PPI of jpg/png and something about vectors

[Nadan5]

Hello people,

I need some help from you when it comes to PPI of images and importing vector images.

Long story short, what I want to know about PPI is this:

1) I'm making a student magazine and ALL of my images look really good in InDesign and in Exported PDF (print) document that I view in Acrobat Pro, but when I go to link panel in Id they are something like 150 effective PPI, others are something like 225 e PPI, and a lot of them are more than 300 e PPI. Do I need to worry about those images that are less than 200 effective PPI? Do I need to worry about those that are below and above 300 e PPI haha?

I've read somewhere that some printer shops kind of require images to be 300 PPI, but i've also read it's a myth. I really hope it's a myth, otherwise it's really frustrating to nitpick about that, especially when I need to compromise between graphic quality and content quality.

Btw, I'm not able to talk to a printer shop because I still don't know which one is going to print (it's a public tender job).

2) Is there any issue if I import vectors (vector images) into InDesign in form of PDF? I don't really know which is the best way to do so. I usally open Illustrator, make something, save as PDF and then import it into Id? That way it acts as an image, just in vectors. I mean it's pdf when i go to link panel, but it looks just like pure picture in Id and Acrobat.

[BobLevine · Accepted solution]

If it’s going to be printed commercially on a press then I would certainly advise you to keep everything above 225 or so. Even at that, it will depend on the content of the images.

300 PPI is pretty much an old wives tale and has been passed down from one generation to another but that doesn’t mean your job won’t be rejected by some cheap online printer that never lets a human get near your job.

I’d love to give you more info, but the best advice you’ll get is to talk to the printer.

As for the vectors, when you save an AI file, you must choose to have the PDF compatibility enabled. This is the default. When you place the AI file, you’re actually placing the PDF portion of the file, so saving as PDF from Illustrator doesn’t change a thing as to how the file read by InDesign.

[Nadan5]

BobLevine Thank you very much! Anyways, what do you do when you find a picture that is born to be placed in a certain spot in page layout, but it just doesn't have proper PPI no matter what you do? Is that just a graphic designer life or is there anthing that can be done about it?

teachbit​  Thank you very much!

rob day​ Thank you very much! Btw, I don't place raster/bitmap image in Ai, I make vectors with pen tool and what not.

[BobLevine]

What do I do? The same thing I would advise you to do…find another image. There is simply no magic button to increase resolution.

[teachbit]

PPI is the acronym from Pixels Per Inch. It is a unit of measure used to quantify the number of pixels found on a square inch surface. To get a clear idea of what it means, imagine a square inch that’s divided and organized in a grid of cells. Each and every cell in that grid has a pixel inside. The number of cells inside the grid, also known as pixels, tells you the PPI.

Usually, the Pixels Per Inch value is used to measure the pixel density of displays, such as the monitor you have on your computer or laptop, on your TV screen, and on your smartphone.

However, PPI is a term that’s also loosely used for describing the pixel density of scanners, camera screens, or images that are stored digitally. Some people use PPI even for telling you the resolution at which printers print on paper.

While PPI refers mostly to screens and digital elements, DPI is a term that’s used correctly when you refer to things like printed paper.

The resolution and the quality of a printed paper are rightly measured by the number of ink dots in any given character or drawing. Both DPI and PPI measure similar things, but dots are not pixels, and pixels are not dots, so DPI is not the same as PPI.

However, it has become commonplace to refer to PPI as DPI, even though PPI refers to input resolution. Industry standard, good quality photographs usually require 300 pixels per inch, at 100% size, when printed onto coated paper stock, using a printing screen of 150 lines per inch (lpi).

In reality, with a good quality digital photo - 200 PPI will achieve photographic quality in print - so even if they ask for 300 PPI, if you have a photo with 200 PPI it will most likely print just fine as long as it is a good quality.

Vector images. You can save you illustrator files as .ai Format. The quality is the as pdf. Actually, as you save the file in Illustrator in the native Illustrator format, Illustrator will include a pdf in the file.

[rob day]

InDesign doesn't change the pixel dimension of an image when you place and scale it, so if you change the image's scale in the page layout, the pixels are scaled not resampled. The scale determines the effective output resolution.

If you place an image with an Actual Resolution of 300ppi and scale it by 200%, the pixels are now 2x larger and the output resolution will be 150ppi.

If you place an image in Illustrator and save the file as an AI or PDF, and then place that file in InDesign, the same rule applies. The image is still a bitmap (not a vector) and will have an effective resolution relative to its scale. You can't get the resolution of images inside of AI or PDF files from the Links panel.