Some questions on Photoshop cropping.


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Eddy777

Guest
#1
Hi everyone,

I use photoshop to crop my 1600 x 1200 pictures to 3:2 ratio so that I can send them for printing.

However, after cropping and saving them, I realised that the file sizes dropped dramatically. It seems that compression was used during the saving. How come? By right, the final file size should only be slightly smaller as I only crop from 1600 x 1200 to 1600 x 1067.

Any way that I can save after cropping without any compression?

Thanks. Regards.

Eddy.
 

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qhelix

Guest
#3
How come when I save using the maximum quality, my picture filesize becomes bigger even though I never made any adjustments to it in the first place?
 

ckiang

Senior Member
#4
Originally posted by qhelix
How come when I save using the maximum quality, my picture filesize becomes bigger even though I never made any adjustments to it in the first place?
Well, when you save, there is actually JPEG recompression (from the uncompressed data you have when you opened it in PS) going on. If you open a JPEG-5 file and save it JPEG-12, then of coz the size will be better lor.

Regards
CK
 

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Eddy777

Guest
#5
Won't the picture quality be poorer after I compress it again even though the file size may be bigger when using the best compression? Can I open my JPG file, crop it and then save it as BMP so that I won't lose further quality? Will the photo printing shops accept BMP files?

Regards.
 

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Eddy777

Guest
#6
anyone??
 

chenwei

New Member
Sep 6, 2002
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#7
Originally posted by Eddy777
Won't the picture quality be poorer after I compress it again even though the file size may be bigger when using the best compression? Can I open my JPG file, crop it and then save it as BMP so that I won't lose further quality? Will the photo printing shops accept BMP files?

Regards.
save jpeg in max size is good enough already... ;) bmp is too big and not needed...
 

StreetShooter

Senior Member
Jan 17, 2002
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streetshooter.clubsnap.org
#8
Jpeg is lossy compression.

What the photo-editing programme does is to decompress the jpeg into something like BMP format for you to work on. After that, you do a recompress when you save.

Much depends on the quality of the original jpeg. If it is high quality (ie not too highly compressed), working on it and resaving it at high quality will not cause you to lose too much detail. For all practical purposes you human eye will not be able to tell the difference (although doing this a hundred times will of course result in jpeg artifacts and loss of detail becoming more prominent).

If your original jpeg is already quite heavily compressed, that means much of the detail has been lost. Even if the programme recompresses at high quality when saving this image, it cannot recover the detail lost at the initial compression.

That's why those who are obsessed with quality save images in lossless TIFF (or RAW format for those using digital cameras). There is no loss of image detail, no matter how many times you save and resave the picture. The drawback, of course, is the huge size of the image file.

Not sure whether the digital developer accepts TIFF files or BMP files, because I always send to them as Jpeg. But no reason they should not.
 

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