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Author Topic: Advice on dpi and interpolation.  (Read 12970 times)
sectionq
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« on: May 04, 2011, 10:50:48 PM »

Hi all,

first off, apologies if this is in the wrong section but I couldn't figure out the best place...anyway.

I'm trying to figure out what is the best way to let Q process my prints.

Typically when preparing a photo for print I'll adjust the dimensions in photoshop to the size required (without resampling) and for something like a 45x30cm print I'll end up with a dpi of around 140 - 180dpi which is fine as I'm printing onto canvas.

There are a couple of things I'd like to get clear...

First off does Q simply honor the dpi of the image and then interpolate it up to 360 (epson) by calculating the dot spacing for the print driver OR does it interpolate it (and invent pixels) up to 360dpi.

Second, If I keep the image at its original size (say 300dpi) and then let Q scale it to the required 45x30cm will it work better?

As for the interpolation method, I'm using pyramid (is that the best one to use?), can anyone explain how the pyramid settings will effect things? There is a slider ranging from smoother (0) through to sharper (10) and the default is 5, what sort of images would benefit what settings?

Hope that all makes sense?

Thanks in advanced.

Jamie




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Terry-M
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« Reply #1 on: May 05, 2011, 07:41:23 AM »

Hi Jamie,
If you are using Qimage (I assume Ultimate) to print, there's no need to bother with "sizing" in Photoshop. Those numbers are merely tags. I prefer the term ppi, pixel per inch and use dpi for a printer's spray pattern. Think about it, an image really has only pixels as real attributes, no inches until it's printed.
Qimage takes away the need to worry about ppi and you just need to decide what size you want to print and specify that, either from a pre-set size or as a custom size. However, Qimage is able to use embedded sizes, like you describe, from the Custom size menu.
All you need to do is use your original image, whether edited or not, and specify the linear dimensions in Qimage; the print ppi is reported in the queue data.

The great feature of Qimage, and the main reason why it produces such good prints, is that it interpolates the image data to the native resolution of your printer, 720ppi for Epson, 600ppi for Canon & HP. You have not got Finest Detail checked in the driver if you are seeing 360ppi.
See - http://www.ddisoftware.com/qimage-u/tech-prt.htm
The other key feature that produces top quality prints is the interpolation method used. The latest & best is Fusion in Qimage Ultimate. If by chance you are not using QU, then Hybrid is the one to go for. Pyramid is now outdated compared to Hybrid and Fusion.
See- http://www.ddisoftware.com/qimage-u/tech-fus.htm

Although I've not answered your questions directly, I trust my explanation does in fact do that. Come back if not.
Terry
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sectionq
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« Reply #2 on: May 05, 2011, 10:50:40 PM »

Thanks Terry,

Unfortunately I do need to resize in photoshop as I only print on canvas so I need to create custom gallery borders, there's always something that needs editing out or tidying up so automation doesn't work for me. What I might do though is create borders for the smallest size only and then crop and resize in Q for larger sizes, as you pointed out it does seem daft to not take advantage of that feature.

As for the finest print settings, I always use the highest quality in the print driver 1440dpi for canvas (2880 for anything else), the highest qimage setting available is 360, the only other setting is 180. I assumed that 360 was all qimage needed as you're just multiplying that by 2 or 4 to send to the driver.

Good to know about the interpolation method, problem is there's little info on this. I actually got Qimage after reading about it about 6 months ago but that was based on info from about 2004 I think. Just downloaded the latest version 129, the version I've been using for the last few months is 105 and it doesn't have fusion so I'll give that a go, Mr Chaney doesn't mess about with his revisions does he?

I assume that fusion will have the same or similar settings to pyramid, if so, I'm still confused as to when you would set it to smoother or sharper?

Anyway, cheers again.

Jamie
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rayw
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« Reply #3 on: May 06, 2011, 01:54:01 AM »

Hi Jamie,

Qimage has canvas wraps, mirrored or stretched or coloured with fold marks which may save some flaffing around in photoshop. As Terry mentioned, Qi will print to Epsons at 720 ppi native resolution if you set the Epson driver to finest detail, (most likely it's a check box which is greyed out for some media, so you may need to fake the media, to get that selection for your particular media/printer). In any case I would be surprised if anyone will see the difference on canvas between 360 and 720 dpi native resolution. If you don't want to waste ink and canvas, there is a method for printing test strips, so you can see the effects of the various sharpening algorithms. Depending on the type of image you are dealing with, you may find that some algorithms and settings are better than others. When you are editing an image, you are dealing with pixels; when you are printing you deal with dots per inch. Resize and convert from pixels to dpi in qi, in comparison the photoshop resizing is not the best  Shocked.

There have been similar questions in the past - such as http://ddisoftware.com/tech/qimage-ultimate/interpolation-in-ultimate/  wrt finest detail and sharpening.

