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Old 7th of July 2011 (Thu)   #1
Ahtz
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Default 50mm 1.4 Soft or focus problem?

Can you help me figure out the problem I'm having. It seems that my copy of this lens is soft or has a focusing problem. I haven't used it much, but I pulled it out for a wedding reception this last weekend and was not happy with the results.

This shot was f/5.6, ISO 200 if I remember right:

Full size link: http://www.jasonallenimages.com/phot...3L4m84P-X3.jpg
It does not seem nearly as sharp as it should be especially for 5.6

This one seems to be a mis-focus. I did a ton of sharpening to make it somewhat usable. Does this lens have a harder time focusing on things farther away. I cant remember the exif on this shot but it was probably ISO 100 and f/2.0. It almost looks like it focused about 2' in front of the couple.

Full size link: http://www.jasonallenimages.com/phot...JJnKbLG-X3.jpg
but then i'll get a shot like this that looks to be fairly sharp.

Full size link: http://www.jasonallenimages.com/phot...9gqsmBS-X3.jpg

So, is this lens just more finicky than others and I have to learn how to deal with it or could there be something wrong with the lens?
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Old 7th of July 2011 (Thu)   #2
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Default Re: 50mm 1.4 Soft or focus problem?

wow this forum section moves fast, second page already! bump?
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Old 7th of July 2011 (Thu)   #3
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Default Re: 50mm 1.4 Soft or focus problem?

Were you allowing the camera to select the focus point?
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Old 7th of July 2011 (Thu)   #4
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Default Re: 50mm 1.4 Soft or focus problem?

No, I select the focus point
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Old 7th of July 2011 (Thu)   #5
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Default Re: 50mm 1.4 Soft or focus problem?

I have been using the 50/1.4 quite a bit lately and find it a little tempermental in the way you suggest (using 7D). Generally your photos are not too bad IMHO with the 50. Mine does search a bit with the focus so a bit of redundancy in poses (couple of extra shots) usually does the trick. When it nails focus, the results are outstanding.
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Old 7th of July 2011 (Thu)   #6
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Default Re: 50mm 1.4 Soft or focus problem?

I've been using the 85 1.8 and the 17-55 2.8 and find them to be spot on all the time. So my comparison comes from those lenses and I find it to be not as sharp and/or more hit or miss.
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Old 7th of July 2011 (Thu)   #7
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Default Re: 50mm 1.4 Soft or focus problem?

I find the 50/1.4 is less hit or miss than my 85/1.2. Does it react the same way with both bodies?
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Old 7th of July 2011 (Thu)   #8
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Default Re: 50mm 1.4 Soft or focus problem?

I only used it with the one body that day. I'll try it with the other and see how it goes. I use the other two lenses interchangeably though with the two bodies and they are fine.
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Old 7th of July 2011 (Thu)   #9
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Default Re: 50mm 1.4 Soft or focus problem?

I don't find the first image particularly soft, but there is a hint of those closer to the camera being a bit sharper. Combined with the second image I'm thinking there might be a touch of front-focusing going on and you might want to take a few test images at those sort of focusing distances and dial a little bit of MA in.
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Old 28th of July 2011 (Thu)   #10
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Default Re: 50mm 1.4 Soft or focus problem?

So I did some more shooting with my other body and in a more controlled environment. What seems to be happening is that when I am close to my subject (3'-4') the focus will be spot on. Then when I back up to say about 10', it will front focus. While back at 10' away I will do the manual focus adjustment and get it so its spot on. Then I move forward again and find that it is back focusing!

Is this a common problem? Do I need to send my lens in? I tested it at f/2.0. Should I forget 2.0 on this lens and give it a try at 2.8 or higher?
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Old 28th of July 2011 (Thu)   #11
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Default Re: 50mm 1.4 Soft or focus problem?

