This report addresses questions concerning the validity and continued use of the Jaeger reading card to check near vision acuity of nondestructive examination personnel. Specific questions were whether there is an unacceptable variation in character size, character and word spacing, and print quality between different Jaeger reading cards and whether using computer generated text would be an acceptable alternative to using the Jaeger reading card.

The results indicated that there is much more variation in character size, character and word spacing, and print quality between different computer printers and software than between different Jaeger reading cards. A comparison of computer generated text with text from the Jaeger reading cards showed that the computer text had worse quality but better contrast, tended to print larger characters, and spaced both characters and words closer together. The poor print quality and closer character and word spacing more than offset the larger character size and better contrast since the Jaeger reading cards could be read at a slightly greater distance than the computer generated text.

 

Introduction
The variables involved in determining whether a computer/printer/software system (computer system) is a viable alternative to the Jaeger reading card (Jaeger system) are font type and size, character and word spacing, print quality and contrast, and paper quality. The Jaeger system J1 text and the equivalent software font and text size (4 pt) were used in this comparison. Also, 20 pound laser printing/copy paper was used for all printing by the computer systems (24 pound laser printing/copy paper was used with the ink jet printer described below).

 

---

Different computers were used for expediency because computer type does not have an effect on these variables.

---

 

In order to determine the validity of the Jaeger system and the appropriateness of an alternative (i.e., computer) system for measuring near vision acuity, the variation in character size, word spacing, and line length was measured, and the variation in character spacing, print quality, and print contrast was evaluated. In addition, the maximum distance at which personnel could read the Jaeger and computer system text was measured.

The effect on the variables mentioned above by printer type and software type was evaluated. Different computers were used for expediency because computer type does not have an effect on these variables. Note that illumination affects near vision acuity but is external to the Jaeger or computer system and, therefore, was not evaluated.

 

Equipment and Software Evaluated
Two Jaeger reading cards were evaluated; the first was obtained from ASNT in 1978 and the second was obtained from ASNT in 1988. Both cards bore a "1-78" printing date at the bottom. A check with ASNT revealed that the current Jaeger reading cards in stock also bear the "1-78" printing date, and that all cards were obtained from a single supplier. Therefore, no attempt was made to obtain a "new" card.

Four printers were evaluated. Laser 1 and Laser 2 were identical laser printers except that Laser 2 had an optional desktop publishing software font cartridge installed. Ink Jet was an ink jet printer, and Laser 3 was a laser printer that was compatible with a different type of computer and operating system than the other three printers. The term "System 1" will be used when referencing the computers/operating systems used with the first three printers above (Laser 1, Laser 2, and Ink Jet) and "System 2" will be used when referencing the computer/operating system used with the last printer (Laser 3).

Five word processors were evaluated. Three word processors (Software 1, Software 2, and Software 3) were made by the same software manufacturer and were compatible with System 1, thus all three used the same software font drivers. The fourth word processor (Software 4) was equivalent to Software 1, and was made by the same software manufacturer, but was compatible with System 2; the last word processor (Software 5) was compatible with System 1 but was made by a different software manufacturer, and thus used different software font drivers.

The J1 text ("I was dirty from my journey...") and sentences containing each letter of the alphabet ("The quick gray fox jumped over the lazy brown sheep") were printed for various combinations of printers and software, and then compared with the J1 text from the Jaeger reading cards. A metallurgical microscope was used to measure character size and spacing. Word spacing and the maximum distance at which people can read J1 text were measured using scales.

The photographs with reticles (Figures 1 through 4) were taken at 100´ magnification. The reticle is divided in 0.01 mm (0.0005 in.) increments (the numbers above the reticle represent hundredths of an inch). The images of the character "a" are reversed in these views due to the optics of the microscope. Even though these images could have been digitally rotated after scanning, rotation was not performed on these views so that the scale would remain readable. The photographs without reticles (Figure 5) were taken at 30´ magnification and the images were digitally rotated after scanning in order for the word "very" to be readable.

