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Author Topic: Clarification on Print Resolution  (Read 59106 times)
Schewe
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« Reply #20 on: June 06, 2011, 04:42:10 PM »
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That said, a question for Jeff (other also welcome to respond): let's say your native resolution is what Andrew started with - 530 PPI. There are three options for printing it: (1) leave it alone; (2) downsize to 360, (3) upsize to 720 (Epson case). What is "theoretically best"?

It would be foolish to down sample from 530PPI to 360. Why throw away perfectly good pixels? The only two viable options are leave it at 530 or upsample to 720PPI. Depending on the image detail, the upsampling to 720PPI (for Epson) is the optimal option and since this is all done inside of Lightroom using it's unique resampling (which Photoshop can't do) and there's no real downside since you don't have to spawn off a file iteration, why not do it? The only slight downside is it takes a bit longer for LR to process the image data and send it to the printer and a bit longer to spool the file. The actual printing time seems the same.

Also, this all presupposes that you are printing to media, generally a photo paper not matte and that you are using the highest res setting in the driver.
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Mark D Segal
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« Reply #21 on: June 06, 2011, 04:55:44 PM »
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OK, based on current LR technology that all makes perfectly good sense. Thanks.
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Mark D Segal (formerly MarkDS)
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Mike Guilbault
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« Reply #22 on: June 06, 2011, 05:47:51 PM »
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No, not really...here's a simpler guideline for Epson printers; if your image's native size is less than 360PPI, set the resolution in LR to 360 for the output resolution, if the image's native size is above 360 but less than 720PPI, set the resolution to 720PPI in LR.

Which is exactly what I said - but perhaps I didn't say it simply enough . . .

 Wink John

That's what I gathered from your post John, and basically what I was doing. I'm glad Jeff concurs with this... just strengthens the reasoning and is what I've been leaning towards as well.

And yes, now I'm interested in the sharpening questions just posted.  I usually sharpen to my liking in LR and then add low sharpening for the print. 
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BartvanderWolf
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« Reply #23 on: June 06, 2011, 05:48:18 PM »
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I printed out of LR with the Resolution check box off. Then on set as Jeff recommends in this case to 720. For my eyes, it took a loupe to see the differences. But the 720 output had a slight edge. For me, it was real pixel peeping but a difference does result.

Hi Andrew,

I think it is important to stress that this is an LR workflow result. For those who print from e.g. Photoshop, there is more contol over the type and amount of sharpening at 720 PPI, both resulting in smoother (because interpolated) gradients and potentially sharper looking results (more sharpening at the output pixel level is possible if the subject benefits from it). Sharpening at the highest spatial frequencies also boosts sharpness at slightly lower frequencies, but with less visible artifact risk.

The control LR offers regarding sharpening at the native output resolution of the printer, is limited.

Cheers,
Bart
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Schewe
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« Reply #24 on: June 06, 2011, 10:34:38 PM »
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The control LR offers regarding sharpening at the native output resolution of the printer, is limited.

Intentionally so because trying to sharpen for output is not a visual activity...it's trial and error at best and believe me when I said a lot of trees died to make Lightroom's output sharpening work well. Unless you can state exactly what you think is missing from LR's output sharpening, I don't see the above statement useful. It's limited to those sharpening routines we think are useful. Facts would be better than opinion...
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BartvanderWolf
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« Reply #25 on: June 07, 2011, 05:41:33 AM »
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Intentionally so because trying to sharpen for output is not a visual activity...it's trial and error at best and believe me when I said a lot of trees died to make Lightroom's output sharpening work well. Unless you can state exactly what you think is missing from LR's output sharpening, I don't see the above statement useful. It's limited to those sharpening routines we think are useful. Facts would be better than opinion...

Hi Jeff,

I'm not sure, but maybe you interpreted my remark in the sense that LR sharpening is bad, or something. All I said is that the control over the sharpening is limited. You ask for facts because you value them higher than my opinon, I'll give you facts.

How about sharpening for printers like a Noritsu or Fuji frontier? Laser printing on photochemical paper is different than printing on an inkjet printer, it can benefit from a different type of sharpening, and they do not all have the same native PPI resolution.. The same goes for certain types of inkjet media, Canvas knows many different structures, and it's quite different from Glossy which is different from non-glossy paper. Perhaps we want to print on non-glossy paper, yet convert it to glossy with a Diasec treatment, or coat it with resin. Or perhaps we need to print it on self-adhesive material or ... I do know there is some limited control/choice in LR, but then I didn't say it was bad.

