AF Question: Hello everyone...I am shooting with a Canon 6D and always RAW. I'm not a beginner, but this may seem like a beginner question. Please forgive me. Am I correct in...

LindaChaplin Loc: South Dakota

Hello everyone...I am shooting with a Canon 6D and always RAW. I'm not a beginner, but this may seem like a beginner question. Please forgive me. Am I correct in "assuming" that when I lock in focus on my granddaughter's eyes, I can recompose the shot, but she must be in the same plane in order for her eyes to stay in focus? I use LR and when I look at 100% zoomed field, her eyes often aren't tack sharp. She's only 2 so I am challenged by quick movement, but I'm still trying to get those really sharp eyes and I generally do recompose for a more pleasing composition. Thanks very much.

SharpShooter Loc: NorCal

LindaChaplin wrote:

Hello everyone...I am shooting with a Canon 6D and... (show quote)

Linda, I don't use a 6, so don't know how they are configured.
Is you DoF super shallow? If so, sure, any movement can be a problem.
Can you use a slightly wider angle, or get slightly farther away, so you don't have to recompose?
You could experiment with back-button-focus in SI-servo and see if the focus will follow the original focus point spot.
Does it have Eye Recognition, as does the 5mklll?
Once you know where the composition will be, can you assign focus to a different focus-point, that will be over the eye.
A possible problem could be that the best point on the 6 is the center point, as it's the only cross-type point on the 6(ala 5ll). I'm sure plenty are using the 6 for portraits, and it works.
Can you put her head in a vice so it can't move, that's what I do?! JUST KIDDING!! :lol:
Linda, what you're doing should work, try the SI-servo/and or assign a different point. I'm assuming your using single point? Good luck. ;-)
SS

CaptainC Loc: Colorado, south of Denver

I'm a Nikon guy, but I would bet the principles are still the same. Your assumptions are correct as long as you are not in Continuous Focus - I think Canon calls it Servo Mode or something. You need to be in Single shot mode so thee is no chance of focus changing. The Servo mode is meant to re-focus (continually focus) as the camera-to-subject distance changes.

You are correct that the camera-to-eye distance has to remain exactly the same with the recomposing.

LindaChaplin Loc: South Dakota

Thank you both for the expertise. I like the "vise" idea, but my daughter might not okay that technique. I'll put your thoughts into practice and keep trying.

f8lee Loc: New Mexico

LindaChaplin wrote:

Hello everyone...I am shooting with a Canon 6D and... (show quote)

Linda, I suspect your confusion stems from your understanding of what it means to "lock focus on your granddaughter's eyes". What the camera does when you position the appropriate focus indicator box over her eyes is focus on them, yes. But that is all - it has no way of knowing that those are her eyes (or that it's focusing on a flower in the foreground or the moon in the background for that matter). That is, the focus is purely a distance-based function - if her eyes were exactly, say, 5 feet from you when you half-press the shutter button and while you reposition a bit she moves 2 inches forward, her eyes may fall out of the depth of field zone and thus not be as focused.

So yes, her eyes must be within the same plane as measured from your lens (well, the focal point of your lens, technically). If you use a smaller aperture (larger f-number) then DOF will "thicken" giving you (her, really) more "wiggle room".

Hope that helps.

wilsondl2 Loc: Lincoln, Nebraska

I don't think the "vise" idea is so bad. Look at the head "rests" they used in the early days of photography. It seems that in the last few years it has been an unwritten rule that you have to chase kids around and take your pictures of them catch as catch can. Even two year olds can understand - We are going to take your picture and you must be still. Why not set up your shoots with a great background and great props. Not long ago I spent an afternoon watching a "store shooter" who did pictures in period (1900) outfits. He posed kids big and little and they knew they were getting special pictures and they held their poses. His pictures sold well. One thing to remember with small kids is have everything set before you start with them. Of course do your grab shots but I think you will like to take pictures when you involve them in the process. - Dave

amehta Loc: Boston

LindaChaplin wrote:

Hello everyone...I am shooting with a Canon 6D and... (show quote)

If she is moving while you recompose, you are basically winging it for sharp focus. And technically, she does not need to stay in the same "plane", but on the "surface of the same sphere", with the camera sensor at the center of the sphere, and the focus distance setting the radius of the sphere. I think, instead, your best option is to use the focus point which gets you closest to the composition you want and crop to finish the recomposing.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Focusing and recomposing can introduce a slight error - often not visible when your working distance and image magnification is lower and your aperture is small. But when you are close it all falls apart because if you focus on the eyes, then move the camera down to recompose, the eyes end up being a tiny bit further away.

This link offers a graphic explanation:

http://digital-photography-school.com/the-problem-with-the-focus-recompose-method

Better to move the focus acquisition point so you don't have to recompose, and use back button focus. The head vise is ok only if Plan A fails.

LFingar Loc: Claverack, NY

You've already gotten plenty of good advice but let me add my 2 cents. Why not set up a stationary object, a focus chart, for example, where your granddaughter's head would be for some practice shots. That should tell you if the problem is with your technique or your subject's movement. You could also determine how it would work if you assign focus to a different point.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

LFingar - if you assign focus to a different point in the viewfinder and use back button focus on continuous servo, this handles any changes in subject to camera distance.

Also, if you go the route of testing on inanimate subjects, I would think that a flat focus chart would not be as good a choice as a mannequin, which would more closely resemble a real person.

LindaChaplin Loc: South Dakota

Thanks again for all the great advice. I have read each post and will try to put your suggestions into practice. I got a smile from my daughter when I suggested that a vise might help keep little Lily in focus. She thinks I'm already getting some great shots, but I'm somewhat of a perfectionist, I think. I do use the center point as my focus point and have been intrigued by the back button focus idea...just haven't actually tried it yet. Again, thanks to everyone for your help.

LFingar Loc: Claverack, NY

Gene51 wrote:

LFingar - if you assign focus to a different point in the viewfinder and use back button focus on continuous servo, this handles any changes in subject to camera distance.

Also, if you go the route of testing on inanimate subjects, I would think that a flat focus chart would not be as good a choice as a mannequin, which would more closely resemble a real person.

Thanks for the info.
As for the focus chart, I mentioned that because it gives a very flat plane and any change of focus should be easier to spot. Plus, I figured it was more likely she has a focus chart then a mannequin! :)

dsmeltz Loc: Philadelphia

A lot of good advice here, especially back button focus and testing on a stationary object, a focus chart. The focus chart can also tell you if your lens is back or forward focusing and might need micro adjustment. There is always the possibility that you are focusing and locking just fine, but the lens is a tad off.

TimS Loc: GA

Dont laugh. With old tin types and duegerrotypes, the person's head was placed in a vice - well, perhaps a 'modified' vice :) to keep them as still as possible for the long exposure times necessary.

Try setting the focus point to one on the periphery where you don't have to recompose. Another thought is to take a shot without any decomposition and check that sharpness. It could be that you might need to micro adjust the lens a little. There are plenty of tutorials on the net on how to do that with a ruler and a tripod.