This page is duplicated in text only for use with the NICAP search engine. To actually view and use the original page, http://brumac.8k.com/trent1.html Charts for the text below and found embedded in the original text are linked here http://www.nicap.org/docs/500511mcminnville_charts.pdf The Trent Farm Photos (This paper was originally published in the proceedings of the 1976 UFO Conference of the Center For UFO Studies. This version has been modified slightly in april 2000 for this Publication. This is the first of two technical and historical papers on The Trent photo case that were presented to and published by The Center For UFO Studies (CUFOS), which is located in Chicago, Illinois. On the possibility that the McMinnville photos show a distant unidentified object (UO) During the Air Force funded investigation of UFO reports at the University of Colorado in 1967-1968 (the "Condon Report"), photoanalyst William Hartmann studied in detail photographic and verbal evidence presented by two former residents of McMinnville, Oregon, Paul and Evelyn Trent. He concluded, mainly on the basis of a simplified photometric analysis, that "all factors investigated, geometrical, psychological and physical, appear to be consistent with the assertion that an extraordinary flying object, silvery, metallic, disk shaped, tens of meters in diameter and evidently artificial, flew within sight of two witnesses." An important part of his analysis included calculations of the expected brightness of the image of the bottom of the Unidentified Object (UO) that appears in the first photo. He pointed out that the elliptical image of the bottom was brighter than expected if the object were close and therefore a small model. The excessive image brightness led him to conclude that the object was at a great distance (over a kilometer), His conclusion was criticized by Philip J. Klass and Rober Sheaffer who argued that veiling glare (caused by surface dirt and imperfections in the lens which scatter light from bright areas of the image into all other areas of the image) could have increased the brightness of the image of the UO, making it appear distant. This investigation revisited and improved upon Hartmann's method with the following modifications: the bottom of the UO in the first photo has been assumed to be as intrinsically bright as possible without being a source of light (i.e., assumed to be white) laboratory measurements have been used to estimate the magnitudes of veiling glare added to the various images of interest a film exposure curve has been used to determine relative image illuminances, and a surface brightness ratio, determined by field measurements, has been included. The results of the new photometric analysis suggest that the bottom of the UO is too bright for it to have been a non-self-luminous white (paper) surface of a nearby object. Hence it could have been distant. Introduction In June 1950, four weeks after they were taken, the photos illustrated below appeared in the local newspaper in McMinnville, Oregon. Subsequently, they appeared in Life Magazine and in
many publications,devoted to UFO reports. Although they
clearly depict an unusual object, they were never
treated as scientifically valuable because it was always
considered probable that they were photos of a hoax
object (e.g., "a garbage can lid"). Nevertheless they
did gain a large measure of scientific "stature" when,
in 1968, Hartmann(1) concluded that the object may have
been distant and, therefore, large (i.e. not a hoax).
Since the publication of Hartmann's conclusion in the
"Condon Report" (1) these photos and the verbal evidence
associated with them have been the subject of a
continuing controversy. A brief history of the analysis
of the photos is given in Figure
3 (click to view). A Brief History of the McMinnville Photos Publication: 8 June 1950. The Editor stated that "expert photographers declared there has been no tampering with the negatives. (The) original photos were developed by a local firm. After careful consideration, there appears to be no possibility of hoax or hallucination connected with the pictures. Therefore, the Telephone-Register believes them authentic." - The Telephone Register, McMinnville, Oregon Subsequent Immediate Publications: The Portland Oregonian, Portland, Oregon, 10 June
1950 (contains further verbal information) Condon UFO Report -Conclusion by Wm. Hartmann, case investigator: Certain physical evidence, specifically relative photographic densities of images in the photographs, suggests that the object was distant; if the object was truly distant, a hoax could be ruled out as beyond the capabilities of the photographer. (NOTE: Hartmann's report contains a good summary of the verbal evidence available up to 1967.) Sheaffer-Klass Conclusion (1974): Present Investigation : New testimony (published in a
companion paper to this) has been obtained and the
original negatives have been studied photogrammetrically
as well as photometrically. The present investigation
has confirmed that there are shadows on the garage wall
(agree with (a) above), but has found that, to within
the resolution of the measurements (using a traveling
microscope), the shadows other than the one at the edge
of the garage did not move with respect to the garage
wall between photos (the shadow at the edge of the
garage does appear narrower in photo 2)(disagree with
(b) above). The present investigation has reviewed and
confirmed the general validity of Hartmann's analysis.
