Effects of exposure compensation don't show on live histogram?

Discussion in 'Sony Alpha E-Mount Cameras' started by ajm80031, Aug 21, 2013.

  1. ajm80031

    ajm80031 TalkEmount Regular

    35
    Jul 16, 2013
    Last night I was doing some experiments on my NEX-6 with the 16-50mm kit lens vs a Minolta AF 50mm f/1.7 on an adapter. As the 16-50mm needs distortion correction in software, I was curious how the edges of an image taken with it at 50mm would compare with a 50mm prime. I didn't really reach a conclusion as I was having trouble getting the camera to take equivalent exposures with the two lenses. Set to aperture priority with both lenses, in lower-light conditions the camera consistently underexposed with the kit lens while pretty much nailing the exposure with the adapted lens. Interestingly, in bright light the differences in exposure between the two lenses went away.

    While trying to compensate for the underexposure with the kit lens, I became aware of something odd: dialing in exposure compensation doesn't seem to affect the live histogram. The histogram at the camera's chosen exposure showed serious underexposure, so I dialed in exposure compensation of +1. No change in the live histogram, so I dialed compensation up to +3. Still no change in the live histogram. I took a test shot and the resulting frame was very overexposed (with the histograms of the stored photo mashed up against the right edge).

    I find this to be very strange. I'm not all that thrilled with the camera taking away the live histogram while I'm making exposure compensation adjustments, but once I've finished the adjustment and gone back to the live histogram I certainly expect it to show me the effects of what I've done. Do I have something set wrong on the camera, or is this just the way it works?
     
  2. Bimjo

    Bimjo Super Moderator

    Oct 28, 2011
    Washington State
    Jim
    Depends on how far off the exposure is. I just tried it @ f.8 and the camera said I needed a exposure longer than 30 seconds. EC had no effect on the histogram. Opening up the aperture to where I had a 13 second exposure the EC changes were visible in the histogram.
     
  3. ajm80031

    ajm80031 TalkEmount Regular

    35
    Jul 16, 2013
    Bimjo, I just did some additional experimentation and you're right. On a more brightly lit scene the histogram does indeed reflect the results of adding exposure compensation, but on a dim scene it doesn't. Weirdness.
     
  4. alaios

    alaios TalkEmount All-Pro

    Jan 11, 2013
    Düsseldorf
    Alex
    Well.. is there a fix for that? Why sony implemented the camera that way?
     
  5. Bimjo

    Bimjo Super Moderator

    Oct 28, 2011
    Washington State
    Jim
    If your exposure is so far over or under exposed that the 3 stops of exposure compensation cannot bring it back within acceptable specs the histogram will not show the compensation.

    It is no different if you are in manual mode and your exposure is grossly over or under exposed. The histogram will not move until the exposure is within a normal range.

    It's like speeding in your car. If your speedometer goes to 130 and you're going 180 the speedometer will read 130. You're going faster, but you don't know how much faster. If you ease off the throttle you won't see the speedometer change until you get below 130.
     
  6. ajm80031

    ajm80031 TalkEmount Regular

    35
    Jul 16, 2013
    I don't think your analogy works here. A speedometer is a point measurement, a histogram is showing you a range of information. I agree that, if the initial metering is way off for some reason, 3 stops of compensation may not be enough to achieve correct exposure. However, it should result in some movement of the histogram 'waveform' to the right. "The histogram will not move until the exposure is within a normal range" is just flat out broken behavior in my book.

    Said another way, the 'live' histogram at the time of exposure should approximately predict the 'after the fact' histogram you see when reviewing stored images. If it doesn't, the live histogram is effectively worthless. I'm finding that, in some situations, the 'live' vs. 'after the fact' histograms on my NEX-6 are wildly different. There's not excuse for that.

    Overall there are two questions here: 1) Why is the NEX-6 picking an exposure that's so dark in the first place? 2) Why does the histogram not show any effects even from a large (+3) amount of exposure compensation.

    I tried my Panasonic GH1 on the same scene with the same lighting and it wasn't thrown, it picked an exposure that was at least close to correct. For a similar ISO setting and aperture, the NEX-6 appears reluctant to set a slow enough shutter speed while the other camera gets it (at least close to) right.
     
  7. Bimjo

    Bimjo Super Moderator

    Oct 28, 2011
    Washington State
    Jim
    Whether it is proper behaviour or not for the histogram to not show changes on a grossly out of spec exposure setting I can't say, I'm not a Sony software engineer. Do I think it should? I'm not sure, since the camera provides a live view that will show either a "always bright" view or the actual view of the scene. Switching back and forth between the two settings can have a large difference in the appearance of the histogram. The shots look the same in the computer, so what does that tell you?

    That your GH1 was closer to "correct" means little since your NEX with an adapted lens acted in a similar fashion. Perhaps your 16-50 is in need of service. I can't say, I have neither a NEX 6 or a 16-50 lens. Again, it may just be how the firmware is written. It could easily be different, but alas it is not.

    In the end I can only shrug and say "I dunno." :confused: