Ad
Ad
Ad
Pages: « 1 [2]   Bottom of Page
Print
Author Topic: Dpi for printing  (Read 7780 times)
TylerB
Sr. Member
****
Offline Offline

Posts: 358


WWW
« Reply #20 on: February 05, 2009, 12:01:50 PM »
ReplyReply

If you simply run the tests for yourself, rather than pondering how it should work based on numbers and characteristics of drivers only partially known to us, or advice put forth by supposed experts putting forth ideas from other experts, you will get to the bottom of this issue. Mike Chaney's tests are revealing, they proved my previous preconceptions false.
How this relates to optimizing a workflow depends on a number of factors. Landing on hard rules that are absolutely optimal for every file and print is a goal riddled with problems, in life, art, and craft.
If the interest is primarily in the hard science, there is too much we don't know about the various driver's scaling. We get these native res numbers, which are somewhat illuminating, but clearly black box driver or RIP scaling methods have been evolving.

Tyler
Logged
Doombrain
Full Member
***
Offline Offline

Posts: 206


WWW
« Reply #21 on: February 09, 2009, 05:59:50 AM »
ReplyReply

Here's a quick test for the people who think print output PPI isn't that important. Epson Pro3800 (doesn't matter which Epson you use) and Epson driver.

Top image is a RAW file from a R-D1 processed at 360PPI and printed at 720x1440
Bottom image is the same only processed at 300PPI.



Edit: make sure you view at 100%
« Last Edit: February 09, 2009, 06:01:23 AM by Doombrain » Logged
neil snape
Sr. Member
****
Offline Offline

Posts: 1432


WWW
« Reply #22 on: February 09, 2009, 02:11:17 PM »
ReplyReply

Yup the above is just one example of the differences seen with varying resolutions.

What you will find is if you print at higher resolution , let's say 360 then source at 720 with maximum printer res, tht gray repeating contrast lines will have less coloration, and less staircasing. Solid flat areas will have less , if not much less mottling.

Quite a few things change , but it takes many tests to actually pinpoint cases where it makes all the difference as shown in the example above.

Logged
Farmer
Sr. Member
****
Offline Offline

Posts: 1630


WWW
« Reply #23 on: February 09, 2009, 04:32:06 PM »
ReplyReply

Quote from: Doombrain
Here's a quick test for the people who think print output PPI isn't that important. Epson Pro3800 (doesn't matter which Epson you use) and Epson driver.

Top image is a RAW file from a R-D1 processed at 360PPI and printed at 720x1440
Bottom image is the same only processed at 300PPI.



Edit: make sure you view at 100%

When you say "processed" what do you mean?  What is the native resolution of the image file?  Did you resample to achieve your 360 and 300 output at that partcular print size?  Or did you print at a size that meant that native was 360 and then you downsampled the file to print at the same physical size at 300 or was the native 300 and then you upressed to 360?

If you resampled the file, what method did you use?  Did you try 720x720 and 1440x1440.  Did you print bi-di or uni-di?

Also, I assume you're saying that the pattern seen in the 300 sample has scanned accurately and is the same as visible in person?  What settings did you use when scanning?

Yes, there are most certainly times (as I think most people have stated) when choosing 360 (or even better, 720) with an Epson driver will help, but in most cases, most people won't pick the differences and in some cases upressing will give you a poorer result.

Did you also try at 240 and 180?  And what about 313 or 297 or something else odd?  If you want to make a sweeping statement that upressing to 360 is always better, then you really need a bit more data and to explain your methodology :-)
Logged

Doombrain
Full Member
***
Offline Offline

Posts: 206


WWW
« Reply #24 on: February 10, 2009, 02:59:27 AM »
ReplyReply

We seem to be running in circles here, this isn't a sweeping statement, it's a fact.

My point is the native res of the print Epson driver is 360 so if you stick to integers of 360 you'll be OK as long as you don't go below 180 to avoid pixelation.

Native Image Res;
The two files are camera RAW files opening in Adobe Camera RAW.
The first one was set to 360PPI then opening in photoshop for printing.
The second image was set to 300PPI and then opened and printed on the same sheet.

The file was printed at 720x1440DPI, but it doesn't matter which DPI you set as long as it's not a draft mode (you might even see it at a draft mode).
Mode was Finest Detail Off, High Speed On.

To scan in I used an integer of the scanners native res, which was 96PPI to capture the effect. The scan is off a single sheet, no trickery.
Logged
Farmer
Sr. Member
****
Offline Offline

Posts: 1630


WWW
« Reply #25 on: February 10, 2009, 04:03:21 AM »
ReplyReply

Quote from: Doombrain
My point is the native res of the print Epson driver is 360 so if you stick to integers of 360 you'll be OK as long as you don't go below 180 to avoid pixelation.

You can certainly print below 180 without pixelation depending on the image and the substrate.  Yes, you need to be careful, but really 120 is the point at which you really need to be concerned in most cases.  Obviously it won't be suitable for some work, but you can certainly get down that far very often.

Quote from: Doombrain
Native Image Res;
The two files are camera RAW files opening in Adobe Camera RAW.
The first one was set to 360PPI then opening in photoshop for printing.
The second image was set to 300PPI and then opened and printed on the same sheet.

OK, so they were both printed to the same physical size?  That doesn't tell me if either of them is the native resolution in print.  If the image is 3000x2000 pixels and you printed it on an A4 with a border you might have printed it at say 11"x7 1/3" then it's printing natively at about 272, so at either 360 or 300, it's being interpolated by Photoshop before being printed, which isn't the query.

The query is whether upressing or down sampling to 360 is better than printing it without any resampling.

Now it's entirely possible (likely!) that one your resses was native for the size being printed, but you haven't confirmed which.  At the size printed, was it 300 native and you upressed to 360?  That's valid.  If both were simply opened at 360 and 300 respectively and then printed without resizing then they would print to different sizes and you're not answering the question at hand, which is if you want a particular size should you resample to 360 or go with what you have?

Quote from: Doombrain
The file was printed at 720x1440DPI, but it doesn't matter which DPI you set as long as it's not a draft mode (you might even see it at a draft mode).
Mode was Finest Detail Off, High Speed On.

It does matter.  It absolutely affects the dot pattern being laid down and that can affect the output.  It's absolutely valid to test at 720x1440 is that's the resolution you want to use, but it's not the most common resolution to choose on an Epson Pro printer, so it's worth checking against other options.

Quote from: Doombrain
To scan in I used an integer of the scanners native res, which was 96PPI to capture the effect. The scan is off a single sheet, no trickery.

I would recommend only scanning at the scanner's native physical resolution in order to avoid any errors being introduced.  I wasn't for a moment suggesting any attempt at trickery!  96ppi is really too low. imho.

I don't think we going in circles.  You have valid points and a worthwhile test to pursue, but there are things that either need to be confirmed or explained or, perhaps changed in order to validate it.

As Neil said, you can make a test to obtain any result that you want.  If I have time tomorrow at work, I'll find an image and print it at various "native" resolutions and then at corresponding resampled resolutions - to be honest it may take a day or two depending on how busy I am.  I like your approach of showing some actual examples for people.
Logged

Ernst Dinkla
Sr. Member
****
Offline Offline

Posts: 2845


« Reply #26 on: February 10, 2009, 04:08:27 AM »
ReplyReply


Nobody takes pictures with the 300 PPI or 360 PPI of resp HP, Canon or Epson printers in mind. Nobody should either.
The moment the print size is set the only thing that counts is getting a workflow with the best extrapolation aboard. There's no way to avoid up or downsampling to either 300-600 PPI or 360-720 PPI as that is part of the system, so do it as good as possible. After that the print quality is the result of the printer quality, the media coating, the extrapolation quality, the original image data. All things equal but the extrapolation algorithms varying will show print quality differences if a certain general quality in the other components is available. To check the print quality of your existing workflow use one of ddisoftware's targets and its test method.

If one describes the print quality difference between 300 PPI and 360 PPI input to a 360/720 PPI system, both input files based on the same image data, one actually describes a difference in extrapolation algorithm quality and not the superiority of either 300 PPI or 360 PPI input.



Ernst Dinkla

Try: http://groups.yahoo.com/group/Wide_Inkjet_Printers/
Logged
Doombrain
Full Member
***
Offline Offline

Posts: 206


WWW
« Reply #27 on: February 10, 2009, 04:55:24 AM »
ReplyReply

@ Farmer

180PPI is the lowest I would ever go for any of my clients simply because I'm sticking to a rule of multiples.

