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Author Topic: Clarification on Print Resolution  (Read 52589 times)
Mike Guilbault
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« on: June 05, 2011, 10:26:29 PM »
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I've been doing some reading on print resolution, namely the 360ppi for Epson printers.  I'm generally printing directly from Lightroom and have the Print Resolution set at 360 and using an Epson 4900.

From what I understand, if the native resolution after sizing the image in LR for the page is below 480, then adding 50% to this resolution will help/improve the quality of the output (in most cases).  So for example, I size an image and the native resolution comes out to 252ppi for the dimensions I want. Does this mean to change the setting in LR's Print Module, Print Resolution from my normal 360, to 378?  Or do you have to send it PS first, resize it to 378, back to LR and then leave the Print Resolution setting off (or does that actually do the same thing)?  

I just want to make sure I understand correctly.

And, if the resolution is below 360 even after this, do I leave it alone or do I set the Print Resolution in LR to 360ppi again?

Thanks,

 
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Mike Guilbault
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« Reply #1 on: June 06, 2011, 01:39:05 AM »
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Mike

In essence, what you should be aiming for is to reduce the number of times that the image file is resampled (up-rezzed or down-rezzed) to as few as possible. Each time it is resampled some loss of IQ will occur, inevitably. Unless you are printing the original image to a size which exactly represents 360 ppi on paper (or whatever your printer's output is) you can never avoid at least one interpolation. So in LR we should be aiming to send the file to the printer at the printer's inbuilt resolution - for most Epsons this is 360 ppi and for many printers you can output at 720 ppi as an alternative. What we don't want is for LR to resample the file to something the printer can't output at (say 293 ppi) and thus force the printer to resample it yet again before printing. So if LR is telling you that the resolution for that image size is below 360, set the resolution to 360. LR will resample it once and the printer will just output the file without further processing. Similarly, with most Epsons if LR reports that the output resolution should be above 360 ppi, set the output to 720 ppi - but make sure that you have the highest quality output enabled in the printer driver, otherwise this is pointless and it will just print at 360 anyway. For other printers the ppi will be different - HP is 300 ppi I believe.

John
« Last Edit: June 06, 2011, 04:35:59 AM by John R Smith » Logged

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« Reply #2 on: June 06, 2011, 06:13:00 AM »
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With the complexity of the screening and dithering algorithms built into modern Epson printers the concept of "native resolution" has become irrelevant. It's been overtaken by other functions for dot placement. Avoid resampling the image altogether. Print at anything between 240 and 480 PPI. The printer will throw away information exceeding 480, and you could see some deterioration of print quality below 240. Generally, higher resolutions are more helpful for smaller printers and lower resolution for larger ones, simply because of differences in viewing distance. You can check all this for yourself by experimenting and observing.
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Mark D Segal (formerly MarkDS)
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« Reply #3 on: June 06, 2011, 06:31:25 AM »
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Yes and I believe this 'native resolution' legend was so very thoroughly discussed a few months ago...

http://www.luminous-landscape.com/forum/index.php?topic=48894.0

« Last Edit: June 06, 2011, 06:34:09 AM by Aristoc » Logged
Mark D Segal
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« Reply #4 on: June 06, 2011, 06:46:44 AM »
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Thanks for the reminder - and yes I stand corrected - nowadays Epson printers can work with up to 720 (I had forgotten because I never get into that stratosphere), but I can't see any difference to anything North of 360, and quite frankly looking for quality difference between 240 and 360 can also be challenging. Much South of around native 240 however one can begin to see evidence of IQ deterioration comparing a print made at native 360 or above. I say this based on some tests I once did on my 4800, and repeated on the 3800.
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Mark D Segal (formerly MarkDS)
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michael
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« Reply #5 on: June 06, 2011, 07:15:20 AM »
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Jeff and I have just done a very thorough examination of this in our new Camera to Print and Screen video tutorial, which will appear later this summer.

In brief, needing an exact multiple of some number (360?) is a myth. The printer's dithering algorithms simply take whatever data you send it and do what it does. Too little and print resolution will be down, and too much and (with Lightroom at least) it automatically resses down to 720ppi so that the printer doesn't choke.

