[filmscanners] Re:Film resolution - 3 year wait

["Op's" <martin@wollongong.apana.org.au>]

doogle@doogle.com wrote:

>
>
> However, the way the scanning beam (flying spot) exposes the image onto film, 
>this is
> a far cry from "photographing a monitor".
>

I was only saying that in simple terms and not how that image is transferred. 
This was to relay an
impression of what happens and that there is a CRT inside the box.

>
>
> Hence my contention that for 35mm, assuming:
> - you have 4096 x 2731 real pixels
> - film recorder can truly image those pixels
> That this 4K resolution, 11.1MegaPixels, is within a MP or two of actual 35mm 
>film resoution (at
> least as far as E-6 and C-41 films go).

>
> Again, you see that your first statement is very much correct:
> "But recording to film is very much dependent on the quality of the Film 
>Recorder
> itself..."
>
> And to echo that, must continue to state that there is little if any 
>discernable diff on
> MY film
> recorder onto 35mm, whether
> -fed a 4K file/run at 4K
> -fed a 4K file/run at 8K
> -fed an 8K file/run at 4K
> -fed an 8K file/run at 8K
>

The slides that I print are mostly at 4K which are very acceptable and are what 
most people scan
optically (2700dpi).


Taking into consideration a projected dot is a blurry spot  - a pixel is 
graphed like a hump and not
a top hat shape. the useful radius is the point 50% power and the common type 
blur is a 0.26 nominal
radius and to provide a useful transition the dots must have overlap to provide 
a smooth transition
- the perceptually useful spacing for this overlap is 1.2 diameters.

For projection from 35mm film onto a screen at nominal theater viewing 
distances, the 50% limit for
spatial discernment is 48 dots/mm on film. But since we are using the middle 
50% of the power of the
dot, that means we only get to count the top 26% of that hump as a "real" dot, 
so the effective spot
radius is (0.265 dots/48 dots /mm)=0.0055 mm per dot. Since the spacing is 1.2 
times the diameter
each dot actually will take up (0.0055 x 1.2) = 0.0066mm. Since 35mm 
transparency film actually has
a useful real estate of about 36x24mm  we would need a resolution of 5454 x 
3636 pixels  or 5Kx3K.

Think that's the correct meaningful way to work it out.

Rob





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