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pixels (again)
Ive read loads on pixel count in the last few days and can see why to some extent fewer larger pixels can result in better contrast ratio's etc.But I still have a question:-.

If you switch a 10 Mp camers to a lower setting say 5 Mp ,does the software remap the image onto grouped pixels or does it just use the centre portion of the sensor?to keep the file size down?..

Comments (8)

Depends on which camera you are talking about.Joel Orlinsky.

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Comment #1

First off,.

Thats a hell of a weapon you got there Joey !.

Secondly ,.

Does that mean that the cameras that do re-map the photons onto the whole of the sensor actually achieve a greater s/n ratio than those that just crop?..

Comment #2

Only in digital zoom does it use a portion of the lens. Otherwise, it is a process of subsampling - it is not quite as simple as just putting pixels into groups and averaging their outputs..

Of course, it is not a case of dividing into two, or four etc. unless you go from 12Mp down to 3Mp. In this example you are talking about an area i.e. 2x2 pixels to divide by 4. So any other reduction in between is not a 'clean' grouping of pixels so there is some processing to get a subsample that looks like a reasonable quality image..

Cheers..

Comment #3

If you want a smaller image (say 5MP from a 10MP camera) it is better to shoot at 10MP - and make the most of the sensor - then downsample later in photoshop, where you can control the process more. If you shoot at 5MP you *may* (depending on the camera) be only using half of the pixels on the sensor. If you use the whole sensor you collect twice as much information to start with..

Best wishesMike..

Comment #4

Thanks for the answers, after further pondering I can see that the only valid case for improvement and less noise, whilst keeping the aspect ratio, is the divide by four scenerio.In this case would a 12mp camera operating @ 3 Mp have a similar combined photon count and hence noise ,saturation value etc as a genuine 3 Mp?..

Comment #5

WILT wrote:.

Thanks for the answers, after further pondering I can see that theonly valid case for improvement and less noise, whilst keeping theaspect ratio, is the divide by four scenerio.In this case would a12mp camera operating @ 3 Mp have a similar combined photon countand hence noise ,saturation value etc as a genuine 3 Mp?.

There is no one answer to your question, because each camera manufacturer does the pixle reduction differently...and they don't tell us or their competitors how they do it (which is silly, as their competitors find out almost instantly)..

For most cameras that I have seen good tests on, they don't appear to improve the IQ much (if any) as the pixel count drops. BUT, theoretically, it should be possible to combine pixels and get better noise characteristics....

Charlie DavisNikon 5700, Sony R1, Nikon D300HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/..

Comment #6

WILT wrote:.

First off,.

Thats a hell of a weapon you got there Joey !.

It is a Bushhawk shoulder stock. You can see them here:http://bushhawk.shopol.com/Group/5YDIQ7IWWOKX6ZMJ.htmThere is also a red dot sight on the hot shoe..

Secondly ,Does that mean that the cameras that do re-map the photons onto thewhole of the sensor actually achieve a greater s/n ratio than thosethat just crop?.

Re-maping the image is essentially down sampling. There is a theoretical improvement in s/n ratio. However, the same thing can be accomplished with post processing. Because you computer has both more processing power, and more time available, the computer can usually do a better job of it..

The other method (used by Panasonic and possibly some others) is referred to as extended zoom (EZ) which is not at all the same as digital zoom. EZ just retains the central portion of the image, and throws away the edges. It is essentially an in-camera crop. The exact same thing can be acheived by post process cropping. There is zero difference..

That being said, in some situations there may still be some advantage to using the in-camera crop. By seeing a magnified image in the EVF or LCD, the focusing and/or exposure may be slightly more accurate. This is especially true if you are using manual focusing, spot focusing, or spot metering..

Joel Orlinsky.

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Comment #7

Thanks Everyone ,.

I think I,m ( slowly ) getting a Handle on this pixel thing ..

WILT..

Comment #8

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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