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Author Topic: Upsample Low-res Images?  (Read 13514 times)
BruceHouston
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« on: September 21, 2007, 04:59:16 PM »
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I would appreciate any thoughts about upsampling techniques to create the best possible prints from existing 5MP images on an Epson R2400.  I realize of course that this is a "pixel stretch."  The images are 2592 x 1944 (4/3), resulting in 150 PPI in the short (limiting) dimension.  

In as much as print file resolution is generally much smaller than printer resolution (even under ideal circumstances when a ~340 PPI print file is sent to the printer), the printer driver itself may be thought of as performing an upsampling operation.

My main question is whether it is better to upsample in CS3 (e.g., "bicubic smoother"), to just send the 150 PPI file to the printer and let the driver do the upsampling, or some combination thereof.  And, if it is better to upsample in CS3, at what point in the workflow is best?  (I.e., should this be done before or after sharpening (which I believe is generally considered to be treated as the final step before printing), or somewhere earlier in the workflow?

Any other suggestions that could help with this resolution dilemma are most welcome.

Thanks,
Bruce
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Jonathan Wienke
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« Reply #1 on: September 21, 2007, 05:22:12 PM »
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You're not going to get crisp images from that size of file, no matter how you upsize. QImage does a very good job of scaling images to the desired size, but you can't create more image detail via software. You have to capture it.
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Alaska
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« Reply #2 on: September 22, 2007, 12:46:34 AM »
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See Uprezzing Digital Images by Jack Flesher.  It is worth a try.

http://www.outbackphoto.com/workflow/wf_60/essay.html

Jim
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BruceHouston
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« Reply #3 on: September 22, 2007, 05:43:36 PM »
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Thanks to both of you; very helpful.  I downloaded QImage and am reading Jack Flesher's tutorial "Workflow Technique #60" now.  I will compare and report.  --Bruce
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francois
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« Reply #4 on: September 22, 2007, 08:54:46 PM »
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Thanks to both of you; very helpful.  I downloaded QImage and am reading Jack Flesher's tutorial "Workflow Technique #60" now.  I will compare and report.  --Bruce
[{POST_SNAPBACK}][/a]
Jeff Schewe wrote an article that might interest you ([a href=\"http://www.digitalphotopro.com/tech/the-art-of-the-up-res.html]The Art of the Up-Res[/url]).
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Francois
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« Reply #5 on: September 23, 2007, 03:36:59 AM »
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Hi Bruce,
 read what I wrote in a previous  topic

Go to PhotoResampling for an article on PPI/DPI and look at samples gallery.

Don't forget to download Printer Data if your OS is Windows or you can run a Windows application.

Jacopo
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kikashi
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« Reply #6 on: September 23, 2007, 02:15:51 PM »
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Jeff Schewe wrote an article that might interest you (The Art of the Up-Res).
[a href=\"index.php?act=findpost&pid=141331\"][{POST_SNAPBACK}][/a]

It's a very interesting article. I'm curious as to what Schewe's view is on the "oversize by 10% then downsize again" method. Does it offer any advantages? Is it necessary?

Jeff?

Jeremy
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francois
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« Reply #7 on: September 23, 2007, 03:09:51 PM »
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It's a very interesting article. I'm curious as to what Schewe's view is on the "oversize by 10% then downsize again" method. Does it offer any advantages? Is it necessary?

Jeff?

Jeremy
[a href=\"index.php?act=findpost&pid=141445\"][{POST_SNAPBACK}][/a]
In Camera to Print, I remember that Jeff said step rezzing was not necessary with the latest versions of Photoshop.
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Francois
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« Reply #8 on: September 23, 2007, 05:15:54 PM »
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In Camera to Print, I remember that Jeff said step rezzing was not necessary with the latest versions of Photoshop.
[a href=\"index.php?act=findpost&pid=141450\"][{POST_SNAPBACK}][/a]

I wasn't referring to the "going up 10% at a time" method: you are quite right in thinking that he has said that bicubic smoother obviates the need for it.

I meant the "if you want 20x16, make it 22x17.6 first, then downsize to 20x16" method.

Jeremy
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Alaska
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« Reply #9 on: September 23, 2007, 06:15:55 PM »
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Bruce:

When you get the chance, please do report your findings.

Good luck with the project.

Jim
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francois
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« Reply #10 on: September 23, 2007, 10:17:06 PM »
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I wasn't referring to the "going up 10% at a time" method: you are quite right in thinking that he has said that bicubic smoother obviates the need for it.

I meant the "if you want 20x16, make it 22x17.6 first, then downsize to 20x16" method.

Jeremy
[a href=\"index.php?act=findpost&pid=141465\"][{POST_SNAPBACK}][/a]
Sorry,
I had the 10% step interpolation in mind...
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Francois
jbrembat
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« Reply #11 on: September 24, 2007, 02:40:35 AM »
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oversize by 10% then downsize again
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going up 10% at a time

When you upsize by a good algorithm, you get original pixels + interpolated pixels.
Original pixels are better than interpolated pixels. Interpolated of interpolated pixel is worse.

It can seem that using some trick the output is better. This do not validate the trick. The trick is able to mask the poor quality of the original algorithm.

Jacopo
« Last Edit: September 24, 2007, 02:41:44 AM by jbrembat » Logged
Nat Coalson
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« Reply #12 on: October 01, 2007, 04:10:50 PM »
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I've had excellent results upsampling as much as 400% in Photoshop.

I usually do it in two steps, using bicubic smoother; the first being slightly smaller than the second, with a small amount of sharpening after each upsample.

If your original 5MP capture is sharp with good tonality I think you can expect to get a good print at 13x19.

And working in 16-bit will produce better results when resampling/sharpening, too.
« Last Edit: October 01, 2007, 04:13:13 PM by Nat Coalson » Logged

nchopp
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« Reply #13 on: October 05, 2007, 08:55:19 AM »
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Good results for one are terrible for another. Personally, I've had 6.3mp images I've printed as large as 24x36", and at a viewing distance appropriate to the size of the image, it was damn solid. I personally was extremely happy with the print, as were those at the exhibition. That doesn't mean that some medium-format, dedicated landscape photographers (neither of which I am) would've agreed that it was a quality print.
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