Canon 30D extra ISOs (1/3 stop)

I finally can confidently read 30D RAW data, as the new version of IRIS
(5.32) reads the RAW files properly.

The bad news is, the "in-between" ISOs new to the 30D are just the old
ISOs pulled and/or pushed arithmetically after digitization. IOW,
inferior RAW data than pushing or pulling, yourself, from the "old" ISOs
on the 20D.

I suspected this would be the case when Canon announced the same sensor
and support circuitry as the 20D, because the 20D allegedly uses
dedicated transistors for different ISOs, in its readout circuitry.
--


John P Sheehy

wrote:

I finally can confidently read 30D RAW data, as the new version of IRIS
(5.32) reads the RAW files properly.

The bad news is, the "in-between" ISOs new to the 30D are just the old
ISOs pulled and/or pushed arithmetically after digitization.

The top ISOs or intermediate steps?

IOW,
inferior RAW data than pushing or pulling, yourself, from the "old" ISOs
on the 20D.

I suspected this would be the case when Canon announced the same sensor
and support circuitry as the 20D, because the 20D allegedly uses
dedicated transistors for different ISOs, in its readout circuitry.

In message ,
Paul Furman wrote:

wrote:

I finally can confidently read 30D RAW data, as the new version of IRIS
(5.32) reads the RAW files properly.

The bad news is, the "in-between" ISOs new to the 30D are just the old
ISOs pulled and/or pushed arithmetically after digitization.

The top ISOs or intermediate steps?

3200 is arithmetic on most, if not all Canons. It is achieved by
doubling RAW numbers, though, so it is non-destructive to the tonal
ranges it keeps, however, a stop of highlights are lost as opposed to
just under-exposing ISO 1600 by a stop.

320 on the 30D is 400 metered for 320, and then the digitized data
posterized with integer math to keep the whitepoint the same RAW level
that it is at for the other ISOs. I haven't looked at an ISO 250 file
yet, but most likely it is under-exposed by 1/3 stop, and then the
result of the digitization is multiplied by 1.25, leaving a hole every
5th value in the RAW histogram, and clipping 1/3 stop of highlights
away.
--


John P Sheehy