There's no resampling in Photoshop. Photoshop was only used to open the RAW files, crop tool was used to make the sizes the same and print the images.

IMO the best possible workflow is not to do any resampling and stick to the native res of the print driver, in this case 360PPI. But only if possable.

DPI, it was just a casual passing comment in terms of this test.

Scan res was set at 96PPI because I wanted to upload the image here and it demonstrated my point.
Logged
Farmer
Sr. Member
****
Offline Offline

Posts: 1630


WWW
« Reply #28 on: February 10, 2009, 05:43:43 AM »
ReplyReply

It's usually not practical to print at different sizes to accomodate natively maintaining a particular DPI.

I printed about 100 images for a major photojournalism awards last year - some were the same pixel dimensions because they were uncropped from the same camera model (despite being from different PJs), but many were different.  All had to be the same physical size output (or at least contained within a certain physical specification, allowing for different aspect ratios).  That's the more commons scenario, printing to a reasonably standard output size.

That being the case, people want to know whether to resample or to leave it "as is" assuming the resolution is within a certain tolerance.  Yes, changing print size to accomodate available resolution will always give you the best results, but it's not a practical real-world option most of the time.  My experience is that resampling the file can often do more harm than good or simply isn't necessary.  There are most definitely situations where it is beneficial, but it's not some holy grail.

I'll find time during the week and do some samples and tests if I can.

BTW, 120 is an "integer" of 360.
Logged

Farmer
Sr. Member
****
Offline Offline

Posts: 1630


WWW
« Reply #29 on: February 11, 2009, 01:15:49 AM »
ReplyReply

Well I had a chance today to run off some prints and scan them in.

All were done on an Epson Pro 11880 at 720x1440dpi super microweave on, bi-directional, no colour management (colour managed from Photoshop) on Epson Premium Glossy Photo Paper 170 using the Epson canned profile with one exception - I made one print from Qimage.

Of a total of 7 prints, 4 were printed to the same physical size (about 16"x9") and 3 were printed physically smaller by using the native pixels at higher resolutions as I'll detail below.

The image is 2076x1168 pixels (a crop of the full frame), opened in ACR 5 where adjustments were done, including sharpening for print at medium level.  For Qimage a PSD was saved out and then printed.  At the chosen print size, the native pixels provided 129ppi resolution.

The following prints were done:

Upressed to 360ppi in PS CS4 standard
Upressed to 360ppi in PS CS4 smoother
Upressed to 360ppi in Qimage as a result of printing to the specified size
Printed at 129ppi native in PS CS4
Printed at 360ppi native in PS CS4
Printed at 240ppi native in PS CS4
Printed at 180ppi native in PS CS4

The last three obviously printed smaller than the approximate 16"x9"

All of the full size prints were scanned in using an Epson V700 at 300dpi with unsharp mask off and descreening off.  The prints that were smaller were scanned at appropriately higher resolutions to provide the same pixel output to the saved scan.  The scans are of just a portion of the prints to avoid the files being too large.

The 7 images are linked here for those who are interested, in no particular order (ie does not match the order above):

Image A

Image B

Image C

Image D

Image E

Image F

Image G

In the next post, I'll list which are which.

The scans don't tell the full story, as the real test is how it looks to direct observers and not a resampled (ie scanned) copy of the print.  I hope some will find it of interest/use to compare.  It's a not a definitive "do it this way" or "do it that way" and I'll let the reader determine their own conclusions (my preferences are well posted :-)
Logged

Farmer
Sr. Member
****
Offline Offline

Posts: 1630


WWW
« Reply #30 on: February 11, 2009, 01:18:42 AM »
ReplyReply

A - 129ppi native

B - 180ppi native

C - 360ppi Qimage

D - 360ppi upres PS smoother

E - 360ppi upres PS normal

F - 360ppi native

G - 240ppi native
Logged

Ernst Dinkla
Sr. Member
****
Offline Offline

Posts: 2845


« Reply #31 on: February 11, 2009, 06:06:45 AM »
ReplyReply

Quote from: Farmer
A - 129ppi native

B - 180ppi native

C - 360ppi Qimage

D - 360ppi upres PS smoother

E - 360ppi upres PS normal

F - 360ppi native

G - 240ppi native

The subtitle of this thread is "What's the science ?". While we are wandering off the original context of this thread it may be a good idea to keep some quality in the discussion. It will have taken you some time to do the job but for me it isn't telling me anything. Comparing image quality of different sized prints on scans made of the prints is already beyond science.  On top of that there will be an extrapolation step in the scanner driver again with the method you used. It also looks like color management between Qimage and Photoshop isn't synchronised or the scanner fluctuates in its color management.