 

Results
In determining variations in character size, the height of the lower case characters "a" and "o" was selected for measurement. The reticle was centered on the characters and measured as follows: each character "a" was positioned with the lowermost portion(s) of the base even with the "01" line of the reticle and then measured to the top arc; each character "o" was positioned with bottom arc even with the "01" line of the reticle and then measured to the top arc (the "01" line was used so that the entire character would be visible when photographed). Widths could not consistently be determined because the widest part of characters merged with adjacent characters for text generated by many of the computer systems. While character width influences the word width and line length measurements described below, individual character widths were not measured.

Variation in Jaeger character height and shape is illustrated in Figure 1, which shows images of a character "a" printed on Jaeger system cards. The top and middle views show the same character "a" from the same word on different cards (the top view is from the 1978 card and was laminated; this card's text was easy to read but difficult to photograph due to the reflective surface). The middle and bottom views show a character "a" from different words on the same card. While the shape of the character "a" varies slightly in the middle and bottom views, the height of the "a" in all three views varies by less than 0.01 mm (0.0005 in.) (character heights were approximately 0.6 mm [0.025 in.] high).

Variation in print quality for the Jaeger system vs. computer systems is illustrated in Figure 2. The top views show a character "a" from different words printed on the same Jaeger card, which are also the middle and bottom views from Figure 1. The middle views show a character "a" from different words from J1 text printed by the Ink Jet/Software 1 combination. The bottom views show a character "a" from different words from J1 text printed by the Laser 1/Software 1 combination. While each character pair was similar in height and varied only slightly in shape, there was more variation in print quality by the computer systems due to an inconsistent amount of ink used to print each character.

Variation in character height due to word processor software is illustrated in Figure 3, which shows a character "a" printed by the Ink Jet printer using four different word processors. The characters printed by Software 1 (top-right view), Software 2 (top-left view), and Software 3 (bottom-right view) were almost identical in shape and varied from 0.68 mm (0.027 in.) to 0.71 mm (0.028 in.) in height. The character printed by Software 5 (bottom-left view) was 0.63 mm (0.025 in.) high, approximately the same as the Jaeger system, and varied slightly in shape compared with the characters printed by Software 1, Software 2, and Software 3. The consistency in the shape and height of the characters printed by the Software 1, Software 2, and Software 3 was expected, as they shared the same font driver; therefore Software 2 and Software 3 are not included in the comparisons described below.

Variation in character height and quality due to printer type plus a comparison of character contrast and quality between the Jaeger and computer systems are illustrated in Figure 4. Figure 4 shows a Jaeger system character "a" (top-right view) vs. a computer system character "a" using the following combinations: System 1/Laser 2/Software 1 (top-left view), System 1/Laser 1/Software 1 (middle-right view), System 1/Ink Jet/Software 1 (middle-left view), System 1/Laser 3/Software 1 (bottom-right view), and System 2/Laser 3/Software 4 (bottom-left view). All printers were connected directly to the computers except for the System 1/Laser 3/Software 1 combination, which was connected via a network. The computer system characters had noticeably more contrast while the Jaeger system character had superior print quality. The System 1/Laser 3/Software 1 combination produced unacceptable print quality, believed to be due to the software driver that enabled the System 1 computer to print to the System 2 compatible printer (Laser 3). The Jaeger system character "a" was 0.63 mm (0.025 in.) high vs. from 0.68 mm (0.027 in.) high (Ink Jet) to 0.73 mm (0.029 in.) high (Laser 1 and 2) for the characters printed by the computer systems.

Character spacing is illustrated in Figure 5, which shows a Jaeger system word "very" (top-left view) vs. a word "very" printed by computer systems using the following combinations: System 1/Laser 1/Software 1 (top-right view), System 1/Ink Jet/Software 1 (bottom-left view), and System 2/Laser 3/Software 4 (bottom-right view). The character spacing was much more consistent in the Jaeger system and, as noted above, the computer systems merged the widest parts of some adjacent characters.

Using Software 1 and 4 (for Systems 1 and 2 respectively) and Software 5, the J1 text was printed by different printers with the margins and justification, plus the indentation of the first line, set such that the wording for each line, justification, and indentation were the same as the Jaeger system. The computer system margins were set as wide as possible while keeping the wording for each line the same as the Jaeger system (in spite of this, the computer system margins were noticeably closer together). The range of the spacing between words and the width of the word "to" (from the first line of the J1 text) was measured by a metallurgical microscope. The length of the middle line of the left column of the J1 text was measured by a scale. For comparison, the line length of an "all letter" sentence ("The quick gray fox...") was also measured. While the width of the word "to" from the Jaeger and computer systems was small enough to measure at 100´ using the microscope (which had a 0-1.27 mm [0-0.05 in.] reticle), it was too wide to fit within the field of view of the camera. The ranges of the spacing between words and the widths of the words "to" are shown in Table 1. The J1 text and "all letter" sentence line lengths are shown in Table 2.

