Nikon D300: 12 bits vs 14 bits test

[Guillermo Luijk]

A member in other forum has posted some tests over his Nikon D300 using 12 bit and 14 bit RAW files over the same scene.

The 14 bit results in better quality in the deep shadows, but it's strange the side effects that appeared when shooting 12 bits and that in my opinion have no relation with the number of bits used in the ADC.

These are the tests: http://usuarios.lycos.es/fotofrikid300/som.../0907/index.htm

The images displayed (see the 100% crops in the end) are the 12 bit versions, and when you move the mouse over them the 14 bit appear. In the 12 bit versions we find:

1. A nasty periodic vertical banding which does not appear in the 14 bit pics
2. A strong green cast
3. Apparently more noise (see specially the red pots of the plants)

On the other side I also find an improvement in the 14 bit versions which in my opinion is the only one we could attribute to the improvement in the number of bits: in the very deep shadows with 14 bit we seem to obtain more texture detail than when using 12 bits. See specially the last 2 shots: the bike's engine pieces in the second last shot, and the pile of wood in the last shot.

What do you think?

[Panopeeper]

What do you think?

I think one has to have the raw files to be able to make some informed thoughts.

[John Sheehy]

What do you think?
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I think the issue here is not just 12 bits vs 14, but readout speed.  Not only may the readout be slower with the 14 bits, but the camera may take the time to compensate for banding in the 14 bits of precision.

To see if the bit depth is really what makes the difference, 3 images should be compared; 14-bit from the camera, 12-bit from the camera, and 12-bit derived from the 14-bit (slow readout) from the camera.

As far as green/magenta color shifts in the shadows are concerned, that can be caused by clipping the blackpoint at different levels in the two formats.

[t.koetting]

i have the impression that Nikon added the 14Bit ADC in order to compete with Canon on the paper ... could it be that the 12Bit ADC is right on the sensor-chip and the 14Bit is external?

[BernardLanguillier]

i have the impression that Nikon added the 14Bit ADC in order to compete with Canon on the paper ... could it be that the 12Bit ADC is right on the sensor-chip and the 14Bit is external?
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Forgive me for asking, but any facts to back up your "impression"?

Cheers,
Bernard

[t.koetting]

Forgive me for asking, but any facts to back up your "impression"?

just a feeling, the 14Bit mode seems less integrated since its limited to 2.5fps if its true what i read about it ...

[NikosR]

I've noticed all the differences you mention apart from the colour cast. I honestly cannot distinguish a colour cast on either of my calibrated monitors.

Read noise is obviously different. 14bit mode might be playing some clever read out and A/D conversion tricks.

[NikosR]

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