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FORUMS Canon Cameras, Lenses & Accessories Canon EOS Digital Cameras 
Thread started 08 Mar 2018 (Thursday) 13:22
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Autofocus problem?

 
Gschimma
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Mar 08, 2018 13:22 |  #1

Hi all, new to the forum. I’m essentially a beginner dslr photographer (for the past 6 years) with a canon 7d. Sometimes it seems the autofocus isnt correct/ sharp. Other times it seems perfect. This was shot with af point expansion and the point of focus is my wife’s nose. It was lightly snowing and was using a canon 50mm prime. Is there some sort of calibration that needs to be done? Am I doing something blatantly wrong? Or is it just chance?
Thanks in advance.


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apersson850
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Mar 08, 2018 13:46 |  #2

At 50 mm and f/1.4 the depth of field is very short. The EF 50 mm f/1.4 USM is also infamous for having a rather coarse focus adjustment mechanism. Using AF with expansion points is efficient if the camera has problems finding something to focus on in the selected point, but it also increases the risk that the camera will actually focus with one of the auxiliary points. It's enough that they find something that's a few centimeters away from the face to focus on, and the face is toast. In the picture above, it looks like focus in on the end of her sleeve instead. Her hands are probably a tad closer to you than her nose.

In a picture like the one above, my opinion is that you don't really gain anything on using f/1.4. You don't need 1/8000 s and you don't really gain anything from the very thin depth of field.
Stop down to f/4 and increase exposure by 2/3, to get a bit whiter snow. I think the result will be better.

If AF is consistently off in the same direction, then a focus adjustment is appropriate. I too have an EF 50 mm f/1.4 USM. It doesn't work without an AF adjustment on any of my cameras.


Anders

  
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Wilt
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Mar 08, 2018 14:05 |  #3

Upon closer examination of a copy of the JPG posted, it does appear to be front focused at a plane near your son's boots and the snow clumps in front of your wife.

Before jumping to any conclusions about AF error, I would do more-controlled testing, where YOU have consciously SPECIFIED which AF zone is used for focus, rather than letting the camera choose.


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Nethawked
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Mar 08, 2018 14:45 |  #4

This isn't a DOF problem, as not even the subject under the focus point is in focus, I agree with Wilt, but would bypass any more testing and just AFMA the lens.

That said, this photo is not the ideal candidate for shooting as wide as f/1.4, and at this shooting distance you would not get both subjects in focus before about f/5.6. This isn't the best lens to shoot wide open either, but it's quite good at f/2 and narrower.

Good luck!




  
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Gschimma
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Mar 08, 2018 16:24 |  #5

Thanks so much for your help. Was in a hurry to get the photo so didn’t realize my shutter speed and aperature settings. Rookue. Certainly not intentional.

When viewing the photo on the camera monitor the af red box is on my wife’s nose. Seems like the actual focus plans are pretty far away for AF point expansion. I thought that if the camera was unable to focus on the chosen spot it would try nearby. The focus box was on her nose when I took the picture.




  
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Nethawked
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Mar 08, 2018 17:01 |  #6

Gschimma wrote in post #18580585 (external link)
Thanks so much for your help. Was in a hurry to get the photo so didn’t realize my shutter speed and aperature settings. Rookue. Certainly not intentional.

When viewing the photo on the camera monitor the af red box is on my wife’s nose. Seems like the actual focus plans are pretty far away for AF point expansion. I thought that if the camera was unable to focus on the chosen spot it would try nearby. The focus box was on her nose when I took the picture.

Pfftt, we all wake up every day as rookies, there's always room to learn.

This lens is an odd one. My AF adjustments, on any of the cameras I've adjusted on (several) are way up in the + or - 10-20 range. Pretty far off. I'd suggest looking into the dot-tune method if you haven't made any autofocus adjustments before and give it a whirl. If you have problems feel free to PM me.

Even with perfect focus after adjustments, this isn't a lens to use wide open, just FYI.




  
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John ­ from ­ PA
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Post edited 3 months ago by John from PA. (2 edits in all)
     
Mar 08, 2018 17:11 |  #7

That lens is known to be soft wide open but sharpens up considerably when stopped down to f/2 or smaller. There is also something called halation in a lens which some people feel gives a soft look to an image. The 50mm f/1.4 is also know for that when wide open. Both factors to various degrees may be contributing to the out of focus look.

