Autofocus & framing technique, & use of Servo mode

[Feanor]

I'd like some advice on how I might improve my technique with regards to acheiving both good focus and good framing.


I have read some of the info already out there and much of it is either basic stuff (ie stuff that's in the manual or the excellent "xy For Dummies" books) or debates about the downsides of focus-recompose and focal planes etc. I've found neither to be particularly helpful as I'd like to think I understand most of the basics and the latter debate just explains a problem without really offering solutions. I'd like to know what people actually do that works.


I generally prefer to select focus points manually. But this has resulted in a lot of missed shots. It also means that I find myself framing shots depending on the location of the AF points on my 5DII rather than on what would look good. If I am photographing a living thing, for example, I want the eyes to be sharp. So I make sure that one of the AF points covers the eyes - but this may not be where I actually want to position the eyes. Although I scoff at my girlfriend's use of Auto AF selection, she does often get very good results with it, capturing moments that I'd have missed by being a perfectionist and manually selecting the point I need.


Furthermore, I have usually used AI Focus instead of Single Shot in most static or slow-moving situations. What I'm not entirely sure about this mode, though, is whether it will switch to Servo if I recompose and refocus on whatever is now under that focus point - basically I'm not sure how clever the camera is at identifying what the subject is and tracking it, rather than just tracking a point in the viewfinder. Frankly, I suspect not very clever is the answer.


So lately I sometimes use Single Shot if reframing. This has given me some good results but I'm still unsure if it's ideal due to the whole lens planes thing.


And as for AI Servo - what bothers me about this is the lack of focus confirmation. In this mode the camera seems to be just as happy to take shots while looking for initial focus lock as it is when tracking - whereas with AI Focus I know to wait until the focus-lock beep before taking the shot. But I don't trust AI Focus to switch to Servo quickly enough to take fast moving images, or to track them properly.


I suspect the ideal approach uses a mix of the shoot-with-focus-point-on-subject and focus-recompose techniques, and others. I guess that, due to a lack of knowledge and understanding of the limitations of the various focus modes, I'm just struggling to take control of my camera's auto-focus and am instead allowing it to dictate how I frame my photos - or even, sometimes, which photos I take at all - rather than allowing the anticipated look of the final shot to dictate the framing and timing.


Any help would be much appreciated .

[Bob]

<span style="font-family: 'Verdana','sans-serif'; color: black; font-size: 6pt;"]


<span style="font-family: 'Arial','sans-serif'; color: black; font-size: 10pt;"]It sounds like you are trying to frame your shots to tight - back-off a little and make perfection by cropping the image in the post processing phase. <o></o>


<span style="font-family: 'Arial','sans-serif'; color: black; font-size: 10pt;"]The servo mode is for subjects moving toward you or away from you, not side to side. You may want to use the assist AF points to help you capture more accurate focus if the subject is moving side to side.<span style="mso-spacerun: yes;"] Also you should note that the metering AF points have different sensitive, so in low light exposures the center point is the best.<o></o>


<span style="font-family: 'Arial','sans-serif'; color: black; font-size: 10pt;"]A shot missed because you are trying to make it perfect is a process that you need to improve.<span style="mso-spacerun: yes;"] You have 21mp, so it is OK to throw a few of them away when you crop your photos.<o></o>

[Feanor]

Thanks Bob - to be honest that is exactly the technique I've taken to using at times (I also understand about the different sensitivities of the various AF points etc). I do indeed sometimes use the center point to focus and crop later. But it's a technique some consider a bit lazy - my girlfriend prefers to get shots right in-camera and, despite being far better at PP than me (I've only dabbled so far), she seems to think cropping is unnecessary hassle. I disagree and most of my best shots were cropped - I really like being able to choose my composition in slow time and really think about it, rather than find that composition isn't ideal but the shot is too tight to improve it.


That said she does have a point in situations where I am not looking to just take a few first class images, rather than a large number of really good images (events, for example). In these situations I might take take one or two hundred shots (or more) that, since I'm just a keen amateur, I want to distribute to friends etc fairly quickly. The trouble is that I just I don't have time to do any editing on so many photos. In those situations I really want to get the shots right in-camera.