Overall, computer system word spacing was much closer than the Jaeger system word spacing; the closest spacing was by the System 1/Ink Jet/Software 1 combination, which was almost half the word spacing of the Jaeger system. There was some variation in the width of the word "to" printed by the computer systems using Software 1 and 4, but both were comparable in width to the word "to" from the Jaeger system. However, the width of the word "to" printed by the computer system using Software 5 was only 80 percent of the width of the Jaeger system word "to." Likewise, the line lengths printed by the computer systems varied slightly among the systems using Software 1 and 4; the J1 text line lengths were approximately 6.35 mm (0.25 in.) shorter than the Jaeger system line length. However, the line lengths printed by the computer system using Software 5 were quite shorter; the J1 text line length was almost 12.7 mm (0.5 in.) shorter than the Jaeger system line length.

A comparison of character height variation was made between the two Jaeger cards vs. computer systems using the following combinations: Ink Jet/Software 1, Laser 1/Software 1, and Laser 3/Software 1. The height of the ten characters "o" contained in the first sentence of the J1 text was measured by the metallurgical microscope. The results are shown in Table 3.

A simple comparison of the ranges of the "o" height measurements (maximum minus minimum measurements) indicates similar variation between the Jaeger and computer systems when considering each Jaeger card and computer system individually. However, the combined range for both Jaeger cards is half the combined range for all three computer systems (0.0381 vs. 0.0762 mm [0.0015 vs. 0.0030 in.]). A comparison of the data for corresponding character "o" locations on the two Jaeger cards showed close agreement; three data points differed by 0.0127 mm (0.0005 in.) while the remainder were identical. The arithmetic mean and standard deviation of the samples are listed, and from them the maximum and minimum values and total range can be predicted for the total population (in this case, predicted for a huge number of characters "o"). From the theory of normal distribution, the value of 99.7 percent of the total population will fall within 3 standard deviations of the mean. Thus, the value for practically all of the population will fall within a total range of 6 standard deviations, which is listed in the "Range *" row of Table 3. Note that in Table 3, the value for the predicted range does not always equal the predicted maximum value minus the predicted minimum value due to rounding. The statistical results were similar to the nonstatistical results described above, including the combined predicted ranges: 0.078 mm (0.0031 in.) for both Jaeger cards vs. a combined predicted range of 0.165 mm (0.0065 in.) for the three computer system combinations.

Finally, a group of non-NDE personnel who had never before seen a Jaeger reading card was used to determine the maximum distances at which they could read the J1 text from both the Jaeger system (unlaminated card only) and from computer systems using the following combinations: Ink Jet/Software 1, /Laser 1/Software 1, and Laser 3/Software 4. The distances were measured by a scale to the nearest 6.35 mm (0.25 in.). The results are shown in Table 4.

A comparison, both statistical and nonstatistical, of the ranges of the maximum reading distance measurements indicates more variation with the Jaeger system than with the computer systems. However, the J1 text can, on average, be read at a greater distance with the Jaeger system than with any of the computer systems tested. The implication is that the computer systems' poor print quality and close character and word spacing more than offset their improved contrast and slightly larger character height.

 

 

Figure 1-Photographs with reticles taken at 100X illustrate Jaeger character height and shape. Top and middle views show the same character from the same word on different cards. Middle and bottom views show a character from a different words on the
same card.

 

Figure 2-At 100X variation in print quality for Jaeger vs. computer is apparent. Top views show a character from different words on the same Jaeger card. Middle views show a character from different words from J1 text printed by the Ink Jet/Software 1 combination. At the bottom is a character from different words from J1 text printed by the Laser 1/Software 1 combination.

 

 Figure 3-Variation in character height due to word processor software. A character "a" was printed by the Ink Jet printer using for different word processors.

