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

["Birkey, Duane" <dbirkey@hcjb.org.ec>]

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.....   :  )  

Duane Birkey
HCJB World Radio
Quito Ecuador
Duane's Photographs of Ecuador
http://duane_birkey.tripod.com



Johnny wrote:

Very simply, Erwin argues that a 960x1440 pixel digital image is
functionally equivalent to the best hand-held image you can get with a
hand-held Leica (ie it has a similar resolution of around 20 lp/mm).


Erwin wrote earlier in part:

I started with a 24x36mm negative of silverbased emulsion and used standard
calculations to find the number of picture elements (pixels) or in classical
terms "image points" for a given resolution in lines per mm. So on the
assumption of 40 lp/mm (80 lines) as an industry standard (BTWthis
resolution gives salon quality exhibition prints of size 40 x 50cm, a 35mm
negative capturing 24 x 80 x 36 x 80 lines has a number of pixels or image
points of 5.5 million. This figure is independent of whatever grain size.
Now a new CMOS chip with 16.8 million pixels needs 4 pixels to repesent one
image point. The 16.8 million divided by 4 gives more than 4 million true
image points. 
So what I intented to note is that with a CMOS of size 16.8 Million pixels
the overall image resolution is close to if not equal to the film resolution
needed for a high quality image and that with such a convergence it could
become difficult to see the differences in print (digital or analogue).
I was not referring to the file size such an image would require. And I am
well aware that file size is pixel number times number of bytes to contain
colour and dynamic range information. THis may be 3 or 4 or 8 bytes, that is
immaterial to my intended reasoning: that is comparing pixel counts per
square area, which according to all handbooks is the equivalent of
resolution figures.
If we scan a 35mm negative with 4000 pixels per inch, that is 160 lines per
mm, we of course get a higher number of pixels and this resolution is closer
to the 200 lines perm (100 lp/mm) that current film can capture. I
incidentally started my calculations with that figure. And with 200 lines
per mm the pixel count/resolution is about 14 milion pixels. More I did not
say. That such an image has a file size of close to 100Mb is evident. But I
was not, I repeat I was not calculating file sizes but do a comparison of
resolution figures to find the current state of the digital versus
silverbased image quality.
I was not discussing printer dots or the relation to pixel amount and print
dots or whatever else can be imagined.