Questions re: a6000 low light photos

Discussion in 'Sony Alpha E-Mount Cameras' started by nighttrain, Dec 7, 2015.

  1. nighttrain

    nighttrain TalkEmount Regular

    40
    Dec 9, 2014
    Hoping to get some feedback on low light shooting with the a6000. I just bought this camera & have been testing it using a Sigma 30mm 2.8. I've taken a few dozen low light photos, mostly city views at dusk or at night, and indoor shots. All JPEGs, Fine. Most shots were Aperture priority 2.8, ISO Auto (always defaulted to 3200) with High ISO NR set to Normal.

    The dark areas of these high ISO photos have a dozen or so red pixels and a few white and gray pixels. The red pixels are not square, they're more like short vertical and horizontal lines. They are in different spots in each photo. They're noticeable at 66% in Photoshop.

    I took similar low light photos using IA and IA+. I could still find a few red pixels viewing at 100% but there were less of them.

    Next I switched back to Aperture priority 3.2, ISO Auto (3200), and took a shot with the cap on (25 sec.). Long Exposure NR was off. This resulted in a black image with hundreds of small red pixel clusters and smaller gray and white pixels. I was expecting a broader range of colored pixel noise.

    By comparison, long exposures at ISO 100 don't have any weird pixels.

    Is it normal at high ISO to get small red pixel clusters with this camera? Are these hot pixels? Noise? If it's noise, why isn't there a range of other colors as well? Thanks!
     
    Last edited: Dec 8, 2015
  2. WoodWorks

    WoodWorks Super Moderator

    Dec 12, 2012
    Ashland, OR, USA
    David
    Can you post some examples, nighttrain? It's much easier to give you a good answer if we can see what you're seeing.
     
  3. davect01

    davect01 Super Moderator

    Aug 20, 2011
    Fountain Hills, AZ
    Dave
    Agreed.
     
  4. nighttrain

    nighttrain TalkEmount Regular

    40
    Dec 9, 2014
    Thanks for the replies. Here are 100% crops from two images, both downsized to 72 dpi. The first is a section of the side of a wood building taken at night.

    f-stop = 2.8
    shutter = 1/13 sec
    ISO = 3200
    Multi pattern metering

    The second shot was taken with the lens cap on.

    f-stop = 3.2
    shutter = 25 sec
    ISO = 3200
    Multi pattern metering
     

    Attached Files:

  5. WNG

    WNG TalkEmount All-Pro

    Aug 12, 2014
    Arrid Zone-A, USA
    Will
    The first shot seems to make me suspect stuck pixels. The 2nd cap-on shot shows too many stuck pixels....BUT, majority of the time, long exposures are done at the lowest ISO possible. ie. 100. I'd repeat the cap-on shot at ISO 100 and see how many pixels are still prominent.
    For example I have <25% of what you got in the cap-on shot (with LENR off).

    The first shot is enough to make me return the body as defective.
     
  6. nighttrain

    nighttrain TalkEmount Regular

    40
    Dec 9, 2014
    WNG, I've done the lens cap photo at ISO 100, 30 sec exposure and there are no red pixels in that shot. I checked it at 300%. Also, I thought for pixels to be considered stuck, they had to appear in the same place in multiple photos. Is that right? I've checked several photos in Photoshop and the red pixels don't overlap.
     
  7. nighttrain

    nighttrain TalkEmount Regular

    40
    Dec 9, 2014
    Is it possible that the sensor operates normally at low ISO numbers but runs too hot at higher ISO settings? Anybody know about the technical design of these sensors? I'd welcome some more opinions on this. Thanks.
     
  8. WNG

    WNG TalkEmount All-Pro

    Aug 12, 2014
    Arrid Zone-A, USA
    Will
    If they aren't there at ISO 100, then it's good.
    And yes, stuck pixel is going to stay at a fixed location. And will remain at a fixed color in all shooting conditions.
    a bad pixel may be weak at one or more of the colors and return a false pixel reading.
    I don't know if it's heating up from high ISO settings during LE.
     
  9. nighttrain

    nighttrain TalkEmount Regular

    40
    Dec 9, 2014
    Thought I'd post a follow-up. I exchanged the a6000 and recently received a replacement. It performs better in some ways and worse in others. Haven't spotted any problem red pixels in low light shots except for long exposures. But the new camera produces more noise at ISO 3200 (NR on) than the previous camera did. I also looked at comparable a6000 test images from review sites, and my new camera is noisier.

    Long exposures with the cap on at ISO 3200 (NR off) produced red pixels on the right and left sides of the image but not in the middle. A 30 second exposure at ISO 100 (NR off) was mostly black but had about a half dozen small red pixel clusters. So I'm considering exchanging it one more time. Just wondering if others who bought the a6000 in recent months have noticed quality control issues?