Another fact is that interpolation, upsampling, usually doesn't add detail (and hopefully few visible artifacts). What few people seem to understand is that the upsampling itself can be mathematically characterized by a Point Spread Function (PSF). That fact can be exploited by using deconvolution sharpening after upsampling. It can even be taken as far as skipping the capture sharpening, thus avoiding any risk of artifacts and enlarging those, and combining the capture sharpening with the output sharpening with a (somewhat timeconsuming) restoration of detail, called deconvolution at the native print resolution. This would help in producing huge magnifications e.g. for tradeshow booths. A good friend of mine shoots & produces huge (6x3 metres or larger) background images each year, often from a single 21 MP 1Ds Mark III frame, and they will be viewed from close up when people come to the stand after stopping in their tracks as they come walking down the aisle when they see the images.

I'm glad you now agree that upsampling to 720/600 PPI has it's merits, after an initial reluctance against my long time suggestions that it can produce better output (depending on subject), because it offers more control (e.g. better interpolation than the printer driver and sharpening at the native reolution). So let's now keep an open mind that while LR has improved (good enough for many), there may still be a need for more user control (perhaps outside of LR, yes there is a life outside LR ...).

Cheers,
Bart
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Ernst Dinkla
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« Reply #26 on: June 07, 2011, 06:24:55 AM »
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I'm glad you now agree that upsampling to 720/600 PPI has it's merits, after an initial reluctance against my long time suggestions that it can produce better output (depending on subject), because it offers more control (e.g. better interpolation than the printer driver and sharpening at the native reolution). So let's now keep an open mind that while LR has improved (good enough for many), there may still be a need for more user control (perhaps outside of LR, yes there is a life outside LR ...).

Cheers,
Bart

While I use that approach too I still wonder what the aliasing effect could be if the actual optical resolution possible in the print (paper/ink/printer/software) is already available/overdone with 360/300 PPI input. When there is image content that could degrade with aliasing I think dealing with it (a good, flexible anti-aliasing filter) in the downsampling of the application (or driver but I doubt it exists there) is a better plan than upsampling and sharpening the image to 720/600 PPI. The driver will not downsample then and aliasing must happen at the printing stage. Qimage (there is life outside LR) can do that downsampling anti-aliasing but it can be a slow process on big files so I tend to set the print quality higher in the driver that it asks for 600 PPI and avoids downsampling. It may not be the best choice for all images.


met vriendelijke groeten, Ernst


Try: http://groups.yahoo.com/group/Wide_Inkjet_Printers/
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deanwork
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« Reply #27 on: June 07, 2011, 07:24:39 AM »
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The Canon plug-in for their LF printers has a built in slider for output sharpening similar to Q-Image ( along with its 16 bit output capability). Apparently you can test and save those adjustments for the future as a preset for your Specific media - such as creating your own presets for brand and texture of canvas, type and degree of textured rag, fabrics, super gloss media or fiber gloss media apart from "satin" media etc. It looks interesting but I have no idea how effective it is for output sharpening compared to other software that's been around for awhile. It does avoid the two category approach - generic photo or matte papers only . Does anyone who has the 8300 know if it is effective in the way the Q-Image output sharpening is? If so I'm very happy to have it available on the fly the way it is.

john
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NikoJorj
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« Reply #28 on: June 07, 2011, 07:52:15 AM »
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It would be useful if LR told us what the current native resolution is when the check box was off so we could more easily decide what to do.
In the "Rulers, Grids and Guides" panel (right side of the print module), check both "Show guides" and sub-item "Dimensions".
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Mark D Segal
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« Reply #29 on: June 07, 2011, 08:05:45 AM »
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It would be foolish to down sample from 530PPI to 360. Why throw away perfectly good pixels? The only two viable options are leave it at 530 or upsample to 720PPI. Depending on the image detail, the upsampling to 720PPI (for Epson) is the optimal option and since this is all done inside of Lightroom using it's unique resampling (which Photoshop can't do) and there's no real downside since you don't have to spawn off a file iteration, why not do it? The only slight downside is it takes a bit longer for LR to process the image data and send it to the printer and a bit longer to spool the file. The actual printing time seems the same.

Also, this all presupposes that you are printing to media, generally a photo paper not matte and that you are using the highest res setting in the driver.

