Size / resolution required for very large images


TPF Noob!
Dec 5, 2007
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I'm a web designer doing a site for a small car selling business, and they were asking me about designing some banner images for them.

But they want some really huge ones - about 18 x 12 foot I'd say.

Print really isn't a medium I'm so familiar with, so if anyone could outline the sort of size and resolution image we'd need for that, that would be great.

I use istockphoto quite a bit to get images for sites - the largest on there tend to be in the region of 3,500x2,300 px at 300DPI - so pretty big, just not sure about scaling up quite so huge!

Any pointers, greatly appreciated!

For starters, you will need REALLY BIG files for posters and banners in that size. I've been involved in similar projects and the company that was printing my material wanted a resolution of at least 150dpi of the images. The ones I was making were appr 3x4m (meters) in size so I needed images with a resolution ranging from 6000 to 8000 pixels in width/height.

A couple of the images I took with a Canon 30D actually looked okay scaled up even though the resolution was way too bad from the start. And for the other images I contacted a 3D visualization company and got practically photo realistic renderings (industrial products) in 150dpi and they looked fantastic.

Well, what I am trying to say is that you actually can use images with seemingly low resolution if the motif allows it and if the final result will be a backdrop or something people only will be able to see from a distance. A photo with soft tones and no sharp edges will be more forgiving than a photo with a lot of small details and contrast.
Also, if you are going 18x12 feet, it sounds more like a billboard printer rather than a high res photo printer. Because of viewing distance on some billboard printers, you only need 25ppi at final size. For the stuff we print, up to 5ft x 10ft, we require 150 ppi at final size. Others require 200 ppi at final size.

So, you need to talk to whoever will be doing the actual printing to find out what they actually need. You may be able to get away with uprezzing the file for something printed at that size, but if it will be viewed up close, you probably won't.

what is the differance in dpi and ppi
From Wiki:
Dots per inch (DPI) is a measure of printing resolution, in particular the number of individual dots of ink a printer or toner can produce within a linear one-inch (2.54 cm) space.

Pixels per inch (PPI) or pixel density is a measurement of the resolution of a computer display, related to the size of the display in inches and the total number of pixels in the horizontal and vertical directions.

I think the best way to think about it is that DPI is for printers and PPI is for displays.
I always say pixels so that I get people to look at the pixel dimensions of the image rather than them saying"it's 300dpi, that's huge" when infact the image is 4"x6"@300dpi which is crap(1200p x 1800p).

I always have to state, 150 @ final size, even then some people don't get it.

Also, I think of the digital file as pixels per inch and printed pieces as dots per inch.


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