How much is too little and how much is too much? We'll it depends on the printer.

Jeff Schewe, who consults with Adobe, and whose sharpening algorithms are in Lightroom believes (and we demonstrate on camera) that you can res up a file in LR by up to 50%, and actually improve output appearance. Epson printers these days are 720ppi. Canon and HP printers 600ppi.

As far as how much is too little, it very much depends on the size of the print and the distance from which it will be seen. A 18oppi print might look lacking in detail on a 11X17" print held at arms length, while on a 36X42" print over the mantelpiece it could look fantastic.

Everyone should do their own tests. All it takes is a bit of time, ink and paper. Trust your own eyes.

Michael
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deanwork
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« Reply #6 on: June 06, 2011, 08:11:08 AM »
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And my experience with the HP and Canon printers is you can do the same at 150 ppi for very large things and achieve quite smooth dither and edge sharpness from a good file, at viewing distance, if you are working with a file size that demands that, say a 40x60 from a 5D Mark 2 as an example where you really don't have a choice.

Questions I would like to know is just what the differences are between using Lightroom to output these large files as apposed to Photoshop CS5, Q-Image, or the Canon plug-in which is also excellent and has sharpening adjustment capability (as does Q-Image). In other words how much of the dither control is happening in the printer driver and how much in the other software used to send it ( apart from sharpening algorithms) these days .

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Mike Guilbault
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« Reply #7 on: June 06, 2011, 08:28:46 AM »
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Trust your own eyes.
Michael

That's the problem... I don't trust my own eyes! Shocked My vision isn't what it used to be so I want to print the best quality I am capable of so that the viewer is satisfied, not just me.  Although, I am probably more critical than the average viewer of my work.

So, based on John, Mark and Michael's comments I'm getting closer - and please correct me if I'm wrong in these summaries of what's been said for my own understanding:   John's 'method' is basically what I've been doing - set the PR in LR to 360 and be done with it.   Mark says use the native resolution if it falls between 240 and (now) 720 and just let the printer do it's thing.  And Michael/Jeff says that if the native resolution is below 720, up-res it by 50% for some IQ improvement (based on the actual image of course).

It seems that John's method is the simplest solution, but Mark's also makes sense, as long as there is no noticeable loss in quality at the lower (below 360?) resolutions (so you have to test). And as John says, the fewer up/down res-ing we do, the better so this again makes sense.  But in some cases, up-resing 50% may improve the quality if the native resolution is below 720. Again, a test may be in order here.

Does that basically sum it up?  I sure hope so! Wink

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Mike Guilbault
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« Reply #8 on: June 06, 2011, 08:43:31 AM »
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That's the problem... I don't trust my own eyes! Shocked My vision isn't what it used to be so I want to print the best quality I am capable of so that the viewer is satisfied, not just me.  Although, I am probably more critical than the average viewer of my work.

So, based on John, Mark and Michael's comments I'm getting closer - and please correct me if I'm wrong in these summaries of what's been said for my own understanding:   John's 'method' is basically what I've been doing - set the PR in LR to 360 and be done with it.   Mark says use the native resolution if it falls between 240 and (now) 720 and just let the printer do it's thing.  And Michael/Jeff says that if the native resolution is below 720, up-res it by 50% for some IQ improvement (based on the actual image of course).

It seems that John's method is the simplest solution, but Mark's also makes sense, as long as there is no noticeable loss in quality at the lower (below 360?) resolutions (so you have to test). And as John says, the fewer up/down res-ing we do, the better so this again makes sense.  But in some cases, up-resing 50% may improve the quality if the native resolution is below 720. Again, a test may be in order here.

Does that basically sum it up?  I sure hope so! Wink



I think you've got a fair handle on what you've read here, largely non-conflicting advice. Whenever I think maybe I shouldn't trust my own eyes, I ask my better-half to just look at the prints and tell me whether she sees any difference, without explaining anything. Then, if I think she's off on a tangent, I tell her what to look for. Those two tests combined with my initial observations are usually sufficient.
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Mark D Segal (formerly MarkDS)
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« Reply #9 on: June 06, 2011, 11:02:22 AM »
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Does that basically sum it up?  I sure hope so! Wink

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.