When the effects of veiling glare and the ratio of
brightnesses of vertical and horizontal surfaces have
been accounted for the Hartmann-type analysis again
indicates a large distance (disagree with (c) above). A Brief History of the McMinnville Photos (cont.) The initial analysis was
carried out by a photographer (Bill Powell) who
worked for the McMinnville Telephone-Register In late 1973, unaware of the work of Sheaffer
and Klass, I decided to undertake an investigation
of the McMinnville case because (a) the pictures
are so clear the object is either a hoax device or
an unusual object (no misinterpretation seems
possible; e.g., it's not a plane at an odd angle),
and (b) Hartmann had devoted considerable effort
and analytical research to the photos and had
concluded on the basis of this physical evidence
that the object was distant (not a hoax).
Considering the general Photometric Analysis of the McMinnville Photos In the spring of 1975 I was able
to locate, with the incidental help of Mr. Klass,
the original negatives. (They were in the possession
of Philip Bladine, the editor of the newspaper.)
Consequently, all density values given in this paper
are from those negatives. They were measured on a
Joyce-Loeble densitometer that was repeatedly
calibrated with a Kodak standard diffuse neutral
density "wedge." Although many areas of both photos
have been scanned to establish consistency between
the exposures, etc., only the density values
pertinent to the range calculation will be listed
here. These values along with other pertinent
photographic data are listed in Table I. The
analysis is based on Hartmann's method with the
following modifications: TABLE I
----------------------------------------------------------------- where Ei is the image exposure, Di, is the
measured density for Di>0.1, Eo and k are
constants that depend upon the film development
"constant," gamma. Table IV contains a listing of
values of E, and k for various values of gamma. B = Ei - Gi (3) The amount of veiling glare added to an image
is proportional to the brightness, Bs, surrounding
the image: Gi = gi x Bs, where values of gi for
particular sizes and shapes of images in particular
surrounding brightness distributions have been
measured in the laboratory. With a brightness
distribution similar to that of the photos (bright
above the horizon, dark below the horizon), a
laboratory simulation has shown that, when a lens is
sufficiently dirty to produce guo ~ 0.12, i.e.,
glare in the UO image is abou 12% of the surrounding
brightness, then g(distant house)~ 0·035 and
g(horizon) ~ 0·05. (a) B(r=0) = intrinsic brightness = Bh + (B(r)-Bh) e^(br) (4) (b) r = range = (1/b)Ln{[B(r=0)- Bh]/[B(r) - Bh]} (5) where B(r) is the measured brightness at range r, Bh is the horizon brightness and b is the atmospheric extinction coefficient. To illustrate the photometric method I shall first summarize Hartmann's analysis, and then I shall present a range calculation based upon the simplified analysis. Hartmann pointed out that the upper bright side of the object appears brighter than the side of the nearby tank and that the elliptical shaded bottom is the brightest shadow in either photo. He attributed the excessive brightness of the bottom of the UO to atmospheric brightening. (NOTE: the contrast between the brightness of an object and that of the sky, assumed to be brighter than the object, approaches zero as the distance to the object increases, i.e., the apparent brightness of the object increases until it matches that of the sky at a great distance.) By definition the intrinsic brightness of an object is the brightness measured from a very short distance. By assuming the intrinsic brightness of the bottom of the UO was the same as that of the shaded bottom of the tank, and using the formula which attributes increased brightness to atmospheric effects over a long distance (Equation 5 in Table 1), he estimated that the range to the object was about 1.3 km, based on his estimate of b (0.289/km.). (NOTE: all his brightnesses were normalized to the horizon brightness so Bh = 1 in his version of Eq. 5). He then pointed out that if the UO were nearby under the wires, the bottom must have been very white, even brighter than the shaded white surface of the distant house which appears near the bottom of the photos. I have modified Hartmann's analysis by assuming at the outset that the bottom is as bright a surface as would have been available to the photographers (white paper) without being itself a source of light. (Note: the witnesses described the bottom as being copper colored or darker than white. Use of a darker bottom in the following analysis would result in a greater calculated distance.) This assumption has led me to compare