Best wishes,

Ray
« Last Edit: May 06, 2011, 02:00:29 AM by rayw » Logged
davidh
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« Reply #4 on: May 06, 2011, 02:32:21 AM »

  
Hi guys ...Related question,
Today I was trying to reproduce some art (painting), on canvas which I shot in RAW and adjusted to what appeared to be a match on my calibrated system and viewed the "soft proof" which looked good. Printed did not match so I decided rather than wasting any more materials to re adjust and do a test "strip". After reading the "HELP" section for doing a test "strip" about 4 times I finally got the hang of how to do it  Roll Eyes

The "strip" is not really a "strip" but a 'section' which appears to be constrained to a specific aspect ratio (I'd really like to be able to do a "strip") but.....Wink
Anywho...
Since I'm using roll canvas on my Epson7900, Is there any way to do mutiple edits (or interpolations of the same image), in a row of lets say 3 or 4 test "strips"  across the 24" width at the same time, to be able to compare at once, which one might be best to print at full size?
Thanks, David
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BrianPrice
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« Reply #5 on: May 06, 2011, 07:58:47 AM »

Quote
Unfortunately I do need to resize in photoshop as I only print on canvas so I need to create custom gallery borders,

Jamie

If you un-tick the 'Resample Image' box when re-sizing in Photoshop you will leave the image at the original resolution without any interpolation. As Terry said, leave all the interpolation to QI. You get the same result if you leave the 'Resolution' box blank when cropping.

Brian
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Fred A
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« Reply #6 on: May 06, 2011, 12:25:44 PM »

Quote
Since I'm using roll canvas on my Epson7900, Is there any way to do mutiple edits (or interpolations of the same image), in a row of lets say 3 or 4 test "strips"  

David,
To the best of my knowledge, the interpolator (Fusion, Hybrid, Pyramid) isn't a factor until you go to print to paper, print to File, ot upsize or downsize an image
You aren't seeing an interpolated image in Full Page Editor; but a High Def image or a low rez image, depending on your selection.

The test strips can be adjusted to aspect ratio of your choice by selecting the print size. You can click on the Test Strip icon and set to the magnification you want, and change the print size (aspect ratio) with a Right click on the image, and select a new size.
You want strips, make a custom print size (Auto crop on). It can do just about anything you want.
This feature is designed to show you on a small sample print what a section of your image will look like; is it sharp enough, wedding dress too light or too dark in print.
You can use 4 x 6 paper or cut some off your roll, and make 3 test prints using 3 interpolators.
That's the way I might do it.

Fred

PS I forgot to mention that the object is to keep the same ppi in the 4 x 6 test print as the large finished print will use.


« Last Edit: May 06, 2011, 12:29:18 PM by Fred A » Logged
sectionq
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« Reply #7 on: May 06, 2011, 02:25:49 PM »

Thanks guys for all chipping in,

Fortunately I never let photoshop resize so that's good I just need to change the dimensions so I can make my gallery wraps the right size, I often get a pretty poor dpi but keep my fingers crossed that qimage'll step in at that point.

Followed the other thread and indeed I've not had it on finest quality, it's sneakily hidden away, it turns out that the highest quality setting that I've been using isn't, so thanks Terry for getting me to scratch my confused head a bit. I did an A4 sized print yesterday at 360dpi and then the same print today with the new 720dpi and even on canvas the level of detail is quite incredible! Ah, failed to mention I also used hybrid instead of pyramid as I haven't installed the latest version yet to try out fusion, but either way I'm getting a better print! It's nice too that you don't have any settings to play with with hybrid so that helps reduce my confusion still.

By the way, the qimage gallery wrap option does a brilliant job as photoshop guides always needs adjustment if the dpi isn't a perfect round number but as I said, for me that's only a starting point and then the borders always need some clone stamping or whatever if the subject is too close to the edge.

Anyway, I'm pretty happy now, I think I've got all my answers cleared up.

Thanks again.

Jamie
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Terry-M
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« Reply #8 on: May 07, 2011, 07:05:11 AM »

Jamie,
Quote
Thanks guys for all chipping in
We're always willing to help  Cheesy
Quote
Fortunately I never let photoshop resize
That's a relief  Roll Eyes
Quote
By the way, the Qimage gallery wrap option does a brilliant job
Qimage can easily be a one-stop-shop what with clever raw processing and all.  Cool
Quote
Anyway, I'm pretty happy now, I think I've got all my answers cleared up
Pleased to hear it  Wink
Terry
PS. This post was not really necessary but I'm trying to catch up with Fred and achieve 1500 posts and Super Hero status  Roll Eyes  Grin

« Last Edit: May 07, 2011, 09:45:54 AM by Terry-M » Logged
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