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(Sometimes I despair) If you crop 2MP out of a 4MP image, you might as well have started out with a 2MP camera in the first place. Except that if your 4MP CCD

by cstross 14y ago

(Sometimes I despair) If you crop 2MP out of a 4MP image, you might as well have started out with a 2MP camera in the first place. Except that if your 4MP CCD is the same size as your 2MP CCD, the light gathering area per pixel is significantly less -- you capture fewer photons, hence less information about what you're pointing the camera at! Raw pixel count is not a good measure of the imaging accuracy of a digital camera. In the case of Curiosity, they may only be 2MP CCDs, but they're the best 2MP CCDs that money can buy, and they're being fed by the best optics NASA could source. It's a far cry from your phone camera ...

deleted 14y ago
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qw 14y ago
That's why I stated "when needed". I thought I didn't have to explain it in more detail, but it seems I do. You obviously have an interest in these things and rightfully have issues with pure MP arguments. In this case you read something into my comment that wasn't there. That's my despair, and one of the reasons why I try to avoid commenting on technical posts. Note that I also stated that I did understand that there were other technical reasons. My comment was limited to the question of bandwidth only. My original question that you didn't reply to still remains. From a pure bandwidth point of view, they could crop the image when they need a high transfer rate so that they can have a higher resolution when they have enough available bandwidth. If they chose 2MP for other reasons, that's fair enough.
- kmaibaum 14y ago
  I don't think you quite understand the difference between cropping and compression. Cropping an image is the equivalent of choosing which part of the image Facebook displays as your profile picture. While this method could reduce the size of the image to transmit down to '2MP', there's really no purpose in taking photos that are essentially cut in half.

by cstross 14y ago

deleted 14y ago

[deleted]

qw 14y ago

That's why I stated "when needed". I thought I didn't have to explain it in more detail, but it seems I do. You obviously have an interest in these things and rightfully have issues with pure MP arguments. In this case you read something into my comment that wasn't there. That's my despair, and one of the reasons why I try to avoid commenting on technical posts. Note that I also stated that I did understand that there were other technical reasons. My comment was limited to the question of bandwidth only. My original question that you didn't reply to still remains. From a pure bandwidth point of view, they could crop the image when they need a high transfer rate so that they can have a higher resolution when they have enough available bandwidth. If they chose 2MP for other reasons, that's fair enough.

kmaibaum 14y ago
I don't think you quite understand the difference between cropping and compression. Cropping an image is the equivalent of choosing which part of the image Facebook displays as your profile picture. While this method could reduce the size of the image to transmit down to '2MP', there's really no purpose in taking photos that are essentially cut in half.