01-13-2018 03:43 PM
Hi, I just wondered if anybody could help me solve a problem? I've only recently purchased a mk3.
When I enable AF point display, to see where I focused during the shot in playback, it always shows as being at the cenre of the image even when I focused in another location of the frame and re-composed?
I use one point AF and shoot portraits on an 85mm at about F2. I'm having a few issues with focusing as all dont seem to be as sharp as they was with my mk2. I thought, i'd just make sure the camera was focusing where I was aiming? Any ideas why it is always located in the centre?
01-13-2018 04:33 PM
It is all about AF point selection, and AF shooting mode. Are you focusing, and then recomposing the shot?
Which shooting mode, One Shot or AI Servo?
Which AF point is your default AF point?
AF point display that you can view in image files can be misleading. When multiple AF points light up, it is showing you which AF points were capable of locking focus, but only one of them was used to acquire focus, and it may not tell you which one.
When a single AF point is lit, you are being shown which AF point was active and locked in focus, but it is not necessarily showing you where in the frame the camera may have locked focus. This latter case could be what you are seeing.
01-14-2018 07:13 AM - edited 01-14-2018 07:14 AM
Thank you so much for your reply. Yes, that makes sense. I'm using AF one shot, manual select, with a central location point (9 points) and re-composing. As you say, this is why its probably just showing in the centre. I just presumed it would show where you actually focused?
I mostly shoot headshots. Would you advise to shoot with the square within the square ticked in the AF area select menu? Some people have suggested to shoot with the 'expand area' mode ticked?
I'm just struggling to maintain consistant focus on the subjects eye. It might be a lens problem, but it is the same 85mm lens that I was using reviously with my mk2. I normally shoot at about F2
01-14-2018 07:58 AM
I am not portrait photographer, but I use this table a lot to select lenses and working focal lengths. This table may be useful to you, though it is a bit dated. Select a camera with the same sensor size, like your Canon 5D.
It can give you some idea of how much DOF you would be working with based upon sensor size, focal length, aperture, and distance to the subject. Wtih an 85mm lens, at f/2, and a subject distance of 6 feet, your DOF is estimated to be 2 inches.
Keep in mind, as your results bear out, that there is only one plane of sharp focus. The DOF is pretty subjective, and describes what is deemed as "acceptable focus", which does not mean tack sharp. So, I always halve whatever DOF distance that the table gives me.
I would estimate that you have a working DOF of about 1 inch, in my hypothetical example. If you focused on an eye, the tip of the nose, or hairline could be borderline going OOF. There are a lot of variables and techniques that go into shooting portraits.
Typically, though, when I am using One Shot mode, I am also using BBF, back button focus. For many of my shots, I do not want the camera to refocus when I press the shutter, because I have already locked focus. Yes, you can use the [AF-ON] button to disable AF when the shutter is pressed, but I prefer the opposite way. Only enable AF when I want to use it.