Re: [APML] Going to the Luminance side?

[Matt BenDaniel <matt@starmatt.com>]

At 09:26 PM 4/2/2002 -0600, Jason Ware wrote:
>Matt BenDaniel wrote:
>
>> you scan 6x7 film at 2000 DPI you get 4300x5500 pixels, assuming you can
>> anti-vignette the entire frame. An equivalent CCD chip would only need to
>> be roughly 2150x2750 pixels 
>
>You lost me here. Why? resolution would be half in the second 
>example. Nyquist holds for CCD or film. (or are you saying
>resolution is lost in the scanning process?).

The information content in an image is equal to 2 to the power of the utilized bit depth times the number of pixels. Negative color film is limited to 8 bits (8 photographic stops) of dynamic range per channel. After reduction, a good color CCD image typically has content at a depth of 10 bits (10 photographic stops) of information per channel. The 2 additional bits of information mean that the information density (per pixel) of CCD is 4 times higher.

>Also, remember that 4000dpi scanners are reasonable now. I 
>agree that CCD has more dynamic range than film, but I don't
>think a CCD has more resolution than very fine grain film
>scanned at 4000dpi (or higher in the case of a drum scan).

Jerry Lodriguss' experience is that a 35mm frame of ISO 400 film has only about 18MB of data, and I agree. Feel free to oversample, but you won't extract much more information out of the film. Of course slower films have somewhat more data because of their finer grain.

The 4000 DPI is useful for Tech Pan, but you get only one channel per frame.
--
Matt BenDaniel
matt@starmatt.com
http://starmatt.com


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