Yes I understand what you meant by the pixelated display, I have came across them sometimes. IMHO that is plain low quality work, but then again, most of these fellas probably ain't interested in the artwork and more about sales. The displays just serve as decoration or secondary information. Their first hand information is still face to face talk with the customers.
When you now mentioned it's a mixture of text and photographers, the situation changes. I find myself not particularly affected by soft images, but rather soft text. Because text are vectors and images are raster, I tend to be more relaxed on images quality as I know with such large poster, you can't expect images to be sharp unless the images used are dedicated for that size of poster and hence the photographer would have tried his/her best to produce images that suit the usage without cropping and then interpolate enlarge.
I suppose the way to produce such poster is using tools like Adobe InDesign, successor to previously PageMaker. You placed your images and text together. When you send such a file or its output in TIFF to the printing house, they will advice like 250dpi to 300dpi, but that doesn't mean your image has to be that fine. Your text is better to be at 300dpi, that means the whole file (if it's a raster), will need to be at 300dpi. That's the target dpi and also the container dpi. Images inside this container can come from source of 150dpi and resample to 300dpi. Here the images will look softer, but with good interpolation algorithm, it can look smooth depending on how much it interpolate and whether the source image contains largely graphical contents or tone contents.
Based on the size you mentioned for mobile poster, I won't be surprised a 10MP camera can do the job just fine. Visually nice images don't just comes from high pixel count. Noises in the image also plays important factor. If your image is largely noise free, it looks good when enlarge, if not the noise will also enlarge at the same time. I say human perception feel disgusted with chromatic noise versus luminosity noise. A good NR software will help you to achieve good output without going for high DPI.
Ah, well. It's more for those mobile road show (e.g.: credit card road show) and the content could be a mixed of photos with words as advertisements. Of course it's meant for people to view from a distance but also likely for others to stand (or sit) close to the banner/poster. Not yet having to tap into this line of work, but I thought it would be good to know.
How large are u printing anw?