 

Figure 4-Variation in character height and quality due to printer type, plus a comparison of character contrast and quality between the Jaeger and computer systems.

 

Figure 5-Photographs without reticles taken at 30x magnification. Images were digitally rotated after scanning.

 

Conclusions
Keeping in mind that this study evaluated a limited number of printers, word processors, and Jaeger reading cards plus a limited number of characters from printed text, the following conclusions were drawn:

• The predicted maximum variation in the height of lower case characters of the J1 text of Jaeger reading cards was less than half the predicted maximum variation in the height of lower case characters of J1 text printed by computer systems (0.078 vs. 0.165 mm [0.0031 vs. 0.0065 in.]).
• There is much greater variation in character height for text printed by different printers and word processors than for text printed on different Jaeger reading cards; there is practically no variation in height between corresponding characters on different Jaeger reading cards.
• Variation in character height of text printed on the same Jaeger reading card is essentially the same as that for text printed by the same printer and word processor.
• Considering the three items listed above, the variation in the character size of J1 text on Jaeger reading cards is not excessive.
• Print quality is worse and varies more in text printed by computer systems.
• There is more contrast between the ink and paper for text printed by computer systems.
• The characters are spaced slightly closer and words are spaced significantly closer in text printed by computer systems.
• The average person can read the J1 text on Jaeger reading cards at a slightly greater distance than the same text printed by computers.

 

Recommendations
There is too much variation in character size, character and word spacing, and print quality between different computer printers and software to consider the use of computer generated text as equivalent to the use of Jaeger reading cards for determining near distance acuity. To minimize variation to an acceptable level, a specific brand of printer and software would have to be specified (which must be avoided in codes and standards).

Table 1 - Word spacing and width of "to"
System/Printer/ Word Processor Software	Word Spacing Range mm (in.)	Width of "to" mm (in.)
Jaeger (software not applicable)	0.762-0.9144 (0.0300-0.0360)	1.219 (0.0480)
System 1/Laser 1/Software 1	0.457-0.635 (0.0180-0.0250)	1.181 (0.0465)
System 1/Inkjet/Software 1	0.469-0.635 (0.0180-0.0250)	1.155 (0.0445)
System 2/Laser 3/Software 4	0.406-0.609 (0.0160-0.0240)	1.143 (0.0450)
System 1/Inkjet/Software 5	0.381-0.558 (0.0150-0.0220)	0.977 (0.0385)

Table 2 - Line lengths
System/Printer/ Word Processor Software	J1 Text Line Length mm (in.)	"All Letter" Line Length mm (in.)
Jaeger (software not applicable)	50.54 (1.99)	-
System 1/Laser 1/Software 1	44.45 (1.75)	30.48 (1.20)
System 1/Inkjet/Software 1	44.19 (1.74)	30.22 (1.19)
System 2/Laser 3/Software 4	44.45 (1.77)	30.98 (1.22)
System 1/Inkjet/Software 5	39.37 (1.55)	27.43 (1.08)

  

