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Need Help Grainy prints on HP Latex L26500

Discussion in 'Hewlett Packard' started by Steve Shaw, Jan 10, 2018.

  1. Steve Shaw

    Steve Shaw New Member

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    Hello guys.

    I need help with print quality issues. I simply cannot get this printer to print with no graininess. I have tried the following

    Changed RIP from Sai Flexi to Onyx (Big improvement but still graininess)
    Cleaned print heads
    Aligned print heads
    Cleaned OMAS
    Calibrated Substrate advance
    Changed media (used 3 different brands)
    Altered curing and drying times up and down
    Altered passes up and down

    The prints look great from a distance, problem is once you get close you can see the coalescence issue. The printheads were changed about 2 months ago and the printer has hardly ran anything on it compared to what it should be doing.

    I have been printing on White gloss and matt vinyl, satin paper and canvas. The canvas appears to be the only media that you cant really see any grain in the print but this could be down to it being textured so it might hide it a little.

    I will post some images below. It seems to be more noticable on lighter colours such as skin tones.
     
  2. Steve Shaw

    Steve Shaw New Member

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    You can see the grain in the green in this image
     

    Attached Files:

  3. Steve Shaw

    Steve Shaw New Member

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    Here u can see the grain on the skin tones. It's all over the print not just on specific colours. More noticeable on lighter colours however
     
  4. dypinc

    dypinc Very Active Member

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    It all boils down to how you setting your light ink curves when your creating your linearization and your GCR and black start percentage when your creating your output profile.
     
    • Like Like x 1
  5. Steve Shaw

    Steve Shaw New Member

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    Here u can see the grain on the skin tones. It's all over the print not just on specific colours. More noticeable on lighter colours however
     

    Attached Files:

  6. Steve Shaw

    Steve Shaw New Member

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    OK, im a bit of a newbie at all this and still leaning so not a clue what that means lol. Any links you can offer to information on how to do these settings?
     
  7. dypinc

    dypinc Very Active Member

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    Do a google search for more in-depth info on this. Essentially the settings you want to reduce graininess in the linearization process is to set your light inks high to replace the Cyan and Magenta and keep your total ink limits low enough (this takes some experimentation with each media) that you don't get coalescing. Then in the output profile creation process set your black start to 25 or 30 percent and your GCR to maybe 60%. It all takes some experimenting to see what works best with each media and the for the effect your looking for.
     
  8. Asuma01

    Asuma01 Member

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    Making a color profile is a pretty difficult undertaking without proper training. I think that's why HP is automating the color profiling in their newer printers. Have you tried finding any premade profiles online for your media?
     
  9. dypinc

    dypinc Very Active Member

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    And there in lies his problem. You really don't know how they were created although in some RIPs you can open the linearization files and the profile and see what settings were used.
     
  10. Steve Shaw

    Steve Shaw New Member

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    Im using the ICC profile from Metamark for Onyx so it should be right shouldnt it?
     
  11. dypinc

    dypinc Very Active Member

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    Well is it? You were complaining about graininess? What are the light ink curves set to in the Linearization file, and the black start set to, and the GCR?
     
  12. bigben

    bigben Moderator Staff Member

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    How many pass do you use? It really look like a profile problem. Did you tried other profiles like the one included in your rip?
     
  13. AF

    AF Active Member

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    As mentioned above, your profile isn't using light inks long enough to reduce grain. Even if you crank the light ink splits to the max, your total gamut will go down and there will still be grain visible (12 picoliter droplets). Drying and curing will take longer if you up the light inks so increase temps, pass counts and interpass delay as needed.

    I make profiles for smooth skin tones and profiles for high gamut for each media type. The extra work saves time in the long run since most jobs don't need a slow skin-tone profile.

    I didn't notice coalescence in the photos you posted.
     
  14. Asuma01

    Asuma01 Member

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    We ended up hiring a professional to come in and make a bunch of profiles for us. It was somewhat expensive, but the time we saved afterwards not having to mess with settings for everything all the time made up for it.

    I should add that with the new HP printers profiling media is all automated. Its not as good as having a professional dial it in. But it still is pretty adequate for all but the most discerning customer.
     
  15. Steve Shaw

    Steve Shaw New Member

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    We use 12 or 16 pass
     
  16. Steve Shaw

    Steve Shaw New Member

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    So you suggest I increase the temps, pass count and interpass delay and then see if that solves it. Not sure I can bump the temp any higher to be honest but ill look.
     
    Last edited: Jan 11, 2018
  17. Steve Shaw

    Steve Shaw New Member

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    Hey, this is a profile I use for satin poster paper. these are the ICC settings as they are. Does this help determine if there is an issue?....might have to save the image to see it properly
     

    Attached Files:

  18. bigben

    bigben Moderator Staff Member

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    there is really a problem somewhere. I have the axact same printer but I use Caldera rip. I always print at 10 pass and my images are alot better than your picture. Like Steve Shaw mentioned, it's most likely a profile problem.
     
  19. dypinc

    dypinc Very Active Member

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    I don't see the light ink curves. Are you using CMYK or CMYKcm?

    In the output profile generation setting the black start needs to be set at 25 to 30. I would also test profiles with the black width set to 80 and 60.
     
  20. AF

    AF Active Member

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    Step 1 is to linearize repeatedly until you get the right curves.

    Step 2 is to set your ink splits to increase your light inks as high as possible. Curing will be a problem, solved by high pass counts, high temps and interpass delay.

    Step 3 is to calibrate. I would build a calibration chart from and image with flesh tones for this.

    Step 4 is to build your profile with the black start mentioned by Dypinc. Test it out and recalibrate with adjustments as needed. I don't think you can control ink limits on your machine so this list is missing that step.
     
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