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vania Neurotic (0) Inmate Newly admitted From: Insane since: Jun 2004	posted 06-12-2004 13:15 Do you know how to do this? I have an image with 40 Mb, at 16 bits. When I convert it to 8 bits I loose half the information and the image changes to 20 Mb. Is it possible to convert the image to 8 bits, duplicating its image size and maintaining its information - 40 Mb.???????
poi Paranoid (IV) Inmate From: France Insane since: Jun 2002	posted 06-12-2004 13:44 vania: Welcome. Yes, of course it's possible, but it's useless. Well, it's easy to convert a 16bits to 8bits and keep its file size. If your image is say : 1000 x 1000 x 16bit, convert it to 8bits, then you can either change its canvas to 1000 x 2000 or add 3 channels ( or 4 if your image is in CMYK ) to your image. And voilà you just wasted 20Mb. More seriously, in 16bits each channel have a precision of 2 ^16 = 65536 tones, while in 8bits its 2 ^ 8 = 256 tones. Once you convert a 16bits picture to 8bits it's NORMAL that the file size is divided by 2 since you go from 2 bytes to 1 byte per channel. (Edited by poi on 06-12-2004 13:57)

Topic awaiting preservation: Converting from 16 to 8 bits, duplicating image size (Page 1 of 1) $Pages that link to <a href="https://ozoneasylum.com/backlink?for=22161" title="Pages that link to Topic awaiting preservation: Converting from 16 to 8 bits, duplicating image size (Page 1 of 1)" rel="nofollow" >Topic awaiting preservation: Converting from 16 to 8 bits, duplicating image size <span class="small">(Page 1 of 1)</span>\$

vania
Neurotic (0) Inmate
Newly admitted

From:
Insane since: Jun 2004

posted 06-12-2004 13:15

Do you know how to do this?
I have an image with 40 Mb, at 16 bits.
When I convert it to 8 bits I loose half the information and the image changes to 20 Mb.
Is it possible to convert the image to 8 bits, duplicating its image size and maintaining its information - 40 Mb.???????

poi
Paranoid (IV) Inmate

From: France
Insane since: Jun 2002

posted 06-12-2004 13:44

vania: Welcome.

Yes, of course it's possible, but it's useless.

Well, it's easy to convert a 16bits to 8bits and keep its file size. If your image is say : 1000 x 1000 x 16bit, convert it to 8bits, then you can either change its canvas to 1000 x 2000 or add 3 channels ( or 4 if your image is in CMYK ) to your image. And voilà you just wasted 20Mb.

More seriously, in 16bits each channel have a precision of 2 ^16 = 65536 tones, while in 8bits its 2 ^ 8 = 256 tones. Once you convert a 16bits picture to 8bits it's NORMAL that the file size is divided by 2 since you go from 2 bytes to 1 byte per channel.

(Edited by poi on 06-12-2004 13:57)