Table 3 - Character "o"height comparison
Sample #	Jaeger (Unlam.) mm (in.)	Jaeger (Lam.) mm (in.)	Laser 1 Software 1 mm (in.)	Ink Jet Software 1 mm (in.)	Laser 3 Software 3 mm (in.)
1	0.6604 (0.0260)	0.6477 (0.0255)	0.7239 (0.0285)	0.7112 (0.0280)	0.7874 (0.0310)
2	0.6477 (0.0255)	0.6477 (0.0255)	0.7366 (0.0290)	0.7239 (0.0285)	0.7747 (0.0305)
3	0.6731 (0.0265)	0.6731 (0.0260)	0.7239 (0.0285)	0.7366 (0.0290)	0.7747 (0.0305)
4	0.6731 (0.0265)	0.6604 (0.0260)	0.7112 (0.0280)	0.7112 (0.0280)	0.7874 (0.0310)
5	0.6477 (0.0255)	0.6731 (0.0265)	0.7112 (0.0280)	0.7239 (0.0285)	0.7874 (0.0310)
6	0.6477 (0.0255)	0.6477 (0.0255)	0.7366 (0.0290)	0.7493 (0.0295	0.7747 (0.0305)
7	0.6477 (0.0255)	0.6350 (0.0250)	0.7112 (0.0280)	0.7493 (0.0295)	0.7620 (0.0300)
8	0.6477 (0.0255)	0.6477 (0.0255)	0.7112 (0.0280)	0.7112 (0.0280)	0.7493 (0.0295)
9	0.6477 (0.0255)	0.6477 (0.0255)	0.7366 (0.0290)	0.7112 (0.0280)	0.7747 (0.0305)
10	0.6731 (0.0265)	0.6731 (0.0265)	0.7366 (0.0290)	0.7112 (0.0280)	0.7747 (0.0305)
Range	0.0254 (0.0010)	0.6604 (0.0260)	0.0254 (0.0010)	0.0381 (0.0015)	0.0381 (0.0015)
Mean	0.6591 (0.02595)	0.6604 (0.0260)	0.7239 (0.0285)	0.7239 (0.0285)	0.7747 (0.0305)
	0.0127 (0.00050)	0.6604 (0.0260)	0.0119 (0.00047)	0.0158 (0.00062)	0.0119 (0.00047)
Max*	0.6959 (0.0274)	0.6604 (0.0260)	0.7594 (0.0299)	0.7221 (0.0304)	0.8102 (0.0319
Min*	0.6223 (0.0245)	0.6604 (0.0260)	0.6883 (0.0271)	0.6756 (0.0266)	0.7391 (0.0291)
Range*	0.0762 (0.0030)	0.6604 (0.0260)	0.0711 (0.0028)	0.0939 (0.0037)	0.0711 (0.0028)
		Jaeger Cards (both)		Computer Systems (all three)
Range		0.0381 (0.0015)		0.0762 (0.0030)
Range*		0.0787 (0.0031)		0.1651 (0.0065)
* Statistically predicted based on sample.

Table 4 - J1 test maximum distances
Sample #	Jaeger (Unlam.) mm (in.)	Laser 1 Software 1 mm (in.)	Ink Jet Software 1 mm (in.)	Laser 3 Software 3 mm (in.)
1	393.7 (15.5)	355.6 (14)	381 (15)	381 (15)
2	355.6 (14)	393.7 (15.5)	419.1 (16.5)	361.95 (14.25)
3	438.15 (17.25)	342.9 (13.5)	419.1 (16.5)	431.8 (17)
4	425.45 (16.75)	330.2 (13)	406.4 (16)	425.45 (16.75)
5	425.45 (16.75)	431.8 (17)	406.4 (16)	457.2 (18)
6	450.85 (17.75)	393.7 (15.5)	393.7 (15.5)	419.1 (16.5)
7	457.2 (18)	419.1 (16.5)	533.4 (21)	482.6 (19)
8	444.5 (17.5)	393.7 (15.5)	406.4 (16)	431.8 (17)
9	546.1 (21.5)	469.9 (18.5)	520.7 (20.5)	495.3 (19.5)
10	546.1 (21.5)	482.6 (19)	508 (20)	514.35 (20.25)
Range	190.5 (7.5)	152.4 (6)	152.4 (6)	152.4 (6)
Mean	448.3 (17.65)	401.32 (15.80)	439.42 (17.30)	439.93 (17.32)
	59.69 (2.35)	50.8 (2.00)	57.404 (2.26)	48.26 (1.90)
Max*	627.38 (24.7)	553.72 (21.8)	612.14 (24.1)	584.2 (23.0)
Min*	269.24 (10.6)	248.92 (9.8)	266.7 (10.5)	294.64 (11.6)
Range*	358.14 (14.1)	304.8 (12.0)	345.44 (13.6)	289.56 (11.4)
* Statistically predicted based on sample.

* Union Carbide Corporation, PO Box 8361, South Charleston, WV 25303; (304) 747-3894; fax (304) 747-3797

Copyright © 1996 by the American Society for Nondestructive Testing, Inc. All rights reserved.

IRRSP, NDT Handbook, The NDT Technician and www.asnt.org are trademarks of the American Society for Nondestructive Testing, Inc. ACCP, ASNT, Level III Study Guide, Materials Evaluation, Nondestructive Testing Handbook, Research in Nondestructive Evaluation and RNDE are registered trademarks of the American Society for Nondestructive Testing, Inc. ASNT exists to create a safer world by promoting the profession and technologies of nondestructive testing.