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I am starting to learn on how to create posters and artwall print (A1,A2, A3, B1,B2,B3, and most posters sizes etc) and then send to printful for . I have searched and viewed many topic and i am still a bit confused and i have some questions. I have learned that for posters prints its better to make the design in illustrator (vector and text based art) and that is better to set up a document size in AI according to the physical size in Centimers or inch or mm. ie : A2 poster = 42.0 x 59.4 Cm or 16.5 x 23.4 inch document size in illustrator. however its hard to design on a laptop screen in real size/ zoom in & zoom out etc...

So i came up that if i use how illustrator calculates exported artwork resolution i can just create an appropriate document size in Px (A2 pixel size in 72 dpi then export final artwork to 300dpi to come up with exact final image A2 sizes in px)

Here is my approch: 1- create a document 1 191 x 1 684 px (which is = to A2 size in 72dpi) A2/300dpi is 4961 x 7016 px 2-design the artwork 3- Export file as a jpeg and then set the resolution to 300dpi

I have checked the final exported jpeg and it's exported at 4961 x 7016 px/300dpi source : Illustrator - Calculate File Dimensions and Resolution for Accurate Output - File Size Demystified

I just want to know if that process of working to output a poster size is a good way rather than working on a real size document.

Ps: printful is asking for a jpg file at 300dpi SRGB for the prints .

thank you

EDIT: Thank you all and thank you @Billy kerr for this thorough answer which is the closest to my questioning. I wanted to clarify some things that were probably not clear in my question:

1- I don't use images in my posters (only vectors and probably some pixelization effects so I'm well aware of the resolution of the images in case I use them).

2- I learned during my research that the dimension of the AI document must be exact than the physical dimension of the real poster. i.e. if it's an A1, the illustrator document must be either in centimeters (59.4 x 84.1 cm.), inches (23.375 x 33.125 in) or milimeters (594 x 841 mm) and not in pixels (because it's a digital measurement), the image exported during the final rendering is expressed in px (7016 x 9933 px ) }@ 300ppi. as you show in the example (this part is understood and tested ).

  • My concern is to be able to draw on a small screen on real measurements in cm, in or mm for a poster size bigger than A4.

So following your steps what if i do like this : If I take the example of an A1 poster and make the design on a smaller document @72ppi as explained on the video above taking the measurements in mm: -width 7016px/300ppi72ppi = 1683,84 px -height 9933 px/300ppi72ppi = 2383,92 px

1-Create a new document, using Print preset. Adjust the size manually to A1 @ 72ppi 1683,84 px x 2383,92 px (that a small size in wich i can design easily without zooming in and out )

2- Set the color mode to CMYK, (the color profile can be converted later to printers that requires SRGB like prihtful)

3-Now design poster, and save the AI file once finished.

4- Do File > Export As, choose a new file name, and set the file type to JPEG, use Artboards, and hit Export

5-When the export dialog appears set it up as follows: set color profile to RGB , ppi to 300 (set up at 300 brings to final jpeg output to 7016 x 9933 px/300ppi

6-The exported file i got is equal to 7016 x 9933 px/300ppi

so if we can get the same correct A1 jpeg px size/ppi by starting with a smaller size & 72ppi is that also correct to process that way rather than the conventional one you have stated ?

The main goal is to work in small canvas on screen and output the excat equal size of A1 as final result from what i have tested so far the final output is always correct. (i am aware if i use images that may be difficult to process that way as per used images resolution)

Any thoughts please. thank you

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  • 1
    Up scaling 72ppi to 300 doesn't nothing but degrade any raster content. You essentially stretch the same number of pixels to fill a lager area. That's not how PPI resolutions work. One actually wants a higher ppi value if working at a reduced scale. But... you may also may never actually need 300ppi for output. graphicdesign.stackexchange.com/questions/487/…
    – Scott
    Mar 26, 2023 at 23:35
  • Also be aware, Illustrator does not interpolate raster content.
    – Scott
    Mar 26, 2023 at 23:36
  • thank you @Scott. please have a look at this video Illustrator - Calculate File Dimensions and Resolution for Accurate Output - File Size Demystified. it explains what i am trying to do.
    – Yassan
    Mar 27, 2023 at 1:24
  • While that video is not really incorrect.... The issue arises when one tries to use pixels to define an output size (i.e. printed). Pixels are not a measurement for a print size. They never have been. Pixels have no size. If one were to open a new AI document at 12x12" or 30.48x30.48cm you would see that it starts at 864px, the correct size. Illustrator is not as dumb as that video would have one believe. In fact, AI behaves logically.
    – Scott
    Mar 27, 2023 at 5:44
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    So.. just create documents in Illustrator at their physical size - i.e. A2@ at 420 x 594mm. You honestly don't need to do all that math she's doing in that video. It's pointless and is only due to her incorrectly using pixels as a physical measurement.
    – Scott
    Mar 27, 2023 at 5:53

2 Answers 2

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You don't have to work out anything yourself. Illustrator is more than capable of making the output file the correct size if you use the correct settings to begin with. Do it like this instead:

  1. Create a new document, using the A4 Print preset. Adjust the size manually to A1, A2 etc, but input the size in mm. So in the example below, I started with the A4 preset, then I changed it to 594mm x 841mm, which the size of A1.

