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Face Detection difficulties on E-M1

Discussion in 'Olympus Cameras' started by barry13, Jun 7, 2014.

  1. barry13

    barry13 Super Moderator; Photon Wrangler

    Mar 7, 2014
    Southern California
    Barry
    Hi,

    I took some pics of some friends and their kid inside and outside a restaurant in the evening a couple days ago, with the 45mm f1.8...

    The E-M1 has firmware 1.4, and the settings are:
    'single small center A/F point'
    Face Priority set to the default (face / near eye)

    While reviewing the pictures, I noticed poor focus selection on some of them.

    At first I thought
    a. the kid's Hello Kitty t-shirt was fooling the face detection (as the shirt was in focus in some images)
    or
    b. the kid's head moved too much (she was jumping frequently)

    However, when I looked at the pics on the LCD of the camera to see the focus point selected (is there some other way to view this??), I noticed it wasn't (a). Also, I can rule out (b) on many shots as subjects were not moving.


    I don't expect perfection, but is the 'single small center AF point' a poor choice for face detection to work properly?

    Thanks,
    Barry
     
  2. Ross the fiddler

    Ross the fiddler Mu-43 Hall of Famer

    If you are able to post the photo here we can give you some helpful feedback without guessing, but my guess is that the DoF (depth of field) may not have been deep enough to get sharp (enough) focus on all of the faces you were photographing. What mode were you using, iAUTO, P, A, S or M? If you used A (aperture priority) then what aperture & focal length were you using & at what distance? The single AF point isn't the best for people group photos if you expect the face detection to be effective, but it can overrule the one focus point.
     
  3. jnewell

    jnewell Mu-43 All-Pro

    Jun 23, 2011
    Boston, MA
    I tried face detection and got results that were inconsistent enough that I turned it back off. Specifically:

    - it sometimes found faces where there were none
    - it sometimes failed to find faces where there was a face
    - it often selected what I considered the "wrong" face

    It's a nice idea that can be potentially useful but it didn't work well for me. YMMV.
     
  4. Ellsass

    Ellsass Mu-43 Regular

    88
    Apr 15, 2014
    I don’t use face detection but I do us the single small AF point. I’ve noticed my EPM2 mis-focuses a lot of shots despite the fact that I can hear/feel the lens searching for a moment before it apparently locks on. With the same lens (Oly 25mm 1.8) on a GF5 I don’t have this issue (I take a lot of the same photos with both, one right after the other, for comparison). This in broad daylight and in low light.

    I think the EPM2 — and maybe your EM1 — are mis-detecting whether focus has been achieved because I make sure the green box is always on the subject and that I wasn’t half-pressing the shutter (and thereby re-using the previous photo’s focus point). With moving subjects (dogs) this happens maybe 15-20% of the time, versus 1-5% on the GF5 in the same conditions.
     
  5. Ross the fiddler

    Ross the fiddler Mu-43 Hall of Famer

    If I were you I'd be using the larger focus box instead & then you are more likely to get better focus consistency with it (for multiple people at a little distance) & use the small focus area for more critical things like birds in trees etc.. A bigger area is going to contain more contrast detail to use to actually focus on.
     
  6. wjiang

    wjiang Mu-43 Hall of Famer

    Face detect works really well, except when it doesn't. I sometimes find that with my 45mm and E-M5, it finds the right face (the only face, as it's a half-length portrait), confirms AF lock, but hasn't actually focused on the face! Fortunately the EVF is good enough that I can tell and either switch to MF, AF single, or power cycle the camera (which tends to fix it). It doesn't seem to happen with any of my 3 other native lenses.

    Overall it works well enough that I still use it for isolated subject portraits. I tend to turn it off by default at events as there are way too many faces around.
     
  7. jnewell

    jnewell Mu-43 All-Pro

    Jun 23, 2011
    Boston, MA
    That is a very interesting observation. I didn't put that in my list of issues, because when it's happened I have assumed it was user error, but maybe it's not - maybe it's a "software" error.
     
