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Old Jan 9, 2003, 10:43 PM   #1
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Default More megapixels or more zoom?

WalterK mentioned, (in the thread 'awesome lens', about the Leica lens installed in the new Panasonic DMC FZ1) that despite the camera having only about 2 megapixels, you can use the zoom function to fill the frame, whereas with a 5MP camera you would have to crop a lot of the frame.

This raises an interesting question. Taking everything into consideration, and assuming you have to choose one or the other but not both, which is preferable - more megapixels or more zoom?

Zoom often seems to be achieved by rather long, bulky lenses & much as I like my Olympus C2100Z, but I often wish it were more compact. (The Panasonic DMC FZ1, judging from pictures of it, is a lot less bulky even though it's 12x and the Olympus is 10x).

And, here's what is perhaps a separate question - on this topic of more megapixels, I got the impression (somewhere) that if you want to post a picture on the web, or as a smaller e-mail file, and you start off with a big - say 6MP - picture, then simply reducing it's size to display at normal computer screen size will seriously degrade its quality by introducing too many jpeg 'artifacts' - whereas if you'd started off with a 2MP picture, downsizing THAT to screen-size will give a better picture. Or have I got it wrong?
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Old Jan 10, 2003, 7:58 AM   #2
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I wish for a wider lens much more often than I wish for a longer lens.

To address your first question, "Mp vs zoom" - to achive the field of view of twice the focal length by cropping, you will need four times the Mp. In general to get x times as much "zoom", you would need x squared times as many pixels.

Quote:
then simply reducing it's size to display at normal computer screen size will seriously degrade its quality by introducing too many jpeg 'artifacts'
That is exactly backwards. If anything, noise of all kinds will be reduced by downsizing since that "averages" adjacent pixels. Reducing the size of an image for the web or email by increasing the JPEG compression will reduce the quality of the image - that has nothing whatsoever to do with starting from a high resolution image.
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Old Jan 10, 2003, 9:44 AM   #3
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If anything, noise of all kinds will be reduced by downsizing since that "averages" adjacent pixels. Reducing the size of an image for the web or email by increasing the JPEG compression will reduce the quality of the image
That's why, given 2 similar file sizes for a web image. The one that became reduced by removing information (downsampling) using no further JPEG compression, will look better and open quicker than the highly compressed file which gets decompressed,opened to full size in your pc with artefacts, and downsampled (re-scaled) afterwards by the browser, to fit the screen.

With digital processing and compression, the order of doing things makes a difference!

Back to the original thread, isn't the argument really electronic gain versus optical? With no weight/size limits for the cam, current sensor performance and large prints, I think optical gain would win. Optical gain is 'uncompressed.' You can push up the Mpix, but post processing for zoom will be on compressed (distorted) images, since the cam speed and storage limits will make shooting 100Mb RAW files tedious, BillDrew is right with his calculations, but I think he must be assuming either perfect compression or non at all. But there is an issue whether digital zoom is done in the cam after sensing the scene and before compression - or afterwards in an editor when compression artefacts have been added.

Sensitivity is another issue. You need it as zoom increases. It's difficult to do well electronically, but relatively distortion free if you can afford good big glass zooms.

So, I can see why a 2Mpix cam with really good big zoom optics can produce pics at lower res. but fewer artefacts- the dominant distortion, over electronic zoom.
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