Forgotten in its old age

by Aditya

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Now a days, almost every DSLR camera comes with many focal points 9, 11, 22 etc. Many of them provide us with settings to chose manual focus point while shooting images, apart from the auto-selection of focus point based on the in-device calculations. What I want to ask here is, can we select multiple focus points while shooting something, say portrait? That said, in the current scenario while I have control over a single point (which we, or the camera can stress upon) and having a shallow DOF, if I focus on the nose, the eyes get blurred slightly. Of course, I can always increase the DOF, but here I don't want to. I want to select multiple focus points. This sounds a little kinda against the rule of optics though.

PS: I have a canon EOS 550D.

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Just found this link. This is possible starting only with the EOS 7D series :| –  Rish Mar 29 '11 at 6:43
    
Why don't you want to close the aperture more? Even a stop will probably bring in focus something as marginal as the eyes to the nose. Anything more than 3 focus points is over the top. I don't understand this whole "so-shallow-DoF-nothing-is-in-focus" opinion... –  BBking Nov 23 '12 at 1:26

5 Answers 5

Just to say what u were feeling ridiculous... Its not rediculous. Im sorry but u need to learn how imp is it to have manual control over aperture n shutter:) rest A-Dep is not the only mode. A+ is also what can achieve u the same... Rest u ll have to buy Mark2 for selective points. And Mark2 is having 44 F poibts ;-)

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With current cameras, you cannot force choose two specific points to be in focus, however there are a couple of options that can help you out:

Allowing the camera to choose focus points will highlight all those in focus (although it may cause the lens to hunt for focus more, and possibly pick something other than what you'd like).

The other option is the A-DEP mode which I believe is available on the 550D - this allows the camera to adjust the aperture to get as many points as possible in apparent focus - this may end up with the background more in focus than you'd intend, and can take some getting used to.

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You're right. The A-DEP mode is probably the only mode that allows multiple focus points to be selected. However, we lose control over aperture and shutter speed which is totally ridiculous :| –  Rish Mar 29 '11 at 6:28
    
@Rish ultimately it's a choice of which variable you control - aperture (and associated depth of field), or shutter speed - A-DEP is effectively calculating an aperture to use for aperture priority, so it doesn't seem that unreasonable to me. –  Rowland Shaw Mar 29 '11 at 7:54
    
Aperture and/or Shutter Speed should have NO effect on focus. Isn't? That's why I find this ridiculous. –  Rish Mar 29 '11 at 8:20
    
@Rish Lenses focus at a single distance -- aperture affects how far away from that distance appears to be in focus (i.e. depth of field). The shutter speed is just the balancing figure to get the correct exposure. –  Rowland Shaw Mar 29 '11 at 9:42

Offhand I don't remember the model, but if memory serves Canon did build at least one model of (film) EOS that allowed you to select a number of focus points, and it would then select the aperture necessary to assure that those all fell within the depth of field. I'm not aware of their ever having done the same in a digital camera though.

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As a matter of fact, older DSLRs had this. The last Canon camera to have this was the 10D (In the prosumer line, I'm not sure about other lines...) When I got my 20D, my friend and former 10D owner wasn't impressed with the lack of this capability... –  PearsonArtPhoto Mar 28 '11 at 21:16
    
@Personartphoto: Ah, I hadn't realized that (obvoiusly!) It would be interesting to know why they dropped it -- it seems like a good fit on a digital camera (with the ability to adjust the ISO to compensate for the aperture, if necessary). –  Jerry Coffin Mar 28 '11 at 22:50
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I suspect it was a very little used feature. It was replaced by the current A-DEP mode. I actually think both of them had the same name, but I'd have to ask someone who actually owned a 10D... –  PearsonArtPhoto Mar 28 '11 at 23:55

As you suspect, it's impossible. The lens can only be focused at one distance. Essentially, there's no need for multiple focus points because aperture control achieves the same thing more easily.

In the example you give of a face, closing the aperture by only a third of a stop should give you enough depth of field to capture both the nose and eyes sharply while keeping everything beyond them out of focus.

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It is kind of "against" the rule of optics, in the sense that there can be exactly one perfectly focused plane in the image. Anything else "in focus" is just within an acceptable depth of field such that your eyes don't know different.

I don't know any cameras that offer multiple selection points in the sense that you're imagining.

You can always focus stack if you can multiple images with different focus points and it MIGHT get the effect you're looking for.

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