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  #1  
Old 08-14-2005, 12:17 AM
jagged jagged is offline
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Join Date: Nov 2004
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Default Portraits

I am having a problem with portraits, I took some photos of my niece and nephew over the weekend with my new 70 - 200 f2.8L. The problem I am having is that when they are sat at different distances from the camera I can get my neice in focus but not my nephew and vica versa. The shot looks good through the viewfinder but when I put it on the computer and zoom in, it looks shocking. My sister wants a good picture of them for the wall so any feedback would be much appreciated.

Thanks in advance

James
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Old 08-14-2005, 12:46 AM
sohrab sohrab is offline
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Default Re: Portraits

hi james this is to do with the depth of field..

depth of field can be affected both by your focal length and your aperture size

1. if you aperture is large for example.. f2.8 then your depth of field will be low which means that the blur in the background will be stronger..
if you keep the aperture small, say f22 or so, then you'll be able to reduce the blur in the background..

2. if your focal length is large.. say you've zoomed out to 200 mm, then the blur in the background will be larger.. as compared to the lens focal length being kept at 70mm..

if you want a sharper background or in this ase.. if you want whoever is sitting in the background to be sharper, then you should use a wide angle lens or something..

if you're using a digital slr , this means that your problems are acdentuated.. because after the focal length of your lens after digital conversion will be equivalent to approximately 112mm-320mm which means that your depth of field will drop even more..

personally i think bokehs are quite nice..

but if you want both of them to be in focus and if this is the only lens you have.. make sure they're as aligned as possible and maintain a little distance from them..

i'm sure you'll get more tips form others i'm just writing in a hurry so may have missed out on some more points

regards...
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  #3  
Old 08-14-2005, 01:57 AM
greg greg is offline
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Default Re: Portraits

Doesn't the 20D have this A-DEP mode on the program dial? At least, I saw it on a 350D. I understand that it should determine the range of distances to your subjects and automatically select the best depth-of-field to include them. I think this is just what you need in this case. This won't be f/2.8, though, so if the light is low, set your ISO higher (maybe 1600) and/or use a tripod.
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  #4  
Old 08-14-2005, 08:14 AM
philip_coggan philip_coggan is offline
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Join Date: Mar 2003
Posts: 247
Default Re: Portraits

Sohrab and Greg are correct. I'd add the following:
1. Make sure your subject isn't too close to the camera - no camera is able to focus on an object within a certain zone (nor are yourt eyes - try moving a finger closer and closer to your eye, and there'll come a point at which you're unable to focus: this is just the laws of optics at work).

2. Select an aperture that will include both children (use the DEP setting that Greg mentions).

3. Turn the auto-focus off (Canon autofocus is frequently inaccurate, particularly at large apertures and close ranges).

Lotsa luck :)
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  #5  
Old 08-14-2005, 12:03 PM
kinginexile kinginexile is offline
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Default Re: Portraits

Hi, james
The advice from others is point on, but i though since the shot has to be for your sister, while still practicing the 70-200, why not use a lower angle lens than 70 for it? less zoom, I think, can help widening the the depth of field, though the bigger aperture may lower the speed, even with a high ISO for which a tripod will help. You are equipped to take great shots, I must say.

H
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