hinting gray scaling legibility

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johnmcork
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hinting gray scaling legibility

Post by johnmcork » Sat Apr 16, 2005 2:02 am

Before moving on to the rest of my project, I decided to check the legibility different fonts at 6 pt and 8 pt sizes with and without hinting but with gray scaling on and Windows character smoothing on. I cut and pasted Arial and Lucida Console into new fonts to remove hinting. The fonts I checked were:

Time
Arial
Courier
Lucida Console
Arial no hint
Lucida Console no hint
My First Font no hint

My First Font was a cut and paste of Arial with serifs added and mapped onto mono space, i.e. increased the size of the smaller characters were increased and added serifs to bulk out the slim characters like I and J.

The no hint fonts looked a little fuzzier and denser. Frankly, the no hinted fonts looked more legible and My First Font was the most legible.

John Cork

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Post by Bhikkhu Pesala » Sat Apr 16, 2005 7:20 am

Have you seen this thread on hinting?

I also came to the conclusion that hinting is not that useful. Adding a greyscale table is almost as good. At very small sizes, greyscale smoothed fonts look much the same as hinted fonts. Where hinted fonts are best seems to be at the widely used sizes between 10 and 12 points, where unhinted greyscale fonts are a bit light or fuzzy, and unhinted fonts without greyscale suffer from "dropout" or missing thin strokes.

When I'm working, I always zoom in to enlarge small fonts because anything less than about 16 points is too small to read comfortably on screen for long periods.Then the unhinted fonts look better than hinted fonts.
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johnmcork
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Post by johnmcork » Sat Apr 16, 2005 5:32 pm

GUIDE FIGURES

The acuity of the eye, ability to separate dots, is 1 minute of arc. The characters on the 20/20 (euro 6/6) row of an eye chart map into a 3 wide by 5 high grid where the size of the elements is 1 minute of arc. The ability to judge the relative positions of dots is the Vernier acuity of the eye, which is 5 seconds precision (repeatability – think of a good marksman who’s sights need calibration) and 10 seconds accuracy (closeness to truth– think of a poor marksman who’s sights are calibrated).

1 A 0.005-inch dot viewed at 18 inches subtends 1 minute of arc, [assume a circle of radius 18 inches. It has a circumference of 113 inches. Then 113/(360*60) give 0.005-inch.

2 A 15-inch (12 inch wide) monitor with 1000 wide pixel resolution gives a dot size of 0.0120 inches 2.4 minutes (0.3 mm).

3 A printer with 1200 dpi resolution gives a dot size of 0.0008 inches give 0.16 minutes of arc, 9.6 seconds of arc (15 times better).

4 1-point size is 1/72 inches is 2.8 minutes of arc.

5 12-point characters printed should be 34 minutes of arc high compared with 5 minutes of the 20/20 row of an eye chart.

NOTES

1 My recollection from work I did back around 1977 at Reuters was that there is a significant (10% to 20%) difference in legibility between Times and Arial characters displayed at about 15 minutes of arc. The reason is that, given a fixed size of character, the serifs take up space and reduce the size of the core shape of the glyph, i.e. the part that conveys the information. And, as I recall that difference in size was about 10% to 20%. However, when characters were viewed at normal reading size 28 to 35 minutes (10 to 12 point size) there was no significance in legibility.

2 Again from early work; Time types, those with serifs, are more readable. There was a distinction made between legibility, readability and comprehensibility. Readability is in part about maintaining the unity of the characters that form words and that’s what serifs and proportional spacing does. In addition I feel that large masses of heavy Arial font pull the words together into a mass of squiggly vertical lines, I just can’t see the words. (a slight exaggeration)

3 Tests we did at Reuters used tatistascope (a projector with a shutter) to flash large characters on a screen at progressively reduced time, but not size. His showed a marked transition from subjects recognizing all 5 random characters to only 3 of the 5 as exposure time reduced. The exception was where the 5 random characters included common sequences such as ere and air. This is useful knowledge for the design of rapid perception in critical display systems such as aircraft instruments.

4 I read the thread on hinting referenced by Bhikkhu Pesala above and went ahhh gocha. My understanding is that there are two general classes of algorithms.

One class takes a matrix of pixels and multiplies each be some weasel number and adds them together, This class has applications in digital sample rate conversion, TV line standards conversion, anti-aliasing, image edge detection and I presume gray scales. It is used in digital photo editing applications. This class of algorithms is ubiquitous and I am familiar with it.

The other class is grid fitting, which I am not familiar with and it is difficult to search for but [“grid fitting” polygon] produces some results. This class seems to have applications in the general area of image recognition and characterization, e.g. recognizing whales by processing images of their tails. This class is also likely to be concerned with extracting and presenting fine detail in graphics such as geographic maps. Hence the “ahhh gocha” because the referenced thread makes the point that gridding improves characters that include fine detail. I would confirm that in the comparison I did above, the hinted/gridded fonts had finer detail.

5. I guess this means that manual / auto hinting is important for two reasons. First it improves the detail in fonts and thereby the discrimination legibility. Second, many people, like me, will not have enabled character smoothing and so for general acceptability one should hint the fonts.

John Cork

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Post by Dave Crosby » Mon Apr 18, 2005 4:04 pm

Bravo John! Very informative!
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Post by sevry7 » Thu Apr 26, 2007 8:16 pm

johnmcork wrote:GUIDE FIGURES

The acuity of the eye, ability to separate dots, is 1 minute of arc.
It's not even that complicated when it comes to the appearance of hinted fonts with font smoothing enable and those which are not with font smoothing off.

But as hinting seems to be presented as a sort of 'black art', a complicated one at that, and as you can't hint with Font Creator at any rate, I simply advise people at my site to turn on Font Smoothing. The text is a bit blurry, grayish, but only slightly compared with hinted fonts. But even in small sizes, it's legible. Without smoothing, it's looks like a bad fourth generation fax even in normal sizes.

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