Hyperfocus, DOF Charts, & Dense Digital Sensors

Discussion in 'Open Discussion' started by MAubrey, Jun 4, 2016.

  1. MAubrey

    MAubrey TalkEmount Top Veteran

    A few weeks ago, there was a discussion about how reliable DOF charts are in this day and age with super high resolution sensors that go well beyond the .03 CoC size for an 8x10 print from 35mm film.

    Jim Kasson, quite on his own, has been blogging about this very question over the past week:

    A new way to look at depth of field | The Last Word
    Hyperfocal distance MTF50 implications | The Last Word
    Hyperfocal distance MTF50 at small CoCs | The Last Word

    In the second post, he shows how resolution suffers if you take the traditional .03 CoC size on a 42MP sensor like that in the A7rII.

    Basically, to get the very best resolution, you need to be working with a DOF chart that gives you a CoC of the pixel size. On the A7rII that's 4.5μm--a CoC of .0045mm. You can enter that information into dofmaster.com's online calculator if you want to create your own charts, though they only give you the options of .004 and .005 if you want to work with pixel size. I'd expect that even if you doubled that to .01, you'd still be in the realm of "good enough" and get a little more flexibility in terms of actually creating a large depth of field.

    Of course, if you have a specific out put in mind (8x10, A3, A2, etc.) then you can be even more flexible don't really need to worry about perfect acuity at the pixel level.

    Still, it's useful to know what it takes.
     
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