RE: [Leica] Whose confused??? Erwin didn't say that....

["Ken Lai" <ken@compose.com.hk>]

A 300 ppi 17x11 print requires a scanning resolution of roughly 3700 dpi or
146 dpmm which is equivalent to 73 line pair per mm which is required to
scan negatives with 73/2 = 36.5 line pair per mm.

On the other hand, Erwin is saying that the best hand held photography gives
you 40 line pair per mm and the average is around 20 line pair per mm. I
don't know where these numbers are from but they aren't far from Johnny's.

****

If the CCD in a digital camera also requires double the frequency to capture
the smallest detail, then a 16.8MB CCD gives you 4.2MB's worth of details,
which is only a quarter the size of the 20MB file size of a salon quality
print.

However if this requirement for doubling the resolution is not valid, then a
16.8 MB CCD does give you the same detail as a salon quality print.

****

So the assertion that 'you need to sample at at least twice that
frequency' - is this a valid assertion for digital camera as well as film
scanner?


Ken Lai


> -----Original Message-----
> From: owner-leica-users@mejac.palo-alto.ca.us
> [mailto:owner-leica-users@mejac.palo-alto.ca.us]On Behalf Of Johnny
> Deadman
> Sent: Thursday, November 02, 2000 7:43 AM
> To: LUG
> Subject: Re: [Leica] Whose confused??? Erwin didn't say that....
>
>
> on 1/11/00 4:44 pm, Birkey, Duane at dbirkey@hcjb.org.ec wrote:
>
> > Johnny,
> >
> > Where in the world did you come up with Erwin saying a 960
> x1440 pixel image
> > was functionally equivalant to film???
> >
> > No wonder you are confused.....   :  )
>
> This is the bit I was referring to, Duane. He says that 40 l/mm on the
> negative, which he says is equivalent to a digital capture of 960x1440
> pixels, is roughly equivalent to the quality 'most people
> would dream about'
> in hand held picture taking. If I have misunderstood it,
> please illuminate!!
>
> > Now for some  steps. It is very difficult and often
> considered unnecessary
> > (pace Mike Johnston) to get on film more than 40 line pairs
> or 80 lines. And
> > if we be even more general, 20 lp/mm are the best. most
> people would dream
> > about. Assume now 20 lp/mm or 40 lines per mm (the best you
> can get in hand
> > held picture taking, generally speaking).
>             *** BEGIN ASSERTION ***
> > Again: 24 x 40 x 36 x 40 = 960 x 1440 = 1.382.400. Three
> colours would be 3
> > times this number, which is 4Mb. And with 40 lp/mm we et
> 5.529.600 bytes
> > times 3 = 16.588.800 bytes or 17 Mb, quite close to the 20
> MB I quoted as
> > the conventional wisdom.
>             *** END ASSERTION ****
> > So any digital capture of 20Mb would be close to the
> resoluton of 40 lp/mm
> > that some on this list would consider as the most one would
> want in 35mm
> > photography and to go beyond this number would qualify as
> being a freak
> > obsessed with lines and test targets and all that. Reread
> the mails by Mr
> > Johnston and Mr. Grant and Mr Goodman at all.
> --
> Johnny Deadman
>
http://www.pinkheadedbug.com