Preserved Topic: Making large posters

I've always wondered how large posters are made. Like movie posters. What size of image would you have to start out with for something that large? Is there a special print method that enlarges a relatively small image without pixelating it?

Just curious. Print media is something I know *nothing* about.

I've had some experience with a Roland CamJet CJ 500.
It will print up to 48" wide to any lenth at 1200 dpi 6 colour Hexachrome,
but depending on the distance involved for viewing, 720 dpi works
fairly well.
You usually should start out with a fairly high res image like a photo shot in medium format or at least 300 dpi image in PS.

It's similar to regular desktop printing in that the quality you start out with, like high res scanning and high res images in PS will usually give better results rather than resampling a small image which will give major pixelation on output.

I've worked with image files as big as 250 megs in order to get the size and quality needed to print on this equipment.
I'm fairly new to this process but I'm sure Steve could elaborate more regarding image size and quality to produce high quality posters.



[This message has been edited by kromaZ (edited 04-28-2001).]

Try Genuine Fractals...demo version at 206.63.152.155/

Demo comes with 20 full function uses. Photoshop plug in.

Highly recommend this as a true lossless way to enlarge an image. I went up 136% with 20 meg files. Amazing. Try to do the same thing with Photoshop alone and you will be disappointed.

Serious tool for print professionals.

Hey Krets! that was my question! ggrrrrr




~Vp~

Yah, posters are one thing, but I've also done a lot of magazine ads at 100 lpi or 133 lpi (lpi = lines per inch, as in 4/c process printing, CMYK) Basically, you want to find out what the lpi the piece will be printed in and multiply it by 1.5 to 2, that will give you the target dpi (dots per inch, 'natch). So, let's say you have an image in a magazine, it will be 8" x 4" at 133 dpi (pretty high quality!) So the pixel size of my PSD file will be 8 x 133 x 2 = 2128 px wide, and high is 1064. Since you usually want to do this as a CMYK instead of RGB, you end up with 4 layers of colors instead of just 3, a file like this can grow and grow on you, heh.

That hypothetical movie poster, the first question is "will this be a limited run using a digital print, or a large print run which will be done on a litho press using 4 color process?" If the latter, follow those rules laid out above, if a digital print you'll need to do things differently for each printer usually.

Your pal, -doc-

Okay, so on a related note - how come I can't get the nice bright vibrant colors using CMYK mode as I can with RGB? Is there something I'm not doing??

Well, DL, that's a whole mess of dialogues there, to come up with that answer.

Are you talking about once their printed?
On screen?
What color management are you doing?

The guidelines for a quality factor of 1,5-2 is true for most things that are printed, however once you start making really big images, that can often be lowered. Even when the lpi it is printed in is a bit lower than usual.

I think the biggest images I have worked with myself was a series of pictures that was to go on the side of a truck. They were probably ten feet high, and if I remember correctly, I used a resolution of 100 dpi.

DL, that is because certain colours are impossible to create by just mixing the cyan, magenta, yellow and black. That is especially true for more vibrant colours. The most common solution to this is to use special colours, like the Pantone colours. Then you can get whatever colour you want, for instance on a logo or something. The problem with this is that it makes the printing more expencive, since you will print with five colours instead of four.
Here is a picture that I made for my company website:
sorry about the Swedish. Of course the colour space is really 3D so it i hard to represent graphically, but the blue line is supposed to be the range of the screen, and the red range is that of the press.
How big that red range is differs from press to press. On a press for newsprint it is very small. As you can notice when looking in any daily paper.
ICC is a tool to make the translation from the bigger RGB colour space to the smaller CMYK colour space. What is usually done the is to print a sample, and then the colours on the output are measured. Therefore, if you always use a certain printer, it is good for you to have the profile for the specific press your work will be printed on. That way you can simulate exactly what it will look like by using the ctrl-y command in Photoshop.
So, If you are talking about the CMYK picture you see in the screen in photoshop, then it matters what CMYK profile you are using.
One important thing to notice on the image above is that at some places the CMYK range is almost as big as the RBG range, and for certain RGB ranges it is evne bigger in some colours. So by using the wrong RGB colourspace in photoshop you could actaully limit the colours more than the print would do, and thereby loosing out on colours that really could have been printed. One RGB colour spaces that is particularly small is the sRGB. So if you do print job you really should change that. Colormatch and Adobe RGB are two colour spaces that are somewhat of a standard in the printing industry.

But none of thse things really matters unless you have your screen calibrated, and are using the right sort of lights around it.

Oh, and some of the newer CMYK printers on the market us 6 or 8 colours instead of 4. Usually the extra colours are lighter version of the CMYK colours. This enables the printer to get a bigger range in what it prints.

When I left the printing biz we were just experimenting with 7/c process printing, where we augmented the CMYK color range with RGB colors, which allowed us to hit some of those impossible colors like electric green and such. The presses that did this kind of printing were *way* expensive though, which meant that the prints were crazy expensive too!

I've still always held to the 1.5 times the line count to get my DPI, even with bigger pictures. We used to do big banners for outdoor use, and actually did a few trucks too, along with a few billboard jobs. The thing with big prints like this is you don't *want* a high line count, you may get more details but you get flat looking images when viewed from far away. Billboards we printed with a line count of 15-20, which can give you dots about the size of a pencil eraser, strange to see from up close, but crystal clear from a distance.

Your pal, -doc-

Doc, I decided, because I'm one of those irritating print folk, that 2x the linescreen works better.

Yah, I usually insist on 2x dpi too, but sometimes when the image is absurdly huge and the deadline is yeatserday you gotta make allowances. Or at least I do, heh.

Your pal, -doc-

You mean you feel you can actually see the difference between a picture in 1.5x and one in 2x?

I like to use 2x also, just in case the client change his mind about something, and want it a bit bigger than planned from the start.

just being curious...