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Thread: Avoïding pixelization ?

  1. #1

    Avoïding pixelization ?

    Hello painters !
    I have a hard time figuring out this little problem : I often see pixelization, it's light, but still noticable, like in these trees, done with the felt-tip pen.
    I set the resolution to 600px/po (I don't know exactly what this means but the higher the better, right ?). With or without the "canvas light", still some noticable pixels here and there.
    How can I try to avoid this ?

    Thanks !
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  2. #2
    Join Date
    Nov 2011
    Posts
    939
    Hello burgzaza
    More pixels is what you need!
    That is more actual pixels, not just packing what you have into a smaller area for print.
    Your posted image is only 258x234 pixels or 60,372 pixels in total. That’s not a lot!
    Setting a high ppi doesn’t add any more pixels to the image it’s still just 258x234 pixels.
    The ppi will be used to tell a printer how tightly to pack those pixels as ink dots on a page. So your sample image would print at about 13mmx12mm.

    Whilst an image is still in digital form ppi/dpi means nothing, there are no “inches” in a computer!
    Image dimensions in pixels are what count, the bigger the image pixel dimensions are the better for high quality print because you will have more of them to pack down and turn into ink dots @ 300 or 600 per printed square inch.
    (OK so that last bit is a bit of a simplification as pixels aren't always translated into ink dots 1 for 1 in some print methods but the point still holds!)

    Have a look at this site: Size: http://www.tutortanith.com/imagesizing.htm
    It provides an intro into understanding ppi/dpi and when and where it’s important for digital artists.
    Maker Of Replica Macoys

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  3. #3
    Very interesting, thank you very mutch Markw ! I was totally confused by this. Now I think I get it !

    However not really thinking about printing mutch stuff, but this will really be handy to know when I'll plan to do so.

    For now I'd want a sharp image without noticable pixels, when it's viewed at 100% scale, on a computer screen. And that's where I'm still a bit lost. I can't put on the internet images of tremendous sizes, I mean I could but it isn't handy for anyone to watch them, in either an undesired default zoom, or at maximum scale witch would be way too big, so I mostly end up posting images at the same size of when I painted : around the size of the screen. Might be a very bad habit.

    My second question would be how, if it's only possible, can I make this tiny image looks sharper without modifying it's total size ? It should be possible as my screen can display images with great details and no apparent pixels.

    I tried to double the size of the image and then resize it back, on Gimp2 (the best quality resizing too I know of). It's slighly sharper. I may use this trick, but maybe not because it also "blurs" it a tiny bit ! I'll post the result in the gallery section when it's done ( few more days ).
    Thanks again for the reply that was super useful, still a bit confused but it's already clearer

    Hum... I just tried with another tool, the simple sketch pen. It has no sutch effects as the felt-tip pen. Or if it has, it's almost not visible ! I think that was it, first time I really make a drawing with this tool that's why I didn't really noticed that before: Name:  flet tip pen vs sketch pen.png
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    Last edited by burgzaza; 03-24-2016 at 07:11 AM.
    Most of my stuff is hosted there : http://burgzaza.deviantart.com/gallery/

  4. #4
    Join Date
    Nov 2011
    Posts
    939
    Hello again
    I understand your concern over file sizes for web viewing but should that really be the primary controlling factor, dictating how and what you want to paint? (Unless of course it’s part of a brief as a commission?)
    I would suggest you paint your paintings at a sufficient size that will give you the line quality that you want.
    99% of people will look at your work and think “WOW, I like this. This person has some talent” But no one is going to look at your work and their first thought be “WOW, nice file size”!

    “My second question would be how, if it's only possible, can I make this tiny image looks sharper without modifying it's total size ?”
    And I would counter with; “Why dose it have to be that small?” “What is dictating the size of 258x234pix?”
    But if you insist, then maybe you could try using something like an ‘Unsharp Mask’ filter in a photo editing app. That might, despite it’s name, crisp things up a bit.

    “I tried to double the size of the image and then resize it back…” “It's slighly sharper. I may use this trick, but maybe not because it also "blurs" it a tiny bit!”
    Yes it would. You just put it through two separate re-sizing algorithms!
    (though again you could try using an ‘Unsharp Mask’ filter on the resulting blurred image).
    The one thing digital files are not keen on is being “up-scaled”. True there are some good algorithms out there these days that can do a pretty good job of it. But there is no escaping that what they are doing is making up new pixels to add to your work.
    And this can be evident afterwards, if they have been asked to go too far, by a slight blurring of the treated image.
    Algorithms have no ascetic judgment so don’t ask too much of them!

    I think you would be better off doing your painting at a larger size (did I mention that already?) and then downscale to the dimensions you need. Digital files tend to be more amenable to this type of treatment as all an algorithm (mostly) has to do is throw out pixels.

