Hello all. I was wondering if any of the more experienced photographers out there could give me a little help on how to practice using these different focus modes. This is probably the one thing that is giving me the most confusion. Does anyone have any ideas on how I can practice these? I have been trying to take photos of my nephew and I use Al-Servo so that I can lock in the focus and then when he moves, I think it should follow. My pics are not as clear as I would like, he moves alot lol, but I am wondering if I am hitting the * button and thinking that is "locking" my focus when maybe I should be hitting the shutter halfway to lock focus.....Ugghhhh I am so confused. Any tips would be GREATLY appreciated!!
Some slight confusion here, but you're nearly there!
The * button on your camera will lock the exposure, not the focus. When you press this button, the camera will calculate the exposure based on what it can see at that moment. This allows you to recompose the shot (adjust where the camera is pointing) and take the photo without the exposure altering, and without having to set up the exposure in manual mode.
This is typically most useful when using something called spot metering, which calculates the exposure based on a very small section of the image at the centre of the frame. For example, when photographing the moon, you can enable spot metering, and if you place the moon right in the middle of the frame, the exposure will be correct (the moon is a tricky subject to expose for as it's so bright, and surrounded by so much dark sky).
The * button would allow you, in this circumstance, to place the moon in the middle of the frame, press the * button to lock that exposure, and then recompose the image (to include, for example, a moonlit lake, a cityscape, etc. etc.) while keeping the exposure correct, even though the moon is no longer centred in the frame.
What all of this effectively means is that, for what you are trying to do, the * button is having no useful effect!
Moving on to One Shot and AI Servo, these modes effectively allow you to choose between the focus being locked when you press the shutter half-way, or the focus going into tracking mode when you press the shutter half-way. One-shot mode, the default, means that when you press the shutter half-way, the camera will attempt to focus the image using the enabled focus points. Once it has achieved focus, it will give you a confirmation (a green circle will light in the viewfinder, and the camera will beep). At that point, the focus will not change unless you release the shutter button, and press it half-way again, regardless of what your subject does.
AI Servo will continually focus the camera whenever the shutter is pressed half-way. Again, it will only use the enabled focus points, but it will keep adjusting the focus all the time. This means that if the subject moves towards or away from you, the focus will adjust accordingly, without having to release the shutter button and re-press it. The camera will also try and predict the movement of the subject, so that it continues to move the focus correctly as the shot is being taken (during this time, the focusing system can't actually see the subject any more). More expensive cameras have more and more advanced tracking systems. In AI Servo mode, you do not get focus confirmation (the green circle and the beep), as the focus will be constantly adjusting.
Therefore, to use this mode, you should enable AI Servo and hold the shutter button down half way. When you press the shutter fully, you should have a sharp photo of your nephew, regardless of where he has moved (provided your shutter speed is also high enough to freeze his motion).
Note that you may wish to alter the focus points in use -- you can use all focus points, and the camera will do a pretty good job of figuring out what to focus on, but sometimes it will fail to do so (particularly in tough situations such as shooting a moving bird across a clear sky). In that case you may find it necessary to select an individual focus point (i.e. the centre point, or a point in the corner, depending on how you want to compose the image), and then the camera will only use that area of the frame to determine focus. This means you must keep the moving subject of your photo in that section of the frame when the shutter button is half-pressed.
Finally, a word on AI Focus -- this is a mode that tries to combine the best of One Shot and AI Servo. AI Servo is great for moving subjects, but doesn't necessarily quite get the focus as pinpoint-perfect for stationary subjects, such as landscape photography, and also it will use battery faster (as the focus motors are running more). This means it's best to only enable it when you need it.
AI Focus starts like One Shot mode, but if it detects that the subject is moving when the shutter button is half-pressed, it will automatically switch into AI Servo mode and start tracking, meaning you don't have to remember to move between these two settings. A nice idea in principle, but I find it seldom works particularly well, especially if you are using a narrow depth of field and intentionally trying to focus on a specific point -- however, you may wish to try it and see what you think.
