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Old Mar 17, 2006, 10:51 AM   #1
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i have a canon s2 is. now the question is how do i focus on small objects which are much much smaller than the auto focus square in the viewfinder or lcd. for example i want to focus on the ear ring of a lady. how do i focus precisely on the ear ring and make the rest of the face blurred. some other cameras have focus points. but how do i do this in canon s2. any suggestions?
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Old Mar 17, 2006, 11:09 AM   #2
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Well, you've more than just focus fighting you. You've also got depth of field issues.

If you are going for a tight head shot, you might be able to get away with it, despite the much greater depth of field a non-DSLR model has. But, for a full length type of shot, forget it.

As for focus, your camera's "Flexizone"' system allows you to choose from any one of 375 points in the frame by pressing the set button and moving the focus point around using the arrow keys.

You can also use Manual focus by pressing the MF button and using the up and down arrows, and the camera can also magnify the area (see your manual and you'll see more on how these features work.

However, if you're looking for more than a tight shot, you'll probably have more depth of field than desired.

The reason you have more Depth of Field with a non-DSLR digital camera is because of the actual focal length of the lens. Non-DSLR cameras have sensors that are very tiny (much smaller than 35mm film).

As a result, the lens on most digicams can have a much shorter actual focal length, to get any given 35mmequivalentfocal length. Look at the front of your lens and you'll probably see the actual focal length printed.

So, your subject occupies a much larger percentage of the frame at any given actual focal length, compared to a 35mm camera at the same distance to subject.

For any given 35mm Equivalent Focal Length, you'll have dramatically more Depth of Field compared to a camera with a larger sensor (or film).. This isbecause Depth of Field is computed by the actual versus 35mm equivalent focal length,focus distance,and aperture.

Your ability to blur the background for any given aperture depends on your subject size, the percentage of the frame you need it to occupy (which you can use focal length or the distance to your subject to change), and the distance to the background that you want your subject to stand out from. You'll also want to use the largest available aperture (smallest f/stop number) to get a shallower depth of field.

Your best bet is to frame as tightly as possible (fill the frame by getting in closer or using more zoom). In other words, go for a tight head shot versus a full length shot. You'll want to use the camera's largest available aperture (smallest f/stop number) in Av mode, and put as much distance as possible between the subject and background to help them stand out from it. Shooting at your longest zoom setting can help create the illusion of less depth of field, too.

You could also try focusing in front of the subject (so that your subject is barely in the area of acceptable sharpness).

Load this Depth of Field Calculator and selectyour camera model. Then, plug in the *actual* focal length of the lens, focus distance and aperture to calculate Depth of Field.

http://www.dofmaster.com/dofjs.html

Of course, keep in mind that when you use more optical zoom, you'll need to be further away from your subject for it to occupy the same percentage of the frame.

The perspective changes you'll get a longer focal lengths (more compressed background from shooting further away), can give the illusion of a shallower depth of field, since blur in out of focus areas will be more obvious (even if the real depth of field isn't changing, since you need to take the photo from further away if you use more zoom for the same framing).

But, given your zoom ability, combined with reasonable large apertures, as long as you stay with a very tight head shot, you might be able to get the results you want.

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Old Mar 17, 2006, 11:25 AM   #3
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P.S.

If I'm misunderstanding what you want to shoot (for example, you want to shoot something other than a person), use your cameras' macro focus mode to get in closer.

If you're very close, with a smaller subject occuping more of the frame, you'll have a relatively shallow depth of field.

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Old Mar 17, 2006, 10:22 PM   #4
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hey thanks for the reply. but then, where are the points of focus in the s2 camera. it only has a green box which can be moved. anything inside the box will be focussed, is it not? had it been a point, focussing on smaller objects would have been easier. pls clarify.
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Old Mar 18, 2006, 1:20 PM   #5
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Try it and see.

You'll need to learn your camera's behavior for best results.

It may lean towards contrast in the center of the box (or it may not). If you're filling the frame enough with a subject where you don't get fine enough focus using box placement, you may have more depth of field than you want anyway.

Lock focus with a half press, reframe and see what's sharp and what's not when looking at images. ;-)

If the area you're trying to focus on doesn't have enough contrast, try focusing on something that's the same distance from your camera's lens that has more contrast, lock focus, reframe so that your subject is the desired spot, and shoot.

If you can't get fine enough focus that way, go to manual focus, setting it to allow you to magnify your focus area to help you see what's sharpest.

Experiment.

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Old Mar 21, 2006, 2:18 PM   #6
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I don't know whether your particular model's manual focus implementation allows focusing at a specific set distance from the lens. If so, you can mount your camera on a tripod, measure the distance to the subject, and set the focus distance. You may have to move the camera or subject slightly to get the camera-to-subject distance to match the focus setting exactly enough. Then, in Av or full manual exposure mode, open up your aperture as wide as you can to reduce your depth of field and shoot.
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Old Apr 20, 2006, 3:58 PM   #7
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Set the camera to manual focus mode
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