Quote:
Originally Posted by Ahtz View Post
...
While back at 10' away I will do the manual focus adjustment and get it so its spot on.
...
do you mean Micro Focus Adjustment (the in-body adjustment)?

or are you saying that you use the manual focus ring, and then afterwards it is backfocusing?

i think you mean micro focus adjustment

~mike
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Old 28th of July 2011 (Thu)   #12
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Default Re: 50mm 1.4 Soft or focus problem?

sorry, yes, micro focus adjustment
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Old 28th of July 2011 (Thu)   #13
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Default Re: 50mm 1.4 Soft or focus problem?

Yeah, you might benefit from doing Micro Focus Adjust aka MFA with that lens... (has to be done on each camera, but the amount of adjustment you dial in will apply to any 50/1.4 you fit to either camera... it's camera specific, but not lens specific).

Canon recommends setting up your MFA target at a distance 50X the lens focal length, as measured from your "film plane" mark on the camera. That would be just over 8 feet with a 50mm lens (50x50=2500mm or 250cm, or approx. 97 inches).

Canon's recommended method is to put the camera on a tripod, focus the lens on a good target using One Shot and just the center AF point, then switch to Live View and - while watching the distance scale on the lens - activate focus again. If the scale moves at all, then you need to dial in some MFA and retest.

The idea behind this mehod is that standard AF uses Phase Detect focus, while LIve View uses a completely separate, slower but generally more accurate Contrast Detect focus. If you dial in the standard AF to match Live View AF, you should get pretty accurate focus. This mehod allows you to use a simple target, just about anything flat with some detail on it that gives AF something to lock onto, and not have to fool around with buying or making or setting up special angled targets and reading scales.

It's a lot easier to use with a prime lens than with a zoom. With a zoom you sort of have to do it two or three times, at different focal length settings and distances to the target, then often will have to average the amount of adjustment you dial in with MFA (unless you use the lens most of the time at one particular focal length, want to bias it to be optimal at that focal length, and don't mind if there's more error at other focal lengths).

At f5.6 your 50/1.4 should be nice and sharp.

Use f2.0 with some caution... It will be sharper than f1.4, but still likely will have a little bit of softness. I usually try to stop down at least to f2.2, but f2.5 or smaller is even better.

At the other extreme, using 50D try not to go beyond f8 or f11 at the smallest, or diffracation will start costing some fine detail.

Other stuff...

Are you using any filter on the lens? If so, be sure it's a good, multi-coated one... or just remove it to get optimal sharpness.

Are you using a lens hood? It's rare, but possible for oblique light striking the front of the lens to effect AF. A hood can help (and the 50/1.4 in particular benefits from storing it with hood reversed, to protect the focus ring from getting bumped... which can damage the AF mechanism).

Second shot, and perhaps the third, was fill flash used? Was the flash focus assist turned on?

50/1.4 is usually pretty accurate focusing... If you continue to notice problems, might be worth sending it to Canon to be checked. It might just need calibration. If the AF system needs to be replaced and the lens isn't under warranty that might cost around $160, just guessing from what I've seen in the past.

Ah... just saw your followup... Since you can't MFA to get both near and far to focus right, it's more likely the lens needs to go in for calibration. I'd run the same test on both cameras, just to be sure. If it does the same on both, send the lens in. If it only does it on one camera, then it's more likely the camera is off somehow.

Last edited by amfoto1 : 28th of July 2011 (Thu) at 15:25.
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Old 28th of July 2011 (Thu)   #14
Ahtz
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Default Re: 50mm 1.4 Soft or focus problem?

2nd one flash was used although off camera with PW's. So no autofocus assist. I have some shots from yesterday I can try to post up.

My biggest question is that if I get the lens to be sharp and focus accurately at 8', then it will only be good at 8'. If I am 15' away it will focus in front of the subject and if I am 3' away it will focus behind the subject. This is the problem i've been having.

I'll try the adjustment tonight at 8' on a tripod at f/2.8 and see if I get better results. The whole reason I got the lens was to shoot wider than 2.8 though. I have a 17-55 2.8 if I wanted to shoot at 2.8.
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