@abirkill You are AMAZING for taking the time to write all this and I really appreciate your expertise! I have saved your response in my "I am learning" folder and will revisit it frequently until it becomes second nature. The only question I really have after your great response is: So do I need to push the little button that is next to the * button to lock in focus or is that little button just to show me which focus points I have lit up? Do I just set the camera to Al servo, pick my focus point or points and then to lock in focus, push the shutter halfway and never have to use that little button again for that shoot unless I want to change my focus points? Thank you so much for taking time to write this Alexis :)
@superbeyotch That's absolutely correct -- the button next to the * displays the currently selected autofocus points, and allows you to change them (by using the dial on the top of the camera on a T2i, I think).
Once you have enabled AI Servo mode and selected the correct focus points (if you want to adjust them from how the camera is currently set up), the only control you need is the shutter button -- just pressing this halfway will enable focus tracking on the focus points that are enabled.
You can test if it's working by enabling AI Servo and selecting the centre focus point. If you look through the viewfinder with the shutter button half-pressed, you should see the focus adjust as you align the centre focus point in the viewfinder with objects at different distances, such as a windowframe and the view out of the window.
@abirkill Thank you Chris for asking these great questions and Alexis for your very clear answers (again). This was my next question for you after your explanation on exposure for me the other day. You're a great teacher!
@abirkill thank you so much! I have no IDEA where I learned this from but I am sure it is something I confused myself. I am so relieved to know that I have been doing it wrong and that I may not be a horrible photographer! I was starting to get a little frustrated and now I have new hope and will practice and practice! Once again, Thank you so much for taking the time to go over this with me. You didnt have to, but you did and I am beyond thankful! :)
Bear in mind that focus tracking is an advanced technique and it does require a lot of practice to get it right. Also, the focus modules in our consumer-level cameras can sometimes fail to work as well as we might wish.
Sports photographers frequently refer to the number of 'keepers' they get with this technique, regarding how many shots are truly sharp and in focus -- even when using Canon's top of the range DSLRs and lenses, a keeper rate of more than about 7 out of 10 photos is considered pretty rare. It's best to take lots of shots (try enabling the camera's burst mode, so that it continues to take photos as you hold the shutter down).
If you're still struggling to get it to work, don't hesitate to ask more questions!
Chris... thank you SO much for asking this... I knew this is kind of what those features were supposed to do, but hadn't a clue how to use them...
Alexis... thanx a bunch for explaining all that! i am printing out this thread and sticking it in my binder for future reference... really wish I'd known this yesterday when i was trying to shoot the seadoo boys... i knew at the time that there was a feature that would help, but didn't know how to use it at all! next time, i'll know and be prepared!!!!
It's worth mentioning that the Canon manuals these days are actually fairly helpful -- they might not be enough for you to figure out how to use the function from scratch, but if you have an idea they can remind you of the details when you're out one day and suddenly realise you can't remember if it was AI Servo or AI Focus you need. (Thank you, Canon, for those really unhelpful names)
I have the manual for my camera loaded onto my smartphone so that if I need to reference something when I'm out and about, I can do (but I don't have the extra weight or bulk of carrying the real manual). You can find manuals in PDF format for most modern cameras really easily -- just search Google for 'Canon T2i PDF' (or whatever model you have) and it's usually the first result. If you do this on your phone you should be able to save the PDF onto it and then access it instantly even if you don't have a data connection.
There's so many features on modern cameras that knowing how they work is only half the challenge, remembering how to enable them can be equally tricky!
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The * button on your camera will lock the exposure, not the focus. When you press this button, the camera will calculate the exposure based on what it can see at that moment. This allows you to recompose the shot (adjust where the camera is pointing) and take the photo without the exposure altering, and without having to set up the exposure in manual mode.
This is typically most useful when using something called spot metering, which calculates the exposure based on a very small section of the image at the centre of the frame. For example, when photographing the moon, you can enable spot metering, and if you place the moon right in the middle of the frame, the exposure will be correct (the moon is a tricky subject to expose for as it's so bright, and surrounded by so much dark sky).
The * button would allow you, in this circumstance, to place the moon in the middle of the frame, press the * button to lock that exposure, and then recompose the image (to include, for example, a moonlit lake, a cityscape, etc. etc.) while keeping the exposure correct, even though the moon is no longer centred in the frame.
What all of this effectively means is that, for what you are trying to do, the * button is having no useful effect!