the relative brightness of the bottom of the UO with the relative brightness of a hypothetical nearby horizontal shaded white surface as seen from below. The brightness that a horizontal white surface seen from below would have had under the circumstances of the photo has been estimated from the relative brightness of the vertical shaded white surface of the distant house (and also from the shaded white surface of the wall nearby Trent house) and from the brightness ratio Rb in table 1. If, in a naive way, the intrinsic brightness of a vertical white shaded surface (house wall) is equated to the intrinsic brightness of a horizontal white surface as seen from below (whereas the horizontal surface actually may be somewhat less than half as bright), that is, if Rb is set equal to 1 , and if the effects of veiling glare are ignored (G in Eq. 3 is set equal to zero), then the range of the UO can be calculated from Eq. 5 using as B(r=O) the brightness of a nearby vertical shaded white surface (the Hartmann method). The shaded wall of the distant house was used by Hartmann to estimate the relative brightness of a hypothetical nearby vertical surface (see the illustration labelled "TrntWhteHouse.gif) by correcting the relative brightness of the wall for atmospheric brightening using Eq. 4 (Table I). If the object were hanging under the wires then, by this (naive) reasoning, the brightness of the hypothetical nearby vertical surface should equal the brightness of the bottom of the UO, and Eq. 5 would yield r = 0. Such a result would be consistent with the hoax hypothesis. However, Hartmann found that the brightness of
the image of the bottom of the UO was actually
greater than the brightness of his hypothetical
neaby vertical surface. Hartmann's calculation is
duplicated in Table II except that I have used b =
0.2/km rather than 0.289/km. The table lists the
pertinent relative "brightnesses," Ei (uncorrected
for glare), the correction of the distant house wall
"brightness" for atmospheric brightening, and the
range calculated from Eq. 5. The calculated range,
1.4 km., agrees with Hartmann's result and is
clearly inconsistent with the nearby UO hypothesis. TABLE II Accurate calculations of object brightnesses require corrections for veiling glare, as pointed out by Sheaffer. Since, in the first approximation, the phenomenon (scattering) which produces veiling glare simply adds light (from the brighter areas) to the darker areas, it is only necessary to subtract the amount of glare from an image to find the object brightness (Eq. 3). The problem is to find the amount of glare on an image. After some considerable thought and experimentation I found a way to estimate the glare on the Trent photos using laboratory simulations. In order to estimate amounts of glare on the
images of interest in these photos, I have conducted
laboratory experiments with several camera lenses,
one of which was comparable (but not identical) to
the lens on the camera that took the photos. I
simulated the brightness distribution of the sky
with a large screen which was illuminated from
behind. Below the simulated "horizon" (the bottom of
the bright area) there were no sources of light. I
then measured brightness distributions in the bright
and dark areas when there were varying amounts of
grease on the lens. (Measurements were made with a
linear photodetector and a small aperture that could
be moved about in the focal plane of the lens.) The
light that "turned up" in·the dark areas was
the glare light, G, which would have appeared on any
images that might have been present in the dark
areas (although no such images were present in the
laborstory simulation). Values of G were
proportional to the "sky" brightness, Bs, so that at
each point on the image plane a glare index, gi,
could be defined as gi = Gi/Bs. For the present work
it was important to have values of gi for images 2
degrees below the horizon (the angle of the image of
the distant house) and for images at (or just below)
the horizon, when the glare index for an image of
the angular size and shape of the elliptical bottom
of the UO was a particular value. The effect of the inclusion of veiling glare is
readily apparent when it is applied to the image
illuminances, Ei, shown in Table II. For example,
the horizon brightness is found to be Eh - Gh = Eh -
ghBs (where, from Table I, gh= 0.05) = 0.039 -
(0·05)(0·07) = 0·0355. Similar
calculations yield the relative brightnesses given
in Table III. Note that in this first order theory
the small loss of brightness from the bright areas
