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Photo Forum / Photo Technique / Nature Photography / December 2004Canon 20D Focus options
Hello All, I recently upgraded from a Canon 300D to a 20D and now have some options available that I didn't have on the DRebel. One is the option of choosing between three focus modes. One Shot AF, AI Focus AF and AI Servo AF. I have read the manual until my eyes glazed over, trying to determine which of these modes best suited my application. I use this camera for wildlife photography only and shoot everything in AV mode. I use the center focus point for AF on a still subject, such as a perched bird. If I want to photo a bird in flight for instance, I change to automatic selection (all focus points). I am wondering if one of the 3 AF options would be best suited for both situations or do I need to be changing the AF mode as well as the focus point? I am just not clear on the functionality of each of the three AF choices. I am hoping someone in this group will have experience with them and could offer some advice.  SignatureBob "Nature Photography by Bob Moul" http://www.pbase.com/rcm1840 >From: "N8urePix" N8urePix@worldnet.att.net >I recently upgraded from a Canon 300D to a 20D and now have some options >available that I didn't have on the DRebel. One is the option of choosing >between three focus modes. One Shot AF, AI Focus AF and AI Servo AF. The Canons I own have only two modes, One Shot and AI Servo, so the answer below references only those. Generally they recommend One Shot for stationary subjects and AI for moving subjects since AI will track something and hold focus while OS locks to one focus point and stops focussing. Dunno what AI Focus does, sorry ... > I use this camera for wildlife >photography only and shoot everything in AV mode. I use the center focus >point for AF on a still subject, such as a perched bird. Either OS or AI will work for this type shot but OS has the advantage of allowing you to lock the focus by pressing the shutter button half way and then re-compose, keeping focus so long as you don't lift your finger from the shutter button. AI will continue to change focus if you re-compose though. So most people would use OS for still subjects and that's what Canon recommends. >If I want to photo a bird in flight for instance, I change to automatic >selection (all focus points). Typically you'd use AI here since it will track the bird and keep it in focus and this is especially useful if the bird is flying toward you or away from you. If the bird is flying parallel then you can use OS and get sharp images so long as the bird is still roughly parallel to you but most experts (and Canon) recommend AI for moving objects. >I am wondering if one of the 3 AF options would be best suited for >both situations or do I need to be changing the AF mode as well as the focus >point? I change modes often, the only problem with the bodies I have is that you can't do it with one hand but other wise it's easy enough. Bill >Generally they recommend One Shot for stationary >subjects and AI for moving subjects since AI will track something and hold >focus while OS locks to one focus point and stops focussing. Dunno what AI >Focus does, sorry ... I found this description of AI Focus on the net ... "There is the usual One Shot as well as AI Servo tracking with predictive autofocus. ... In addition there is AI Focus mode which locks focus in Single Shot mode but then automatically switches to AI Servo with tracking if the subject starts moving while the shutter release is partially depressed." This sounds like a very useful mode to me (all I have is the technologically deprived 1D Mark II and the ancient 1Ds so I don't have this mode :) >>Generally they recommend One Shot for stationary >>subjects and AI for moving subjects since AI will track something and hold [quoted text clipped - 9 lines] > This sounds like a very useful mode to me (all I have is the technologically > deprived 1D Mark II and the ancient 1Ds so I don't have this mode :) Bill, On the 10D and D60 cameras, I never found the AI, or AI focus were of much good for fast subjects, especially when unpredictable, like birds at takeoff or landing. On the IDII, I've set the AI to maximum rate and then it does real well (but my dogs playing are still faster). Back to the 10D and D60: for fast action, I learned to use single shot, and to lift my finger off the shutter and then press it completely again. I got a higher number of in focus shots. With AI or AI focus, I got a lot of slightly out of focus images as the cameras always lagged behind. Example, my Great Egret in Flight 1 image, at http://www.clarkvision.com/features/natures.best.win.2004/index.html was done on a D60 in single shot mode. So, I wonder if the 20D is more like the 10D or 1DII in its AI tracking ability. So to Bob, if you find the birds out of focus with AI, try single shot. Just remember to lift your finger completely off the shutter button