On 2 May, 05:13, Joe <j...@[EMAIL PROTECTED]
> wrote:
> Hmmm I don't think 1200-PPI vs 200-PPI is same or have anything
to do with
> turning blurry 8MP image into sharp 2MP image without loss. Or, most
people
> would agree with you that it's kinda crazy for an average people to keep
the
> 1200-PPI when it may do just find or more than good enough at 200-PPI or
> sometime even 150-PPI and depending on the image it may even be better
with
> less than 100-PPI than more.
>
> Some people may even think it's crazy to scan at 1200-PPI to
begin with.
> And I hope you understand why in some case I agree smaller may be
better,
> while disagree in other case. And that's why I never care to set my
image
> to 300-PPI or 150-PPI or why not enjoy the one more than 300-PPI or
> increasing the PPI higher than its real value won't do no good.
Joe,
thanks for your effort but I have the impression it has still not
become clear what I mean in the first place.
Let me explain with a concrete example. This is a fairly random photo
from flickr's most interesting:
http://www.flickr.com/photos/21301000@[EMAIL
PROTECTED]
is an excellent shot but it is slightly blurry.
To prove this, do the following test:
1. Download the original size and open the image in PS
2. Reduce the resolution from 300 dpi to 200 dpi using normal bicubic
3. Increase the resolution to 300 dpi using normal bicubic
4. Select all
5. Copy
6. Revert
7. Paste
Now you can switch on and off that layer to compare it to the
original. You will see no degradation.
Then, do the same test but instead of going down to 200 dpi, try 100
dpi. In the end you _will_ note degradation compared to the original.
What does this test tell us? We can work with this image at 200 dpi
without any quality loss of qulity but we cannot go down much further
than that. If I had taken the photo and wanted to rework it and store
it, say, as TIFF then I would downsample it to 200 dpi (without going
back to 300, of course!), saving more than half the data size. There
is absolutely no reason to keep it at 300 dpi no matter what the
intended output is, no matter how big my hard drive and no matter how
fast my computer. Note that this does not give me "more for less" but
"the same fore less".
But, how far exactly can we go down in resolution? If you have lots of
time you could try 150 dpi, maybe more or maybe less and so on until
you have found out how far you can go. Don't you agree that it would
be handy to have this done my the computer? There are issues as
described in the earlier posts but it is not impossible and it does
not require magic.
In the case of photos it may not be crucial to avoid data size because
they are typically not that large but when I am working with scans I
really do not want to work at an unnecessarily high resolution. If I
have a scan with 300 MB pixel dimensions which I can reduce to 100 MB
without a loss in quality I will definitely do so because it speeds
things up and frees resources on my computer.
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