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

[Thali-Hoo]

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.]

[Guest · Accepted solution]

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]

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.

[osgood_]

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]

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]

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

[Peter Spier]

Stocahsitc screens work by varying the density, rather than the size, of the dots, i.e. they put a lot of tiny dots in a small space to make a dark color, or just a few for a lighter tint. This tends to reduce interference patterns, I think, as well as help with drying.

[Eugene Tyson]

Some notes I have written down here are:

With Stochastic Printing you get:

Good points

No Moire patterns

Print 4+ colours in one pass

easier for touch plates

No jagged edges in screens

Shadows have more detail

Continous Tone

Better reversed prints

Bad Points

Can be hard to proof

You can get too much detial esp with skin tones

If it's wrong on press it's very noticeable

You need a lot of control

20%+ Dot gain

Small dots are hard to handle on press

[Harbs.]

Dye sublimation (photo developer) equipment doesn't use dots...

Harbs

[Jeremy_bowmangraphics-DQuh1B]

Harbs. wrote:

Dye sublimation (photo developer) equipment doesn't use dots...

Assuming that dye sublimation still uses dyes, I wonder how differences in amounts of dye are realized?

I know very little about printing, but I'm guessing that a "perfect" dye/ink would be one that absorbed exactly the right wavelength(s) of light, letting other wavelengths through, so the thickness of the ink layer would not matter. Hence even a large bottle full of "perfect" ink should still look remarkably light and clear.

Since the thickness of a layer of "perfect" ink would not matter, the only factor that could count is the proportion of the paper area the ink covers. Hence the necessity for some parts of the paper but not all to be covered. Hence the necessity for shapes of some sort such as dots, even if they are microscopic.

Jeremy

[Eugene Tyson]

Sublimation occurs when a substance transitions between a solid and gas state without being a liquid stage. Dye-sub printers heat the printing dye until it is a gas and then that diffuses onto the substrate and becomes solid.

[osgood_]

P Spier wrote:

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

I meant inkjet of course, not digital.

The size of the poster 8ft x 4ft is going to be printed on a large format injet printer or in sections (screen printed) but that maybe a specialist area now.

[Eugene Tyson]

This is getting too confusing.

Is it being

1. Screen Printed
2. Digitally printed
3. litho printed
4. fm screening
5. am screening
6. dye sub printed
7. ?

Being viewed 4 - 5 feet away, 150 dpi will do at finished size.

[Peter Spier]

osgood_ wrote:

I meant inkjet of course, not digital.

Inkjets definitly produce dots...

[osgood_]

P Spier wrote:

osgood_ wrote:

I meant inkjet of course, not digital.

Inkjets definitly produce dots...

I don't look at digital or inkjet in the same way as conventional litho/screen. Your right, dots are present but not in the same sense in my opinion....more like pin-points.

[Eugene Tyson]

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.

[Thali-Hoo]

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]

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

[osgood_]

Was DYP wrote:

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

hummm....I would'nt want to work on an 8ft x 4ft banner at s/s size on a 21" inch screen, each to his/her own I guess.

[Was DYP]

hummm....I would'nt want to work on an 8ft x 4ft banner at s/s size on a 21" inch screen, each to his/her own I guess.

I don't see where that would make any difference in working with the file, but it sure makes it convenient for printing. I work on lots of full size banners all the time. The only time a make them less than full size is when I am working on something bigger that 18' which is IDs maximum size.

But doing them half size at 300 dpi is fine to. You just need to be careful that your graphics are not to low a resolution or you will be in for some surprises from IDs output, especially if you trying res-up when printing.

[Eugene Tyson]

Don't forget the max size of a PDF is 200 inches.

So sometimes you have to work to scale and let the printers rip upscale the pdf or final file.

[Dov Isaacs]

No, the 200 inch by 200 inch limitation was removed several versions of PDF ago! What InDesign will produce is a separate issue!

          - Dov

[Eugene Tyson]

That's good news. But some of us haven't evolved to later versions. I'm still on Version 7. And I know some printers who still use 5 and 6.

[osgood_]

Was DYP wrote:

hummm....I would'nt want to work on an 8ft x 4ft banner at s/s size on a 21" inch screen, each to his/her own I guess.

I don't see where that would make any difference in working with the file, but it sure makes it convenient for printing. I work on lots of full size banners all the time. The only time a make them less than full size is when I am working on something bigger that 18' which is IDs maximum size.

But doing them half size at 300 dpi is fine to. You just need to be careful that your graphics are not to low a resolution or you will be in for some surprises from IDs output, especially if you trying res-up when printing.

I was really trying to suggest its easier to move around on screen if the artwork is not size for size.

I guess everyone has their own particular way of working. I don't even produce A2 output at s/s size. I'll do that at either A4 or A3.

I agree with the low res graphics. I don't seem to have any issues with just supplying 300dpi for any sized output to be honest. I've produced largish exhibition stands and A4 hand-outs from the same file. Seems to work ok for me.

[Eugene Tyson]

Well you can work full size at 150 dpi - to round it up.

The file size would be the same - should be anyway.

For screen printing they have a thing called tpi - threads per inch.

The mesh count for screen printing can range from 85 TPI to 355 TPI.

This has two things going on, the thickness of the ink deposits and the size of the halftones that can be printed.

85 - 110 TPI gives more space between the threads and this gives a thicker deposit of ink when printed.

Typically the mid range of TPI - around 200 - 250 - would be used for halftones of an acceptable nature.

Higher mesh counts, up in the 300 - 355 range have smaller thread diameter and used for halftones.

So:

You may want to make sure your printer has screens that can be printed in the higher range of 300 - 355 TPI to create halftones.

When you know this - the same still applies, how far away you have to be from the halftone for it to be visible.

And the previous calculations still stand.