between shots. I could frame at almost 3 per second with this method once I learned it. Also, use only one sensor as with multiple sensors, the camera can get confused and focus on the wrong thing from what you want. Roger So, I wonder if the 20D is more like the 10D or 1DII in its AI > tracking ability. So to Bob, if you find the birds out of focus > with AI, try single shot. Just remember to lift [quoted text clipped - 3 lines] > the camera can get confused and focus on the wrong thing > from what you want. So what you are essentially doing Roger, is re-focusing before each frame. Am I following you there? That may work on the 10D and 20D but I found that on the DRebel the focus was so slow and each time I lifted my finger off the shutter release and depressed again the camera would start searching again. By the time it found the bird(?) valuable time was lost and consequently I would get very few frames until the moment was lost. Next time out I will try your method first chance I get. After using the 300D for a year and 15,000 shots later, I am finding the 20D to be a whole new ball game. For one thing, at 5 fps, you better have a large CF. :) There is really no comparison between the two. Some may disagree with me there. BTW, an excellent photo of the GREG. I will return to your web page later when I have more time to browse. SignatureBob "Nature Photography by Bob Moul" http://www.pbase.com/rcm1840 >Bill, >On the 10D and D60 cameras, I never found the AI, or AI focus [quoted text clipped - 4 lines] >learned to use single shot, and to lift my finger off the shutter >and then press it completely again. I use AI nearly in 95% and Custrom Function for putting the AF to the AE-Button on the back reachable easily with my thumb. If I am following a subject and I think it is perfectly sharp I release the AE-Button and press the shutter where no focussing is happening anymore. When I have to recompose the frame a little bit and the AF sensor normaly would be somewhere on the background and the subject would have been out of focus this method works perfectly by dividing AF and shutter! Gruß Stefan Signaturestefan@jondral.de People: http://www.stefanjondral.de/ Naturfotos: http://www.jondral-naturfoto.de/ Bill, this is the mode I have been practicing with after reading the text in the manual. I have not had much of an opportunity to try it on birds in flight because of the weather, but I have tried focusing on objects like a tree trunk, than while half depressing the shutter release, move the camera to another object at a greater or lesser distance and the focus almost instantly locks onto the latter. That is while using the center focus spot. I agree with you, this seems to be the most versatile mode. SignatureBob "Nature Photography by Bob Moul" http://www.pbase.com/rcm1840 > >Generally they recommend One Shot for stationary >>subjects and AI for moving subjects since AI will track something and hold [quoted text clipped - 12 lines] > technologically > deprived 1D Mark II and the ancient 1Ds so I don't have this mode :) >> Generally they recommend One Shot for stationary >>subjects and AI for moving subjects >From: "N8urePix" N8urePix@worldnet.att.net > >Bill, this is the mode I have been practicing with after reading the text in >the manual. I have not had much of an opportunity to try it on birds in >flight because of the weather Bob, here's a link to a Canon publication by senior tech guru Chuck Westfall describing the AF modes in detail ... it's written primarily for the 1D class cameras so the custom function and 45 AF point info isn't applicable to the 20D but most of it is useful for 20D owners too. For example I learned you're supposed to run USM at 300/.3/0 to clean up after the anti-aliasing filter and that the focus lock and recompose trick isn't recommended inside of 15 ft or for portraits ... good reading. http://www.photoworkshop.com/canon/EOS_Digital.pdf (a 35 pg 1 MB pdf so takes a while to download ... I recommend saving it and reading it at your leisure) There is something specifically for the 20D on this page ... http://www.photoworkshop.com/canon/ Back to the AF modes and flight shots ... here are some sample images taken with various AF modes which illustrate the problems ... http://members.aol.com/bhilton665/T5220.jpg ... hand held with a 400 mm, the AF mode isn't important here since there was a narrow orange patch of clouds in the sky and I just wanted to freeze the birds while they were flying in it. Hard part was getting a group of birds that weren't "touching" each other, and getting a fast enough shutter speed, I think I went to iso 800 and then ran Neat Image to clean up the noise artifacts. Either AI or OS would work here. http://members.aol.com/bhilton665/T5314.jpg ... bird is just taxiing for take-off, I'm in AI mode with the sensor on the neck ... so long as I keep the sensor on the neck the head is in focus but if the wing gets in the way it will shift focus to the wing, which is a problem. 