is ignored, so Esky = Bsky. TABLE III From Table III one can observe that a major effect of the inclusion of veiling glare is to make the brightness of the bottom of the UO equal to (or slightly less than) the brightness of a vertical shaded white surface. Naive use of Eq. 5 with B(r=0) = 0.014 and B(r) = Buo = 0.0136 would yield a range of zero (negative numbers are not allowed), so Sheaffer's conjecture that the apparent distance of the UO could be explained by veiling glare has merit. (NOTE: If guo were 0.07 and the other values of gi were proportionately lower, the range would not be zero but about 400 meters.) If there were no other correction factors this would be the end of the analysis. However, field measurements with a spot photometer have shown that it is incorrect to equate the brightness of a shaded vertical white wall with the brightness of a horizontal surface as seen from below. A shaded vertical wall which is on the order of ten feet above the ground and which is not closely surrounded by trees is illuminated by direct sky light as well as by light reflected from the ground. On the other hand, the horizontal bottom surface of a body which is less than ten feet above the ground is illuminated only by light reflected from the ground. Since the ground reflectivity is not particularly high (15-30% for grassy ground), one would expect the illumination on the horizontal (or nearly horizontal) bottom of an object to be less than that on the vertical surface. Thus, from a priori reasoning one should not equate the relative intrinsic brightness of a white shaded vertical surface to the relative intrinsic brightness of a white shaded horizontal surface seen from below. To provide a quantitative estimate of the ratio of brightness of a vertical surface to a horizontal surface, Rg, (see Table I) I made field measurements with a calibrated panchromatic 3.5 degree field of view spot photometer. I measured the brightness of the white wall of a house when the wall was shaded by the eave and when the sun angle and sky conditions were similar to those at the time of the UO photos. Under the same environmental conditions, I measured the brightness of an opaque white paper surface held about seven feet above the ground. Many measurements of the surfaces were made with the result that the house wall was found to be 1.5 to 2 "stops" (photographic terminology) brighter than the bottom of the white surface, depending upon the exact nature of the ground (grassy, dirt, etc.) and upon the sky brightness distribution. Allowing a 1/4 stop possible error in the readings, the brightnass ratio lay within the range 2^1.25 = 2.4 to 2^2.5 = 4.7 (see Table I). To be "conservative" I have used Rb = 2.4 in these calculations. (NOTE: This ratio was measured with panchromatic meter. If a filter had been used to simulate the orthochromatic Verichrome spectral response, the measured ratio might have been as much as 30% greater.) The measured brightness of the bottom of the horizontal surface did not change noticeably when the surface was tilted by as much as 20 degrees. From Table III the relative brightness of a
nearby vertical white shaded surface was 0.014. From
the field measurements this value should be divided
by a number at least as great as 2.4 to obtain the
relative brightness of a nearby horizontal white
shaded surface, which is assumed to be the
brightness of the bottom of the nearby UO. With Bh =
0.0355, Buo = B(r=0) = 0.0136 (see Table III), with
B(nearby horizontal surface viewed from below)
=·0.014/2·4 = 0.0058, and with b = 0.2
(Table I) the range calculation yields about 1.5 km.
TABLE IV IF NEARBY UNDER THE OVERHEAD WIRES: 5m 14 cm 2
cm Table IV also contains a list of ratios of the brightnesses of the bottom of the UO to the expected brightnesses if the object were close and had a white bottom (the brightnesses of a nearby horizontal shaded white surface). Since the expected relative brightnesses were calculated using a white surface (the distant house wall or the nearby house wall - see Appendix) as a reference, the ratios imply that the bottom of the UO was "brighter than white" whenever reasonable values of gamma, i.e., gamma > 0.6, were used in the calculation. White surfaces reflect most of the incident light (both white paint and white paper have reflectivities in the range(6) of 60-80%). If we assume, for example, that the white paint on the distant (or nearby) house reflected only 60% of the incident light, then a brightness ratio greater than 1/0.6 = 1.67 would imply that, if the UO were a small nearby model. then its bottom was a source of light (it could not reflect more light than 100% of what was incident on it; 1.67 X 60% = 100%). As shown in Table IV, for reasonable values of gamma the calculated ratio Buo/B(r=0) exceeds 1.67 by a considerable margin. Actually 1.67 is an upper bound on the ratio if the distant house reflected 60% of the light because any