Image Size and Compression.
in [Digital Cameras]
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From: Ryan McGinnis on 30 Jul 2010 10:56 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 7/30/2010 9:12 AM, ray wrote: > On Fri, 30 Jul 2010 01:25:37 -0700, bobwilliams wrote: > >> Let's assume I have a 10MP camera >> My sensor is say, 3650 X 2740 pixels. But say I want to create an image >> at 1825 x 1370 pixels. How does the camera actually reduce the 5.0MPs to >> 2.5MPs Does it choose groups of 4 pixels and somehow average them out to >> groups of 1 pixel each? >> How does this process differ from compressing the 10MP image by a factor >> of 4. >> I know that in one case the image SIZE is reduced (as well as the file >> size) whereas in the other case, the image SIZE remains the same but the >> file size is reduced. >> How exactly does each process affect the appearance of say an 8x10 >> print. Bob Williams > > I would imagine you are talking about JPEG compression here. Suggest you > experiment a little with your favourite photo manipulation software. > You'll find that most images can be very highly compressed without any > noticeable degredation. The same is not true for dropping resolution. I'd take a different approach: why try to reduce filesize? Storage is incredibly cheap and getting cheaper by the hour. If you are not shooting RAW, a terabyte drive will hold more photos than you're likely to take in your lifetime on a 10MP camera, and they run around $150. You can't go back and re-take your photo in a higher resolution or with less compression, but you can always buy more hard drives. - -- - -Ryan McGinnis The BIG Storm Picture -- http://bigstormpicture.com Vortex-2 image licensing at http://vortex-2.com Getty: http://www.gettyimages.com/search/search.aspx?artist=Ryan+McGinnis -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQEcBAEBAgAGBQJMUugUAAoJEIzODkDZ7B1bEZ8H/3rWsrx4rVNtfLgWgC3m7KbF fRARn+2nwQVpWUxLIg3ijWmAY0wM1dFlQNJEU040uwSKqXLzZj348gTwRYHEANf1 yAFhfwF2AGY5ir6X1wvhM5b14+tHdm4adqwCoFYH3Jnli9WtQqcVxvhfI8Mbklrv xKsu7pR0B5ykLIWKCzr6PCgueMyLWer43ldJnmxd9ykjtIM5yIm0bIwRu1tfbFTd RriZ5IQPuDuTE3l/ZPChFNV3ot1iiwglzVxl9BcQo+M6u0lt2GhJlW801iMgQb4H qRNFDj0bDhvmkAi9YaeJxSdoLEQgYt9/TzxjwwlV4+KUDyZZp04AZtZF1aubJb0= =6sW7 -----END PGP SIGNATURE-----
From: Dave Cohen on 30 Jul 2010 12:47 Ryan McGinnis wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 7/30/2010 9:12 AM, ray wrote: >> On Fri, 30 Jul 2010 01:25:37 -0700, bobwilliams wrote: >> >>> Let's assume I have a 10MP camera >>> My sensor is say, 3650 X 2740 pixels. But say I want to create an image >>> at 1825 x 1370 pixels. How does the camera actually reduce the 5.0MPs to >>> 2.5MPs Does it choose groups of 4 pixels and somehow average them out to >>> groups of 1 pixel each? >>> How does this process differ from compressing the 10MP image by a factor >>> of 4. >>> I know that in one case the image SIZE is reduced (as well as the file >>> size) whereas in the other case, the image SIZE remains the same but the >>> file size is reduced. >>> How exactly does each process affect the appearance of say an 8x10 >>> print. Bob Williams >> I would imagine you are talking about JPEG compression here. Suggest you >> experiment a little with your favourite photo manipulation software. >> You'll find that most images can be very highly compressed without any >> noticeable degredation. The same is not true for dropping resolution. > > I'd take a different approach: why try to reduce filesize? Storage is > incredibly cheap and getting cheaper by the hour. If you are not > shooting RAW, a terabyte drive will hold more photos than you're likely > to take in your lifetime on a 10MP camera, and they run around $150. > You can't go back and re-take your photo in a higher resolution or with > less compression, but you can always buy more hard drives. > > - -- The op beat me to the same question. My concern was not with file size but with noise. Canon do use a lower resolution when higher iso is selected by them for low light scene settings. I'll just run a bunch of test shots including using the noise reduction layer in PhotoPlus (could never afford PS).
