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Author Topic: which enlargement method gives a better picture  (Read 10570 times)
bwana
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« on: February 16, 2012, 06:48:20 PM »
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Which of the following enlargement strategies gives a better picture
enlarging an image 400% and printing at 360 dpi
or
enlarging an image 300% and printing at 270dpi

in both cases you will end up with the same size picture. Say for example
you have an image that is 900 pixels by 900 pixels

the first method gives a 3600 pixel square image that is printed at 360 dpi giving 10 inches
the second method gives a 270 pixel square image that is printed at 270 dpi giving 10 inches.

in the first case there is more enlargement but more downsizing compared to the second method.
my gut feeling tells me the second method is better but some of you have probably already figured this out so i ask.


Assume the same interpolation procedure is used in both methods and that the printing device has at least a resolution of 360 dpi.
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Schewe
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« Reply #1 on: February 16, 2012, 06:54:49 PM »
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Which of the following enlargement strategies gives a better picture
enlarging an image 400% and printing at 360 dpi
or
enlarging an image 300% and printing at 270dpi

Uh huh...what have YOUR tests indicated?

Do you really expect others to do your work for you?

All I'm saying really is it's your work and you should test the options on your images and prints...

(I have an opinion but it won't do you any good to tell you).

In any event, your starting resolution is way too low...
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bwana
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« Reply #2 on: February 16, 2012, 09:21:33 PM »
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schewe, why even bother to make such a useless reply.. Huh..if you cannot say anything positive, what do you gain? I am sure you'll probably have some equally irrelevant comment to this post. In any event, the starting resolution was given as an EXAMPLE to make the numbers work easily. The original question goes to a fundamental relationship between enlarging and reduction algorithms. method 1 seems to give higher local contrast at the cost of detail. or maybe i said that backwards?
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Schewe
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« Reply #3 on: February 16, 2012, 10:08:52 PM »
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schewe, why even bother to make such a useless reply.. Huh..if you cannot say anything positive, what do you gain? I am sure you'll probably have some equally irrelevant comment to this post.

Because your question indicates a severe lack of understanding and little or no effort on your part? Maybe that's why I answered the way I did. Do some research on your own and get back to us.

The Right Resolution

And The Art Of The Up-Res

Read those and get back to us...
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BartvanderWolf
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« Reply #4 on: February 17, 2012, 04:02:11 AM »
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Which of the following enlargement strategies gives a better picture
enlarging an image 400% and printing at 360 dpi
or
enlarging an image 300% and printing at 270dpi

in both cases you will end up with the same size picture. Say for example
you have an image that is 900 pixels by 900 pixels

Hi,

Given that you mention a 360 PPI printer, there is a high probability that most good interpolation methods do a better job than the printer driver (which is built for speed). Asuming that is the case, which obviously depends on your software's upsampling quality, the 400% enlargement should produce a higher quality output. In addition to that, it alows you to apply sharpening and/or to add noise at the 'native' printer resolution and thus more accurate and effective.

Also understand that a 240 PPI image will be again resampled by the printer driver to reach that 360 PPI, but most likely a lower quality resampling that you could have achieved in a single operation, and it will not use an optimized sharpening.

Cheers,
Bart
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Schewe
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« Reply #5 on: February 17, 2012, 02:28:38 PM »
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But trying to get a 10" print at 360ppi from an original that started at 900 pixels is a fool's errand...upsampling from that few pixels to make a print will never be good regardless of what you may try to do to it. A simple test by the OP would have shown that.
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BartvanderWolf
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« Reply #6 on: February 17, 2012, 03:16:59 PM »
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...upsampling from that few pixels to make a print will never be good ...

Hi Jeff,

Could you define 'good', and would that apply to any subject matter?

The reason I'm asking is that a friend of mine almost routinely produces wall size (2 x 3 metres or larger) backgounds for exhibiton booths in specialized trade shows, based on a single 1Ds3 image. I've seen it myself, it has the visitors stopping in their tracks as they walk through the aisle and it still looks 'good' when they come over and view it up close. Is it razor sharp? Of course it isn't, but it's a hell of a lot larger than a mere 400% enlargement (in pixels), in fact it's more than 8300% enlargement (in size). And no, the images couldn't be shot with a MFDB or even larger sensor because they sometimes are from a 500mm telelens, handheld.

Cheers,
Bart
« Last Edit: February 17, 2012, 06:05:34 PM by BartvanderWolf » Logged
Schewe
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« Reply #7 on: February 17, 2012, 04:40:35 PM »
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Could you define 'good', and would that apply to any subject matter?

