Re: time to get digital camera?

[Kennedy McEwen <rkm@kennedym.demon.co.uk>]

In article <20011213010443.RRFZ12575.mta04.onebox.com@onebox.com>, Harry 
Minoru Shin <ring-of-fire@onebox.com> writes
>Hi:
>1.  I'm wondering if it's getting time to finally get a digital camera;
>specifically I'm interested in the upcoming Contax N Digital etc...
>
>2.  Question:  How do I calculate maximum print size based on the variables
>of megapixel amount (camera) and printer (dpi--ex: 300)?   Pragmatically,
>I'm wondering what size print I can get out of these 6 megapixel cameras.
>
>3.  Thanks for the info--I figure some folks in the scanning community
>are wondering when they should buy digital cameras etc...
>
There is a lot more to it than just the number of pixels.  Probably more 
important, and frequently overlooked, is that a real merit figure is 
just the size of the focal plane - that is why 6x6cm is better than 35mm 
and 4"x5" better than 6x6 etc.  In this respect digital is no different 
from film.  You can frequently get situations where a 2Mp camera will 
actually provide higher resolution (and therefore a bigger satisfactory 
print) than a 3, 4 or 5Mpix camera!  All digital chips are not the same, 
and the results from a digicam depend critically on the chip used in the 
camera.

IIRC, the Contax N is based on the Philips FTF-3020C 6Mp chip.  That has 
a 24x36mm focal plane, with 12um pixels and fabricated from 6-stitched 
sub-arrays - a pretty expensive chip, reflected in the cost of the 
Contax.  This is the same chip that was slated to go into the now 
defunct Pentax digital SLR, but the production cost turned out to be too 
high for the Pentax's target market slot.

The big pixels and the large focal plane make the Contax N a "true-35mm" 
digicam SLR.  Moreover, assuming good optics, at all apertures below 
f/16 it behaves as a true 6Mp camera with resolution limited by the 
pixel count, not the optical laws of physics, so estimating acceptable 
picture size is relatively simple.

You should be able to produce excellent prints at sizes up to 10x15" 
before pixelation becomes visible at close inspection at 200ppi.  By 
using bicubic interpolation, or something similar, to bump the pixel 
density up you should be able to produce prints of 16x24" and larger 
without any visible pixelation at close inspection that look perfectly 
acceptable at normal viewing distances.

You might even want to add a layer of grain in Photoshop after resizing 
- just give your print that "olde worlde" scanned film look!  ;-)

Yes - it is possible to get higher resolutions from scanned film, but 
not if the original image was shot at an aperture of around f/11 or 
greater.
-- 
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers
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