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Old Oct 11, 2006, 12:10 PM   #1
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I primarily do maternity and newborn portraits in home. Nothappy lately with the focus performance of the 50mm 1.8. Its soft on images I thought I got a focus lock on, and I'm throwing away way too many images that areWAY out of focus. Plus even shots at ISO 100 they seem noisy to me, maybe I need to USM every image, but that's just too much work IMO.

Since 85mm is the ideal focal length for portraits, and I hear great things about the 85mm 1.8,I would buy it....except with the crop factor we're talking 136mm and I'm typically very limited with the varied spaces I shoot. Is it a total mistake to get something like the 20mm 2.8? Or should I get the 50mm 1.4...I don't need the 1.4 but if I could gain USM and optic quality maybe I should consider it.

I'm also open to a zoom but the $$ for a constant aperture is an obstacle, esp. since I already have a 17-85mm that covers the wide-standard end.

Thanks
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Old Oct 11, 2006, 12:18 PM   #2
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here's a 30% crop of an image I focus locked on the silver finial

exif: 50mm - f1.8 - ISO400 -1/60th
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Old Oct 11, 2006, 12:19 PM   #3
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and the 100% crop
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Old Oct 11, 2006, 12:39 PM   #4
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It looks to me that you have a shallow DOF, which is focused on the fabric fold in front of the main subject.

So I wonder if the problem is really soft focus?

In any case, I have the 50mm 1.4 and love it.



Good luck.
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Old Oct 11, 2006, 1:10 PM   #5
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I use my 50mm 1.8 quite a bit, and don't really have this issue, my seems pretty sharp. I'm wondering if maybe you have a bad copy. Do you have any sort of filter on your lens? A cheap filter may cause some problems too.
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Old Oct 11, 2006, 1:30 PM   #6
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no filter, and I do see the point about shallow DOF, and the part of the fabric that is in pretty tight focus. I have stopped it down in other instances...not with much better luck. I guess it could be an ID10T error but when I use a focus point, at a proper shutter speed, I expect that point to be in focus, and not a point 6 inches to its left. Any thoughts on combatting this? Its difficult for me to always use center point as the point I'm typically interested in being in focus is eyes, and that doesn't lend itself to center compositions.

Also am I expecting too much of this lens if I say the orangish solid color section on the left hand side is noisy/blotchy?
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Old Oct 11, 2006, 4:29 PM   #7
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Do you always shoot indoor portraits wide open? :shock:

... and again are you using one-shot AF (or any of the Artificial Intelligence AF modes)?
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Old Oct 11, 2006, 6:27 PM   #8
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urbanaries wrote:
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Its difficult for me to always use center point as the point I'm typically interested in being in focus is eyes, and that doesn't lend itself to center compositions.
A couple of ways to handle this is to focus on the eyes with the shutter still half way down, re-compose the shot. A better way in my opinion is set custom function 4 to 1, this changes your AE lock button * to the auto focus button. Then you can focus on what ever you like, pressing the shutter button half way locks the exposer, but doesn't re-focus. It takes a little getting use to, but you don't have to hold that shutter button half way down while your trying to re-compose the shot.
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Old Oct 12, 2006, 12:29 AM   #9
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Also you must remember that the center AF point is the only one which has the high-precision mode enable for lens of f/2.8 or faster
--> You are using an f/1.8 so any other AF point is of course less accurate than the center one! :idea:

FYI (same 9-point AF sensor) - http://www.canon.co.jp/Imaging/eos5d/index.html

Quote:
Of the 9 primary AF points, the high-precision cross-type center AF point is compatible with f/2.8 and f/5.6 lenses

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Old Oct 12, 2006, 6:32 AM   #10
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The 5D doesn't have the same AF system. It has a 9+6 point system of which 3 points are high-precision.

Most people usually forget this. :-)

Be careful with focus-recompose and wide apertures.

http://visual-vacations.com/Photogra...pose_sucks.htm

http://www.mhohner.de/recompose.php

From the shots posted above I believe the most likely problem is user error. There certainly is a part of the picture that is in very sharp focus. It'sjust not the part you wanted.

It's possible that there is a focus problem with your camera or lens, but far less likely IMO.






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