What is the difference between ppi dpi and lpi

I even saw a Trendsetter at dpi pushed to expose lpi jobs, sound weird, the dot structure is bad indeed star shaped or anything but round or square but they say offset sheets are sellable as a final product. IMHO it's only true for average quality jobs. I'm so glad you brought up this topic. On my site I have an article on just this subject.

Graficworx - Honolulu, Hawaii It by no means covers everything, but it should give you a general idea. J Well-known member. For example, first you say: "Dots per inch DPI are tangible marks on media, and is a measure of the resolution of a printer.

Then you say: "In offset printing, to print at LPI, the input resolution needed is dpi. That appears to say that the scanned image I need to print at lpi needs to be dpi. Which is ridiculous. It's not at all ridiculous. The DPI values listed are what is required by an imagesetter or platesette to produce a halftone image.

If you input a DPI image the RIP Raster Image Processor interpolates the remaining dot pattern and sends the output device the correct image for whatever line resolution it's set at. The printer driver, which takes the place of a RIP, must do the same thing, and interpolate the data the printer needs.

Maybe my post was on the more technical side of how an output device works, but I assure you it's correct. Click to expand The printer driver, which takes the place of a RIP, must do the same thing, and interpolate the data the printer needs Thank you very much all for such informative posts. I shall study more about this topic.

A number of people here have offered opinions and self-made rules, as well as a divergence that includes relevant information about PPI. Let me try to provide some factual answers, because it's worth a detailed explanation of how all three of these numbers interact.

I've taught a lot of printers and graphic designers how these three figures interact in a print environment for nearly 20 years now, so I'm willing to take a shot. Be forewarned that this will include some math. But I'll provide answers as I go through this explanation that should reduce the pain factor dramatically.

First, let's break these abstract numbers into simple mechanics: Pixels, Dots and Spots. Pixels are magical things. They are what are input into your computer prepress system when you bring in a digital image through a digital camera, a scanner or most types of digital image files. They're also what you see when you look at digital images on the computer screen.

The great thing about pixels is that they're square, so they fit together perfectly and there are no gaps in the information. The only problem is, you can't print a pixel. You have to translate that information into Output Dots and Printer Spots halftone cells to translate those pretty pixels into printable pictures. Output Dots-DPI. This is the resolution of your output device. Name required. Email required. Please note: comment moderation is enabled and may delay your comment.

There is no need to resubmit your comment. Notify me of followup comments via e-mail. Written by : Amitash. User assumes all risk of use, damage, or injury. You agree that we have no liability for any damages. Summary: 1. Author Recent Posts. For commercial offset printing , images have to converted electronically or by traditional litho film and halftone screens to a pattern of dots, with a resolution measured as so many lines per inch.

This step forms a grid of equidistant dots of varying sizes on the printing plates, each dot attracting ink and simulating a specific percentage of solid color. The resulting printed images are called halftones. Higher quality printing uses finer screen values. Finer dot patterns can be used under ideal conditions. Silkscreening and rubberplate printing for printing directly on uncoated corrugated boxes may use very coarse values with very visible dot patterns.

In addition, there are stochastic screens that use a random pattern to create a less visible dot with offset pinting. You can certainly use images that are sampled at somewhat higher rates. But there is no benefit. Vector-based images, such as those created in Illustrator, or most editable fonts, are based upon mathematical curves, not pixels. As such, they are infinitely scalable, and will be absolutely sharp at almost any size. But when they are finally output, these vectors are still first converted to to the finite elements of the desktop printer or commercial press, just as pixel-based images are.

This is the usual specification for resolution of output devices , such as desktop printers, film recorders, RIPs imagesetters , and again computer monitors. For computer monitors and film recorders, there is a ratio between the ppi of the digital image file and the dpi of the output device.