For Canon and HP the numbers are 300/600PPI...
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John R Smith
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« Reply #10 on: June 06, 2011, 12:32:41 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.
For Canon and HP the numbers are 300/600PPI...

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

 Wink John
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« Reply #11 on: June 06, 2011, 02:06:07 PM »
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Which is exactly what I said - but perhaps I didn't say it simply enough . . .

Not really...you got wrapped up in the question of resampling and interpolation–incorrectly I might add since print drivers don't really interpolate the image data they receive. The drivers simply convert whatever image resolution they receive into a dither for determining what droplets of ink to print and where.
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« Reply #12 on: June 06, 2011, 02:53:53 PM »
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Here’s the test I just did to an Epson 3880. Image was shot on a 5DMII, ISO 100 of some very fine, high frequency subject. Printing at 10.6X7.1, Photoshop reports that native resolution of the un-cropped data is 530ppi.

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.
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Andrew Rodney
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« Reply #13 on: June 06, 2011, 03:04:23 PM »
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Printing again but letting the check box default to 240 (on), now under the loupe, the differences are pronounced as one would expect. The 530/720 resolves fine lines much better.

FWIW, output was done on Premium Luster paper.
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Andrew Rodney
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« Reply #14 on: June 06, 2011, 03:06:51 PM »
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When you need to examine an enlargement with a loupe to see any difference of print quality within such a broad range of resolution settings, it tells me that within the ranges being discussed here, this isn't much of an issue with today's technologies, and therefore perhaps not worth obsessing over.

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"? There would appear to be some possibly conflicting principles here, or maybe one or more just aren't true any longer: (a) the less you resample the better the IQ; (b) if you resample you do less apparent harm to IQ by downsampling rather than up-sampling; (c) if your Epson printer can print at 720, it's best to take advantage of all that resolution. Huh? Different principles give different answers.
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Mark D Segal (formerly MarkDS)
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« Reply #15 on: June 06, 2011, 03:08:02 PM »
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240 versus 530 under a loupe I would expect the differences to be visible. What about without the loupe?
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Mark D Segal (formerly MarkDS)
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« Reply #16 on: June 06, 2011, 03:17:44 PM »
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240 versus 530 under a loupe I would expect the differences to be visible. What about without the loupe?

In this particular image, a bit difficult to see without the loupe unless you know where to look. Its a shot of some buildings where many have windows with venetian blinds that resemble at a distance very, very fine ruled lines in the print. I see the differences there. With 240dpi, they blur together more, almost like a moire where with the higher rez, they look clean and distinguishable.

But while I could be happy with either print at viewing distance or even up to my nose (this is only an 8x11), I think what I learned is not to be careless with the check box and its default. I suppose, based on this one test, if I know I have a higher rez image going to a smaller print size, just leave the check box off as in this case, default 240 and on just wasn’t as sharp. Would I open up Photoshop or pull a calculator based on all kinds of print sizes to see if the image is above 360? Not sure although I’d certainly consider doing the math for my print templates as once I build em, I can set the check box and resolution appropriately. 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.
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Andrew Rodney
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« Reply #17 on: June 06, 2011, 03:21:39 PM »
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Thanks. Fair enough.
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Mark D Segal (formerly MarkDS)
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« Reply #18 on: June 06, 2011, 03:44:31 PM »
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With my Epson 9800 my rule of thumb is to send an image of 200 to 400 for paper and 150 to 400 for canvas. I can't tell the difference between prints in those ranges.
What I find of immense importance in image quality is the degree of sharpening. All of my prints within the above ranges using NIK's output sharpening are far superior to what I was printing before I used NIK.
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« Reply #19 on: June 06, 2011, 03:59:24 PM »
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All of my prints within the above ranges using NIK's output sharpening are far superior to what I was printing before I used NIK.

What did you use before NIK?

Terry.
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