Large format printing, a couple of...

Hi thanks for reading my post. and just a couple of questions regarding large format printing.



How big can you blow up a bitmap image and not worry about the quality degrading?



Say for example if you have a 300dpi 12''x8'' TIFF photograph, and you need it blown up to say 84'' x 56''. I have recently done this with a photograph and when I zoom all the way in to 100% I was suprised to see that it wasn't that pixelated (very high quality photograph I suppose). Which makes me think I will be safe come print time.



But another example I had was, I needed a 9''x6'' photo blown up to 54''x36'', the photo was 300dpi, but when I blew it up that big it looked pretty bad. So I went with another photo that was much much bigger.



I find it odd that some photographs will blow up great and some will not when it appears there properties are identical.



Also can anyone clear up my confusion on sizing a large document. I once created a banner that was 20ft x 10ft, because no program has dimensions that big I scaled it down 50 percent and told the printer to print it 200% to achieve my desired size. It was all vector art so it worked perfectly.



But let's say on something smaller, 4ft x 9ft with bitmap images. Is it common to scale down a document of that size? If so, how could you tell if a photograph would blow up with proper quality? OR is it more common to create the document (4ft x 9ft) in Indesign at the full size, so that what you see is what you get?



Thank you very very much

Kevin
Large format printing, a couple of...
Blowing up a bitmap is simple: double the size, halve the effective

resolution. The bigger you make it, the worse it's going to look.



OTOH, a banner stretched across Main Street is going to be viewed from a

distance, so it probably doesn't really matter.



It's quite common to scale banners down, but you should ask your printer.



--

Kenneth Benson

Pegasus Type, Inc.

www.pegtype.com
Large format printing, a couple of...
300 PPI is not necessarily the most important aspect in most respects. Was it a jpeg? If so, how much compression was used? Was the image upsampled to get it to the size and resolution it currently has?



These are important factors in image quality. If the image is crap to start with, it won't get better when you print it big.



I used to work in a large-format output shop and we routinely asked for 150 ppi at print size, but as ken points out, viewing distance makes a large difference. I once printed slightly-larger-than-life people for wallpaper in a retail store. The viewing distance was typically at least 10 feet, and the resolution at print size was under 75 ppi. They looked fine for their intended purpose.



Peter

Hey thanks a lot for the info, and that is good to know about ppi and distance, also if I half the resolution it will bring the whole file size down considerably. But...



The output is going to be a stand up billboard, 4ft x 8ft. Because it is going to be standing in the middle of a big lobby with hundreds of people walking by it, it will be viewable very close, say 1-3 ft away at least. I have seen bad pictures that were blown up for signage and the result was very poor, even from distance....Is halfing the resolution still a good idea?



Thanks a lot...

You missed the point there. If you make the image twice as big, the resolution is cut in half. It's an inverse-ratio thing. You DON'T want to reduce the resolution before printing unless it's way too high.



If people are going to walk up close to this, you really will most likely want 150 ppi or more AT THE PRINT SIZE, which means you should start with an image captured at 300 ppi at 1/5 the size, or around 9'' x 18'' (for your example). If you start with a 4 x 6 it should have been captured at 2400 ppi. And you want it captured as a high-quality jpeg, or (better) a TIFF or PSD.



Peter

%26gt; Is halfing the

%26gt; resolution still a good idea?



I wasn't clear. I meant that when you double the size of a bitmap, the

effective resolution is cut in half. For instance, if you start with an

8'' wide photo at 300 ppi and blow it up 200% (to 16'' wide), it will now

effectively be 150 ppi.



I didn't mean that you should cut the resolution. Quite the opposite. If

you're blowing up bitmaps you want to start with the highest resolution

you can get.



--

Kenneth Benson

Pegasus Type, Inc.

www.pegtype.com