I think you are both in the right here, although Chuck more so.
On 12/13/2011 7:20 PM, Chuck Norcutt wrote:
> The screen image you've pointed me to is only 598x762 pixels. I
> wouldn't consider making a 5x7 print unless there were at least 1750
> pixels along the long edge and preferably 2100. In the drastic
> downsizing from the original to a screen image you have lost very
> considerable detail in the image.
All correct. And still, the image on my screen is 8 3/8" x 6 5/8", and gives a
good sense of the subject. For people
interested in their grandchild more than photographic quality - and probably
used to mass processing prints and/or
looking at images on their camera's LCD, it probably seems quite nice at 5x7"
> JPEG file size is only tangentially related here.
Brian, you have shown an obsessive in interest in JPEG file size and talked
about it as though it is some sort of
indicator of image quality since I started on this list. I've put it down to
slow download speeds and possibly limited
storage capacity on your computers. Now you've got high speed internet and
massive storage is really cheap, so lets get
down to it.
> I believe you have lost significant detail in the child's eyes, lashes and
> brows.
Absolutely! When you downsize a 2736x3648 pixel image to 598x762, you lose
tremendous amounts of image detail in the
process of combining pixels, even before saving as JPEG. You are combining more
than four pixels into one. Detail a
pixel or two wide simply disappears.
Inkjet printers are generally 240 or 300 dpi, native resolution. There's a lot
higher resolution in the spacing of ink
droplets, but much of that is used up in mixing and dithering the many ink
colors.* So when you print this image, the
software that drives the printer has to up sample any image of lesser
resolution to match the printer mechanics.
The poor image has then been down sampled from over 500 ppi to about 110 ppi,
for a 5x7 print, then back up for 240 or
300 dpi printing. A nice way to make sure to get any sharp edginess out of it.
And about those JPEGs ... Now try an experiment. Take two images, one with very
little detail and another just chock
fill of nice, high sharpness detail. Downsize them both the same way and save
both with the same JPEG quality setting.
The file sizes are wildly different, no? File size is affected as much, if not
more, by the amount of detail in the
image as by the pixel dimensions.
The only sensible way to save JPEGs is to experiment, using good images with
lots of detail, to determine at what point
of the quality settings of your application you start to be able to see image
degradation. Then set one step higher
quality setting for all JPEG saving. Unfortunately, the quality settings on
different applications seem to bear no
relationship to each other, so one must experiment.
> If you were to go back to your original E3 image file and make a properly
> sized print file (1500x2100)
I'd simply send the whole, original size to the print provider. Let the printer
software figure out the best way to
print it.
> I think you'd be quite surprised to see what your present print is missing.
Yup!
Moose
* Yes, experts, I know that's too simplistic, but I'm only making a different
point here.
--
What if the Hokey Pokey *IS* what it's all about?
--
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