Re: TECH-3D digest 177

[T3D Eric Goldstein <egoldste@xxxxxx>]

John Vala asks:

>    Is this typical for motion picture folks to use Negative Film?  I always
> figured they would use positive film and just go with it.

Yes. Negative film has been the medium of choice pretty much from the
start of commercial film production. Latitude and ease of post
production and duplication are two key reasons...

And to my question regarding dymanic range of computer imaging and
monitors, John Ohrt replies...

> Yes and no.  One of the great differences between film and electronic
> devices is the transfer function.

and goes on to give us his scholarly discourse of transfer function and
gamma differences between mediums.

> I fear I have muddied the waters.

I agree and would add that I think this information is largely
irrevelent to the user. 

Transfer function and gamma differences have existed between media for a
looooong time. Film transfer to video tape/display is a perfect example.
Set up and gamma variation in *display* media (such as home TVs) has
also been something we've been contending with for decades. There is
nothing new to dealing with these issues; it is essential for there to
be an expression of equivelence between disparit medias so that the
people actually creating the images can compensate. Typically, contrast
is the greatest issue (though issues relating to color fidelity and
transfer are not unknown) and equivelences are typically arrived at
through a mix of math and real world experience and expressed in f/stops
as I posted. It is very common for creatives to shoot for the contrast
range of the final media, taking advantage of whatever compression
techniques are available, if we know what that range is.

So, acknowledging that yes, there are transfer function and gamma
differences between photographic medias and computer imaging/display
software and hardware which are currently being compensated for, does
anyone know the equivelent contrast ranges in f/stops of computer
imaging versus traditional photographic materials?


Eric G.


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