Jeff, just reviewing this contribution - the one aspect of it that causes me a bit of a lingering concern is the proposition to upsample say from 530 to 720. I think you would agree that if there is no need to upsample for getting the print size one wants at satisfactory resolution, there's no point doing it. Regardless of how capable LR's upsampling math may be, does it still remain correct that upsampling is inventing information, therefore it is an approximation of immediately contiguous data, and therefore may not yieldt quite the same image quality as achieved without the upsampling? If the answer to that question is "Yes", then follows the next one: you need to make a very big print relative to the native resolution of your file, which for sake of discussion here is say Andrew's 530PPI. If you don't resample when you change the linear dimensions, PPI goes down to 180, which I think we may agree is usually below a safe lower limit for viewing large prints at their appropriate viewing distance (we're not talking about using a loupe here). So we'll resample - say from a comfort level of 300 to a maximum of 720. Does it remain fair to expect that (i) the upsampling from 180 to 300~360 will definitely improve IQ and (ii) beyond the range of 300~360, the more one upsamples, the less the incremental return in terms of IQ, or that it may even turn negative at some level?
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Mark D Segal (formerly MarkDS)
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« Reply #30 on: June 07, 2011, 08:30:42 AM »
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In the "Rulers, Grids and Guides" panel (right side of the print module), check both "Show guides" and sub-item "Dimensions".

I always have that set. It does show you dimensions but at what native PPI of the image, such we can use the new “Schewe rule” for setting the Resolution field (if your image's native size is less than 360PPI, set the resolution in LR to 360 for the output resolution, if the image's native size is above 360 but less than 720PPI, set the resolution to 720PPI in LR.).
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BartvanderWolf
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« Reply #31 on: June 07, 2011, 08:39:04 AM »
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While I use that approach too I still wonder what the aliasing effect could be if the actual optical resolution possible in the print (paper/ink/printer/software) is already available/overdone with 360/300 PPI input.

Hoi Ernst,

You are correct that aliasing artifacts are lurking around the corner when there is more high frequency detail than can be resolved. However, when we upsample, that by itself will not lead to aliasing because we acually reduce the amount of detail per pixel. Another thing that helps is that aliasing manifests itself best in an ordered grid, but the (inkjet) printer uses a dithering pattern which actually reduces the risk of those artifacts showing. But there are also other output technologies, e.g. RGB laser output on photochemical paper with resolutions from 254 PPI to 600 PPI, and for those it would indeed make a lot of sense (even more than for inkjet) to tune the output resolution to that native resolution. Especially for the lower PPI machines the risk of creating downsampling/resampling artifacts in an ordered grid is very real. There is an increasing possibility of being confronted with high MP images (think high MP sensors, and/or stitching). Hence my plea for adaptability.

Quote
When there is image content that could degrade with aliasing I think dealing with it (a good, flexible anti-aliasing filter) in the downsampling of the application (or driver but I doubt it exists there) is a better plan than upsampling and sharpening the image to 720/600 PPI.

For most media, I don't think the risk of introducing aliasing related artifacts is a real concern. The most care should be given to downsampling and minor resampling of images (= regular grid) with lots of detail (sharp edges, fine lines, repetitive patterns at an angle, etc.). A proper resampling algorithm will automatically adjust it's resampling filter, a Lagrange type of windowed filter is a nice choice with some speed benefits over full blown Sinc windowed filtering.

Quote
The driver will not downsample then and aliasing must happen at the printing stage. Qimage (there is life outside LR) can do that downsampling anti-aliasing but it can be a slow process on big files so I tend to set the print quality higher in the driver that it asks for 600 PPI and avoids downsampling. It may not be the best choice for all images.

I'm not sure I follow what you're saying here.

I do remember that it took a bit of discussion before I convinced Mike Chaney that for downsampling one should do proper pe-filtering. He then deviced a specific type of AA-filtering (perhaps because of speed concerns) and added that as an (default) option to Qimage that's used when downsampling is involved. For upsampling the available algorithms offer a good trade-off between speed and quality. I still like Qimage's Hybrid SE resampling a lot, also because print file output responds well to deconvolution sharpening.

Cheers,
Bart
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BartvanderWolf
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« Reply #32 on: June 07, 2011, 09:11:23 AM »
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Jeff, just reviewing this contribution - the one aspect of it that causes me a bit of a lingering concern is the proposition to upsample say from 530 to 720. I think you would agree that if there is no need to upsample for getting the print size one wants at satisfactory resolution, there's no point doing it.

Hi Mark,

If you don't mind me responding to the question directed at Jeff ..., most printer drivers have dithering optimizations only at a few fixed final output resolutions (the printer driver even tells which resolution it wants, when asked, and they are fixed numbers, e.g. 720 PPI). For speed reasons that dithering will most likely not be calculated but indexed from a lookup table, hence the required preconditioning to a given PPI. There will always be resampling involved if not offered exactly that resolution in PPI. Either the printer driver upsamples (with some unknown black box method) or the application that sends the data to the driver does it (with a very likey much better method). Presumable both will add a bit of sharpening after the resample to output size, with the application offering various settings.

Cheers,
Bart
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Mark D Segal
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« Reply #33 on: June 07, 2011, 09:17:23 AM »
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Hi Bart,

It's an open forum - I don't mind at all, and appreciate your contribution.

