Focus technique
I tend to use a single focal point. In the old days, it was just the central one, now with my 7D, I have the benefit of being able to select a single focal point off centre, both landscape and portrait, which corresponds with where the subject's eyes will be (aprox).
I was reading that the Canon AF system tends to focus better on areas of clear deliniation over softer areas, though I got the impression, the poster was saying the auto-multipoint focal system would choose say eyebrows over pupils.
I understand using a centre spot and recomposing is apt to compromise the focus, but I'm not sure what the poster was inferring by the use of the term "riding Herd" in this post from a thread in the camera forum:
David, how do you use the AF points in your camera? Do you use a solitary, single AF point, placed precisely where you want the focus to be in the image, and then not recompose the image but fire the shutter?
Or do you use multiple AF points and let the camera choose one? When I look at the images you have posted, the focus seems better on higher contrast, sharper bordered areas, like teeth, lips, eyebrow hairs, and not on pupils, lid margins, or edges of noses. The AF algorithms on the 40D, 50D, and I'll bet the 7D as well, favor sharply bordered, high contrast areas over softer edged , lower contrast areas like noses, ears, etc, unless you are very precise in placing a single AF point. I call this skill "riding herd on the AF system" All of my cameras require it when I shoot if I want the image to be critically sharp.
Also, when shooting faces at a distance of less than 3 feet ( as I suspect many of your shots are captured ) focus and recompose is a serious no-no. If you focus with the center AF point and then recompose, there will be not insignificant errors in focusing induced by recomposing. If you are shooting at 8-12 feet the errors of "focus recompose" merge toward non-existence.
Was he saying it is a better skill to have, or best avoided, and if it is best avoided, am I right in thinking that at close range, multi focal point auto focus is also best avoided.
I tend to get most images sharp, but I do tend to over focus, pressing maybe three times to get a solid lock I'm happy with.
What do you chaps do?
I was reading that the Canon AF system tends to focus better on areas of clear deliniation over softer areas, though I got the impression, the poster was saying the auto-multipoint focal system would choose say eyebrows over pupils.
I understand using a centre spot and recomposing is apt to compromise the focus, but I'm not sure what the poster was inferring by the use of the term "riding Herd" in this post from a thread in the camera forum:
David, how do you use the AF points in your camera? Do you use a solitary, single AF point, placed precisely where you want the focus to be in the image, and then not recompose the image but fire the shutter?
Or do you use multiple AF points and let the camera choose one? When I look at the images you have posted, the focus seems better on higher contrast, sharper bordered areas, like teeth, lips, eyebrow hairs, and not on pupils, lid margins, or edges of noses. The AF algorithms on the 40D, 50D, and I'll bet the 7D as well, favor sharply bordered, high contrast areas over softer edged , lower contrast areas like noses, ears, etc, unless you are very precise in placing a single AF point. I call this skill "riding herd on the AF system" All of my cameras require it when I shoot if I want the image to be critically sharp.
Also, when shooting faces at a distance of less than 3 feet ( as I suspect many of your shots are captured ) focus and recompose is a serious no-no. If you focus with the center AF point and then recompose, there will be not insignificant errors in focusing induced by recomposing. If you are shooting at 8-12 feet the errors of "focus recompose" merge toward non-existence.
Was he saying it is a better skill to have, or best avoided, and if it is best avoided, am I right in thinking that at close range, multi focal point auto focus is also best avoided.
I tend to get most images sharp, but I do tend to over focus, pressing maybe three times to get a solid lock I'm happy with.
What do you chaps do?
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Comments
If there isn't time for a selected focus point, like candids and photojournalism, I'll revert to a center focus point, especially in low ambient light since the center focus point is most sensitive.
If it's a studio or other similar session I do like the Live View option. Live view feels a lot like ground glass in a larger camera and allows very accurate focus.
I absolutely love the flexibility and options of these most recent dSLRs and modern AF systems.
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Thanks for that. Can I ask what you;re shooting with?
Like Ziggy, if the light is too low, I will use the center AF point and recompose. You gotta do what you gotta do, but I am aware of the potential costs of that as well.