Starting from 900 x 900 pixels and trying to get anything that will be what I would call an acceptable print at 10" x 10"  would fall into the category of not "good". Do you disagree?

I know if you have enough native resolution such as from a 1DsMIII, that very large enlargements can be "good". But that's starting from a 21MP file with 5616 x 3744 pixels. That's a far cry from 900 x 900 pixels. Upsampling from a higher MP size will always be better...
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BartvanderWolf
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« Reply #8 on: February 17, 2012, 05:15:27 PM »
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Starting from 900 x 900 pixels and trying to get anything that will be what I would call an acceptable print at 10" x 10"  would fall into the category of not "good". Do you disagree?

I know if you have enough native resolution such as from a 1DsMIII, that very large enlargements can be "good". But that's starting from a 21MP file with 5616 x 3744 pixels. That's a far cry from 900 x 900 pixels. Upsampling from a higher MP size will always be better...

Hi Jeff,

900 pixels enlarged to 10 inch at 360 PPI is 4x enlarged or effectively 90 PPI, 5616 pixels enlarged to 3 metres at 360 PPI is 7.57x enlarged or effectively 47-48 PPI. I don't see how the former could be worse than the latter, and the latter can look darned 'good'.

Cheers,
Bart
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Schewe
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« Reply #9 on: February 17, 2012, 06:40:17 PM »
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900 pixels enlarged to 10 inch at 360 PPI is 4x enlarged or effectively 90 PPI, 5616 pixels enlarged to 3 metres at 360 PPI is 7.57x enlarged or effectively 47-48 PPI. I don't see how the former could be worse than the latter, and the latter can look darned 'good'.

I just did a test...going from 900 x 900 to 10" at 360 prints out like crap, lots of ringing and artifacts from the upsample (bicub smoother in PS)....taking an image that is 5616 to 3 meters will also look like crap unless the viewing distance is from a lot further away than a 10" print. Yes, you can massage it and make a larger native file size look better, but it'll never look as good with a close viewing distance as a higher rez original. And no, I didn't print the 3 meter image out...just looked at it at a 50% screen zoom. I suppose if you did a lot of work on the file and added grain, you could look at the printed piece and find it acceptable from a distance.

I once did a job for Motorola that was printed 48' x 96' and it looked pretty good coming off a 60MB file. Course it was for a billboard at the Atlanta Olympics and the intended viewing distance was the other side of the stadium...

But trying to get a good print at 10" from 900 x 900 starting pixels? No, not unless your acceptance is a lot lower than mine...maybe I'll adopt yours.

Jeeesh that would mean I wasted a ton of money buying an 80MP MFDB and stitch images together to get high rez prints. What a waste on my part, huh?
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AFairley
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« Reply #10 on: February 18, 2012, 09:42:42 AM »
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I think it's a given that for any particular scene the more information in the file (i.e., pixels), the better the print will be at any size and any viewing distance.  The sliding line is what is personally acceptable.....
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BartvanderWolf
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« Reply #11 on: February 18, 2012, 10:22:11 AM »
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I just did a test...going from 900 x 900 to 10" at 360 prints out like crap, lots of ringing and artifacts from the upsample (bicub smoother in PS)....taking an image that is 5616 to 3 meters will also look like crap unless the viewing distance is from a lot further away than a 10" print.

Hi Jeff,

I tend to agree that Photoshop's Bicubic Smoother is not the best tool for the job, but I wouldn't base my judgement about feasible enlargements on it either. What you describe, "ringing and artifacts from the upsample", clearly points to artifacts being introduced where they didn't exist in the original (I have to assume, unless your image was incorrectly sharpened which I suppose it wasn't).

Quote
Yes, you can massage it and make a larger native file size look better, but it'll never look as good with a close viewing distance as a higher rez original.


But then nobody said that more pixels wouldn't make a difference, so your argument is a red herring. The OP's question is based on a given amount of real samples, and it was just a theoretical amount to allow an easy calculation. The issue was if the print benefits from upsampling to 360 or not, and it does.

Quote
But trying to get a good print at 10" from 900 x 900 starting pixels? No, not unless your acceptance is a lot lower than mine...maybe I'll adopt yours.

You're being silly, for argument sake. Maybe your time is better spent looking into better techniques/tools for upsampling, and learn something that would also benefit you MFDB images?

