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8ft x 4ft poster...but how many dots per inch for images?

Forum|Forum|16 years ago
June 15, 2009
3 replies
120331 views

I've read a online somewhere a while back that the bigger the end product, the less the amount of dots per inch needed. is this true? if so, when do I start changing from 300dpi for A3 sizes to smaller DPI's on larger size prints?

is there a way to calculate this? I'm always thinking it might for spending less ink on the larger size prints, etc

and what should I use for a 8x4ft poster when:

1. people are gonna see it up close

2. when the closest they get would be about 4-5 feet away

with this particular poster, people are gonna be up close.

thanks for any info

[Posted June 2009 and now locked. Please start a new thread.]

Correct answer

Talk to the company who will make the final print. They will tell you what is best for their equipment. I use a company that makes display booths for conventions and such. They use 100ppi. the images look great even up close.

Always talk to the printer.

E

Eugene Tyson

Community Expert

The physical size of the final print has no impact on what resolution you use. You only need to know the viewing distance.

The formula is

(working in inches)

1/((distance x 0.000291) / 2) = ppi

Seen as you're viewing from 4 feet away (48 inches)

You need

1/((48 x 0.000291) / 2) = 143 ppi for final size

And you wouldn't work on full size. But the resolution of your images need to be equal in proportion to the final size.

So say for example you take your 8 feet height (96 inches).

Now start a new document at 1/10 that size, that's 9.6 inches for the slow ones out there.

So your actual document size is now 9.6inches x 4.8 inches.

So the resolution of all your images that you're using should be placed @ 1430 ppi minimum; at that scale.

T

Thali-HooAuthor

Participant

Hi guys,

Thanks for the responses!

Is it typical to work at 1/10 or 1/4, etc for this kind of project? I've always worked to scale on previous (but much smaller) jobs with Indesign. working to scale at the moment isn't causing any slow-downs at all PC wise. so that's good. but I would like to know if this is how most of you work?

Eugene, very helpful info! but with your technique wouldn't the file size increase drasticaly? (or it's weighed out by the fact of using a smaller size/higher dpi image?) thanks for your great explanation by the way!

It's being screen printed as far as I know. standard process colors only.

Was DYP

Inspiring

I print many banners or posters like this. I always ask that it be done at full size at 150dpi.

O

osgood_

Legend

You wouldn't produce artwork for a poster 8ft x 4ft at s/s size would you. It would be too large for the screen, the file size massive and moving around the artwork would be a nightmare.

I would produce artwork for this at a quarter of the size 2ft x 1ft and still use 300dpi.

Also you don't say if this is going to be screen printed or digitally printed. Digital printing produces no dots.

Peter Spier

Community Expert

osgood_ wrote:
... Digital printing produces no dots.

I'm curious why you would say that. Many digital printers use conventional halftoning, and many more use some sort of stochastic or FM screening algorithm that don't show a traditional screen spot patterns, but all of those use dots of ink to do it. As far as I know the only digital output that doesn't produce dots is a pen plotter or cutting plotter, and I don't think you'd find either of those in use on this sort of job.

Peter

Jeremy_bowmangraphics-DQuh1B

Inspiring

P Spier wrote:
all of those use dots of ink to do it.

...And I would have thought that modern inks work so efficiently as "filters" (cyan ink filters out red light, magenta ink filters out green, etc.) that differences in "degrees of pigmentation" would have to be realized by differences in area of paper covered -- in other words, by different sizes of dots.

Jeremy

A

Anonymous

Correct answer

Talk to the company who will make the final print. They will tell you what is best for their equipment. I use a company that makes display booths for conventions and such. They use 100ppi. the images look great even up close.

Always talk to the printer.

Peter Spier

Community Expert

The correct resolution is a compromise based on printing method, size and viewing distance. As you get further away resolution can go down (think billboards -- no way anyone would be able to see individual dots even a few inches across from the typical hundreds of feet they are viewed). The 300 ppi rule of thumb is calcualted fro an "arm's length" viewing distance. How close is close up on this poster? You may not be able to get as much resolution as you'd like simply because the file will become so large you can't handle it.

I used to work for a large format output service. 150 ppi was our typical request for poster-size pieces, based on the assumption that they would be viewed from a distance sufficient to see the whole thing at once, or 4 to 6 feet. I printed wall-size images on occastion at around 75 ppi, and could have probably gotten away with far less.

Talk to the printer, and look at some samples.

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