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Thread: Real base ISO Phase One

  1. #1
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    Real base ISO Phase One

    Hi,

    Just wanted to clarify before doing my own tests. As there were some graphs posted which show noise development through different ISOs with Phase backs.

    Why is there ( or is there actually ) a difference between the 350 and 3100? (100iso vs 50iso)

    Is 35on the IQ180 really base or is there no real difference to 50 ?

    All the best and thanks for any input.

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    Senior Member ErikKaffehr's Avatar
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    Re: Real base ISO Phase One

    Hi Christopher,

    I don't know what graphs you refer to…

    DxO used to measure "true" ISO. I think vendors take a lot of liberty with ISO numbers. What is base ISO can be discussed. One way to see it is that it is the ISO that gives best DR. My guess would be around 100 ISO, but that is just a guess.

    Increasing full well capacity lowers base ISO, all other factors assumed constant.

    Best regards
    Erik


    Quote Originally Posted by Christopher View Post
    Hi,

    Just wanted to clarify before doing my own tests. As there were some graphs posted which show noise development through different ISOs with Phase backs.

    Why is there ( or is there actually ) a difference between the 350 and 3100? (100iso vs 50iso)

    Is 35on the IQ180 really base or is there no real difference to 50 ?

    All the best and thanks for any input.

  3. #3
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    Re: Real base ISO Phase One

    I'd also be very interested in an official answer to this, since Doug posted in the following thread that the best results would be at ISO 50:

    http://www.getdpi.com/forum/medium-f...omparison.html

    That was news to me: I was assuming that ISO 50 was a "pull" setting and that ISO 100 was the true base...

  4. #4
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    Re: Real base ISO Phase One

    Coming from a Leaf/Credo 50 to a Phase 100 I just automatically assumed that 100 iso would be identical and very acceptable. It certainly is. However when shooting the same scene at 50 iso the noise level does decrease slightly. In the real world this would never be seen but at 100% pixels or 200% pixels it is slightly noticeable..... emphasis on 'Slightly'. Really, really splitting hairs here!

    Victor
    Likes 1 Member(s) liked this post

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    Senior Member bab's Avatar
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    Re: Real base ISO Phase One

    Quote Originally Posted by vjbelle View Post
    Coming from a Leaf/Credo 50 to a Phase 100 I just automatically assumed that 100 iso would be identical and very acceptable. It certainly is. However when shooting the same scene at 50 iso the noise level does decrease slightly. In the real world this would never be seen but at 100% pixels or 200% pixels it is slightly noticeable..... emphasis on 'Slightly'. Really, really splitting hairs here!

    Victor
    I would think CMOS has less pixel noise but maybe some electrical noise that 100 Might get hot...hotter than the 50 credo. Running the 100 must have a lot of back end smoke and mirrors to get that puppy to jump huh!

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    Re: Real base ISO Phase One

    This is the thread I think you refer to:http://www.getdpi.com/forum/medium-f...sure-mode.html

    50 posts and you want a straight answer?

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    Senior Member Steve Hendrix's Avatar
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    Re: Real base ISO Phase One

    Don't you find it interesting that all the cameras and all the lenses, and even all the tripods, across the entire industry, from numerous manufacturers, have nearly identical specification markers?

    Cameras - ISO 50-100-200-400-800, etc.

    Lenses - 28mm-35mm-50mm-80mm-110mm-120mm-150mm, etc.

    Tripod Weight Capacity: 8.8lbs-11.0lbs-17.6lbs-22.0lbs, etc.


    How likely is it that the products displaying all these measurements, that are shared by multiple manufacturers, have somehow been independently designed and manufactured and are really exactly as stated? Is it really ISO 50? Or is it 100? Or is it really 74? Oops, can't use 74. The Schneider 35mm APO Digitar XL. Or, err... 36mm.

    https://www.schneideroptics.com/ecom...=1325&IID=1886
    Schneider / ALPA Apo-Switar 5.6/36 mm, LB


    This goes back to the film days, of course.

    With regard to sensors from digital backs, most I've assumed are somewhere between the base and the next stop higher, since you can extract similar noise/dynamic range characteristics. In other words, I've generally treated them the same, unless my testing has shown me otherwise. 2 stops up from base (for CCD), is where I have really started paying attention.


    Steve Hendrix/CI
    Steve Hendrix, Sales Manager, www.captureintegration.com (e-mail Me)
    Digital Cam: • Phase One | Leaf | Leica | Sinar • Authorized Reseller
    TechCam: • Alpa | Cambo | Arca Swiss | Sinar • Authorized Reseller

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