1

I was working on some selfportraits using interval timer shooting and I found that the camera focuses one of 3-4 shots on the subject.

Obviously, it recognizes the face but most of the times, it has scattered focus points around everywhere.

Ideally I would like to use a setting which would only pick one focus point, not a group from completely different areas. However, the only choice I have for the number of focus points is 11 or 39. Whether I'm in AF-A or AF-S there are two options - use all focus points or only the center one. The subject is not always right in the center and I end up using all focus points resulting in 1 out 4 focus images.

AHhh.

Just a follow-up. I found that the best way to detect faces is of-course in live view which is inactive when interval timer is used. I also used a remote, but I find it less convenient than interval timer and I have similar focusing issue with it.

Example: enter image description here

  • That's for Canon with the answers like place an object, use remote, increase F stop. I – user173570 Dec 20 '15 at 16:20
  • That's for comments with answers like increasing F stop and using remote. My question is a lot more specific. I understand that the camera may not pick up my face. However, I need to figure out how to have an autofocus pick up ONE focus point, not a bunch (which are at least 5 feet apart in my example) – user173570 Dec 20 '15 at 16:22
  • See also How can I get correct focus when taking a self portrait with a DSLR? for more general advice on focus and self-portraits. – mattdm Dec 20 '15 at 16:58
2

When multiple AF points light up such as in your example, it means the camera interprets the information from its AF system to indicate all of them are within the acceptable depth of field. With a maximum aperture of f/3.5, shallow depth of field is not your problem.

But, since you asked, you can just look through the viewfinder at where you plan to be in the frame and select the single focus point that corresponds to that position. The Nikon D7000 allows for using a single selected focus point. Please note that designating it as a manually selected focus point doesn't mean you must manually focus to use it - it just means that you get to manually tell the camera in advance which focus point to use for autofocus! The instructions on how to select a specific focus point are located on page 96 of your D7000 User's Manual

Please see this answer for more on how the area of each focus point is larger than the little square in your viewfinder as well as why the far left and right AF points might not be as accurate as the center one(s). Although the camera is a different model from a different manufacturer, the concept is shared across brand and model lines in cameras with a large number of AF points. Nikon does tend to not include as many cross-type AF points as Canon, so it is more likely that half of your outer AF points are horizontally sensitive and half are vertically sensitive, rather than all cross-type as in the example at the link.

I think you will ultimately find that at least some of the blurriness you are blaming on AF is more a result of shooting with that lens wide open, at a shutter speed that can be particularly affected by mirror movement vibrations, and in poor lighting that is a different color temperature than what you've set your camera.

  • Stopping down will work wonders for a lens such as your 18-200mm f/3.5-5.6. Those type of lenses are never that great, but they're usually not even good when the aperture is wide open. Of course stopping down means even less of the limited light you are shooting in will reach the sensor so it is time to think about adding your own light to the scene. Welcome to the world of portrait photography, where most all of that beautiful, natural looking light is totally artificial!
  • Shutter speeds in the 1/80 second to about 1 second range are particularly susceptible to the vibrations caused by mirror slap. Any shorter and the exposure is over before the vibrations reach the critical parts of the optical path: the lens and the sensor. Any longer and the percentage of the exposure affected by the vibrations before they dissipate is low enough to reduce their significance in much the same way that you can take an extremely long exposure of a street scene and none of the people walking through are visible in your photo because they didn't stay in one spot long enough. Use mirror lockup with shutter speeds in the 1 second to 1/100 second range when the camera is properly stabilized to eliminate these vibrations.
  • Selecting the correct white balance for the light will give better contrast and make your photos appear better focused. To test this shoot a few raw frames and then use a raw conversion application to look critically at the perceived sharpness as you change the WB to match or mismatch the shooting conditions. Look closely at the lines between darker and lighter areas in the frame (local contrast) and how they are affected by an incorrect white balance the over saturates at least one of the color channels. Overexposing a low contrast scene in subdued lighting can also have the same effect as rather than getting a few locally blown highlights as you would in a higher contrast scene, you see more general blooming all over the frame and the brighter spots bleed onto the adjacent areas that are dimmer.
  • Thank you very much for a detailed answer! "I think you will ultimately find that the blurriness you are blaming on AF is more a result of shooting with that lens wide open, at a shutter speed that can be particularly affected by mirror movement vibrations, and in poor lighting that is a different color temperature than what you've set your camera." PLease note, the camera produces sharp (acceptable) images in the exact same spot when focused on one spot. – user173570 Dec 20 '15 at 20:08
  • 2
    Then why not prefocus on that spot and then turn off AF? Regardless of how many focus points are lit up, your lens can only be focused at a single distance at any one time. If focus points indicate more than one distance is in focus it is only because the amount of contrast detected by each of the focus points is within the tolerance of the system's parameters. In general when multiple focus points indicate focus has been achieved in all of them it is because even if they are in different areas of the frame the items in the frame are all the same distance from the camera. – Michael C Dec 21 '15 at 4:28
  • Your sample photo is a little odd in this respect and leads one to question how it was produced. It appears to be a screenshot of a photo viewing application? – Michael C Dec 21 '15 at 4:30
  • Also note that the active areas of focus points are almost alway larger than the square in the viewfinder that indicates each one. WIth multipoint systems such as found in your D7000 the areas of sensitivity from one focus point to the next often overlap and even share space on the same sensor strips in the AF array buried in the floor of your camera's light box. Although the specifics are for the Canon 7D, the concept is the same and shared by many current models. photo.stackexchange.com/a/70013/15871 – Michael C Dec 21 '15 at 4:38
  • Michael Clark, yes it was a screenshot because I wanted to show the focus points – user173570 Dec 22 '15 at 11:46

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.