[ This article was first published in the September, 2010, issue of
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David Gates writes:
I’m really confused about text in video.
Have a client that is publishing a book – she had them send me the page layouts to use,.. but they were PFD files, and the weight of the lines surrounding some paragraphs of the book were FINE for print – but crap for motion graphics (as well as the size of the text she used – which again was fine for output for a book, but NOT dealing with scanning lines/refresh rates for TV – especially HD).
So here’s the question — is text then which is created at 80 points the equivalent of 80 px?!?!
So what is the equivalent and/or difference between dpi vs ppi….. (dots per versus pixels per…)
And does it make a difference if that 80 point letter is created within a resolution of 440 or 1080?
Larry replies: David, this gets very confusing very quickly.
Text is text, however, the resolution of the text varies by device.
Video is a VERY low resolution device. Print is a high-resolution device. So, text that looks good in high-resolution, such as thin lines, curved text, look very poor in video.
All forms of video are bit-mapped. This means the dpi and ppi are NOT relevant, only the total number of pixels across by total number of pixels down count.
For an SD image, your pixel count is 720 x 480.
For an HD image, your pixel count is either 1280 x 720 or 1920 x 1080.
Why is DPI irrelevant? Imagine watching your video on a 13″ monitor. Now imagine watching it on a 60″ display. The pixel density is different, because the total number of pixels is fixed. To fit into a smaller display, we squeeze more pixels per inch. To fit pixels into a larger display, we enlarge the pixels, making them taller and fatter. This is why video on a large monitor looks grainier than the same video on a smaller monitor. You are changing the SIZE of the pixels, but not the NUMBER of the pixels.
Ignore lines of resolution. It will only confuse you. Think only of pixels.
Remember – the total number of pixels across or down does not change, even as the monitor size changes. You can not make an HD image by displaying an SD image on a larger monitor.
Total pixel dimenstons are fixed.
In video, but not in print, pixels and points are synonymous.
In print, the number of pixels that make up an image is a combination of resolution and point size. However, it is a true statement that a 100 point letter at 600 ppi will have FAR more pixels than a 100 point / pixel letter in video.
Scanning at higher resolution for photographs is fine if you are doing moves on the images, but not fine for creating text.
A 1 point line in print, will be about 10 pixels thick at 600 ppi. In video, that same line is only one pixel thick. And, in an interlaced format, it will flicker on and off.
So, in video, ignore dpi, ignore ppi, and ignore lines of resolution.
In video one pixel equals one point. (In fact, this is what your computer screen does as well.)
Technically, the scanned graphics will never look good. They assume the device you are viewing them on has the same resolution as a printing press. Video has less than 10% of the pixels of print.