problems with focusing

Discussion in 'Nikon' started by angela_parker, Oct 23, 2011.

  1. I use Nikon's 50mm 1.4 lens with my D300 and shoot manual {usually in the 2.8 range} for my most of my portrait sessions and I am having difficulty getting good focus when I am not within the 1-2 foot range from my subject. I have my camera set on spot metering mode and 51 point selective focus. So for example, when photographing a child sitting outdoors in the shade of a structure {midday}, when I place my focus indicator on the child's eye and press my shutter release button or AF button, the image is most in focus at the edge of her knit cap and not at her eyes. Even if I move the focus indicator to a spot a little below her eyes, her face is still out of focus. If I switch to manual focus, the difference I can see through the viewfinder is not accurate enough for me to be able to tell whether her face is sharp in focus or not {I have to zoom in on the LCD screen to check}. Is my technique incorrect or is it my camera? Should I use a different lens? Thanks for any suggestions!
    00ZVO0-408841584.jpg
     
  2. in the full body image, the subject's face is out of focus, even though i put the focus selector on her eyes. the most sharp part of the image is on the edge of her cap.
     
  3. Before blaming your camera or lens, make sure that you have set up *ALL* the knobs and switches on the camera body *AND* the menu options correctly for your purpose. In this case, the eyes are off center, and you want to make sure that once focus is set, it remains *LOCKED* if you recompose, and/or if the subject moves. Perhaps you can tell us what *ALL* your settings are, such as is Predictive Focus Tracking on/off, is Focus on Closest Subject on/off, ect., etc., etc.
    In many settings, the exposure is metered at the same point as the focus point. Focusing at one point and metering exposure at another point is yet another challenge. Boy, how I miss my simple film bodies.
    I have posted the following in other threads about this topic.
    =======
    I have found accurate focusing with AF on my D200 very challenging, especially when the critical subject is off center and/or moving. These cameras' AF features are cleverly designed to suit many different shooting situations. But the setup for each are scattered among knobs and switches on the body and entries in the menu. While Nikon's manual describes the function of each, they do not clarify the interactions between the individual settings very well. Get one of the settings wrong, and the AF would behave in ways you don't expect.
    Thom has this to say:
    The D200's autofocus system is actually very difficult to describe clearly. I've come up with a number of interesting observations and idiosyncrasies that are too elaborate for this review (obviously, they'll be in my eBook). Most of those derive from the fact that the AF sensors in the D200 are just much different than you'd expect from Nikon's description of them. First, there are only seven (not 11), though at least two of these apparently have multiple personalities, which is where the wide versus narrow AF area mechanism comes from. The shape of the sensing areas is also much different than you'd expect from Nikon's descriptions. This is almost certainly going to cause the all-automatic users some grief, as the AF system will do things they aren't expecting. However, once I finally tuned into the subtle differences the underlying AF part makes, I found my own focusing performance improved dramatically.​
    Perhaps his ebook can help. Or try this link:
    http://www.nikonians.org/nikon/d200_multi-cam_af/
    I have found it is impossible to accurately MF by the viewfinder on my D200. Perhaps my next body with live view and/or a better viewfinder can help.
     
  4. SCL

    SCL

    Try not using the 51 point selective focus, use only 1 point and center that on the nearest eye, that should solve your problem.
     
  5. try shooting at a smaller aperture
     
  6. I have yet to find an f/1.4 aperture lens that focuses absolutely accurately using AF or focus confirmation. I've previously theorised about the reason for this in a previous thread, but to reiterate, IMO the poor focus performance is due to residual spherical aberration in these wide aperture lenses.
    IME, the only way to get truly accurate focus is to use Liveview to magnify the actual image seen by the sensor at taking aperture. Obviously this isn't at all suitable for many subjects; informal portraits being one of them. Another alternative is to use the focus confirmation and adjust for whichever way the focus is usually out. For example you might find that when the focus confirmation looks like this [>o ] or this [ o<] you get sharper results than when only the centre circle is lit up. You can also tweak the focus for a particular lens using a menu option on some cameras.
     
  7. Maybe this will help :
    http://www.photozone.de/nikon--nikkor-aps-c-lens-tests/413-nikkor_50_14g?start=1
    Look at the bottom of the page, move the cursor over the blue F-stop numbers in order to observe the sallowness of the depth of field related to the F stop.
     
