Second, with regard to Judy=D5s testing with gum printing, a=20
couple of observations: =20
1) The blue pigment used in the tests could give results=20
very different from other colors. In three-color carbon=20
printing, for example, the cyan tissue will always have higher=20
contrast than the magenta and yellow. I have already=20
suggested that for my own carbon tests I should have used a=20
more neutral black tissue, however since I know from long=20
experience that the tissue used has printing characteristics=20
very similar to some of my black tissues I felt it ok for the=20
tests.
2) It is important to note that in my tests=20
the same strength sensitizer is not producing like results=20
with the different tubes. The daylight and cool white tubes=20
can produce useful exposures but only with higher strength=20
sensitizers than used with BL. I believe that the kind of=20
dichromate you are using in gum printing could make a big=20
difference in terms of the results. Ammonium dichromate is=20
more sensitive than potassium, and sodium quite a bit more=20
sensitive than the other two. Since you are using saturated=20
solutions in gum printing this could make a big difference. I=20
believe that Davis used sodium dichromate for his test -- he=20
does say in the article in Photo Techniques that this is the=20
dichromate he uses.
This is a repost of the comparison test results I posted last=20
evening between GE Daylight (peaking at about 450 nm),=20
Sylvania BL (350 nm), and GE Cool White fluorescent tubes=20
(550 nm). Apparently my posting was very garbled by the time=20
it made it to the list. I hope this clarifies the results. As=20
noted earlier, the data provided for the BL and Cool White=20
tubes is the same reported earlier. The tissue used for the=20
current test with Daylight bulbs was from the same batch and=20
was sensitized, exposed and developed according to the same=20
procedures used with the BL And Cool White tubes. All other=20
parameters reported in the original tests, including=20
clarifications in subsequent messages, were identical.=20
There is no question that in my working conditions the=20
Daylight tubes give better results because they are able to=20
print negatives with very high density ranges, yet at the same=20
time retain high Dmax values in the shadows. This will be=20
apparent in comparing the test results. Especially, compare=20
the BL step sensitized at 1% of Test One with the Daylight=20
step sensitized at 3% of Test Two. Both show density to step=20
18 but the Daylight step has a much greater Dmax, and is=20
actually more sensitive when sensitivity is judged by the=20
first step to reach maximum density.
Test One (Comparison of Sylvania BL, GE Daylight, and GE Cool White tubes=
at sensitizer strengths of 1/4% and 1%)
Sden 1/4% 1/4% 1/4% 1% 1% 1%
BL Daylight Cool BL Daylight Cool
1. 1.73 1.73 1.38 1.32 1.72 1.40
2. 1.67 1.68 1.32 1.25 1.72 1.34
3. 1.51 1.57 1.21 1.20 1.72 1.34
4. 1.48 1.44 1.07 1.18 1.70 1.24
5. 1.39 1.18 .96 1.14 1.57 1.13
6. 1.33 1.00 .81 1.05 1.50 1.05
7. 1.24 .69 .59 1.00 1.41 .88
8. 1.16 .47 .37 .95 1.27 .74
9. .95 .17 .13 .90 1.13 .49
10. .83 .15 .11 .82 .94 .19
11. .63 .13 .08 .73 .65 .14
12. .46 -- -- .68 .50 --
13. .25 -- -- .63 .31 --
14. .13 -- -- .57 .13 --
15. -- -- -- .37 -- --
16. -- -- -- .37 -- --
17. -- -- -- .16 -- --
18. -- -- -- .08 -- --
19 -- -- -- -- -- --
Test Two (Comparison of GE Daylight tubes and GE Cool White tubes at pota=
ssium
dichromate sensitizers of 2% and 3%.=20
=20
Sden C. White 2% Day C. White 3% Day
1. 1.58 1.70 1.60 1.70
2. 1.55 1.67 1.56 1.70
3. 1.46 1.65 1.44 1.70
4. 1.29 1.60 1.39 1.66
5. 1.22 1.54 1.24 1.61
6. 1.09 1.45 1.17 1.53
7. .93 1.31 1.02 1.47
8. .78 1.21 .95 1.32
9. .62 1.09 .86 1.22
10. .42 .91 .68 1.07
11 .30 .77 .62 .88
12. .29 .58 .54 .79
13. .20 .43 .26 .58
14. .13 .23 .20 .44
15. .10 .17 .10 .33
16. .08 .13 -- .24
17. -- -- -- .13
18. -- -- .10
19. --
=09
=09