Re: Digicam vs. Scanner resolutions

[Kennedy McEwen <rkm@xxxxxxxxxxxxxxxxxxxx>]

In article <3D000891.F1BE1BAE@worldnet.att.net>, Phil.Lippincott 
<phil.lippincott@worldnet.att.net> writes
>Big Apples Sign scanned an Ektachrome E100SV 35mm slide for me at 8000 
>dpi optical.  This scan produced a 250 mega byte flawless with no grain 
>full fidelity histogram file that they directly printed from the Aztek 
>Digital PhotoLab scanning software (without Photoshop) on their Lambda 
>to a 50 inch by 150 inch print.  We have a one of these prints on our 
>wall (in California) from this picture and you can walk up with your 
>nose to the print or look at it from across the room, and it is perfect.

Perfect?  I find that difficult to believe.  As has been mentioned many 
times on this list and elsewhere, an average eye can easily resolve over 
100lppi at a close viewing distance of 10".  A 150in print from a 35mm 
frame is a magnification of over 100.  So, to have a perfectly sharp, 
ungrained result, the combination of both film and taking lens must have 
a resolution of 10,000lppi.  Assuming that film and lens contribute 
equally to this resolution then we need a lens AND film capability of 
15,000lppi - and that doesn't even include the scanner limits, which you 
state is only a quarter of this perfect performance!

1.  Kodak don't have any ISO100 versions of Extrachrome which come close 
to 15,000lppi resolution on their website - and I am fairly certain they 
would be shouting it from the rooftops if they did.  Their best 
published figures look like limiting Ektachrome resolution less that a 
fifth of this.

2.  A perfect lens will only produce this sort of resolution if opened 
up beyond f/2, and very few lenses are this close to perfect, especially 
at wide apertures.

3. Even just using the 8000ppi scanning resolution as the only 
limitation, the effective resolution on a 150in print reduces to 80ppi, 
which, although difficult to focus on "with your nose to the print" is 
CLEARLY visible when viewed from 10".

My conclusion can only be that whilst your 50x150inch print from 35mm 
film looks impressive, it certainly is a long way short of perfect on 
the resolution stakes alone.

To paraphrase Scotty "Ye cannae brek the laws o' physics, Phill!"
-- 
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers
-
Turn off HTML mail features. Keep quoted material short. Use accurate
subject lines. http://www.leben.com/lists for list instructions.