500 mm f/4 on a Wimberly pivot head ... I got about 8 frames of this guy. http://members.aol.com/bhilton665/T4956.jpg ... different bird, same mode, same problems ... http://members.aol.com/bhilton665/T4897.jpg ... AI mode, in this one the wing got in the way so the head/eye isn't sharp but the wing is ... this is the kind of problem Roger avoids by using One Shot instead of AI ... so there are advantages and disadvantages to each mode. http://members.aol.com/hiltonfotography/pribilofs/puff_feather.htm ... tough problem here, the people beside me with 10D's (two) and a Nikon 1Dx couldn't focus on these puffins but with the 1D Mark II I was able to catch them about 1/3 the time ... AI mode, 400 f/5.6 hand-held, 45 AF points ... small dark target flying fast in bad weather ... tough conditions for flight photography. http://members.aol.com/hiltonfotography/pribilofs/kitti_flight.htm ... same trip but an easy bird to photograph in flight since it's white, flys slow and is 4x bigger than a puffin ... piece of cake, even the 10D gets this one almost every shot. One more, this one sitting ... http://members.aol.com/hiltonfotography/dove_blossom.jpg ... if you use the center focus point for a shot like this you'll get the breast sharp but the eye isn't sharply focussed so I used one of the off-center focus points in One Shot mode to lock on the neck, which is about on the same plane as the eye. This is with the 500 f/4 and a 1.4x t/c on a Mark II and prints beautifully at 16x24" ... using the center point and recomposing would probably not work as well (see the Westfall publication above) at this close range ... the problem with using an off-center focus point is if the bird moves his head to the other side (for example) and you no longer have a good composition ... I tried this several times on a bear in Denali and when it worked it was perfect but the bear kept swinging his head side to side sniffing the air so sometimes my focus point was on the wrong side of the frame ... My advice is to learn all the modes, practice with them and hope that you're in the right one when something good happens :) Bill Bill, Thanks for the urls. I will read them as time permits. Placed them in my "favorites" folder so I can refer back to them later. Great pix of the cranes, I guess they are Sandhills, I have only ever seen a few of them in FL, but will never forget their "call". Really fine shots of the Puffin and Kittiwake too. I really appreciate your comments as well as Roger's. I am waiting for the weather to clear so I can head for the lake and put some of these tips into practice. SignatureBob "Nature Photography by Bob Moul" http://www.pbase.com/rcm1840 >>> Generally they recommend One Shot for stationary >>>subjects and AI for moving subjects [quoted text clipped - 112 lines] > > Bill >>>Generally they recommend One Shot for stationary >>>subjects and AI for moving subjects [quoted text clipped - 70 lines] > My advice is to learn all the modes, practice with them and hope that you're in > the right one when something good happens :) Bill, These are great examples. With the 1-D Mark II, I work similarly to they way you do. For flight images, the AI mode works well, and I'm constantly shifting AF points for the specific scene and desired focus point, all while working with AI mode. For "portraits", I switch to one shot mode. Because I use a 10D as backup, or with a shorter lens, it's hard remembering the different button sequences between cameras ;-), especially in the heat of action. I was never satisfied with the AI mode on the 10D (or D60). The manual says the camera will do its best effort to focus, but will fire even if not in focus. With birds in flight action (and my dogs at play), the 10D just usually never seemed to get that great of focus in AI mode. The 1D Mark II does great in this regard. So on the 10D I found I got a higher percentage of critically sharp focused images with action shots in one shot mode, rather than a higher number of images, but each slightly out of focus with AI (by this I mean an OK 8x10 could be made, but looking a little soft). I probably get 5 to 10 times as many critically focused action shots with the 1DII as I did with the 10D, given similar conditions, and with the 1DII it is usually my fault for not keeping the sensor on the desired subject during fast action that ruins focus. With the 10D it was usually the camera failing to track and lock fast enough. I suppose with "little brown birds" or fast birds like puffins, the 1DII can be challenged as you say (with of course, lenses being an issue too). Roger Roger, The 20D has two AI focus modes, one named "AI focus AF" the other named "AI Servo AF". When you refer to the AI mode on your 1-D, I wonder which 20D focus mode that is equivalent to. Since discussing this with Bill and yourself, I have been doing some experimenting and find the AI Servo AF works best in most of my applications even if it is following a subject