  8. barry13

    barry13 Super Moderator; Photon Wrangler

    Mar 7, 2014
    Southern California
    Barry
    Hi Ross,

    Most of the photos had a single person (1 adult or 1 2.5 year old kid)...

    I was using 'P' mode, which (in my setup on the E-M1) still allows tweaking of the aperture (like 'A' mode), and I shot the outdoor (evening) shots at f2.5, and indoors at f1.8 (except for the shots with more that one person). All shots were with the Oly 45 f1.8 on the E-M1, firmware 1.4.

    I reviewed the pictures once more, and most or all of the ones with focus problems were failure to detect the face.

    Here's an example... focus point is on the top edge of the shirt collar, towards our left.
    Oddly, that is neither on the face NOR is it the center of the image (the image center (according to gimp) is approx on the back of the jawbone, on our left)

    E6023321-sm.JPG (sooc, resized in gimp)
    E6023321-crop.JPG (sooc 100% crop in gimp). Note the hair & lint on the the shirt is very sharp but the face isn't. f2.5, 1/100s

    Many similar pics in the series did detect the face, so I'm not complaining too much.
    However, there are also quite a few where her face may have just happened to be in the center (I can't see any way on the LCD to distinguish when face detection worked if the focus point happens to be centered).

    Here's an example; focus point is in the image center which is just under the nose:
    E6023343.JPG

    BTW, I've taken advice from another thread and increased the sharpness setting in the camera, which reportedly helps the AF speed.


    Anyways, I'm (still) wondering if there's a better AF selection that might help the face detection work better?

    Thanks!
    Barry
     
  9. barry13

    barry13 Super Moderator; Photon Wrangler

    Mar 7, 2014
    Southern California
    Barry
    Also there's several pics where it focused above the eyebrow instead of on the eye.

    Barry
     
  10. Ross the fiddler

    Ross the fiddler Mu-43 Hall of Famer

    Looking at those I would have used a small focus box, I know I said otherwise above, but.....(although moving young children can be quite a challenge) then set the target for the eyes (eyes are always the most important part of a persons or animals or any creatures face) & used Aperture Priority so I could select the aperture as I desired which sets the DoF (depth of field) to suit the subject or subjects (for a number of people). You were using a reasonably shallow DoF here & therefore it was important to get accurate focus precisely where it was most important & that would be the eyes first (nearest eye). Theoretically the face detection with the nearest eye should do that, although algorithms for detecting all types of faces obviously struggles with some faces (I don't know why) but had you closed the aperture a little more you would have got more of the face in focus. Stylised portraits deliberately focussing on the eye(s) & blurring everything else is often desirable by many photographers, but for family record shots it is usually better to have a greater DoF to get more of the subjects, people in focus, although it can become necessary to use a large aperture for indoor photos without using a flash (as well as allowing a higher ISO).

    Two lovely photos all the same, but I would suggest getting used to using Apeture Priority, adjusting aperture with the Rear Wheel & the Exposure Compensation with the Front Wheel. It can be the 'go to' mode for most applications (with Shutter Priority & Manual for critical timing or exposure shots).
     
  11. barry13

    barry13 Super Moderator; Photon Wrangler

    Mar 7, 2014
    Southern California
    Barry
    Hi,

    It was rather dark to do higher (smaller) aperture; was already at 1/100 and kid was moving a lot, although I supposed I could have set the ISO higher.

    I was trying to do a stylized portrait, although the background was too close to subject to get any real blur...

    In the future I will try to aim for the eye in shots like this.

    AFAICT, Aperture Priority doesn't do much different than 'P' mode the way I have things set up; the rear wheel changes the aperture and front is EC, in 'P' mode for me.
    It will still sometimes raise the aperture in 'P' mode if the light drops off, but usually it stays where I put it.

    Thanks!
    Barry
     
  12. tyrphoto

    tyrphoto Mu-43 All-Pro

    May 25, 2014
    Seoul | NYC
    ㅇtㅈyㅅr
    Face detection is quirky and not always accurate. IMO, better to just spot focus and use the proper aperture for the given scenario of distance, focal length and wanted effect.

    Sent from my SHV-E300S using Tapatalk