white surface which the witnesses would have available to place on the bottom of their hypothetical nearby UO would have a reflectivity lower than 100%. If the bottom were white paper, the reflectivity would be, at maximum, about 80%, in which case the maximum expected ratio of the brightness of the bottom to the expected brightness would be 0.8/0.6 = 1.33. (NOTE: If the white painted surface were known or assumed to be dirty, the reflectivity would be decreased and the brightness ratio increased. For example, to obtain the brightness ratio 2.34 which is obtained when gamma = 0.6 (see Table IV) with 80% reflective paper on the bottom of the object, the distant wall reflectivity would have to be as low as 0.8/2.34 = 0.34. On the other hand, measurements of the image density of the shaded wall of the nearby Trent house, after correction for veiling glare, yielded an upper bound on the relative brightness of a shaded white vertical surface of 0.0171, which is only 0.0031 units higher than the value 0.014 in Table III. This house was reportedly painted in the year previous to the sighting date, so the paint must have approached its maximum reflectivity. Use of this value, after dividing by 2.4, with the other brightnesses in Table III yields a distance of about 1.3 km, and a brightness ratio of 1.9, which is still larger than 1.67 and 1.33.) The implication of the brightness ratios for reasonable values of gamma is that the bottom of the UO was itself a source of light if it were nearby (e.g., within 20 feet under the wires). To be a source of light it would have to have (a) contained a source of light, or (b) been made of translucent materials so that light could filter from the sky above through the bottom surface. Requirement (a) is considered beyond the capabilities of the photographer because a very small illumination apparatus would have been required and because the illumination mechanism, a small light bulb, would have produced a very uneven distribution of light over the bottom surface in contradiction to the fact that there are no "hot spots" of brightness in the image of the bottom (see TrntDensUO1.gif and TrntDensUO2.gif). Requirement (b) above is considered a possibility if the upper body of the UO were a translucent material.(7) Any holes through the upper body would allow direct sunlight through, and these would cause brightness "hot spots" on the bottom surface. On the other hand, a translucent or transparent material such as glass would probably not "look" the same in a side view as the object appears in photo 2 (apparently shiny like the nearby tank, but not a mirror - like specular surface). Any hypothetical translucent UO must appear, in a side view, as bright and "shiny" as does the object in photo 2 (also, it must be shown that an appropriately translucent or transparent material in the proper shape was available to the photographers). Independent tests of the density distributions·of the images of the object and its surround and of the density distributions of nearby objects in the photos have been made (8). Color contouring (using a computer to assign specific colors to specific density ranges) has shown that (a) the "back" end (left hand end in photo 1) of the object appears slightly non-circular (actually it comes to a slight or shallow "point"), and (b) the edges of the image are rough or jagged (the color contour boundaries are not smooth curves), whereas the edges of the images of nearby objects, and particularly of the wires "above" the UO, are relatively smooth. Observation (b) may be related to an atmospheric effect on images: the distortion of an image increases quite rapidly as the object distance increases up to about a kilometer, and then the distortion increases very slowly or not at all with further increases in range. The atmospheric conditions assumed for a hoax (morning, no wind) may have been conducive to the production of image distortion.(9) Thus, the jaggedness of the edge of the UO image may be an indication that it was more than several hundred meters away, thus contradicing the hoax hypothesis. (NOTE ADDED IN THE YEAR 2000: this was considered a theoretical possibility 25 years ago. Now I consider it unlikely that any edge fuzziness could be directly related to distance.)In conclusion
To echo Hartmann, the simplest interpretation of
these photos is that they, indeed, show a distant
object. However, simplicity does not necessarily imply
truth. ·Further research will be necessary to
resolve this case "once and for all."
NOTE: <http://brumac.8k.com/trent1b.html>APPENDIX
A provides further data and analysis regarding the
brightness of a white vertical surface and also provides
data to support the veiling glare analysis presented in
the text.