  2. Set the colour mode to RGB, ignore the yellow warning triangle, and hit Create. The warning is just to remind you that your document isn't in CMYK.

enter image description here

  1. Now design your poster, and make sure to save the AI file once you have finished.

  2. Do File > Export As, choose a new file name, and set the file type to JPEG, use Artboards, and hit Export

enter image description here

  1. When the export dialog appears set it up as follows

enter image description here

  1. The exported file should be the correct size in pixels and ppi. Check it by looking at the file properties

enter image description here

  1. If you want you can check that size to make sure. So the calculation is as follows: 7016px/300ppi=23.3866667" x 25.4 = 594mm

Notes:

300ppi is probably overkill for a large A1 poster, it's often enough to use 150ppi, however that's not what your printer has asked for. Also, the file size won't be massive or anything since your are saving as jpeg anyway. Should be absolutely fine to stick with 300ppi.

If you have already made your design by using a document intitially defined in pixels, it might be better to copy and paste it into to a print document as created using the above instructions to avoid any missteps. You may have to rescale/resize some of the content, although I can't be sure since I can't check what you've got.

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  • thank you for you answer please see my answer to my own post as it is too long to be posted as a comment.
    – Yassan
    Apr 1, 2023 at 4:54
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printful is asking for a jpg file at 300dpi SRGB for the prints

Let me start there. Sometimes employees only repeat mantras they do not understand.

Let me do a really fast recap of that number. You can skip this part if you want, or memorize it.

Typical lineature on coated paper for magazine-like prints is 150LPI and for the best interpolation on the RIP process, it is recommended to double that number, therefore 300PPI. The explanation contains several things. "Recommended", typical magazine print (size), coated paper. The magazine-sized print includes a viewing distance, so angular resolution, etc.

Note that the final resulting image has not 300PPI, now has 150LPI. And at 150 (units) it looks fine.

When using an error diffusion print, like any normal Inkjet based system, (plotters, digital photo printers) 200PPI has a final higher resolution, and it is almost indistinguishable vs a 300PPI print. You need a magnifying glass to notice anything, and even then you need to be picky about it.


Back to your question. There are a lot of topics...

If your poster is vector do it in vectors. If your poster is not vector... do some part in vectors.

Keep some elements like text and logos, in vectors. The vectors will remain vectors, regardless of A1, A4, or whatever A sizes.

But if your main image is raster: a photo, a 3D render, or a digital paint, you have two options.

1. A fixed number that simply works on your workflow.

A typical digital photo, and a number I Like a lot is 24Mpx. That is 6000px on the long side. I like that number a lot more. Let me spam another answer of mine. Billboard sized layout

But what will happen to your image is that depending on the final size it will be upscaled. To some extent, there is NO need to resample it. Upscaled means that you do not touch it when making it bigger or smaller, the number of pixels remains the same. Resampling means changing the number of pixels.

6000 pixels on the long side, on A papers, will give you these numbers.

enter image description here

181ppi on an A1 poster you will be viewing at some distance is perfect. An A0 print will be 128 PPI which is fantastic. If it is for a billboard 10mts although the pixels will be bigger, the viewing distances render those almost invisible.

If your computer can handle a typical 24Mpx image, if your 3D program can render that size; if your painting program can handle 6000px on the big size, it is a great starting point.

If your computer struggles to paint that size, try a smaller one. Try for example 4500px on the longest side.

Those are still good numbers.

If needed you can later upscale your image with some new fancy AI-powered resampler.

Then add texts and logos on a vector program.


2. You have some very specific conditions.

  1. You need to make art to be printed exactly on a given paper size. Let's be specific A3 paper. 42cm.

  2. Define if you need some specific bleeding. 3mm on each side. 42.6cm. (Did you notice the word specific?)

  3. Convert to inches. 42.6cm/2.54 = 16.7716in (I am keeping this in decimals for the math behind it)

  4. Multiply for the desired PPI resolution. 300PPI x 16.7716in = 5,031px as we do not have fractional pixels. Ok, that is the size of the raster document you need, a 3D render, a Digital paint, etc. (The size is a bit less than my favorite number 6000)

  5. When adding text, Make your document on Illustrator or Indesign or whatever vector software you are using. Define the bleed and paste your image. It will be exactly 300PPI.

  6. If you find out that you now need to use that image on a poster twice the size, again 150PPI is just fine, or resample it on an AI software exactly at 200%.

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