on the ground or in a tree. By depressing the shutter key half way and holding it there, the camera will continue to refocus as I follow the bird, etc. I find this to be very helpful and much more effective in most situations. I can focus on a bird jumping from branch to branch, even if it locks on a nearby twig a slight movement back onto the bird will cause the camera to refocus. It also continues to refocus on a bird flying directly toward you which on my 300D I would have to lift my finger from the shutter button and refocus and in most cases lose the shot. SignatureBob "Nature Photography by Bob Moul" http://www.pbase.com/rcm1840 Bill, These are great examples. With the 1-D Mark II, I work similarly to they way you do. For flight images, the AI mode works well, and I'm constantly shifting AF points for the specific scene and desired focus point, all while working with AI mode. For "portraits", I switch to one shot mode. Because I use a 10D as backup, or with a shorter lens, it's hard remembering the different button sequences between cameras ;-), especially in the heat of action. I was never satisfied with the AI mode on the 10D (or D60). The manual says the camera will do its best effort to focus, but will fire even if not in focus. With birds in flight action (and my dogs at play), the 10D just usually never seemed to get that great of focus in AI mode. The 1D Mark II does great in this regard. So on the 10D I found I got a higher percentage of critically sharp focused images with action shots in one shot mode, rather than a higher number of images, but each slightly out of focus with AI (by this I mean an OK 8x10 could be made, but looking a little soft). I probably get 5 to 10 times as many critically focused action shots with the 1DII as I did with the 10D, given similar conditions, and with the 1DII it is usually my fault for not keeping the sensor on the desired subject during fast action that ruins focus. With the 10D it was usually the camera failing to track and lock fast enough. I suppose with "little brown birds" or fast birds like puffins, the 1DII can be challenged as you say (with of course, lenses being an issue too). Roger >From: "N8urePix" N8urePix@worldnet.att.net >The 20D has two AI focus modes, one named "AI focus AF" the other named "AI >Servo AF". When you refer to the AI mode on your 1-D, I wonder which 20D >focus mode that is equivalent to. AI Servo ... the "AI Focus" mode is new with the 20D, even the expensive 1D series pro models don't have it yet (maybe the 1Ds Mark II but not the 1D, 1D Mark II and 1Ds). >>From: "N8urePix" N8urePix@worldnet.att.net > [quoted text clipped - 5 lines] > series pro models don't have it yet (maybe the 1Ds Mark II but not the 1D, 1D > Mark II and 1Ds). The 10D, D60, and (if I remember correctly) Elan (film) series all had the AI focus mode. It means the camera "watched" the focus and if focus point started to move, the camera would shift from one shot to AI servo mode. I never found that it worked very well on these cameras, as it always seemed to lag behind the best focus in my experience. Roger >> AI Servo ... the "AI Focus" mode is new with the 20D >From: "Roger N. Clark > >The 10D, D60, and (if I remember correctly) Elan (film) series >all had the AI focus mode. Roger, I "borrowed" my wife's 10D for a year and never knew it had this mode, though it's right there in the Spanish novella "Manual" shipped with the camera :) Next you're going to tell me it's on the 1D Mark II? Gotta re-read the guide now ... Bill >>>AI Servo ... the "AI Focus" mode is new with the 20D > [quoted text clipped - 9 lines] > > Bill Bill, Since it was on all the other cameras I had, I was surprised to see it was not on the 1D Mark II. But then I didn't care, since I never use it. Roger > Hello All, > [quoted text clipped - 11 lines] > the three AF choices. I am hoping someone in this group will have > experience with them and could offer some advice. ----------------------------------- I have a 10D with same AF than 20D. With one shot focus, the reaction of the focus is not fast. This is the best mode (with one focus point) for a bird perched in tree with many branches, leaves, etc. Press gently the button release. You can recenter if desired. If you choose AI Servo in this situation, and if a leaf arrive in the focus point, the bird will be out of focus. With AI servo the reaction of AF is very fast. It's the best (with automatic focus point) for the bird in flight. The focus point "catch" the bird, the AF ajust itself with all movement of the bird. The AI Servo is a mode in between. Daniel > The AI Focus is a mode between One Shot and Ai Servo. > > Daniel Thanks for your input, Daniel. Some of it is starting to make sense now. :) I just need to put into practice before I forget it SignatureBob "Nature Photography by Bob Moul" http://www.pbase.com/rcm1840 > >> Hello All, [quoted text clipped - 30 lines] > > Daniel |
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