Why file size differs when taking photos

[Pete Stockdale]

Novice question - answer in simple terms requested...

Just taken some shots of flowers in a greenhouse - with same settings the
picture file size (jpg) varies between 157 and 218kb - why is that?
Thanks.

[pmg]

I am not fully familiar with the way jpegs compress but it's something like
this;
A completely black image saved as a jpeg will have a very small file size.
An image composed of many colours randomly disorganised in disorganised
patterns will have a very large size when saved as jpeg. This is because
jpeg compression somehow uses a lack of variation between pixels to produce
it's compression. The less variation between pixels the smaller the image
size. For some reason rotating an image 90 degrees and saving it may also
produce a different file size to saving it unrotated.

Pete

"Pete Stockdale" <Pe...@pjcactus.freeserve.co.uk> wrote in message
news:bbthd0$1n6$1...@news8.svr.pol.co.uk...

[Gerald Newton]

Also, by using Adobe PhotoShop 6.0 the jpg image can be reduced in size
through several steps by using the saving for web feature. I have seen 300
k files shrink to 35k with not noticable difference using this feature.

.
"pmg" <p...@replytogroup.com.au> wrote in message
news:3ee25f9f$0$15841$afc3...@news.optusnet.com.au...

[PeptoP]

Just think of it somewhat this way (visually)

If you have one line that is all black (10x1), the file code would look
like:
BBBBBBBBBB
Or, if compressed, it could just say B(x10)

Multiple colors:
ABBDDFGGIJ
Code could read - A(x1)B(x2)D(x2)F(x1)G(x2)I(x1)J(x1)

So the more color variations you have the more code there will be to make up
for it.

"pmg" <p...@replytogroup.com.au> wrote in message
news:3ee25f9f$0$15841$afc3...@news.optusnet.com.au...

[John]

A little bit of reading for you. Hopefully this helps.

http://computer.howstuffworks.com/framed.htm?parent=file-compression.htm&url=http://www.faqs.org/faqs/compression-faq/part1/preamble.html

JR

"Pete Stockdale" <Pe...@pjcactus.freeserve.co.uk> wrote in message
news:bbthd0$1n6$1...@news8.svr.pol.co.uk...

[Mike Collier]

I have noticed this too. I think it is due to the complexity of the
picture. Take a picture of a clean blue sky and its a small file; a picture
of a complicated setting (lots of detail) makes a bigger file. Probably
part of the jpg compression.

"Pete Stockdale" <Pe...@pjcactus.freeserve.co.uk> wrote in message
news:bbthd0$1n6$1...@news8.svr.pol.co.uk...

[Karl Heinz]

"Pete Stockdale" <Pe...@pjcactus.freeserve.co.uk> wrote in message
news:bbthd0$1n6$1...@news8.svr.pol.co.uk...

[J. A. Mc.]

Jpeg's a compressed format - compression varies by amount of detail.

On Fri, 4 Jul 2003 20:51:56 -0500, "Karl Heinz" <Khei...@aol.com>
found these unused words floating about: