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BASS
| the reversal of a). Therefore the values obtained are identical. The den-
| sity value determined after these two principles is called diffuse trans-
mission density (DIN 4512 and ANS PH2.19-1959). With the arrangement in
| case c) one obtains the specular density; the arrangement in case 4)
| leads to the double diffuse density. Cases c) and d) have not yet been
defined until now. A reason for that can be gathered from fig.2. In order
to determine the diffuse density there are no strict instructions as to
the observance of the illuminating and the receiving arrangements of the
instruments laid down in the standards. In the measuring range of the
diffuse density the curves are nearly levelled. This changes, however,
if the double diffuse density is to be determined and becomes very un-
favourable in the case of specular density. Small alterations of the
angles a. and a, can already involve considerable variations of the
measuring values.
Therefore the examples cited in chapter 3 refer exclusively to the deter-
mination of the diffuse density. (9
2. EXPERIMENT DESCRIPTION
Ihe aim of these exemplary experiments was to find out to what degree
the density values of several film types with different scattering
characteristics determined with various measuring instruments are com-
parable with each other. For the performance of the task a Kodak photo-
graphie step tablet no. 3 (calibrated) was printed on the films. The
following material was used:
Kodak Plus-X Aerographic Film 2402,
Kodak Tri-X Aerographie Film 2403,
Kodak Infrared Aerographic Film 242k,
Kodak High Definition Aerial Film 341k,
Agfa Aviphot Pan 30.
The measuring of these step wedges was performed at five different in-
struments (in brackets the angles: gq. of the condensing lens and the
: . 1,1 f
objective lens). (9
Macbeth TD-100 (259/909),
Macbeth TD-102 (129/909),
Gretag D 33 (109/909 for the apertures of 2 mm and 3 mm,
159/909 for the aperture of 1 mn),
Joyce-Loebl 3C8 (60/159 for the numerical apertures of 0.1/0.25,
2 69/339 for the numerical apertures of 0.1/0.5k
of the condensing lens and the objec-
tive lens, fO um slit width, 100 pm
slit height, referred to the sample),
Optronics P-17003(159/7° Por ali pixel sizes).
The measurements were carried out in a way as is the general practice.
With instruments with direct readings first the zero point had to be
adjusted. Then a step of high density of a calibrated step wedge was
placed into the ray path and the corresponding density value quoted in
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