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DxOMark reviews the A7S II

Discussion in 'Sony Alpha E-Mount Cameras' started by quezra, Dec 11, 2015.

  1. quezra

    quezra TalkEmount Top Veteran

    916
    Aug 22, 2012
    Full review up. Is it just me or it doesn't make much sense? It looks worse than the A7r II and the original A7S. Did IBIS/heatsink ruin it or something?
     
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  2. adwb

    adwb TalkEmount Regular

    126
    Sep 30, 2015
    Bristol UK
    Alistair
    not much to worry about the figures are less than most can see
     
  3. quezra

    quezra TalkEmount Top Veteran

    916
    Aug 22, 2012
    Just realised it doesn't actually have IBIS... still puzzling!
     
  4. Amin Sabet

    Amin Sabet Administrator

    Aug 6, 2011
    It does have IBIS. The sensor measurements look very similar to A7S.
     
  5. quezra

    quezra TalkEmount Top Veteran

    916
    Aug 22, 2012
    Oh heh! I was wondering how I misremembered something that significant...
     
  6. WestOkid

    WestOkid TalkEmount All-Pro

    Jan 25, 2014
    New Jersey, USA
    Gary
    Overall it does, but it is curious that the A7SII low-light ISO rating is 2993, versus 3434, and 3702 for the A7RII and the original A7S respectively. DXO says this is a –0.3 EV difference.

    In fact, if I read the ISO performance correctly, the A7SII is closer to the original A7R than it is to the original A7S. How copuld this be?
     
    Last edited: Dec 11, 2015
  7. Amin Sabet

    Amin Sabet Administrator

    Aug 6, 2011
    ISO performance in terms of SNR looks the same (within measurement error):

    iso.

    DR is weird with one camera better than the other depending on ISO, basically a wash:

    dr.

    TR also looks to be a draw (within measurement error):

    tr.

    The only significant differences are in color sensitivity:

    cs.

    I bet it's the same sensor. Maybe a slightly different CFA.
     
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  8. MAubrey

    MAubrey TalkEmount Top Veteran

    Sensor variation from camera to camera is easily at least 1/3rd of a stop in difference and 2993 to 3702 is barely 1/3rd of a stop--it's more like 1/4th!

    A full stop over ISO 2993 would be ISO 5986 and in thirds that would be:

    2993 (0/3rd stop)
    3990 (1/3rd stop)
    4988 (2/3rd stop)
    5986 (3/3rd stop)

    In fourths it would be:
    2993 (0/4th stop)
    3741 (1/4th stop)
    4489 (2/4th stop)
    5237 (3/4th stop)
    5986 (4/4th stop)
     
    Last edited: Dec 11, 2015
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  9. WestOkid

    WestOkid TalkEmount All-Pro

    Jan 25, 2014
    New Jersey, USA
    Gary
    Thanks Amin,Mike. I understand the difference is only 1/3 stop. What I didn't understand is there was such a thing as sensor variation from camera to camera. I thought that only applied to lenses because or their mechanical nature.
     
  10. MAubrey

    MAubrey TalkEmount Top Veteran

    Yep, lithographic processes like those used with CMOS also involve variation. The same thing happens with CPU's and GPU's. There are always flaws in the silicon wafer. Sometimes they are fatal flaws and must be thrown out, but other times they are minor enough that chips still fall with in the specifications established by the manufacturer.
     
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