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Old Jan 7, 2008, 12:37 PM   #1
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Wondering if anyone could give me some advice on whether one would experience an increase in picture "quality" by setting a digital camera to a lower megapixel setting than the max available on the camera.

For example, I have a Canon G9, which has a maximum megapixel quality setting of 12. Being as I will never print anything larger than 8x10, using the 12 megapixel setting seems overkill. Thus, will setting my camera to 6 or 8 megapixels produce any noticable difference in picture quality?

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Old Jan 7, 2008, 1:44 PM   #2
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same quality, different overall size


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Old Jan 7, 2008, 2:12 PM   #3
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Thanks.

Is that to say that the only difference one would experience is in the size of the picture file? Thus, there is no other impact in lowering the pixel count?

Less megapixels captured on the same size sensor doesn't help quality wise?
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Old Jan 7, 2008, 2:34 PM   #4
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Nope - no difference in quality. The light is still hitting all the photosites so you still incur the 'penalty' of them jamming 12mp on a tiny sensor. All you get is a smaller file. The only thing it does is save you space on the memory card. And with memory cards so cheap, what's the point in that?

So, if you're not running out of memory you should always leave it at it's max resolution - that will give you more pixels for cropping even if you don't print large.
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Old Jan 7, 2008, 8:26 PM   #5
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If you are shooting in low light, using a lower MP setting may help with noise levels. It depends on how your camera lowers the pixel count. Try setting up a test shot using a tripod, and make the same shot at the different settings and compare for yourself.

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Old Jan 7, 2008, 9:14 PM   #6
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The G9 is capable of producing images up to 4000x3000 pixels (12 MP). The best quality prints will occur at even multiples of that resolution. That is, printers typically have a vertical resolution of 1440 pixels per inch (in one direction, if not both.) So you would get the highest possible image quality when printing the image at 2.778 x 2.083 inches, or even multiples of that size (5.556x4.167, 8.33x6.25, etc.). Any prints in these sizes will give you the best image quality.

Reducing the resolution of the image to, say, 2592x1944 (5 MP) will disgard more than half of the available image detail. The result will be having the best possible image quality on prints of 1.8"x1.35", 3.6"x2.7", 5.4"x4.05", etc.

To be sure, this does not account for the visibility of the detail in each of those printed images, but the images printed from a 4000x3000 pixel JPEG will certainly be higher quality than those printed from a 2592x1944 pixel JPEG.

The key work here is "noticeable". If you can't tell the difference between the quality of an image printed in a magazine and an image printed in a newspaper, then, no, you won't notice the difference between a 12 MPimage and a 6 or 8 MP image.

And the true utility of a high resolution image isn't just the ability to make enlargements, but also the ability to crop images in post processing and still having enough resolution left to produce a reasonably detailed print.

And you definitely will not get better image quality by reducing the resolution.
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Old Jan 8, 2008, 6:36 AM   #7
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I agree with the general gist of the coments above: So long as you don't crop, and never print larger than 8x10", you are not likely to notice and loss of quality by droppeing the resolution to 6 or 8 Mp from 12 Mp. There will not be an increase in quality, but there will be no noticable decrease.

Being able to do a serious crop is often usefull, e.g., enlarging a single face from a group photo. An ability I do not want to loose without good reason. Memory and hard drives are cheap enough that neither of those should not be a reason to cut resolution.
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Old Jan 8, 2008, 2:01 PM   #8
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TCav wrote:
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The G9 is capable of producing images up to 4000x3000 pixels (12 MP). The best quality prints will occur at even multiples of that resolution. That is, printers typically have a vertical resolution of 1440 pixels per inch (in one direction, if not both.) So you would get the highest possible image quality when printing the image at 2.778 x 2.083 inches, or even multiples of that size (5.556x4.167, 8.33x6.25, etc.). Any prints in these sizes will give you the best image quality.

Reducing the resolution of the image to, say, 2592x1944 (5 MP) will disgard more than half of the available image detail. The result will be having the best possible image quality on prints of 1.8"x1.35", 3.6"x2.7", 5.4"x4.05", etc.

To be sure, this does not account for the visibility of the detail in each of those printed images, but the images printed from a 4000x3000 pixel JPEG will certainly be higher quality than those printed from a 2592x1944 pixel JPEG.

The key work here is "noticeable". If you can't tell the difference between the quality of an image printed in a magazine and an image printed in a newspaper, then, no, you won't notice the difference between a 12 MPimage and a 6 or 8 MP image.

And the true utility of a high resolution image isn't just the ability to make enlargements, but also the ability to crop images in post processing and still having enough resolution left to produce a reasonably detailed print.

And you definitely will not get better image quality by reducing the resolution.
The 1440 dpi (or 5660 or whatever some manufactureres claim) resolution is a nominal value, derived from the mechanical increments the stepper motors can drive the print head and the spacing of the printer nozzles. It is not the real printing resolution, which is basically the same for all inkjet printers at 300 dpi. The higher pixel count (density) is only used to make the dithering less obvious. Thus any print resolution beyond 300 dpi is unneccessary. This is not my private theory, but comes from measurements and is in accordance with the experiences some seasoned printers (not the boxes, but the people using the printer) have published.

If you want to optimize your file sizes for printing at those 300 dpi, this is best done on a computer using a capable application, like Photoshop, which makes a much better job scaling an image, than the printer will do.

This is a fairly independent process from what the thread starter originally meant: Reducing the pixel count while capturing an image. This could be of advantage, increasing the contrast ratio the sensor is capable of capturing and reducing noise IF, but only IF, the camera is able to do something, that is known as "binning". Binning means to group together four or nine (2x2 or 3x3) neighbouring pixels into one super-pixel. This is a standard procedure in scientific ccd-cameras, but very rare with consumer grade digital cameras or even DSLRs. There have been a few modells, which offered that, but I am not sure, the Canon G9 offers binning.

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