Canon 7D - 50mm 1.4 Focus Issues

Discussion in 'Canon EOS' started by tom_collins|3, Sep 1, 2011.

  1. Good Morning! I mainly shoot portraits and weddings and I have been forcing myself to shoot with my 50mm 1.4 lens more often because of all of the rave reviews that I hear about it, but to be honest I haven't had the best luck with it. WHEN my images are sharp with the 50mm 1.4 lens, they look amazing, but I have WAY too many OOF images. I tend to believe that this is because of my focus and recompose technique, especially at more wide open apertures like 1.8 but don't know any other way around it. I shoot with a Canon 7D that has 19 AF points, which seems like a lot but I still don't seem to have a point exactly where I want to put the subject's eye. I guess it's possible that I have a bad copy of the lens, or that it needs micro-adjusting in camera, but I'm fairly certain it's more a technique issue. Is anyone else having this issue? How can I alter my technique to get sharper images after recomposing at apertures like 1.8? Thanks for any insight!
     
  2. A couple things:
    1. At the very largest apertures (particularly f/1.4 but possibly on or two 1/3-stops smaller) this lens starts to produce low contrast that can look like OOF. When possible, if sharpness is critical, you might try to use f/2.
    2. Virtually any lens is going to be a bit less sharp at its largest aperture. You'll see that with this lens, too, especially if you look at 100% crops. On the other hand, do you see this in actual final output - e.g. prints?
    3. Because DOF becomes increasingly small as you open up the aperture, small focus errors are more likely to result in visible softness. This means that a slight misfocus or a slight lens/camera adjustment error that would not otherwise be seen can end up being an issue at f/1.4.
    4. In some cases, you might want to try a different AF focus point such as center only, rather than using the full array of AF points.
    5. If you haven't tried micro-adjusting the lens, do so.
    Dan
     
  3. At such wide apertures focus and recompose is asking for trouble. Try this, "shoot to crop" (I'm trademarking that expression :) ), by that I mean use the focus point closest to your preferred composition and shoot, then in post just crop to your chosen composition.
     
  4. You appear to have a problem - while the AF on my 50mm F1.4 is not the fastest focusing lens you should not have AF issues at F1.8 (I find my copy is soft until F2). On a 7D the DOF is 3.5 inches at F1.8 and 6 feet so focus and recompose should be fine. Do you have any other fast / shallow DOF lenses you can play with to see if it technique, the camera or the lens?. When I need critical focus I almost always just use the center point and re-compose. If you are using multiple AF points you can sometimes have the AF set to the wrong distance. If you do just use one point at re-compose make sure that you are not releasing the pressure on the shutter button (or AF button on the back if you configure the camera this way - I find it useful).
    Best technique is either to use the center AF point (the most sensitive) and re-compose or select a single AF point located where you need it (this is slightly slower and easier on cameras like the 1 series bodys but works fine on the 7D). You should be in one shot mode (AI-Servo is for moving subjects and One shot for static). By the way ignore AI Focus - this mode is a waste of time and they do not put it on 1 series bodys (indeed they did not put it on higher end non 1 series bodys like the EOS3).
    For very accurate AF you can use spot AF mode. The 7D AF is quite complex and I suggest that you take a read of this document before you do anything too drastic. AF micro adjustment can help but I think that your problem may be technique
    http://www.learn.usa.canon.com/resources/articles/2011/whats_news_eos7d_article.shtml
     
  5. You're miles ahead of me. Mine won't focus at all 90% of the time. It'll blink the focus point, pretending that it achieved focus. But often it doesn't move at all and when it does it's almost always wrong. The mechanical design of that particular lens is spectacularly lousy. It was an early '90s lash-up to allow full-time manual focus. When it is properly focused (using live view, for instance) it's really quite good. I could send it back to Canon and they'd "fix" it for close to $200. But that seems like good money after bad since I only paid around $300 for the lens when it was new.

    All of that being said, I think the micro-adjustment is probably in order. If your copy works, then it sounds to me like you (and the others who have commented) are thinking in the right direction.
    Joe
     
  6. In addition to the above re:1.4 and thin focus, -have you set the camera for back button focus and disabled af assist on your flash? The focal plane is so thin and focus finicky at such wide apertures that even the slightest attempt by the camera to tweak it could render the desired area OOF. I also recommend spot af, remove AF from front button and set the AF zone adjust to the toggle switch along with manual focus touch up.
     
  7. Have you tried using just one point AF? (you really don't need 19 for portraiture) I can focus and recompose comfortably @ f1.8, maybe try it and see?
    Also - Definitely do MFA (microfocus adjustment)! that may be a critical source of error, esp. at large apertures, and in particular w/ this lens.
     
