Good question: The number of pixels required in an image is important because to consistently make too many pixels for the intended use is a waste of time and money. And high resolution images make phototextures look bad. Less of an issue since LightWorks uses many procedural shaders that adapt to any size.
Regardless of printer quality, an inkjet printer has an absolute resolution of 360 dpi. When printer manufacturers claim 2880 dpi, they refer to a routine in ink jet printing called "dithering" where successive layers of ink are applied to the page in those tiny "two picolitre" spits [you can see this happen if you watch a print head working] to make the impression of a continuous tone. The "overlap" of a 2880 printer = 8x360.
Most guys you ask for advice about this say 180 dpi in the file is adequate to describe ArchiCAD models of average detail. What we mean by "detail" is the finesse of the photo texture in the material. If you needed to show fine brocade in an upholstery fabric, stick to the 360. My experience is that users tend to make too many pixels relative to the resolution their materials support. The guy goes and makes a outrageously big rendering but when you look closely, the textures are blurry and videoed. Waste of time.
We have a similar discussion going on right now about antialiasing in LightWorks where the "Better" setting resolves edges best whie the "Best" setting resolved surface patterns best.
Another issue in imaging is "sharpness" of edges. Using a sharpening tool like Nik Sharpener Pro goes a long way to making even a high resolution image have more sharpness - the routine asesses the image for "Edges" and increases contrast along them. This makes a rendering have more depth, accuracy and definition without more pixels. Nik can be set to ignore surfaces so that textures stay smooth.
I use artificial sharpening in my photography all the time and when I do it right, the edge sharpness successfully exaggerates the detail.
Also, printer drivers also "sharpen" images in this artifical way and can fool the eye into thinking that excess pixels is the answer.
My recommendation is that 300 dpi is the most versatile size to work at since it is close enough in inkjet and right on for offset printing in color. The printer of my book asks for 300dpi images. For inkjet only, I still think that 180dpi is adequate if you apply a little sharpening through Photoshop's Unsharp mask tool or the expensive Nik Sharpener Pro. Post processing always improves an image.
There's a big time difference between 180 and 300. You want to test your system to see if the extra time, repeated many times over again in successive renderings is actually worth it.
Dwight Atkinson