The use of the term "native" gets confusing too, for some it means the resolution of the original image but then it only has meaning if the size of the image is included too, for others it means the resolution required by the printer driver for certain media settings (= print quality) in the driver. As written before the last varies for different printers and printer brands. Today that's more or less 360-720 (-1440) PPI and 300-600 (-1200) PPI, the last high number for printing of vector designs and text. Some RIPs are able to use different numbers like 450 PPI on my Wasatch RIP for an Epson 10000. I don't think it is wise to use the term "native" resolution for image data, it is as flexible as the size is (even without extrapolation).

If there are samples to be compared it is C, D and E while Qimage actually knows a lot more of extrapolation routines that may suit the subject better. Smart print sharpening considered? Compare the prints at eyesight with a lot of diffuse light or if there has to be a representation here, scan them all on the V700 at 1800 PPI, way beyond the print resolution and reducing the influence of extrapolation in the scanner driver. Small image crops may show area artefacts of the paper coating so will not tell what the general quality difference is. I prefer a written comment on the quality difference by someone who can judge prints above scan samples on the web.


Ernst Dinkla

Try: http://groups.yahoo.com/group/Wide_Inkjet_Printers/
Logged
Farmer
Sr. Member
****
Offline Offline

Posts: 1630


WWW
« Reply #32 on: February 11, 2009, 02:38:12 PM »
ReplyReply

Thank you for the feedback, Ernst and I do agree with you.  In respect of "native" I did make a point of listing the ppi that was sent and explained what was going on, so hopefully people can understand the process in each case.

I also agree that scanning adds variables but shor of sending sample prints to everyone I've little choice :-)  I can tell you that my observation is that there is little difference between those images printed at the same physical size (I indicated 16"x9" as the "full size" prints) and in a quick blind test at work, no one was able to pick between the same sized PS prints (all prints observed in a light booth).  Obviously the Qimage one looked different in this case, but there was no particular preference or otherwise against it in terms of apparent resolution and sharpness.  I might try a Genuine Fractals enlargement and see if tht is any better.

I can certainly scan again at higher resolutions - it just needs to be a sample of a smaller area to avoid massive files.  You also need to be familiar with looking at high-res scans I think to make use of that.

I would encourage those keen to know to run their own tests and observe the results directly, as you're quite right that direct observation is much better than 3rd hand via a scanner.
Logged

fike
Sr. Member
****
Offline Offline

Posts: 1373


Hiker Photographer


WWW
« Reply #33 on: February 11, 2009, 04:35:14 PM »
ReplyReply

I don't really think that native resolution means anything.  What are the dimensions in pixels?  That tells you how much data you have to express your image.  From there, I try to keep the printer output resolution above 240 DPI--divide the pixel dimensions by 240 and that will give me the largest dimension in inches.

If you need to modify your sharpening, resizing, whatever to get better results, go for it.  I use Qimage and it is give me very good results as long as I stay above 240 DPI (220 in a pinch).  Beyond that, if I go to 800, 900 1000DPI who cares.  I decide the DPI based upon the size I want the image to be printed, not the dimensions of the image.  

It is almost like saying that you have a 5DMKII with an image output size of 5616 x 3744, therefore if you assume at 360 DPI then its native image size is 15.6" x 10.4".  That is crazy!  The image is whatever size you want it to be.  Resize the crazy image and then sharpen or blur the image as needed to get the best results you can eek out.  You may need to experiment with various preparations based upon the subject.  

There are no hard and fast rules.  There are thresholds that people might discuss like 240 DPI versus 360 DPI as the minimum resolution, but print some images and make up your mind yourself.  Different images, paper, and printers may demand different preparation.  There are lots of variables to mess with, but some notion of native resolution of the image is not relevant.
Logged

Fike, Trailpixie, or Marc Shaffer
marcshaffer.net
TrailPixie.net

I carry an M43 ILC, a couple of good lenses, and a tripod.
Pages: « 1 [2]   Top of Page
Print
Jump to:  

Ad
Ad
Ad