    And so to Image Compression!
    Some file types compress their data better than others, jpeg giving one of the smaller sizes but perhaps is the more aggressive in throwing away data.
    But is possibly still a good match for web needs as you can set, when saving a jpeg, how aggressively the compression should be applied.
    There is also one more “trick” you might want to try in reducing the overall data size of an image and that is third party image compression apps. Some are free others paid.
    Note these algorithms are not trying to change the number pixels but rather reduce the overall data contained within an image file. Although it is true image quality can suffer if they are too zealous in the pursuit of their work!
    Here’s a link to a free web based service where you can upload jpeg, png and pdf files for compression, which I’ve found to give reasonable results for my occasional needs: http://compresspng.com
    Last edited by markw; 03-24-2016 at 11:40 AM.
    Maker Of Replica Macoys

    Techie Stuff:
    ArtRage 5.0.5 ~ 15" Macbook Pro
    + 22" HD Monitor ~ macOS 10.12.6 ~ 4 Core i7 3.1GHz CPU ~ 16GB RAM ~ Wacom Intuos4 M and a Spyder4Pro (to keep the colours true!)

  5. #5
    Quote Originally Posted by markw View Post
    Hello again
    I understand your concern over file sizes for web viewing but should that really be the primary controlling factor, dictating how and what you want to paint? (Unless of course it’s part of a brief as a commission?)
    I would suggest you paint your paintings at a sufficient size that will give you the line quality that you want.
    99% of people will look at your work and think “WOW, I like this. This person has some talent” But no one is going to look at your work and their first thought be “WOW, nice file size”!
    I'm doing a drawing for a little contest right now. The theme is a mix between two video games, Chivalry and Terraria. I'm enjoying it
    I get what you say about doing it on a big size, that will for sure enchance quality, eliminate the pixelization and add possibilities for printing.
    My concerns with this are that oddly, I moslty if not only like to look at my work at 100% scale. I also like a lot more the results of a tool when it's looked at 100% zoom.
    I almost never resize paintings because I lose all the details, textures, subtile things here and there that I did. That's also why I'm concerned to how people will look at my paintings, I'd like them to have the same thing as I had when painting; because watching an image at diferent scales changes it, a lot.
    Posting a 4000x4000 image guarantees that people will see the image at different scales, destroying the intent of the painting, because people have different screens, and websites will display it at different sizes.
    The only way to be sure that everybody has the same result is to post an image little enough, nowadays I'd say something like 1600x1000.
    I'd be happy to try to take the habit of big images, but the problem remains, how will it be displayed by people ? At what zoom should I draw and paint on Artrage, to see the same thing they'll do ? No way to be sure, so no way to know at what zoom work on details and sutch
    That's a pretty existential question isn't it, maybe only for people like me that like to detail everything. I don't know if it's the same feeling for real life paintings that are displayed on magazines for example, but I assume it is the same problem.

    Quote Originally Posted by markw View Post
    “My second question would be how, if it's only possible, can I make this tiny image looks sharper without modifying it's total size ?”
    And I would counter with; “Why dose it have to be that small?” “What is dictating the size of 258x234pix?”
    But if you insist, then maybe you could try using something like an ‘Unsharp Mask’ filter in a photo editing app. That might, despite it’s name, crisp things up a bit.
    Thanks I'll try that ( but I think it's that felt tip pen that is a bit pixelized, I'll try to mess with the settings of the tool a bit ), and you know better my obsession in expecting people to see what I see



    Quote Originally Posted by markw View Post
    Algorithms have no ascetic judgment so don’t ask too much of them!
    I think you would be better off doing your painting at a larger size (did I mention that already?) and then downscale to the dimensions you need. Digital files tend to be more amenable to this type of treatment as all an algorithm (mostly) has to do is throw out pixels.
    Very right ^^

    Quote Originally Posted by markw View Post
    And so to Image Compression!
    Some file types compress their data better than others, jpeg giving one of the smaller sizes but perhaps is the more aggressive in throwing away data.
    But is possibly still a good match for web needs as you can set, when saving a jpeg, how aggressively the compression should be applied.
    There is also one more “trick” you might want to try in reducing the overall data size of an image and that is third party image compression apps. Some are free others paid.
    Note these algorithms are not trying to change the number pixels but rather reduce the overall data contained within an image file. Although it is true image quality can suffer if they are too zealous in the pursuit of their work!
    Here’s a link to a free web based service where you can upload jpeg, png and pdf files for compression, which I’ve found to give reasonable results for my occasional needs: http://compresspng.com
    Thanks again Markw, I'll keep all that in mind, super useful !
    Most of my stuff is hosted there : http://burgzaza.deviantart.com/gallery/

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