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Author Topic: Output PPI vs. Printer DPI  (Read 3862 times)
joedevico
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« on: September 03, 2006, 11:15:55 PM »
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Hello All,

I came across this statement on the net the other day refering to the Noritsu Printers at Costco and was wondering if it has any validity...

"Further supporting that image resolution and printer resolution are not the same, is something called a moirČ pattern.  This can occur on any digital printer if your image resolution matched exactly that of the printer resolution.  You will see a result much like on television when they video tape a screen door.  You get interference patterns when the pixels in your digital file match up with the printing matrix of the printer.  In short, do not set your files to exactly 320 DPI ever."

I have always interpolated my images either up or down to 320dpi once I've cropped them so that the printer doesn't do it on it's own. I've tried sending large images with and without the interpolation and have seen no difference - meaning that at prints up to 12x18 from a Canon 20D, the Noritsu Interpolation seems to be as good as Photoshops Bi-cubic Interpolation. I am usually more concerned with sharpness issues which is why I interpolate myself and then do final sharpening after the fact.

Anyway - should I not be setting the file to exactly 320dpi (the resolution of the Noritsu) and instead somewhere around 300dpi?
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Joe DeVico
the PhotoGraphic Design Group
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JeffKohn
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« Reply #1 on: September 04, 2006, 01:15:11 AM »
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Sounds like nonsense to me. 320ppi is the input resolution of the printer, not the output DPI. In fact the Noritsu machines are continuous tone so the whole notion of actual dots per inch does not apply. If anything I would think you're more likely to get moire, aliasing or other artifacts if you fed the printer a 300ppi image because it would have to be interpolated to 320ppi by the driver and such an interpolation may cause artifacts.
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joedevico
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« Reply #2 on: September 04, 2006, 09:36:27 AM »
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That's what I thought   - but I still learn new things every day!  
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Joe DeVico
the PhotoGraphic Design Group
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Wayne Fox
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« Reply #3 on: September 16, 2006, 02:43:47 AM »
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We have used 5 models of Noritsu printers, and other than the MP1600 (old model) which was 400 DPI, all models I am familiar with are 300 DPI.  I could not find one that is 320 DPI on Noritsu's website...  Not saying there isn't one, but since most of them share the same laser/imaging subsystem, seems strange they would throw a 320 dpi one in the mix.  I really do not believe there is a 320 DPI noritsu printer.

As far as moire, I think they may be blowing some smoke at consumers, they are telling them to not size to 320 dpi because they believe there printer is 320 dpi ... doesn't make much sense.

 We've been producing digital prints on various photo printers since the early days of Kodaks CRT printers,and all digital output on fixed ratio output devices like this (dye-sub/ LED/Laser) that we've used we size the the print to a 1-1 pixel ratio ... image size equals output size.  We currently have 140 studios and photograph over 1 million sittings a year, producing over 8 million 8x10 prints.  Moire is something that we only see as the result of the raw file demosaicing process.

These printers work very differently than inkjet ... instead of a series of various color dots in various sizes, each pixel can contain any color within the printers gamut.  There can be a true one to one relationship.

If you send a print to this printer that does not match its 300dpi resolution, I believe all it will do is resize it.  It does not go through the same process as an inkjet printer ... it will just resize it.

So personally ... I would prefer to resize them myself and have complete control rather than let the printer do it.

Wayne Fox
www.kiddiekandids.com
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« Last Edit: September 16, 2006, 02:46:30 AM by Wayne Fox » Logged

bjanes
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« Reply #4 on: September 16, 2006, 06:25:33 AM »
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Quote
We have used 5 models of Noritsu printers, and other than the MP1600 (old model) which was 400 DPI, all models I am familiar with are 300 DPI.  I could not find one that is 320 DPI on Noritsu's website...  Not saying there isn't one, but since most of them share the same laser/imaging subsystem, seems strange they would throw a 320 dpi one in the mix.  I really do not believe there is a 320 DPI noritsu printer.

Wayne Fox
www.kiddiekandids.com
www.cwaynefox.com
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I checked the DryCreek site and found the following:

"Noritsu Laser printers (Model 3xxx) are problematic. Some machines print at 320 ppi, while Noritsu recently changed others to print at 300 ppi. There is no way to tell which resolution the machine runs at without making a print, nor does there appear to be any consistency as to which machines run at 300 ppi and which ones use 320. If the lab can not tell you what resolution their printer uses, the safest course is to use the 300 ppi values in the table below for your first print order. Check the print sizing status string. If it says Z93.7/100 (or something close to 93.7), the printer is set to 300 ppi resolution."

As I recall, they previously stated that the Noritsu 3101 used by my local Costco was 320 ppi and I have used that size without problems, but now I am going to have to do some investigation.

Bill
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