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> Picture quality test
Nishka
post 8 Mar 2015, 15:06
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Full size JPG from camera, 300 ppi, 100%, baseline. (3.41Mb)

Attached File  Full.jpg ( 3.41MB ) Number of downloads: 1


1024 x 768 JPG, 300 ppi, 100%, baseline. (719kb)

Attached File  1024_300ppi_100_.jpg ( 719.36K ) Number of downloads: 0


1024 x 768, 150 ppi, 100%, baseline. (719kb)

Attached File  1024_150ppi_100_.jpg ( 719.36K ) Number of downloads: 0


1024 x 768, 150 ppi, 100%, baseline optimised. (696kb)

Attached File  1024_150ppi_100__base_opt.jpg ( 696.35K ) Number of downloads: 0


1024 x 768, 150ppi, 100%, progressive. (693kb)

Attached File  1024_150ppi_100__prog.jpg ( 693.22K ) Number of downloads: 1


1024 x 768, 150 ppi, progressive, Save for Web, 100% (712kb)

Attached File  1024_150_prog_web_100.jpg ( 712.45K ) Number of downloads: 1


1024 x 768, 150 ppi, progressive, Save for Web, 80% (356kb)

Attached File  1024_150_prog_web_80.jpg ( 356.91K ) Number of downloads: 0


1024 x 768, 150 ppi, progressive, Save for Web, 60% (216kb)

Attached File  1024_150_prog_web_60.jpg ( 216.46K ) Number of downloads: 0


1024 x 768, 150 ppi, progressive, Save for Web, 30% (112kb)

Attached File  1024_150_prog_web_30.jpg ( 112.32K ) Number of downloads: 0


1024 x 768, 150 ppi, progressive, Save for Web, 10% (68.6kb)

Attached File  1024_150_prog_web_10.jpg ( 68.61K ) Number of downloads: 0


Full size, 300 ppi, progressive, Save for Web, 100% (3.86Mb)

Attached File  Full_web_100.jpg ( 3.86MB ) Number of downloads: 0


Full size, 300 ppi, progressive, Save for Web, 80% (1.98Mb)

Attached File  Full_web_80.jpg ( 1.99MB ) Number of downloads: 0


Full size, 300 ppi, progressive, Save for Web, 60% (1.16Mb)

Attached File  Full_web_60.jpg ( 1.16MB ) Number of downloads: 0


Full size, 300 ppi, progressive, Save for Web, 30% (571kb)

Attached File  Full_web_30.jpg ( 571.62K ) Number of downloads: 0


Full size, 300 ppi, progressive, Save for Web, 10% (375kb)

Attached File  Full_web_10.jpg ( 375.99K ) Number of downloads: 0


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wolseley
post 8 Mar 2015, 15:55
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but they are the same car lol
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Nishka
post 31 Oct 2015, 11:53
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Fred Oldham
post 31 Oct 2015, 13:37
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For the benefit of the computer thickkies among us, what was all that about?
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Mrs Nishka
post 31 Oct 2015, 22:39
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Nishka was just using the post for testing Fred.

Mrs Nishka
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Fred Oldham
post 1 Nov 2015, 17:02
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No wiser!
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Paul Sanderson
post 9 Mar 2016, 00:11
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It's a test to see how small a file size you can use for a digital image before it's lack of quality becomes apparent. The smaller the file size, the quicker it downloads to computers at home to be visible to impatient Wolseley Forum users.

It's different for printing on paper and for websites. If your 6in x 4in happy snap of your Wolseley is going to be printed in a magazine, the digital image file needs to have a density of no less than 300dpi (dots per inch) when seen at 6x4 size. Saved as a JPEG, a method of compression, that'll be somewhere near 3 megabytes. These are high-resolution images.

Happily, our PC screens are only about 72dpi (sometimes 90dpi), so images meant to be seen only on-screen via a website need only be 72dpi themselves. These are refered to as low-resolution images. There's no point in making them finer detailed than that (eg: 300dpi) since you won't see the difference. I won't go into why the human eye allows this to happen (er, because I can't; I didn't understand the explanation). A 6x4 72dpi image is only about a tenth the file size of a 300dpi image that has the same 6x4 boundaries, and so downloads through the Internet much, much quicker. If you have a number of images on the same web page, that's going to be a big saving in download quantity and therefore download speed.

Note that an Internet-quality 72dpi low resolution image printed on paper will look blocky and pixelated since the fine quality required by 300dpi ink-on-paper printing simply isn't there. Bumping up the 72dpi image to 300dpi in photo editing software is easily done but is not the answer; technically it will pass muster, and the pixelation will have disappeared, but the image looks unfocused and mushy since the fine detail has not been replaced (the rough 72dpi quality has simply been smoothed-out via smaller more closely-packed image dots). For this reason photographers shoot in high-resolution in the first place, because you can always go down to website quality but can't come up from there to print quality.

Ever faster Broadband means big file sizes are not such an issue now, and of course desktop computers and iPads, etc are now being built with higher resolution screens for more sparkling image quality. But until everyone has such future technology there is no point in having images bigger than they need be. And, obviously, 'small' digital images take up less space on your hard disc.

Paul Sanderson
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Fred Oldham
post 9 Mar 2016, 09:42
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Thanks Paul. Very informative.
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