Moving on to One Shot and AI Servo, these modes effectively allow you to choose between the focus being locked when you press the shutter half-way, or the focus going into tracking mode when you press the shutter half-way. One-shot mode, the default, means that when you press the shutter half-way, the camera will attempt to focus the image using the enabled focus points. Once it has achieved focus, it will give you a confirmation (a green circle will light in the viewfinder, and the camera will beep). At that point, the focus will not change unless you release the shutter button, and press it half-way again, regardless of what your subject does.
AI Servo will continually focus the camera whenever the shutter is pressed half-way. Again, it will only use the enabled focus points, but it will keep adjusting the focus all the time. This means that if the subject moves towards or away from you, the focus will adjust accordingly, without having to release the shutter button and re-press it. The camera will also try and predict the movement of the subject, so that it continues to move the focus correctly as the shot is being taken (during this time, the focusing system can't actually see the subject any more). More expensive cameras have more and more advanced tracking systems. In AI Servo mode, you do not get focus confirmation (the green circle and the beep), as the focus will be constantly adjusting.
Therefore, to use this mode, you should enable AI Servo and hold the shutter button down half way. When you press the shutter fully, you should have a sharp photo of your nephew, regardless of where he has moved (provided your shutter speed is also high enough to freeze his motion).
Note that you may wish to alter the focus points in use -- you can use all focus points, and the camera will do a pretty good job of figuring out what to focus on, but sometimes it will fail to do so (particularly in tough situations such as shooting a moving bird across a clear sky). In that case you may find it necessary to select an individual focus point (i.e. the centre point, or a point in the corner, depending on how you want to compose the image), and then the camera will only use that area of the frame to determine focus. This means you must keep the moving subject of your photo in that section of the frame when the shutter button is half-pressed.
Finally, a word on AI Focus -- this is a mode that tries to combine the best of One Shot and AI Servo. AI Servo is great for moving subjects, but doesn't necessarily quite get the focus as pinpoint-perfect for stationary subjects, such as landscape photography, and also it will use battery faster (as the focus motors are running more). This means it's best to only enable it when you need it.
AI Focus starts like One Shot mode, but if it detects that the subject is moving when the shutter button is half-pressed, it will automatically switch into AI Servo mode and start tracking, meaning you don't have to remember to move between these two settings. A nice idea in principle, but I find it seldom works particularly well, especially if you are using a narrow depth of field and intentionally trying to focus on a specific point -- however, you may wish to try it and see what you think.
Questions welcome!
Once you have enabled AI Servo mode and selected the correct focus points (if you want to adjust them from how the camera is currently set up), the only control you need is the shutter button -- just pressing this halfway will enable focus tracking on the focus points that are enabled.
You can test if it's working by enabling AI Servo and selecting the centre focus point. If you look through the viewfinder with the shutter button half-pressed, you should see the focus adjust as you align the centre focus point in the viewfinder with objects at different distances, such as a windowframe and the view out of the window.
Bear in mind that focus tracking is an advanced technique and it does require a lot of practice to get it right. Also, the focus modules in our consumer-level cameras can sometimes fail to work as well as we might wish.
Sports photographers frequently refer to the number of 'keepers' they get with this technique, regarding how many shots are truly sharp and in focus -- even when using Canon's top of the range DSLRs and lenses, a keeper rate of more than about 7 out of 10 photos is considered pretty rare. It's best to take lots of shots (try enabling the camera's burst mode, so that it continues to take photos as you hold the shutter down).
If you're still struggling to get it to work, don't hesitate to ask more questions!
Chris... thank you SO much for asking this... I knew this is kind of what those features were supposed to do, but hadn't a clue how to use them...
Alexis... thanx a bunch for explaining all that! i am printing out this thread and sticking it in my binder for future reference... really wish I'd known this yesterday when i was trying to shoot the seadoo boys... i knew at the time that there was a feature that would help, but didn't know how to use it at all! next time, i'll know and be prepared!!!!
I have the manual for my camera loaded onto my smartphone so that if I need to reference something when I'm out and about, I can do (but I don't have the extra weight or bulk of carrying the real manual). You can find manuals in PDF format for most modern cameras really easily -- just search Google for 'Canon T2i PDF' (or whatever model you have) and it's usually the first result. If you do this on your phone you should be able to save the PDF onto it and then access it instantly even if you don't have a data connection.
There's so many features on modern cameras that knowing how they work is only half the challenge, remembering how to enable them can be equally tricky!