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Resolutions, passes and what they mean.

Discussion in 'Newbie Forum' started by PointED, Nov 24, 2015.

  1. PointED

    PointED New Member

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    Hi guys, or girls..

    I'm not exactly a newbie to the sign industry but I am new to the printing end of it. I've always been a designer, recently however I've been doing more printing. Large format printing. We use the Epson GS6000. My question is about resolutions and passes. When designing obviously you want the best possible PPI resolution, but for printing, Im not too clear on what 720x720 or 720x1440 or what passes mean. Is it a rule of thumb, that like in designing the higher the resolution the better the print? (If thats the case why not choose the higher resolution for all prints?) Is the size of the print file important when choosing a print resolution? If anyone could help me out, I'd greatly appreciate it! Thanks!
     
  2. VanderJ

    VanderJ Take two Dampers and Call me in the Morning

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    The resolution of your designed files has more to do with the quality of the print than the print resolution does. If you print a high res file on a low res profile, it will look pretty darn good. If you print a low res file on a high res profile, it will look bad no matter what you do. Low res is fast and high res is slow. As a rule, the higher the print resolution, the less grainy the print will be and solid colors look smoother. High res also allows for better transitions like gradients and shadows. Higher resolution also uses more ink and can make color more vibrant or darker depending on the color.

    Print passes are how big of a path the print head prints each pass. The lower the pass setting is, the bigger the path but defects can become more apparent. A higher pass setting makes each pass smaller and prints much slower but defects show up less. In general, if your printer is clean and calibrated correctly, you can get by on 8 pass 720x720 on most any job. Banners are generally printed on low pass count, low res profiles for speed. High quality prints are done closer to 16 pass 720x1440 but are much slower.

    Print a file out on every setting you can think of and look at the differences. I am willing to be you will almost never need to use anything higher than 16 pass 720x720 and most of the time I can get by on 8 pass 540x720 with no quality issues.
     
  3. PointED

    PointED New Member

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    Hi Vander J,

    Thank you for your response! It makes a lot more sense now. And at the risk of "abusing" your kindness, what can you tell me about ICC profiles. Recently we purchased the Epson Surecolor50675 and we are having a lot of issues with banding. I read in a previous post that it could be due to the profile. All media profile was created by the tech when the printer arrived. Yet we still get banding. Is there something I can change in the ICC profile? Could there be something else I should be looking at?
     
  4. player

    player Major Contributor

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    The Roland heads (and others) also use variable droplet sizes. I think I remember being told that the high pass will use the smaller droplets while the medium (720 x 720) will not, making it faster but lesser in quality and detail.
     
  5. paperstrategies

    paperstrategies Member

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    Banding issues

    Hi there, I see this thread is a few months old. If you're still looking for an answer, you shouldn't have to mess around too much with your profiles. Increasing the pass count should give you smaller bands and most of the time will get rid of the banding. Banding is usually a result of an issue regarding the print head. Whether it be clogged nozzles or bidirectional alignment. Another solution would be to slow down your scan speed, as this gives more time for the ink to set. Troubleshooting gets easier as you go so don't fret too much! Best of luck.
     
  6. oksigns

    oksigns Member

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    You are correct[for Rolands]. You can literally see how the droplet size effects the fine details- especially when the printer sees compressed art, all those fine compression artifacts are multiplied due to the variable droplet size.
     
  7. Correct Color

    Correct Color Merchant Member

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    Basically, resolution is how many dots per inch the printer prints.

    There's a confusion out there, but the way it works out is that resolution in and of itself doesn't really have any bearing on print quality other than in being a major determinate in gamut size. And the reason is because in large format printing, there's always a smallest dot size. It's not like litho amplitude modulation halftoning where a five percent screen equals a five percent dot. In large format, even if a printer is a multi-dot printer, typically there's a smallest dot size, and it's frequency of that smallest dot that carries highlight and mid-tone detail.

    So your prints will tend to be just as grainy -- or not -- at 360x360 as 1440x1440.

    The real reason for higher resolutions in large format is to be able to use more ink. And the resolutions are simply stated as a measure of dots per square inch.

    So, as I recall, I think the smallest drop size in your GS6000 is 6 picoliters. So if you're printing at 540x720, you can do this equation: 540x720 (the number of drops you're putting down in a square inch) = 388,800 x 6 (picoliters per dot) 2,332,800 (total ink volume per square inch.)

