On 5/5/2015 2:47 PM, Chuck Norcutt wrote:
But lets work backwards to the actual resolution requirements as opposed to arguing that A is better than B. B is
fine if it meets or exceed the requirements.
Let's start with an 8x10 print as the output target. Many places will produce this print at 250dpi. 300 dpi on 8x10
would be luxurious (except for Moose)
I dunno. The only printing I've 'done' in ages is photo books. My Publisher prints @ 300 dpi, but their RIP seems to do
a great job uprezzing from lower rez.
250 dpi over 8" is a total of 2000 lines. That needs to be extracted from a
negative that's 57mm square.
The things I didn't know ... Apparently 56 mm is more commonly accepted. I just
measured an Oly Six - 54 mm sq.
The bottom line is that the resolution requirement from the negative is only 35 lines/mm. Who cares if a dedicated
film scanner can do much better than that?
ps: The actual resolution on the film is likely to be 30 lines/mm or even less unless the camera was on a tripod.
Yes, actual resolution of old, hand held film images is actually rather poor.
Yup. Scanning 6x9 negs form my dad's old folder, 300 dpi got all the detail
that is there.
40 lines/mm is considered very good.
OTOH, none of this math is necessarily meaningful. You are scanning clumps of film grain, and there are sampling issues.
300 ppi over 56 mm is 1360 pixels. 40 lp/mm over 56 mm is 4880 individual lines to resolve. AG can give you the math,
but I suspect that something like 9600 ppi is needed in theory to do that when the lines and pixels aren't aligned.
Assuming a practical 30 lp/mm, you get 3660. And I know from testing that the actual resolution of a 4800 ppi flatbed
scanner is slightly less than a 4000 dpi film scanner. So yes, it's possible with excellent equipment and technique and
recent film, that a dedicated MF film scanner would resolve more detail than a flatbed.
For Boris' wedding negs, I imagine a 4800 ppi flatbed would easily get all
there is.
Medium Calculated Moose
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What if the Hokey Pokey *IS* what it's all about?
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