If you uncheck "resample image" then you are not resizing the image and
anything you do with altering size or resolution has no physical effect
on the image. As I said, the numbers are merely advisory and have no
more effect than if you were to write them down on a slip of paper and
stick it on your pocket so you could remember it. They go no further
than some field in the EXIF data that's attached to the image.
Your notion to send the specific output device a file with its native
resolution may be a good one but you're not accomplishing that if you
haven't physically resized along with selecting the resolution. For
example, if you want an A4 print at 300 dpi you need to:
1) crop the image to the right proportions for an A4 print
2) set the A4 dimensions into the height and width fields
3) set the dpi to 300 or whatever value you want
4) make sure that resize image is checked
Sorry, without thinking I realized I'm telling you how to do it in
Picture Window Pro which I prefer for cropping. In PhotoShop you could
do it the same way but also have the option of forcing the resizing to a
specific resolution at the same time you do the crop. Actually, PW Pro
allows you to do the same during the crop but I never use it that way.
I always prefer to crop an image to the correct aspect ratio but without
any resizing. If the image is edited and cropped to the correct aspect
ratio specific resizing can be done later for multiple print sizes
(within the same aspect ratios) and sharpening all based on the same
base image.
Now for more practical advice. It could be that the Frontier machine
has more sophisticated resizing and interpolation algorithms than you
have available to you. You might try a test with and without you doing
the resizing. On the other hand, sharpening should only be done after
resizing so you give that up if you let the print processor do the work.
It's probably not going to sharpen the image for you.
Chuck Norcutt
Fernando Gonzalez Gentile wrote:
> I tend to think it the other way 'round.
> Tell me if I'm wrong Chuck: first I find out which resolution does the
> output printer achieve.
> Say, a Frontier minilab prints at 300 dpi, but an Epson plots at 150 dpi
> (those are the machines commercially available here).
> To avoid interpolation, I uncheck 'Resample Image' _ then_ I write 300
> or 150, then I phone and ask if that image fits into any of the paper
> sizes the lab happens to be working on at the moment (last year Fuji
> changed paper size but didn't warn anyone, nice guys)
> Should I decide to change print W*H, then I judge how much interpolation
> will PS introduce.
> File size in megapixels should not vary, and if it must vary I decide
> how much increase do I accept.
>
> It took me some time to understand it this way ... I cared nothing about
> it until when I had my own 4000ED ... is ignorance bliss?
>
> Fernando.
>
>
>
> Chuck Norcutt wrote:
>> Just remember that the image itself is nothing but *dimensionless*
>> pixels. Dimensions only come about when we decide at what density those
>> pixels will be diplayed or printed. Photoshop will happily add or
>> delete pixels if you allow it to in order to meet your request for a
>> certain size image at a given resolution.
>>
>> Chuck Norcutt
>>
>
>
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