of fast toddlers without a new camera - benedryl will slow them down, but not enough. |
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07/22/2005 12:06:41 PM · #20 |
Originally posted by tazza:
Can't be arsed to read all that, in a nutshell please? |
If it's not worth the effort for you to read it and learn something it's not worth the effort for someone else to hold your hand and spoonfeed it to you.
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07/22/2005 12:08:47 PM · #21 |
well you hold the shutter button down half way untill it beeps :)
damn i'm smart!
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07/22/2005 01:11:36 PM · #22 |
Thanks for the replies and the explanations! I did read some of the above link, I didn't know about the active (P&S) and passive (SLR) AF systems. But it looks like digital P&S also use passive AF if they look for contrast from the sensor... |
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