How Do I Prepare Images for Digital Projectors?

[anonymous]

I was wondering if anyone has done any tests of digital projectors and preparing images for projection? Or if you might have any resources you could point me to?

The situation is that I’m getting involved in some local camera clubs and for their meetings and competitions they require 1024x768 images that get projected to around a size of around 152x114 cm. And then the commentator stands right up next to the screen and comments that every image lacks sharpness. I’d like to give them some reference as to what should be expected in this situation and what distance the commentator and judges should view these projected images from.

Thanks in advance for any direction on this.

[McQ]

One could actually use the last two calculators I provided on the page about digital photo enlargement to first back-calculate the minimum viewing distance (based on 20/20), and then for that distance one could apply the appropriate sharpening (by calculating the PPI projected on screen at that distance/resolution).

Just by crude estimates, for your scenario this would come to a viewing distance of 15 ft for someone with 20/20 vision (when projected to ~150cm max dimension). At that distance there would be roughly 18 pixels per inch.

This calculation is actually in part based on an old Adobe white paper on sharpening from a long time ago. Even though it was intended for print enlargement, it should follow that it applies equally to projection images. The only difference might be that some projectors soften the image more than others (DLP vs Lcos vs LCD, etc), so you may need to over-sharpen a bit to compensate. Hope this helps.

[anonymous]

Thanks! I will try out the calculators and pass along the information to the group.