Screen fonts,
from Adobe’s point of view

After the item on screen type appeared, several friends at Adobe pointed out some confusion or even errors, and Emmy Huang, the product manager for the Adobe Flash Player, offers some useful clarifications.--RB

tHE COMMENTS IN recent entries on this blog about text in Flash and PDF highlight that Adobe is doing a poor job of making our text features easily discoverable for designers, developers and end-users. I would like to address some of your misconceptions about Flash and PDF text, and encourage you to provide feedback on how we can continue to improve text within Adobe technologies. We’d love to talk to you.

“Flash and PDF just take the font outlines and blur them (like Photoshop) to make the edges less jaggy.”

These applications and technologies don’t simply “take the font outlines and blur them,” however they do use oversampling, which renders the text at a larger size and filters it, in combination with hinting. I admit that text in Flash used to be rather poor in older versions, but text is important to us and we continue to improve in this area. We introduced a new type engine in Flash Player 8 (released August 2005) to improve text fidelity, and it leans towards preserving the aesthetic of the text.

“They ignore TrueType hints that can make better letterspacing, consistent letterforms, at sharper body type on the screen. ClearType fonts use hints that work at the sub-pixel level, using the three colors of the screen, red, green and blue.”

To clarify for folks, fonts don’t come with special sub-pixel level hints—it’s the rendering that works at the sub-pixel-level. Also, I’d like to separate out Acrobat and Flash Player since Adobe and Macromedia recently merged and the products aren’t using the same technologies.

Acrobat’s CoolType, like ClearType, discards some of the hints and uses the ones it thinks will work well with its special rendering approach. PDF rendering achieves sharpness by using non-linear shaping of glyphs. This means that it has minimal distortion and generally has high-quality inter-glyph spacing. There is also a "Smooth Text for LCD Screens" setting in Acrobat/Reader that is, unfortunately, turned off by default. With smoothing on for both CRTs and LCDs, we use font hinting as well as sharpening of edges, both horizontal and vertical effects. This is the same general approach to sub-pixel rendering that ClearType uses.

In Flash Player, the rendering technology doesn’t use the original hints in the font, but converts the outlines to its internal format, and then applies auto-hinting to the result. The options are under the developer’s control - so again we need to do more here to make sure folks know how to create more readable text. On Windows, if you use the default text—device text—it is ClearType (if you have it enabled on the system) so text in Flash Player should look exactly like all other system-generated text in desktop applications and the browser. Also, if font smoothing is enabled for Windows, the sub-pixel rendering is on by default. When using embedded fonts, sub-pixel rendering is used when the developer enables “publish for readability” and you also get the benefit of consistency across platforms.

We’d love to hear more about your experiences with PDF and Flash text and understand how to make it easier to create high quality, high fidelity text experiences with Adobe technologies.

Your Thoughts (1 comment)

2009-03-11 by Krancis

Thanks for putting up an article having to do with legibility on a red background.

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