Exporting PNG files with a specific resolution (pixels PPI) from Illustrator

[Dejan31773612ntt5]

Hi, 

Here is a question regarding exporting files from illustrator in a specific resolution (pixels and ppi).

1. I choose to create a "New File" in Illustrator. 

2. I choose the resolution in pixels (in this case 4134 x 4724).

3. I choose Raster Effect "high" (300 ppi). 

4. I Create a artwork and want to export is as a PNG. 

5. I click "Export" in Files and "Export As" as PNG. 

6. I choose to export resolution "High" (300ppi) the same raster effect I used when I created the file. 

7. The file that is exported png file that is created has gone from 4134 x 4724 to 17225 x 19683 pixels. That is rougly the same ratio as between 72 (ppi) and 300 (ppi) which is 4.16666667 times the pixels. 

Why is this? Shouldnt the file be 300 ppi and 4134 x 4724? is ppi 72 some sort of default in illustrator and if I choose higher ppi it will increase the pixels equally. I would really need to understand the dynamics here since I want to create files in illustrator that I want to export to photoshop and I want them to have a specific resolution i pixels and ppi when I open them in photoshop. Now when I open the file it will have the right ppi (300) biut it will have 4,16x the pixels (17225 x 19683). 

/Dejan

[Ton Frederiks]

Illustrator is a vector application and is resolution independent.

What you see for resolution is for raster effects.

Because pixels do not have a fixed size, Illustrator will assume that a pixel has a size of 1/72 of an inch, just like points.

If you export at a resolution of 72 ppi you get the exact amount of pixels you have specified for the size in pixels/points.

If you increase the resolution on export Illustrator will add additional pixels so that the dimensions stay the same but the amount of pixels in an inch will be increased to fit in the same space.

You can check that by placing the image back into the file that created it. Whatever the resolution you used for exporting, they will all have the same dimensions.

So export at 72 ppi to keep the amount of pixels. If you want to have that amount of pixels, but change resolution, use Image Size in Photoshop (or Apple's Preview) to set the resolution without resampling.

[Dejan31773612ntt5]

Thanks for clarifying!

When I create a new file in illustrator what is the difference in creating 72 ppi or 300 ppi for raster effects when I will export in 72 ppi? Does it make any difference? Should I always create 72 ppi and why is there an option for 300 ppi in that case? Is this for something else than exporting PNG for example?

The second thing is that when i open the file in Photoshop it will have the right pixels but it will be in 72 ppi and I want it to be in 300 ppi. If I go to image size and change resolution to 300 ppi from 72 it will also increas the pixels by roughly 4x and I´m back at square 1 with a document that is 4x higher in pixels than I initially was out for. 

Sorry for all the confusion and many thanks for the help 🙂

/Dejan

[Dejan31773612ntt5]

I can change the resolution to 300 ppi and then change back the pixels to the initial resolution manually that was 4x lower (from 17225 x 19683 to 4134 x 4724 pixels). Will this affect the quality? Then I will have a file that is 300 ppi and 4134 x 4724 in pixels, but as mentioned will this affect the quality of the picture?

[Ton Frederiks]

Resampling (increasing or decreasing the amount of pixels) will always have an effect on quality.

Always export the amount of pixels you need.

[Ton Frederiks]

Changing the Raster Effects Settings will change the way the effects are calculated.

Your second question about changing the resolution in Photoshop, if you turn off Resample, no new pixels will be generated, it just change how many of the current pixels must fit in an inch. It changes the size of a pixel (a pixel does not have a fixed size) without changing the amount.

[Dejan31773612ntt5]

So what would your reccomendation be? How would you do in my case for minimal quality loss? 🙂

/Dejan

[Ton Frederiks]

If you want to keep the amount of pixels that you specified when creating the document, use 72 ppi on export.

If you are intending the artwork for printing, increase the ppi (or use PDF).

[Dejan31773612ntt5]

Yes I intend to print on apparel and posters. So in this case you would preffer to export as PDF or SVG for example? The problem is that the print provider wants to have 300 DPI and has a max resolution i pixels that creates this problem for me. And they dont take PDF or SVG only PNG 🙂

/Dejan

[Ton Frederiks]

If they require a certain amount of pixels, create a document with that size in pixels.

Don't worry about the resolution, that is just metadata telling how many of the pxels have to be squeezed in an inch, it does not change the amount, it just changes the density.

If you want to change the ppi info after exporting, use Image Size in Photoshop and turn Off Resample

[Ton Frederiks]

Sometimes working for web or devices, 144 ppi is recommended for higher resolution displays., this will use the double amount of pixels on your phone or computer screen.