The following images also provide further
information:
Blbliography and Footnotes
1. Scientific Study of Unidentified Flying Objects,
E.U. Condon, Ed. (Bantam, 1969, pg. 396)
2. P.J. Klass, UFO's Explained, Random House, New
York (1974)
3. R. Sheaffer, private communication
4. C. Grover, private communication (Grover was a
Navy professional photographer)
5. Note that the range increases with assumed
darkness of the bottom of the UO. If the bottom were
black, B(r,O) = 0, the range would be about 2.4 km with
gamma = 0.6·
6. Handbook of Chemistry and Physics, Forty-first
Edition, (Chemical Rubber Publishing Company, Cleveland,
Ohio 1960)
7. Measurements have been made of the brightnesses of
the bottoms of several model UO's made of uniformly
translucent materials. The models were oriented with
respect to the sun in the same way as it would have been
if the UO in photo 1 were a model lit by the morning
sun. The brightness of the bottom of each model was
measured as a function of position, with the "front"
part being that part closest to the sun (in photo 1 the
front part of the elliptical image is at the right hand
side). The front part of the bottom was found to be from
20% to 40% brighter than the back part for each model.
However, the brightness variation of the image of the
bottom of the UO in photo 1 is only (+/-)5% with the
back somewhat brighter than the front. These
experiments, and the comparison with the image of the
UO, suggest that if the UO were a nearby model it was
not made of a uniformly translucent material.
8. W. Spaulding, GSW Inc., Phoenix, Arizona, private
communication. An electron microscope test of the
negatives has shown that the grain structure is
consistent with that of known Verichrome film, but not
with Plus X.
9. However, experiments (e.g. R. S. Laurcnce and J.
W. Strohbehn, "A Survey of Clear Air Propagation Effects
Relevant to Optical Communications," Proc. IEEE 58, 1523
(1970))have shown that there is a period of time just
after sunrise when the turbulence is quite low. The
pictures may have been taken during this period. If this
were so, even a very small amount of atmospheric edge
distortion would correspond to a rather large distance
to the object.
10. I thank Charles Grover, William Hartmann, and
Robert Sheaffer for instructive comments on earlier
versions of this paper. I also thank NICAP for free
access to their files and for assistance in obtaining
the negatives.
11. Note added in proof: the fog density of the
negatives is consistent with the range of values
expected when gamma = 0.5 to 0.6, but is larger than
expected when gamma = 0.3. The brightness of the
illuminated part of.the distant white wall and the
brightness of the shaded part of the same wall have been
calculated for gamma = 0.3, 0.4, and O.6. The calculated
brightness ratios, (illuminated/shaded), are,
respectively, 10(+/-)2, 3(+/-)0.5, and 2(+/-)0.2. A
field measurement of the same ratio under conditions
similar to those when the pictures were taken yielded
1.5 to 2. Thus both the fog density measurement and this
brightness ratio measurement indicate that gamma is
greater than 0.3 and perhaps even greater than 0.6.
Postpublication Notes
a) Experiments with a Kodak Vigilant lens of 153 mm
focal length yielded the same or lower values of veiling
glare than assumed in this paper.
b) Shadows on a surface that faces the east when the
sun was in the west have been observed when a cumulous
cloud was in the sky to the east of the surface.
NOTE 1 ADDED IN APRIL, 2000: A larger paper in which
I discussed the "rest of the story", including cloud
shadows and verbal testimony, was presented at the
second conference of the Center for UFO Studies which
occurred in 1981. That paper was eventually published by
the Center in the Spectrum of UFO Research in 1988. See
"The McMinnville Photos," the companion paper to this
one.
NOTE 2 ADDED IN APRIL, 2000: A very recent
re-investigation of the Trent sighting (ca. 1999) has
demonstrated that the camera used was probably not a
Kodak type but rather a "Roamer 1" built by Universal
Camera Corp. of New York for several year starting in
1948. It was a very inexpensive camera with a minimum f
stop of f/11 and a fixed shutter time of 1/50 sec. The
focal length was rated at 100 mm. The camera was
designed to be held in the "landscape" orientation (long
dimension horizontal) and the direction finder was to be
viewed from above, that is, the the operator held the
camera at stomach or chest level and looked downward
into the viewfinder to point the camera at the scene
before taking the photo. The fact that the focal length
of the camera was 100 mm rather than the 103 mm assumed
here has no effect on the photometric calculations in
this paper. Use of this shorter focal length does make
the calculated size of the UO 3% larger, e.g., in Table
IV all the diameters and thicknesses should be
multiplied by 1.03. I thank Brad Sparks, Joel Carpenter
and David Silver (President of the International
Photographic Historical Association) for successfully
identifying the camera that was actually used.
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