Re: Digest Number 1783

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Re: Digest Number 1783

Greg Ackerson
> If I heavily crop a photo, does that mean I lose quality if I zoom it
up to print (eg 8x10)?

Friday.... TGIF!!!

Any time you crop you are LOSING data... data that is used by the print
engine to give you detailed (and non-jaggy) hard copies. This is a little
off-topic, but when you take pictures you should really try to get it so
that little to no cropping will be necessary.

But to answer your question, not really... there are ways to "smooth" a
jaggy image that has lost data, but it probably won't look good. The only
8x10s I've printed (after using the GIMP to touch them up, of course!)
were scanned from 3x5s at about 6 megapixel res. I think the JPEGs were
over 1 MB.

--GAck

----------------------------------------------------------------------
Greg Ackerson -- Senior Seeker of Silliness            ph:757-890-2951
http://supersilly.com/~greg                          cell:757-812-0759
"Let every student be plainly instructed and earnestly pressed to
consider well, the main end of his life and studies is, to know God
and Jesus Christ, which is eternal life..."
      -- Rule #1, Original Harvard Student Handbook
----------------------------------------------------------------------


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Re: Digest Number 1783

James Button
Technical answer:
 It depends on the pixels in the original, the pixel count in the result, and the number of dots your printer will use to print the
result

Printer -
10 x 8 @ 600dpi = 4,800,000 pixels
10 x 8 @ 2400dpi = 19,200,00 pixels

Your original was perhaps from a 6,000,000 pixel camera

So printing the original as 10 x 8 @ 600dpi means that the print process has to lose 1,200,000 pixels  -
i.e. merge 5 source pixels into 4 print dots -
You lose detail

Crop it by 1/5th of its area  - Note area not width and height
Print it as 10 x 8 @ 600 and the printer is printing 1 colour dot for every pixel in the cropped version of the source.
No detail lost, but you lost the bits cut off

 Crop it by 1/5 th of the width and height and you lose 2160000 of your original 6000000 pixels, leaving 3,840,000
Now print that as 10 x 8 @ 600 dpi, and the printing process has to generate almost an extra 1,000,000 pixels to make up the
4,800,000 to be printed
You do not lose anything in the process - BUT your print will start to look (very slightly) odd

The actual results depend, on the match between the both the
actual horizontal pixel count, and the horizontal printed dot count as well as the
actual vertical pixel count, and the printed dot count

And - when considering the printed dot count - remember that the dot count must be the count of dots of the picture's colour 'depth'
that the printer can produce - and if it's 2400dpi is of possible ink splashes - with 6 different inks useable - then is the real
possibility on paper only 400 different coloured dots


So consider the source colour depth ( 16, 24, or 32 bits) the pixel count horizontally and the pixel count vertically
then consider the printer's capability colour depth ( 16, 24, or 32 bits) the 'colour dot' count horizontally and the count
vertically
Match these and
any excess from the source means you lose detail
any lack of corresponding source entry for the print and it has to make something up

Then crop as appropriate to get a pixel /dots match
that will actually improve the result

Resize in multiples to match the printer capability

Then consider if your eyes can see the difference at the resolution being used.
(who cares about jagged edges if the jags are only 1/1200 of an inch because you printed horizontally at double the source
resolution to maintain the aspect)

JimB.



----- Original Message -----
From: "Greg Ackerson" <[hidden email]>
To: <[hidden email]>
Sent: Thursday, May 19, 2005 11:19 PM
Subject: Re: [gimpwin-users] Digest Number 1783


> > If I heavily crop a photo, does that mean I lose quality if I zoom it
> up to print (eg 8x10)?
>
> Friday.... TGIF!!!
>
> Any time you crop you are LOSING data... data that is used by the print
> engine to give you detailed (and non-jaggy) hard copies. This is a little
> off-topic, but when you take pictures you should really try to get it so
> that little to no cropping will be necessary.
>
> But to answer your question, not really... there are ways to "smooth" a
> jaggy image that has lost data, but it probably won't look good. The only
> 8x10s I've printed (after using the GIMP to touch them up, of course!)
> were scanned from 3x5s at about 6 megapixel res. I think the JPEGs were
> over 1 MB.
>
> --GAck
>
> ----------------------------------------------------------------------
> Greg Ackerson -- Senior Seeker of Silliness            ph:757-890-2951
> http://supersilly.com/~greg                          cell:757-812-0759
> "Let every student be plainly instructed and earnestly pressed to
> consider well, the main end of his life and studies is, to know God
> and Jesus Christ, which is eternal life..."
>       -- Rule #1, Original Harvard Student Handbook
> ----------------------------------------------------------------------
>
>
> List archives: <http://groups.yahoo.com/group/gimpwin-users/>
> To unsubscribe send a blank message from the address you're subscribed
> to <mailto:[hidden email]>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>



List archives: <http://groups.yahoo.com/group/gimpwin-users/>
To unsubscribe send a blank message from the address you're subscribed
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<*> To visit your group on the web, go to:
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