[Tig] Re: HDR format

Digital Praxis digital.praxis
Fri Mar 31 17:03:00 BST 2006

Thanks to oktobor for supporting the TIG
Hi Jim,
While I appreciate the desire to specify a format that fixes the various parameters, the way you have described present dpx/cin workflows is a tad too negative.

As I see it, all film scanners are calibrated to the Cineon/dpx format, which specifies a scan from D-min, to D-max in 10bit Log, with easch sample representing 0.02 density, with D-min set to a count of 95, 18% grey to 445 and 90% white to 685.

So, all correct scans will be within tolerance of these values

If you are seeing scans that are significantly different, they are wrong - plain and simple. Reject them.

The limit to the colour of the scan is primarily the film its self, as the spectrum OCN captures is fairly limited compared to what a RGB data file can hold. And as scanners use a similar 'white light' and filters to extract this colour information, they are again within tolerance, and no file specification is going to alter this scanning colourimetery.

All DI systems understand 10bit Log dpx/cin files, and so understand what the digits refer to with regard to the original film density.

Film recorders too understand the dpx/cin density map, so again are accurately calibrated by the manufacturers. The variable here being the film lab, which again is beyond the control of any file format. But if 'Kodak calibrated' will agin be with tolerance.

As far as montors and projectors go there is a problem as they have to be correctly calibrated to account for their individual display characteristics, but again, knowing what a dpx/cin file relates to, it is possible to calibrate very accurately.

So, knowing what a dpx/cin density map is, I can scan anywhere, post anywhere, and film-out anywhere, and every step will be within tolerance, if every system is setup correctly.

If there is a problem, something is not setup correctly, and so must be rejected.

I really have no problem with dpx/cin working throughout the whole chain.

So why do people seem to think there is a problem that needs fixing? An I missing something?

I will be very interested in your comments.


Steve Shaw
Digital Praxis Ltd
+44 (0)7765 400 908
steve at digitalpraxis.net
skype: shaw.clan
msn: shaw.clan

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