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Old Oct 23, 2006, 6:39 PM   #1
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Does anybody have insight into the way most cameras function?

Say you have a 2MP camera (1600x1200) and you have it setup to store images at 800x600. Say there is also a continuous shooting mode that lets you take a burst of 5 pictures (regardless of resolution). How will most cameras implement this?

First off, I'm not sure if cameras generally use 24-bit color internally, but I'll just assume they do, so a 2MP image is 1600x1200x24 / 8 / 1024^2 = 5.5 MB. A raw 800x600 image is 1.4 MB.


option 1
- camera Buffer A is 27.5 MB, Buffer B is 5.5 MB
- 1600x1200 image is captured from CCD directly to Buffer A
- if 5 pictures are taken, 5.5 MB x 5 = 27.5 MB Buffer A is required
- after shooting, each image is resized to 800x600, written to Buffer B, then written to the memory card as JPG
problem = needs a lot of fast buffer memory, which could be expensive


option 2
- camera has a single 27.5 MB buffer
- 800x600 image is interpolated directly from CCD to buffer memory
- if 5 pictures are taken, 1.4 MB x 5 = 7.0 MB buffer is required
- after shooting, images are encoded as JPG onto the memory card
problem = needs to be able to quickly interpolate to any resolution directly from the CCD, which makes it the most difficult.


option 3
- camera Buffer A is 5.5 MB, Buffer B is 27.5 MB
- 1600x1200 image is captured from CCD directly to Buffer A
- image is resized to 800x600 and written to Buffer B
- if 5 pictures are taken, 1.4 MB x 5 = 7.0 MB Buffer B is required
- after shooting, images are encoded as JPG onto the memory card
problem = needs to scale images and move them between buffers in the middle of continuous shooting, which slows things down


Or is it something completely different from any of them? Note that option 2 & 3 could offer you 5 shots of continuous shooting at 1600x1200 and 20 shots of continuous shooting at 800x600. Do most cameras let you shoot more frames the lower the resolution?


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Old Oct 23, 2006, 9:35 PM   #2
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I've always assumed it was either A or C.
In C, you you do something fancy with higher speed memory being used for the first-tier buffer.

I don't believe you'll really know without getting into the guts of the camera (or the camera company.)

I don't know of any camera that allows you to buffer more images as you lower the resolution. But I don't pay much attention to that as I only shoot at the higest resolution.

Eric
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