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Old Jul 7, 2008, 4:18 AM   #1
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hi all,If Im using a canon 40d with the 50mm 1.8 lens to take some pictures of 2 people, how can I ensure that both people are in focus but still keep a blurred background effect? whats the max AV setting I'd get away with

also, my friend wants me to take a couple of pictures of her 2 dogs, they are both jet black, how can I get as much detail as possible on them?
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Old Jul 7, 2008, 5:21 AM   #2
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To answer your first question:

It depends .

Short answer: Use f2.8, keeping the faces in the same focal plane and get your subjects as far away from the background as possible - think 50 feet if it's close to full body, 20 feet if head shot.

The subject involves depth-of-field - i.e. from the point in space where your focus is, how much in front of and behind that point is in focus. Given you have a fixed focal length lens (50mm), and a set sized sensor (40D) there are 2 factors left that contribute to DOF and are under your control: Distance from you to your subjects and aperture setting. Distance to your subjects will be largely impacted by the type of photo you want to take (full body, vs. 1/2 body vs head shots). Since you have a prime lens rather than zoom you're stuck with having to change your distance based upon the type of shot you want. After that is figured out, the answer then becomes - how much DOF do you need? That answer is impacted by the type of pose. The closer to the same focal plane both faces are in, the less DOF you need. The following chart will help you:

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


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Old Jul 7, 2008, 5:24 AM   #3
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2nd question - the black dogs:

Shoot in RAW. I would suggest you set the camera to bracket the exposures so you can take a series and determine which exposure provides the best details. Do NOT shoot in bright sunlight - shoot in nice, even light (light shade is good) and if you have an external flash, use it. Make sure you get down at their level though and that you have deep enough DOF for the subject.
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Old Jul 7, 2008, 3:02 PM   #4
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With any camera setting the following applies:

X is you

y = your subjects

o is background



the following situation will give you more blurry background:

XY O

your distanceto Y is shorter then Y to O



The next situation will give sharper background:

X YO

XY 0
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Old Jul 8, 2008, 6:38 AM   #5
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thanks very much, its a lot clearer now
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Old Jul 9, 2008, 8:36 PM   #6
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You could try using the DOF preview button to test your selected f-stop.


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Old Jul 10, 2008, 3:28 AM   #7
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There is an easy way to get this type of shot in focus and that is using the A-DEP feature, check out page 91 of the user manual for how to do this. For anyone one who does not have the manual to hand or is interested in this then check out http://www.the-digital-picture.com/O...40D-Manual.pdf

I don't advocate using this as a long term solution but it is a great way to learn the settings desired so you can increase your understanding for the future.
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