Cheers,
Bart
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Schewe
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« Reply #12 on: February 18, 2012, 12:39:22 PM »
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The issue was if the print benefits from upsampling to 360 or not, and it does.

I agree...I wish the OP had left the question this simple. It would have been a lot easier to answer :~)

And I know that you know that I do advocate upsampling to the reported resolution of the printer which for Epson is 360/720 and for Canon/HP is 300/600.

And yes, I was being silly...but not so much for argument's sake...I was just being silly. Silly is fun some times.
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Tim Lookingbill
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« Reply #13 on: February 18, 2012, 04:13:46 PM »
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Don't know about you guys but I swear I doubled my resolution with ACR 6.6's improved Process 2010 sharpening. Fine duck feathers that used to look like clumps of frayed strands on a cotton towel now look much finer and tack sharp on 100% previews of my 6MP Pentax PEFs. It's incredible.

Upsampling using Bicubic Smoother from 3000x2000 at 12.5"x8.4" @ 240ppi/17M to 11381x9600 60"x40" @ 240ppi/395M 8 bit shows very little signs of softening viewed at 25%. Now I had to spend a bit of time tweaking all the sharpen/noise sliders to get the optimal sharpening on the 6MP source, but this is beyond my expectations.

Wonder if camera sensors with triple the pixels squeezed into the same APS-C size are getting the same upsizing appearance.

I know for sure the increased appearance of fine noise cranking up sharpening using the 2010 Process disappears upon extreme upsampling leaving the fine detail intact.
« Last Edit: February 18, 2012, 04:24:49 PM by tlooknbill » Logged
bwana
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« Reply #14 on: February 18, 2012, 11:17:52 PM »
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thank you for your lively debate. my research shows that greater enlargement and subsequent greater reduction results in softening of boundaries. so an image scaled up 10 fold with bicubic resampling and then resized to 360 dpi from 72 shows softer edges than an image scaled up 7.5 fold and resized to 270 dpi.

Intuitively that also makes sense. But this is only based on what I see on a monitor. When the images are sprayed onto inkjet paper, I cant really see a difference. I think this may be because the epson printer is resampling the 270 dpi image to 360 dpi and thereby softening the edges. or maybe my old eyes just cannot see.

whether or not an image looks like crap from this kind of extreme rescaling and resizing is not the question. i am trying to determine which rescaling algorithm would produce the least crappy image when you need to upsize your image. And rather than split hairs over subtle differences, I am using an extreme example so I can magnify the effects to come to a clear conclusion.

Since my original post, I have also been reading about others' experience with epson printers. It seems the most critical variable is to maintain the dpi of the output image as a factor of 360. This eliminates the printer from the rescaling/resizing loop and removes another cycle of image degradation. So the subtle difference I was trying to measure in my initial post, is actually overshadowed by something I never took into account-the printer nozzle density which is fixed at a specific dpi. This renders the initial question moot .
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Schewe
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« Reply #15 on: February 18, 2012, 11:21:03 PM »
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I'm glad hat you spent the time to do additional research and your own tests–which was really the original point I was trying to get at–sorry if you took offense and my approach...
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bwana
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« Reply #16 on: February 19, 2012, 12:23:39 AM »
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Well, I always try to learn from my betters. I do this for fun and make no money from it. I was hoping to read something from the wizard who did the code for photokit but was saddened to discover his passing in 2005. What surgery was it? He looked so young?! If you feel that question is out of bounds you can yell at me in a pm. Still, I appreciate the contributions of those who share their experiences.
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langier
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« Reply #17 on: February 19, 2012, 12:27:14 AM »
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Best thing to do is test this on your own printer because YRMV...

By taking a few minutes to try this and but a few sheets of paper, you'll see what you like, what works best for you and learn that much more to improve your workflow and your knowledge.
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Larry Angier
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Schewe
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« Reply #18 on: February 19, 2012, 12:33:42 AM »
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I was hoping to read something from the wizard who did the code for photokit but was saddened to discover his passing in 2005.

Actually, it was 2006 when Bruce passed away...and it was lung cancer that took him. And Mac Holbert took over PhotoKit Sharpener 2. But as it regards to sharpening, I guess I'm the current resident "wizard" having coauthored Real Work Image Sharpening with Bruce, posthumously...
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bwana
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« Reply #19 on: February 19, 2012, 12:38:45 AM »
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Actually, it was 2006 when Bruce passed away....

Sry, I was still in a fog about M. Skurski who had complications and was thinking about him.
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