Archived posting to the Leica Users Group, 2000/04/08

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Subject: RE: [Leica] Analog vs. digital (long and barely OT)
From: Austin Franklin <austin@darkroom.com>
Date: Sat, 8 Apr 2000 22:12:48 -0400

> What does it take to convert your photo made on film to the printed page? 
> Its pixels. Imagine your photo chopped up into zillions of little bits.
> All in particular order. The most extreme jigsaw puzzle you ever 
imagined.

You don't "need" pixels.  Pixels are "picture elements" and is an 
electronics term, it has nothing to do with printing, per se.  Halftoning 
has been used for years, long before 'pixels' were ever thought of...  In 
halftoning, the dots are referred to as, well, dots.  The dot is not the 
same as the pixel, they are two entirely different concepts.

> The usual resolution for average (133 to 150 line screen) magazine or
> brochure printing is 300 pixels per inch. Thats 300 pixels per inch at
> the final reproduction size.

You are mixing about pixels and line screens (halftone term) here...and 
they aren't related in this sense...

> A 4 inch X 5 inch image will require
> 4X300=1200 pixels by 5X300=1500 pixels. Measured in pixels you'll want a
> 1200X1500 pixel image. For black & white you'll need 1,800,000 pixels or
> as commonly expressed, 1.8 mb.

Black and white has gray scale, and you still need some number of bits per 
pixel (if you are talking about pixels), unless you want a monotone image.


> When digital sensors catch up to film I want a lens that will be
> excellent. Just like I wanted better lenses to use with film, I want the
> best lens to image digitally and on film.

They are different requirements.  Physics governs the minimum size of both 
a pixel and film 'resolution'.  The problem is a pixel is going to be much, 
much larger than film resolution.  Why this is important is the sensor will 
have to be larger to get the same 'resolution' (what same means is up for 
debate, because film grain is not in a fixed xy pattern like an image 
sensor is...so you would need to scan at some factor higher resolution than 
film using a fixed xy pattern to actually faithfully duplicate the true 
resolution of film...but that's a different discussion)...  Point is, the 
same nice Leitz lense you have that renders your 35mm negative beautifully, 
may not work as well on a digital sensor as you may think.