I got a call the other day from a client asking whether taking a still frame from a video (aka known as a “frame grab”) would adequately work as a source for a printed image.

In the days before HD, the answer was almost always, “not unless a grainy shot will work for you.”

300+ dpi (dots per inch) is the standard for quality print.  Television / video is rated at the equivalent of only 72 dpi.

But what about an HD source, as this client’s tape was?

HDTV turns out to be only 72 dpi as well, but the other enhancements of the HD process will allow for a higher quality frame grab. 

So, in short, the HD still frame should work fine for a printed brochure; however, blowing it up to poster size would not be advised.

OK, what’s going on here?  If HDTV is also 72dpi, what exactly are “those other enhancements” that make it look better?

I asked one of our Video Labs multimedia experts, Juan Carlos Elizalde, to help explain.

DPI (again dots per inch) is a measurement of quality in digital imaging that can be tricky, since the measurement was first used for print quality, not relative to video.

DPI is used to measure how many dots of color or image can be placed in a 1″ line.

Since LCD screens have a 4 color system to display an image, you can’t really use DPI as an adequate comparison measurement.  Video Resolution is better interpreted in lines, or frame size.  Standard Def TV is 720 x 480 lines, horizontal x vertical. 

HDTV is 1280×1080 for 1080i screens.  Because of this, the HD quality is better.

But another factor is that the coloring differences between SD & HD screens.

Standard definition is based on RGB 256 coloring, which means that the TV can interpret 256 x 256 (65,536) colors when a dot (now pixels in the digital age is displayed).

HDTV on the other hand can interpret millions of colors, actually 2 Megapixels (2,001,280), consequently making HD images look better also because of color depth perception and adjustment to 3D imaging.

To further explain, let’s say you have a picture of a tree in standard def.  The monitor can interpret the tones of green in the leaves and branches only until it hits its maximum limit of coloring.  The rest of the dots will be filled by the screen with the closest color in the realm to it.

Meanwhile, with that same image in HD, the range of color is virtually limitless, which allows the tree to appear with more detail and overall better quality.

Still, as said above in the short answer, while the HD frame grab will be better than SD, and it will be fine for a brochure, it will indeed be grainy if “blown up” to a large poster.  While we are often “blown away” by HDTV, in reality, when a still of it is printed, one can see its limits too.

Hope that helps!  As always, your comments are most welcomed below.

Contact David Ryan at dryan@videolabs.net or Juan Carlos Elizalde at juan.carlos@videolabs.net

If you enjoyed this article, you may also like to read Chris Vazquez’ piece on OLED monitors: http://tinyurl.com/kq9xw7

Remember to contact David Ryan dryan@videolabs.net  (301-217-0000 x104) for all of your CD, DVD and videotape duplication and replication and related multimedia needs.

Be sure to follow me on Twitter www.Twitter.com/DRMediaSolution for exclusive discounts.