What you are saying about the printer sounds a bit like a scanner in the sense that it has fixed stages of resolution at which it operates. That in itself raises other interesting questions about how one optimizes its output between what the user can control and the printer and printing application do. As usual, the devil in the details?
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Mark D Segal (formerly MarkDS)
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« Reply #34 on: June 07, 2011, 09:32:51 AM »
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I always have that set. It does show you dimensions but at what native PPI of the image, such we can use the new “Schewe rule” for setting the Resolution field (if your image's native size is less than 360PPI, set the resolution in LR to 360 for the output resolution, if the image's native size is above 360 but less than 720PPI, set the resolution to 720PPI in LR.).
This confused me too for the last few minutes until I realized that you have to uncheck the "Print Resolution" button (which I always leave checked  Smiley) and then the native resolution figure appears next to the print dimension on the image.
Rob P
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Hening Bettermann
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« Reply #35 on: June 07, 2011, 09:44:03 AM »
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Bart,

What is the software that will allow me to use deconvolution sharpening after the upsampling? And under which circumstances would it be an advantage to skip capture sharpening in favor of deconvolution at the native print resolution? Well, maybe I do part of it already - I do not capture sharpen in the traditional sense of the word. I use Raw Developers deconvolution in the processing to TIF and no other capture sharpening. I have not printed yet.

> But there are also other output technologies, e.g. RGB laser output on photochemical paper with resolutions from 254 PPI to 600 PPI, and for those it would indeed make a lot of sense (even more than for inkjet) to tune the output resolution to that native resolution.

My plan is to have made prints of about 1 m on the long side on a Lambda or the like. The Lambda prints natively at 200 and 400 dpi. The Canon 5D2 files set at 200 dpi would print about 70 cm on the long side. What could I do to enlarge this to about 1 m?

A scaling factor of 1.5 applied in my editor (PhotoLine) would give 106 cm @ 200dpi. However, I have been advised to only use integers as a scaling factor and leave the rest to the print shop. Don't know what they will do.

Kind regards - Hening.
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Mark D Segal
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« Reply #36 on: June 07, 2011, 10:09:03 AM »
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Every time I read Forum threads showing users into all kinds of issues over sharpening, I have to ask myself whether I'm missing something by continuing to work with the most flexible and refined sharpening application I've ever tested - Photokit Sharpener 2. Unless you're into reverse-engineering of the image, there's something for everything here, and it works.
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Mark D Segal (formerly MarkDS)
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Schewe
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« Reply #37 on: June 07, 2011, 10:20:03 AM »
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How about sharpening for printers like a Noritsu or Fuji frontier? Laser printing on photochemical paper is different than printing on an inkjet printer, it can benefit from a different type of sharpening, and they do not all have the same native PPI resolution..

Have you tested the LR output sharpening when saving out an image in LR's Print to JPEG? What seems to be lacking? Sharpening strength or sharpening type? There is some traction towards improving the Print to JPEG output sharpening in the future so it would be useful to get users' feedback.
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Schewe
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« Reply #38 on: June 07, 2011, 10:31:39 AM »
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Jeff, just reviewing this contribution - the one aspect of it that causes me a bit of a lingering concern is the proposition to upsample say from 530 to 720. I think you would agree that if there is no need to upsample for getting the print size one wants at satisfactory resolution, there's no point doing it.

Have you actually tested this? "Thinking" about this stuff is ok...but it's best to actually test it in practice. It was through testing that the LR team determined that upsampling and then sharpening produced a better result particularly for images with a lot of high frequency textural detail. As Andrew indicates with his test, the results can be subtle and you have to know what to look for, but his test proved to him that absent a reason not to, upsampling then sharpening to 720PPI produced a better result. Until you actually do the tests yourself, you won't really know what your eyes will be telling you, right?

When Mike & I were shooting the Camera to Print & Screen video we picked an image from his GH2 camera with lot's of high frequency texture. The native rez was about 450PPI. He printed out an image at native then upsampled to 720PPI. Even with the naked eye (and also through a loupe) he could see the improvement in the resulting print–which was done on Premium Glossy paper. So, I think Mike is now convinced that taking a native rez image and upsampling can produce finer/better detail.

This whole thing came about because with my P65+ files, Lightroom was downsampling (wasting) resolution to 480PPI. So the decision was to increase the resolution cap in LR 2 to 720PPI in LR 3. Aside from slightly (and I mean slight) longer processing time and spooling time there's no real downside to doing this. Try it yourself...
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Mark D Segal
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« Reply #39 on: June 07, 2011, 10:35:33 AM »
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I've previously tested a lot in the range of 180 to 480, but I have not tested LR3 at 720. It goes on the list........thanks for the heads-up.
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Mark D Segal (formerly MarkDS)
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