    Then the question becomes: At that resolution, are you getting full gamut capability out of the printer.

    And the answer to that question is in the profiling process.

    Of course typically at that resolution you wouldn't get full gamut capability out of that printer a that resolution and at that size dot, and that's why the printer manufacturers have gone to multi-dot configurations. So then you'd have three dot sizes, with six pl being the smallest, and let's say 12 pl and 18 pl as drops two and three.

    And that's the only purpose of multi-dot ink systems: To be able to achieve full gamut at lower resolutions.

    Of course, that does come with a price. Fact is, inkjet printers love to print slow. The slower they print, the better they print. Only problem is that it's also true that the slower they print, the less money you make.

    Many times, a given media will take a given amount of ink just fine as 6 picoliter dots laid down in 16 passes.

    But try to lay down the same amount in 4 passes of 18 picoliter drops and the media will reject the ink.

    This is typically seen as coalescence.

    And that's the reason higher resolutions are available. You may be able to get the same basic gamut at 540x720 multi-dot as you can at 1440x1440 single dot, but it will likely not be as smooth a print, and might be fine as a banner, but not as a point of sale piece.

    The way it breaks down is that all the things that have to do with how the RIP creates the actual printing dots are part of a profileable machine state. And that boils down to ink splits, dot sizes, ink densities and printing resolution. In order to change any of them, a new profile must be created.

    Then you have the mechanical aspects of how the printer reproduces those dots. Typically those include number of passes -- the number of passes of the printhead over its printhead path to fill in that path completely with dots -- bi-directional or uni-directional, and printhead speed.

    Those typically are not profileable.

    As far as ICC profiles themselves go, what an ICC profile is in actuality is a characterization of a device reproducing color in a certain state. An ICC profile is made after all the variable machine-state settings have been set, and then becomes a part of the media profile for that machine printing in that state.

    So no, changes to your ICC profiles are not going to help your issues.

    Bottom line is there is a very lot to this. If you're really serious about getting answers, this is what I do for a living.

    Please feel free to drop me a line.
     
    • Like Like x 3
  8. limacchina

    limacchina Member

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    Hi , I am more familiar with cnc routers. In our arena, resolution is the distance between two same cut. Pass is the number of cuttings in z axis that the machine needs to go to cut the full thickness. Not sure if it is the same case for printing machines.
     
  9. Peeters

    Peeters New Member

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    I work with 2,5pl to 7 pl and have banding in with variable 2,5-7pl. When I print with 7 pl only there is no banding. When I print with only 2,5 pl then I have the most banding. Can it be possible that 2,5 pl can't give enough inkt ?
    Thanks for your feedback
     
  10. eahicks

    eahicks Very Active Member

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    Banding is caused by nozzle drop out or head misalignment, almost 99% of the time. Banding will occur most often with your lower pass printing. Stick to 8 pass or above on most machines, and ensure you have no clogged nozzles and all heads are aligned.
     
    • Like Like x 1
  11. Andy_warp

    Andy_warp Member

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    It may have more to do with the state of your heads. Are you getting clean nozzle tests? If the heads are clogged, you'll tend to see varying levels of defects across varying color channels.
    You may be having better results with the larger dots because the ink spreads more on your substrate...hiding the deficiencies in your heads' ability to create the smaller drop size.
     
  12. Peeters

    Peeters New Member

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    The nozzeltests are perfectly no nozzles missed and the heads are clean. The heads are Ricoh G5s 2,5-7pl. The printer is a Signracer ( Handtop ) 320 led hybride. Even in the best quality 1200x1200dpi 16 pass the banding is there in full colors shapes. The banding is best visible in the reflection of a light.
     
  13. Andy_warp

    Andy_warp Member

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    Other culprits I've seen for this are:
    -air in the system
    -media slippage
    -head misalignment
    -printhead carriage height

    Is it across all channels? Do you see it more prominently in reds, blues or greens?
    Does it happen on every type of media?
     
  14. Peeters

    Peeters New Member

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    No air in the system the media transport is good I think. The banding is in all channels magenta cyaan yellow and black and on all materials.
    Signracer do tests on other printers with the same heads ( Ricoh 5220 genS 2,5-7pl ) and the banding problems are the same. Signracer haven't a solution....
    No we are printing without light cyaan and light magenta. Perhaps add heads with light cyaan and light magenta solve the banding problem, because you can give more ink. What do you think ?
     
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