Problems exporting large banner image

IIRC, it is based on twice a 150 line screen, which was the most common prepress line screen at the time, and 300 ppi gave satisfactory results when printed...not pixelated nor soft.

Exactly right, Bevi. The rule of thumb was that an image's resolution could be calculated by doubling the value of the line screen. 150 lpi (lines per inch) was commonly used for better quality printing in magazines and books.

Eventually it was proven that more pixels don't always equal a better looking image on the page. There's a point at which more information becomes a case of diminishing returns, whereas too much information can result in a muddy or soft looking image. Many designers (myself included) settled instead on a resolution formula expressed as Lines Per Inch x 1.75 (instead of 2). For example, if your printer is using a 150 lpi screen, the proper image resolution would be around 262.50 pixels per inch.

Today, with the ubiquity of digital printing, the rules have changed again. Once more, I refer to my previous advice on this subject: talk to your printer first. Let him or her tell you how best to prepare your images for print. Hopefully, you'll get good results in the end. If, on the other hand, your job goes south, your printer and client won't be able to blame you for dropping the ball.

Bob,

Yes, that is a screenshot. All content, incl. the background image, is @ 300dpi (or more). Not sure what press it is going on - I assume something fairly new, obviously digital - I'm a bit short on details, just subbing in for a colleague on vacation.

I just rendered   the file again, using the background image at 100% at 300dpi - I realized it was even higher res image placed at 61% ... and it came out clean!

Thank you for your quick response.