From: ray on 30 Jul 2010 13:50 On Fri, 30 Jul 2010 09:56:21 -0500, Ryan McGinnis wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 7/30/2010 9:12 AM, ray wrote: >> On Fri, 30 Jul 2010 01:25:37 -0700, bobwilliams wrote: >> >>> Let's assume I have a 10MP camera >>> My sensor is say, 3650 X 2740 pixels. But say I want to create an >>> image at 1825 x 1370 pixels. How does the camera actually reduce the >>> 5.0MPs to 2.5MPs Does it choose groups of 4 pixels and somehow average >>> them out to groups of 1 pixel each? >>> How does this process differ from compressing the 10MP image by a >>> factor of 4. >>> I know that in one case the image SIZE is reduced (as well as the file >>> size) whereas in the other case, the image SIZE remains the same but >>> the file size is reduced. >>> How exactly does each process affect the appearance of say an 8x10 >>> print. Bob Williams >> >> I would imagine you are talking about JPEG compression here. Suggest >> you experiment a little with your favourite photo manipulation >> software. You'll find that most images can be very highly compressed >> without any noticeable degredation. The same is not true for dropping >> resolution. > > I'd take a different approach: why try to reduce filesize? Storage is > incredibly cheap and getting cheaper by the hour. If you are not > shooting RAW, a terabyte drive will hold more photos than you're likely > to take in your lifetime on a 10MP camera, and they run around $150. You > can't go back and re-take your photo in a higher resolution or with less > compression, but you can always buy more hard drives. I'm not arguing about the cost of storage - I'm answering a question. There could be any number of reasons to concern oneself with file size - for one, when you're doing web pages. Huge files can take a long time to download even with broadband connection - and not EVERYONE has high speed connections. > > - -- > - -Ryan McGinnis > The BIG Storm Picture -- http://bigstormpicture.com Vortex-2 image > licensing at http://vortex-2.com Getty: > http://www.gettyimages.com/search/search.aspx?artist=Ryan+McGinnis > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.10 (MingW32) > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ > > iQEcBAEBAgAGBQJMUugUAAoJEIzODkDZ7B1bEZ8H/3rWsrx4rVNtfLgWgC3m7KbF > fRARn+2nwQVpWUxLIg3ijWmAY0wM1dFlQNJEU040uwSKqXLzZj348gTwRYHEANf1 > yAFhfwF2AGY5ir6X1wvhM5b14+tHdm4adqwCoFYH3Jnli9WtQqcVxvhfI8Mbklrv > xKsu7pR0B5ykLIWKCzr6PCgueMyLWer43ldJnmxd9ykjtIM5yIm0bIwRu1tfbFTd > RriZ5IQPuDuTE3l/ZPChFNV3ot1iiwglzVxl9BcQo+M6u0lt2GhJlW801iMgQb4H > qRNFDj0bDhvmkAi9YaeJxSdoLEQgYt9/TzxjwwlV4+KUDyZZp04AZtZF1aubJb0= =6sW7 > -----END PGP SIGNATURE-----
From: Ryan McGinnis on 30 Jul 2010 13:54 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 7/30/2010 12:50 PM, ray wrote: >> I'm not arguing about the cost of storage - I'm answering a question. >> There could be any number of reasons to concern oneself with file size - >> for one, when you're doing web pages. Huge files can take a long time to >> download even with broadband connection - and not EVERYONE has high speed >> connections. That's true -- though I guess I just assumed that the easiest method was to take full res photos and downsample them with software. But it's true that not all users will ever need the high-res shots for any reason. This might come into play with some of those wireless shooting setups, too, where bandwidth is at a premium. - -- - -Ryan McGinnis The BIG Storm Picture -- http://bigstormpicture.com Vortex-2 image licensing at http://vortex-2.com Getty: http://www.gettyimages.com/search/search.aspx?artist=Ryan+McGinnis -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQEcBAEBAgAGBQJMUxHDAAoJEIzODkDZ7B1bAd0IAJLbH+GI9bKpHvdispIW8ofZ bmx4E6RJIfikYkJmuiFFW0d9bOOc/4vOzkc0m2ZL43/Vsm/AtvMs673vpq7aoO+R 9mUZeb6BC6DaDCHKLkNZ3oFPKmYb6DOsQFz5ZeVUgkpF8+y9aVYDds7CWJh6NOJM 7kjJRQyRwOfRohgjZZFBTaLZSDuprq81CSxJPatEJj2OrjR4qJCqXNoOWaKu96S+ L4rCbkicH16c6yDHrer0DxCoEbkv+/TcLZE2eXAzNADAje842sfcHrW2A/YgqQQB WkC/KqjpD9xDtT85PcXH7+nIjD5M0v/cCE7ofxff5Ba+pfFF9H+mzo1JfmaOfF8= =IBmz -----END PGP SIGNATURE-----
From: bobwilliams on 30 Jul 2010 16:05
ray wrote: > On Fri, 30 Jul 2010 01:25:37 -0700, bobwilliams wrote: > >> Let's assume I have a 10MP camera >> My sensor is say, 3650 X 2740 pixels. But say I want to create an image >> at 1825 x 1370 pixels. How does the camera actually reduce the 5.0MPs to >> 2.5MPs Does it choose groups of 4 pixels and somehow average them out to >> groups of 1 pixel each? >> How does this process differ from compressing the 10MP image by a factor >> of 4. >> I know that in one case the image SIZE is reduced (as well as the file >> size) whereas in the other case, the image SIZE remains the same but the >> file size is reduced. >> How exactly does each process affect the appearance of say an 8x10 >> print. Bob Williams > > I would imagine you are talking about JPEG compression here. Suggest you > experiment a little with your favourite photo manipulation software. > You'll find that most images can be very highly compressed without any > noticeable degredation. The same is not true for dropping resolution. That is what I have noticed too. I was just wondering how such good quality was retained after losing so much image information either by compression or image size reduction. Bob |