SUBJECT>Re: Camera Question (Capt. Zot)
POSTER>Dr.D
EMAIL>DrD@MarsDawn.com
DATE>Monday, 1 December 1997, at 8:24 a.m.
EMAILNOTICES>no
IP_ADDRESS> REMOTE_HOST: 206.1.147.2; REMOTE_ADDR: 206.1.147.2
STAFF>Yes
PASSWORD>aaROv4mYL6q/Y
PREVIOUS>3634
NEXT>
IMAGE>
LINKNAME>
LINKURL>
<P>I pick this out of a new group that I look at.. I am not sure of the numbers here but see if this helps..
<P><hr>
<BR>The pixel of a photographic slide image is the grain of the emulsion,
<BR>the distribution of the actual light sensitive crystals. Although this
<BR>grain density varies from spot to spot in the same roll of film and from
<BR>emulsion to emulsion there are accepted average estimates for most
<BR>commercial filmstock. Ektachrome 100 averages a little less than 2000
<BR>pixels per inch. Which doesn't really mean much 'cause very few people print slide images at an inch and a quarter wide. Most slides are printed at 8x10 (8x12 really, but the top and bottom two inches are
<BR>lopped off. We'll return to this when I touch on aspect ratio). So the
<BR>8x10 blowup from an Ektachrome 100 slide carries an image information density of about 200 ppi (the math says 208.33 but the five passes this film makes through analog information exchange systems will cover *at least* that much slop).
<P><hr>
<P>What this comes to is how are you going to use the picture? If you are printing it most printers use 300 to 600 Dots Per Inch. So scanning it at a higher res will make the picture bigger. A good scanner will scan at 1200 DPI .. I only know of a few printers that will print at that. As you know a image on the screen is about 72 DPI.
<P>So a two inch square on the screen should be about 144x144 but printed at 300 DPI is about 600x600.
<P>So look at a full page (8.5'x11') scanned at 1200 DPI or 10200x13200 and full color (32 bit) = 4,308,480,000 uncompressed. divide by 8 to get to bites and you get 538,560,000 ... To large to save... At 300 DPI you get 32 meg image... ( compression like puting it into a JPG format will reduce this number but at a cost ) ...
<P>Hope that helps....
<BR>Dr.D
<P>PS: Sorry if I just jumped into the message.. But it is something that I know a little about :-)


<P>