[meteorite-list] Iron Meteorite on Mars (Color Photo)

[Chris Peterson]

Hi Darren-

Replacing the Pancam sensor with, say, a 5MP array wouldn't yield better 
resolution. If the physical size of the sensor were larger, you would have a 
greater field of view. But even if the sensor had smaller pixels, the 
resolution wouldn't increase because the simple, three element f/20 lens of 
the camera has a spot size of 32um, twice the current pixel size. So packing 
in more pixels would just be empty resolution- there would be no real 
increase in the amount of information available. A blown up image from this 
5MP image would look the same as the image from the 1MP sensor after you 
resized it to 5MP.

In this case, what we'd really like would be the ability of the Pancam to 
switch in a longer focal length lens. Maybe the next mission!

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message ----- 
From: "Darren Garrison" <cynapse at charter.net>
To: <meteorite-list at meteoritecentral.com>
Sent: Wednesday, January 19, 2005 10:46 PM
Subject: Re: [meteorite-list] Iron Meteorite on Mars (Color Photo)


On Wed, 19 Jan 2005 22:18:33 -0700, "Chris Peterson" 
<clp at alumni.caltech.edu> wrote:

>The number of pixels has nothing to do with resolution. What matters is the
>size of each pixel and the focal length of the camera. In the case of the
>Pancam, that's 16um and 38mm, giving a resolution of about one arcminute-
>slightly better than the human eye.
>

Okay, then, cut the word "resolution" out of my reply and replace it with 
whichever word means

"total number of pixels available in the image, this being the factor--  
assuming good optics-- that
determines the size at which an image can be printed and still look good"

which is what 99 percent of people concider "resolution" to be, and will 
continue to do so (and
hopefully this won't degrade into an argument similar to the recent ones on 
what "magnetic" means).

Whichever word is used to mean what I obviously meant when I use 
"resolution" the same way most
people use the word "resolution", the CCDs on the rovers are only 1 
megapixel-- which means that the
photo will never be as high(whatever the word is that almost everyone else 
accepts as "resolution")
enough to make a large print that looks as sharp and detailed as would come 
from a film camera or
higher-end digital camera.

Yes, the one megapixel CCDs on the rovers are better than the 3ish megapixel 
camera on
consumer-grade digitals, but the 10+ megapixel CCDs on pro models are better 
than the one megapixel
CCDs on the rovers.  And, IMHO, if I were somehow standing on Mars and my 
camera surviving the
conditions, I think that my 5 megapixel Sony F707 would take a better 
picture ("better" meaning
being of higher captured detail and able to be magnifed more and printed at 
a larger size and stil
look good) than the composite color photo from the rover's CCD.