Jim Kasson Tests show a7R IV Dual Native ISO and No PDAF Pixel Banding

Sony a7R IV dynamic range tests

Engineering Tests by Jim Kasson show Sony a7R IV has Dual Native ISOs of 100 & 320 and none of the PDAF Pixel Banding that plagues Fuji GFX 100 and Nikon Z7 cameras.

Jim notes conversion gain changes at the transition from ISO 250 to ISO 320, which is lower than Fuji GFX 100 and Phase One IQ4 150 MP, which use the same 3.76 um pixel pitch BSI Sony sensors. This jump in dynamic range indicates a7R IV has dual native ISOs of 100 & 320, which means is that you’ll actually have more dynamic range when shooting at ISO 320 than you would from ISO 160 to 250.

Please note this is purely a comparison of dynamic range – not noise – though noise is extremely low across this entire range. It’s simply good to know the “sweet spots” for any sensor. For instance if you were shooting a7R IV at ISO 250, you could actually get better results bumping the ISO to 320.

By comparison, Sony a7R III has dual native ISOs of 100 & 640.

In case you’re wondering why the figures here differ from Sony’s published 15-Stop Dynamic Range, Jim explains that EDR is a per-pixel measurement that is not normalized by the number of pixels in the image height.

The even better news is that a7R IV tests show periodic spiking in the spectra of the images that would indicate PDAF-striping “fixes” that cause banding in the Fuju GFX 100 and Nikon Z7 cameras. Quoting Jim, “From this data, I’m surmising that the a7RIV wont have the same PDAF banding the plagues the GXF 100 and the Nikon Z cameras.”

Jim also notes:

• There is low-pass filtering on all channels above ISO 12800.
• There is low-pass filtering on the blue channel; probably to interpolate over the PDAF pixels.

Read Jim Kasson’s full post

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11 thoughts on “Jim Kasson Tests show a7R IV Dual Native ISO and No PDAF Pixel Banding”

  1. Love this stuff.

    True pixel peeping at the nerdiest of levels.

    Jim Kasson is an excellent engineer and is quite good at explaining it.

    Thanks for passing this on.

    1. I believe a7 III dual native ISOs are 100 and 800 with ISO 800 exhibiting similar dynamic range to ISO 200 but less than ISO 100-160.

  2. I guess this is a good thing but is the lower stepping better than starter higher up?
    Truly, I have ni idea about this stuff 🙂

  3. Right.
    One thing I have noticed on my a7R III is that when going up from ISO ~640 to 800 and above shooting at dusk with slight sunset colors it’s a very noticeable change in tint or what is called.
    Perhaps it will be earlier now with R IV so it’s not so obvious at lower light.

    At least I hope so, so I don’t have to limit high ISO to 640.

    1. Nope. ISO 100 is the base ISO. Anything below that simply clips highlights to compress dynamic range. Don’t use expanded ISOs unless you’re really in a pinch.

    1. Applying different tone curves changes the relative sensitivity in much the same way as shifting gears in a car. The max speed an acceleration in 1st Gear is very different than it is in 4th Gear…

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