  8. thanks so much for the suggestions!!! they are greatly appreciated!
     
  9. gdw

    gdw

    Angela, be absolutely certain that you have your Nikon set to Single Focus Mode not Continuous Focus Mode. In Continuous Focus the camera will continue to refocus as you recompose your photograph even is you are half pressing the shutter release or even holding down the AFON. In Single Focus Mode, in the menus, you can set the AFON button to lock the focus as long as the button is held down but it still won't solve the Continuous Focus problem. BTW, I have a 50mm f/1.4 which presents absolutely no focusing problems when used on Single Focus Mode without using liveview, guess it's an aberration.
     
  10. Paul B's Photozone link is a great illustration of what happens with most wide aperture lenses, as I tried to explain above.
    May I draw attention to this quote from the Photozone site?
    "In addition, these shots also show the focus shift when stopping down..."
    You'll notice as you mouseover the various apertures, that not only the depth-of-field changes, but the plane of best focus shifts as well. In the case of the AF-S 50mm f/1.4 Nikkor G, the plane of best focus shifts from 100 on the scale at f/1.4 to about 80 at f/8. That's not an insignificant focus shift! And IME it's fairly typical of lenses with a maximum aperture of f/1.4.
    Perhaps now you see why I recommended Liveview as the only real accurate way to focus a wide aperture lens.
     
  11. I'd try the single point trick and also I'd try f4.
     
  12. I agree with others here. Use Single-point AF. Move the single focus point over an eyebrow. Choose AF-S Priority.
     
  13. erik_christensen|3

    erik_christensen|3 Self-employed

    Robert - where in the menu do you set Single-point AF?
     
  14. Another alternative is to use the focus confirmation and adjust for whichever way the focus is usually out. For example you might find that when the focus confirmation looks like this [>o ] or this [ o<] you get sharper results than when only the centre circle is lit up. You can also tweak the focus for a particular lens using a menu option on some cameras.​
    What you are suggesting is that the focus confirmation dot is NOT accurate, and needs to be tuned by trial and error. I have found this to be the case on the D200.
    On all my film bodies, the focus confirmation dot is ALWAYS accurate, with every lens I use.
     
  15. Angela, be absolutely certain that you have your Nikon set to Single Focus Mode not Continuous Focus Mode. In Continuous Focus the camera will continue to refocus as you recompose your photograph even is you are half pressing the shutter release or even holding down the AFON. In Single Focus Mode, in the menus, you can set the AFON button to lock the focus as long as the button is held down but it still won't solve the Continuous Focus problem.​
    This is a good example of how these modes/switches/menu options are NOT clearly explained in my D200 manual:
    - The manual is clear that if in Continuous Servo AF mode *AND* if Predictive Focus Tracking is ON, then the camera will refocus when recompose or if the subject moves. But it never explains what will happen if in Single Focus Mode *AND* if Predictive Focus Tracking is OFF.
    - The manual explains clearly how each AF Area Mode works. But it fails to explain how each mode interacts with each Focus Mode, i.e. Single, Continuous and Manual.
    - The manual never explains whether the AFON button needs to be pressed ONCE or needs to be held down to lock focus. I have found on my D200 with my settings, the AFON button only needs to be pressed once to lock focus. That's how I'm able to focus at one point, recompose and meter at another point.
    As I said, these dslrs' AF settings are really complex and difficult to get absolutely right for each shooting situations. Nikon could have done their customers a great service by suggesting *starting* settings for each common shooting situation, such as static subjects landscape and still life, fast moving subjects like sports, slow moving subjects like children' portraits, etc., etc. But then if Nikon does provide such help, the company would lose a lot of potential customers who like to blame their equipments and "upgrade", instead of learning how to get the most out of their equipments.
     
  16. What you are suggesting is that the focus confirmation dot is NOT accurate...​
    No, what I'm suggesting is that some wide aperture lenses fool both the AF module and consequently the confirmation light into a misfocus when the lens is stopped down. For most lenses of more modest maximum aperture the AF confirmation light is very accurate and it's certain lenses that cause the issue, not the camera.
     

Share This Page