Image Size - What Does It Really Mean

TeriTerryTarry

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On my SJ4000 Wi-Fi there are menu selections for Image Size of 640 x 480 up to 4032 x 3024. In another thread I've already posted information about interpolation and I think I understand that pretty well, but then again . . .

I did an experiment where I took a photo of the same scene at each of the image size settings offered by the camera. All the photos are in 4:3 aspect ratio except the 2Mp is in 16:9. When looking at the photos in Windows Explorer (i.e., not in any viewer or editing programs) all the photos are the same size and angle of view except the 2Mp has a wider but shorter angle of view and the VGA 640 x 480 takes up less screen space. So the question is what do the camera menu selections actually do?

For example, if I select 640 x 480, that's 0.3 Mp. But which ones? Although the physical size of the image on my screen is smaller, it still takes in the same angle of view. If the camera has a 3Mp sensor, does that mean a 0.3Mp picture only uses 10 percent of the pixels but they're still spread out across the entire active portion of the sensor? Similarly which 41 percent of the pixels does the 1280 x 920 use? To get an image of the same physical size on my computer monitor or printed out on paper, has the image already been interpolated?

Furthermore, let's say you're going to print a photo on A4 or 8-1/2" x 11" glossy photo paper and it's an image that hasn't been cropped and enlarged. If the interpolated 12Mp photo has the same physical size as the 3Mp native resolution photo, what's the difference which one you print?
 

Nigel

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Furthermore, let's say you're going to print a photo on A4 or 8-1/2" x 11" glossy photo paper and it's an image that hasn't been cropped and enlarged. If the interpolated 12Mp photo has the same physical size as the 3Mp native resolution photo, what's the difference which one you print?
I would use the 12MP photo because it is likely to suffer less from jpeg compression. If there was zero compression then they should both contain the same amount of detail so it wouldn't matter which you used, the printer will have to add some interpolation anyway since it has higher resolution than both images.

...does that mean a 0.3Mp picture only uses 10 percent of the pixels...
For the best quality image, I would expect it to average all the source pixels in the area of the target pixel as doing so should reduce noise, although that may not actually be what it does.
 
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TeriTerryTarry

TeriTerryTarry

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Thanks very much Nigel.

Regarding the 0.3Mp photo, why would anyone want such a low res photo if they could take a better one with the same camera, the exception being to save memory space? Would there be any other advantage to such a low resolution photo?

Cheers :)
 

jokiin

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Thanks very much Nigel.

Regarding the 0.3Mp photo, why would anyone want such a low res photo if they could take a better one with the same camera, the exception being to save memory space? Would there be any other advantage to such a low resolution photo?

Cheers :)
the SDK has a lot of dumb default options, plenty of manufacturers leave all the dumb options there because they don't know any better, somehow the more options there is must mean it's somehow better right, right?
 
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TeriTerryTarry

TeriTerryTarry

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the SDK has a lot of dumb default options, plenty of manufacturers leave all the dumb options there because they don't know any better, somehow the more options there is must mean it's somehow better right, right?
LOL! Amen jokiin! AMEN brother!!!
 

Nigel

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Thanks very much Nigel.

Regarding the 0.3Mp photo, why would anyone want such a low res photo if they could take a better one with the same camera, the exception being to save memory space? Would there be any other advantage to such a low resolution photo?

Cheers :)
Processing speed would be another, if you were taking 1 million images, then 0.3MP would be far faster to deal with than 16MP images.

The 0.3MP is actually a nice size for a web page, maybe if you were an estate agent and wanted to photo a house for a website and didn't want to include too much detail. I can't see many people actually using it though!
 
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TeriTerryTarry

TeriTerryTarry

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If I ever personally plan to take a million photos in my lifetime, please just put me in the loony bin now before I even start! :confused:
 
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