There is some content on halation with this lens at https://www.dpreview.c​om/forums/post/2230846​1 (external link).

I realize you grabbed the camera and were in a hurry to get the shot, but is there some reason you used ISO 200. I think my go to setting is 400, perhaps 640 on a cloudy day.




  
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apersson850
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Mar 09, 2018 03:00 |  #8

To me, it looks like the wrinkels in the green sleeve, where it meets the glove on her left arm, are in focus.
Even if the AF point was on her nose, the camera may have misread the contrast there slightly. The AF points are in reality often quite a bit larger than their depiction in the viewfinder, so it's pretty common that the camera finds something a bit outside the AF box to focus on. The camera may also have found that the contrast between sleeve and gloves was more definite than those found in the face. Perhaps one of the auxiliary AF points was close enough to the glove the for the camera to consider that.

My EF 50 mm f/1.4 USM requires +7 to +12 in AF adjustment, to work properly with my different cameras. It's not really useful on the old 40D, as that camera doesn't support AF adjustment.


Anders

  
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Mar 09, 2018 07:01 |  #9

I would try out AFMA, go to the Microfocus Adjustment menu, and dial in +8 (to add distance between you and the focal plane). See where that puts you on subsequent shots. If you start to see focus fall behind the subjects, halve that amount. I suspect you will settle in around 6-7 as Anders found on his, based on what I am seeing in the photo.

Again though a single shot doesn't make for a great test subject for focus checking. I would put something brightly colored on a table, stand back about as far as you were here, and do your adjustments with a controlled set up. Use the table surface to see where focus actually ends up each test shot.


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Gschimma
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Post edited 3 months ago by Gschimma.
     
Mar 12, 2018 18:53 |  #10

Thanks everyone for your thoughts. I wish I had more time to learn. Again, I have a 7d and these two lenses, Canon EF 28-135mm 3.5-5.6 IS and a canon EF 50mm 1.4. The majority of my pictures are of my kids. My biggest challenge and frustration is photographing them in low light situations (indoors, the gym, etc.)...dark, misfocus. I’m continuing to learn in manual mode. I wonder, however, if there might be a better lens for these situations. Any suggestions for my next lens upgrade? (I asked a similar question on a different forum and received some fairly critical responses. I take full responsibility for my inexperience and am not blaming my equipment. I understand that a new lens will not solve my ineptitude. Just looking for thoughts on my next lens...)

Thanks




  
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amfoto1
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Mar 12, 2018 23:12 |  #11

In addition to all the suggestions about fine tuning AF of that particular lens on your camera and the points about shallow depth of field....

1. The EF 50mm f/1.4 is not at it's best wide open. I usually stop mine down to f/2 for better sharpness. f/2.8 is even better.

2. Why are you using Expansion Point AF mode? Why not use Single Point or even Single Point Spot Focus for more precision? Any time you enable multiple AF points, you are giving up some control over the focus to the automation of the camera. That might work perfectly.... or it might not.


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apersson850
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Mar 13, 2018 04:43 |  #12

If you check the price list for lenses, you'll find that the cost is vastly different for different lenses. Asking for suggestions for a lens, without any cost estimate, will render wildly varying results.
Also, "kids in low light" is a good benchmark, but what's also important is how far away they are. Wide angle, medium, telephoto?


Anders

  
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Gschimma
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Mar 13, 2018 13:30 as a reply to  @ apersson850's post |  #13

Yes, I apoligize for not giving a budget. I’d say <$1000 US. 10-15 feet away, sometimes more when playing sports in a gym...




  
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Nethawked
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Mar 14, 2018 00:55 |  #14

Check out Sigma Art, the 50mm f/1.4 is very nice. If you like 50mm check out Sigma refurbished, you can pick this lens up for just over $700. That said, with what you most often take photos of my suggestion would be to find a Canon 85mm f/1.8, used about $250, and see if you like it better. You can then decide on which to sink the big bucks. My guess is you'll eventually own both.




  
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Nethawked
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Mar 16, 2018 11:26 |  #15

There's a good deal going on now at Canon Refurbished, you can pick up the 85mm f/1.8 for less than $300.

https://www.cpricewatc​h.com …-refurbs-5d-mark-iv-2379/ (external link)




  
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Autofocus problem?
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