Now I know that sportshooters, PJs, and lots of other photographers do not always have the luxury of choosing the AF point for each individual frame in Single frame AF mode - that they do use multiple AF points or let the camera choose an AF point. If you are shooting in high frame rate, the AI servo should be very helpful. I just don't shoot that much that way.
I just find in my experience, that I get more accurate focus in my images, if I choose the precise AF point, in the precise position in each frame, If I am allowed the luxury of doing that. Since much of what I shoot is wildlife and landscapes, I frequently do have the time. When shooting candids, at close range, with large apertures, anything less just does not work for me.
I shoot with a 40D, a 50D and a 5DMkII among other cameras. I have used 1DMkII and a 1DsMkII from time to time as well. Their focus systems are better, especially with AI and Servo modes.
You can check the focus in my images in my gallery listed in my signature.
Most of my comments are directed toward the 40D, 50D, 5D, 5DMKII. The AF systems on the 1Series cameras are just that much better.
I am still debating whether to upgrade to a 7D, or just buy the 1DM4 that I really want. And AF is the reason.
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Canon 1D MKII
Canon XT/350D
Canon 40D
Canon 5D MKII
Only the last 2 cameras have Live View of course.
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Thanks for that.
I've never used the live view. I might try that, though I have my focus st up for thumb on star button, which doesn't seem to work with live view. I might have it set up wrong, though. I'll have to experiment.
One of the features in the 7d which most appeals to me is the ability to keep the same focus point - relative to the orientation - selected for both portrait and landscape orientation. When I'm shooting portraits I'll frequently switch to vertical and back, and this would make things sooooo much easier.
That would be a very desirable feature, and makes the 7D even more desirable if I understand you correctly, divamum.
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"Orientation Linked AF Point Switches on the use of one AF point when the camera is held horizontally, and another when the camera is held vertically"
I'm not sure of the exact details (ie, if you have to set each point manually, or does it just keep the same one) but it's a feature which would be hugely helpful for the way I shoot.
PS the section about AF can be read at Rob Galbraith's site http://www.robgalbraith.com/bins/multi_page.asp?cid=7-10042-10239-10240
There are actually 3 AF selections... portrait left/right and landscape. It's kind of wild when you press the "Q" menu button... the AF point it shows in the menu depends on which way you are holding the camera.
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That's right. I love the feature. At first, I thought it was going to be just one rotation in the portrait, but then when I found it was both, I was impressed. The focus point (next out from centre, I think) corresponds nicely with eye-level, too.
I'm going to ask a dumb question but one I've never really figured out (completely new to portrait work). If you're choosing a specific focal point, will that need to be exactly over the eye, or just very close? With only a few AF points to work with, it still seems like I have to recompose because no single focus point can be on the eye and still frame the shot exactly the way I want it.
I sometimes miss the old days of my manual focus camera where you could see very clearly what was in focus and what wasn't. Is it just me, or is manual focus 10 times harder on digital SLRs? I recently experimented with live view for some night shots, and it worked very well.
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Well, that's the problem, really. You can use centre point, and put it right on the eye, but then you have to move to recompose, and because, in recomposing, you may be pulling back a bit, or moving forward, suddenly you're focusing on an eyebrow instead of an eye, esp if you're using a f1.8 or 1.4. With the 7D, you can set a focus point which is really close to the eye, and so, you don;t have to move so much to recompose.
My problem is, I understand the centre point to be more sensitive, and so have tended to use the centre technique, but the more I've read, the more it seems this technique is not regarded as good practice. Luckily, my 7D allows me to place a focus point very close to the eye (as mentioned), but if it's not as sensitive as the centre spot...
I know what you mean about the old days, though. That old split focus screen the the diamond haze around it. Very simple to use, and probably about as fast as auto fucus when you were used to it.
And the best one is live view combined with USB tethered shooting. You can do a remote manual focus, clicking with the mouse to adjust focus.
cheers,
Nick.
Nick.
my equipment: Canon 5D2, 7D, full list here
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