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Maybe
this is just an excuse to post my own favorite pic'
.... the muzzle flash from my Raging Bull .454 Casull
! 
I am using it though to further illustrate sizing, relative
dimensions on the screen and actual file size. The original
was taken on a 3.1 MPix camera ... my Kodak DX6340,
with a shutter open time of 1 second (helped by my son)
... by some miracle (considering how the beast jumps!)
the gun is all but frozen. My working original pic is
1494 x 1059 - only actually 1.6 MPix, but it had to
be cropped from full size to get rid of unwanted and
unnecessary peripheral matter.
This is compressed to yield a file of around
330k at approx 10:1 compression. In both file
size and dimensions it is way too large to
post ''as is''. Anyone wanting it BTW as a
desktop image you can download
it.
From choice my first reduction would be to 600
pixels but to fit this page layout we have first a 550
x 390. It is 230 DPI, and represents 37%
of the large original ...... file size being 43k
at 14:1 compression. I think personally, it is
large enough to ''do the job'' in a post. |
Just
for interest' sake ...... rather like I did with the
1911 ..... here I have shown an example of a 500
x 390 section of the original. As much as anything
for comparison purposes. This too is compressed 14:1
and a file size of 42k .... so very much on
a par with the reduced version. This is nominally
a 37% portion.
Bearing in mind the ''square law'' aspects with image
sizes .... it might be useful to realize that if we
expanded this to match the original image size of
1494 x 1059 ... we would multiply by 2.7
(the 37 percentage, inverse) and if we then
square that (image has 2 sides!!) we arrive
at a factor of 7.3. Multiply this file size
of 42k by that and we get ...... 310k
... an approximation to the original file size! It
all holds good! |
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Again
working from the large original - this version is
sized down to 400 x 284, which is now 27%
of original. Compression is 13:1 giving a file
size of a mere 25k.
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Once
more sizing down from original - two more even smaller
versions. The first is 200 x 142, 13%
of original .... and compressed now 9:1 for
a file size of 8k.
The last and smallest ..... barely a ''thumbnail''
.... is 100 x 71, 7% of the original,
compressed 6:1 and a file of 3k.
Note with these two, compression has been ''backed
off'' ...... because once things get this small
they are even more sensitive to over-compression
distortions.
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Of
course, the last two are obviously well on
the small side! It is interesting to note
though that even the smallest almost conveys
the meaning of the image (just!). The 200
x 142 certainly does manage reasonably (well,
for other shooters!).
The point is ... although resolution and definition
do inevitably drop off badly, the scale of
the image when smaller allows us to still
''see'' almost more than is really there -
a bit like ''filling in the gaps'' with incomplete
text.
I would reiterate that for most
purposes, and speed of download
- the first reduction to 500
x 390 is a very adequate representation.
(JMHO!).
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