  8. The 50mm f1.4 is a very demanding lens, and heaven knows this forum has documented plenty of QA problems; so it's worth while shooting a few yardsticks to see where the focus point really is. But I doubt that this is the problem. Focus and recompose means that you swing the plane of sharpest focus away from the eye. With apertures of less than 2.8, at typical portrait shooting distances, this does cause variations in sharpness visible on a big monitor or print. Even a non photographer can tell that the nose, say, is sharper than the eye. Because of the psychologic importance of the eye, this can make an otherwise excellent portrait unsatisfactory. The higher the resolution of the lens and sensor, the worse this problem is, because it's the variation of sharpness across the image that is so striking.
     
  9. 1) Put the camera on a tripod, point at the wall, test AF versus MF with live-view. Set microadjust if necessary.
    2) Select single AF point, and map the joystick to AF point selection. It's in custom functions.
    3) When shooting, select AF point with the joystick. Don't focus-recompose unless you're at f/4 or something like that.
     
  10. If you do that, make sure the tripod is about where you shoot the majority of your images, I found that my 50 f1.4 is very good when I use it as I do, when I stand back 3 or 4 yards it is not as accurate. I can MF adjust it to work there better, but I prefer it as it is.
     
  11. Tom, I had a very similar problem with my ef 50mm 1.4 which was reproducible on both the 5DMII and 40D bodies. Microadjustment on the 5D did not help. Because this lens is one of my favorites I sent it in to Canon. $120 and a few days without the lens yielded a fine piece of optics. Focus was faster and spot on. Of all my lenses, I find this one is on the body more than most of the time and the money was well spent.
     
  12. Tom, I had a very similar problem with my ef 50mm 1.4 which was reproducible on both the 5DMII and 40D bodies. Microadjustment on the 5D did not help. Because this lens is one of my favorites I sent it in to Canon. $120 and a few days without the lens yielded a fine piece of optics. Focus was faster and spot on. Of all my lenses, I find this one is on the body more than most of the time and the money was well spent.
     
  13. Thanks everyone for the tips! Just to clarify a few things:
    • I am one-shot focus mode
    • I am choosing a single focus point manually (spot focus), but even the points closest to the area I want (typically on the edges) are not exactly where I want to compose my subject's eye. Thus I have to focus and recompose. But I always choose the closest AF point to start with
    • I realize that the lens is not going to be sharpest at 1.4, so I rarely go larger than 1.8, and I would hope the lens would be fairly sharp at 1.8
    • I use the "AF-ON" button on the back of the camera and have disabled the focus feature from the shutter half-press
    @Scott, I'm liking the "shot to crop" idea except for the fact that I'm throwing away pixels that I might need, especially for an enlargement from a wedding.
    I'll have to shoot some measuring sticks or focus charts to see if micro-adjustment is in order.
     
  14. Try using F1.4 to F4 (this is where my lens gets sharp) and try with a flat test target (e.g. newspaper on the wall. Use the center AF point and a tripod. Then repeat using MF and live view with 10x enlargement. Try shooting from about 8-10 feet and look what happens. This will isolate the lens effects from the AF effects (i.e. I find my lens is quite soft at F1.4 and F1.8 so if your images are not sharp in MF or AF at these apertures it is the lens). If it is just the F1.4 and F1.8 shots in AF mode then it needs micro adjust. If all the shots in AF are OOF then it is a bigger problem (at F4 and 10 feet the DOF is almost 2 feet).
    If all looks good try the focus and re-compose handheld and see if you also have a technique issue. I have never found an issue with this technique for portrait use (macro is a different issue) as your DOF is usually at least 3 inches. Even with an 85 F1.2 on full frame (or my GX680 180 F3.2 at 6 feet) with a DOF of about 1.2 inches I can focus and recompose. This is because an 85 f1.2 has a horizontal FOV of about 24 degrees - even a subject towards the edge is probably only 8 degrees from the center. Thus with a 6 foot distance and a 8 degree offset the range only changes by 0.7 inches so while the center of the focus may have moved it is still within the in focus region. Usually if you have a problem with focus and re-compose it is due to you are the subject moving slightly as you re-compose.
     
  15. Tom, using 19 AF point with an f1.4 portrait lens is asking for trouble. I'm surprised you got as many keepers as you did. Use center point single AF, focus, recompose, shoot. I've never had any problems that way. I do the same with my Nikon D700 and 50 f1.4 and 85 f.14
     
  16. You might want to read this tutorial on the 7d AF system: http://www.learn.usa.canon.com/resources/articles/2011/whats_news_eos7d_article.shtml
    I don't have a 7d, but now I want one! That spot AF function would be really nice.
    After reading it, and the above discussion, I'd say the following: if your lens is working correctly, this camera will have no trouble focusing it wherever you want. While my own 50/1.4 is sharper and more contrasty at every aperture than any other lens I own, including the awesome 100mm f2.8 USM macro, it's just not good enough at f1.4-2.0 for portrait. The eye won't be sharp enough with a high resolution camera like the 7d. If you focus-recompose, you need to stop down to at least f2.5 or 2.8, which will still allow good background blur at head and shoulders shooting distance.
     

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