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Old Jul 14, 2006, 2:42 PM   #21
DBB
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nelmr wrote:
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DBB,

I think we are saying the same thing just in different ways. I am saying as a general rule 150ppi is the cutoff but yes, there may be some images that can be enlarged quite well. It's all about the detail and if there is enough of it to begin with.

I do however, still think a side by side comparision of a 150ppi or less print next to a 300 ppi print at 16x20 inches of t he same subject would have a noticable difference.

BTW, no hard feelings.
Yes, a side by side comparison would EASILY be visible. The question is, what if it's interpolated UP to 300 ppi?

You probably could tell the difference - but if the original is sharp, detailed and crystal clear, we can easily print it out with marvelous results.

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Old Jul 14, 2006, 4:15 PM   #22
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The viewer, if unaware of what a 300 native ppi print looks like at 16x20 could be fooled. But if you had a 300 native ppi 16x20 print (29 megapixel camera) of the same subject next to the 121 native ppi 16x20 print (5 megapixel camera) I am sure that he could tell a difference at 1 foot. The resolution difference is 2.5x. Thats as big a difference as an 8x10 printed from an canon 350d verses a 1.3 megapixel camera.
300 PPI is a little over 6 times the resolution of 121 PPI – 90,000 pixels sq/in compared to 14,641. PPI is a linear method of representing a two dimensional image. You have to multiply the width times the height to get the two dimensional image resolution.

I'm a little surprised you saw no improvement over bicubic with SI. I occasionally prefer a Genuine Fractals upsample to SI, but I always prefer one or the other over bicubic. SI has a couple strikes against it from the gitgo because it is so non-intuitive. If any resample slightly deteriorates an image then a series of upsamples should look really crappy.

Something nobody has mentioned is sharpening. There are much more sophisticated sharpening methods than unsharp mask, and it is worthwhile learning a little about sharpening if one is going to press resolution limits in a large prints.

Another is noise reduction. Often images that need no noise reduction in a smaller print will need it for a large one. But noise reduction always softens the image slightly. Often just part of the image needs noise treatment and I select out those areas and sharpen only the parts that need it. It isn't that hard with a stand alone program but it is easier with a plug-in.


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Old Jul 14, 2006, 4:17 PM   #23
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!!

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Old Jul 14, 2006, 5:14 PM   #24
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When blowing one up what is the prefered sharpening method? High Pass?
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Old Jul 14, 2006, 6:57 PM   #25
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RP33 wrote:
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When blowing one up what is the prefered sharpening method? High Pass?
High pass is a good technique if combined with masking, edge selection etc.

This is as good an overview of sharpening as I've seen. Dr Mitchell occasionally posts on the board as gmitchel and always announces his new tools on the plug-in forum. He has two sharpening toolkits and I find the action set easier to use than the script version. You really have to read the PDF that comes with either. http://www.thelightsrightstudio.com/...ningSkills.pdf And the companion to his sharpening toolkit: http://www.thelightsrightstudio.com/...ng-toolkit.htm

I find the little freeware SharpControl to be the best simple sharpener I have found. For a couple of years I had to e-mail it to people and I'm glad it is back online. It was part of a medical program someone with the handle of Vtie wrote. Unfortunately he stopped posting on dpreview because he was tired of all the Canon versus Nikon DSLR bickering. There is a larger program called PhotoControl that includes SharpControl, but I have only SharpControl on my computer. You might like PhotoControl but I found I could do as well in Photoshop and didn't have to export the image. SharpControl is a nuisance because you have to export the image as a tiff and re-import back to your image editor after sharpening. I haven't had much luck with the copy/paste it is supposed to support. I find it worth the effort if I want a quick and good sharpening. I have the NK Sharpener Pro plug-in for Photoshop and think SharpControl does a better job. Maybe I'm just not good enough with the NIK Sharpener. You can get the download link for SharpControl and PhotoControl here: http://www.valsphotography.co.uk/inf..._Software.html


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Old Jul 14, 2006, 6:59 PM   #26
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bernabeu wrote:
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!!
Thanks for the chart - It fits in nicely with both my "bias" and my "prejudice." :G

Is there a link for this so I can preen my feathers? ()

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Old Jul 24, 2006, 11:30 PM   #27
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now I have a chart to use to help me. Thank You it will help me and others a lot.

Now if I have a small image and I am upsizing it to meet the numbers on the chart, How do I know that I am pushing the image too much without printing it? What will I see or is there something to look for. Obviously I cant to a 640x480 picture and upsize it big enough to make a 20x30 picture. What do I watch for?
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Old Jul 25, 2006, 10:27 AM   #28
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RP33 wrote:
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now I have a chart to use to help me. Thank You it will help me and others a lot.

Now if I have a small image and I am upsizing it to meet the numbers on the chart, How do I know that I am pushing the image too much without printing it? What will I see or is there something to look for. Obviously I cant to a 640x480 picture and upsize it big enough to make a 20x30 picture. What do I watch for?
After a while you will know - but until then, simply interpolate up to the desired size, crop out a small part, and do a test print of that small crop. You will see right away of it will work.

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