Combination photographs change entirely the character of the initial negative and have been made for the past fifty years.The earliest, simplest, and most harmless photographic deception is the printing of clouds into a bare sky.But the retoucher with his pencil and etching tool to-day is very skilful.A workman of ordinary skill can introduce a person taken in a studio into an open-air scene well blended and in complete harmony without a visible trace of falsity.
"I need say nothing of how one head can be put on another body in a picture, nor need I say what a double exposure will do.There is almost no limit to the changes that may be wrought in form and feature.It is possible to represent a person crossing Broadway or walking on Riverside Drive, places he may never have visited.
Thus a person charged with an offence may be able to prove an alibi by the aid of a skilfully prepared combination photograph.
"Where, then, can photography be considered as irrefutable evidence?
The realism may convince all, will convince all, except the expert and the initiated after careful study.A shrewd judge will insist that in every case the negative be submitted and examined for possible alterations by a clever manipulator."Kennedy bent his gaze on McLoughlin."Now, I do not accuse you, sir, of anything.But a photograph has come into the possession of Mr.Travis in which he is represented as standing on the steps of your house with yourself and Mr.Cadwalader Brown.He and Mr.Brown are in poses that show the utmost friendliness.I do not hesitate to say that that was originally a photograph of yourself, Mr.Brown, and your own candidate.It is a pretty raw deal, a fake in which Travis has been substituted by very excellent photographic forgery."McLoughlin motioned to Hanford to reply."A fake?" repeated the latter contemptuously."How about the affidavits? There's no negative.You've got to prove that the original print stolen from Travis, we'll say, is a fake.You can't do it.""September 19th was the date alleged, I believe?" asked Kennedy quietly, laying down the bundle of metric photographs and the alleged photographs of Travis.He was pointing to a shadow of a gable on the house as it showed in the metric photographs and the others.
"You see that shadow of the gable? Perhaps you never heard of it, Hanford, but it is possible to tell the exact time at which a photograph was taken from a study of the shadows.It is possible in principle and practice and can be trusted.Almost any scientist may be called on to bear testimony in court nowadays, but you would say the astronomer is one of the least likely.Well, the shadow in this picture will prove an alibi for some one.
"Notice.It is seen very prominently to the right, and its exact location on the house is an easy matter.You could almost use the metric photograph for that.The identification of the gable casting the shadow is easy.To be exact it is 19.62 feet high.The shadow is 14.23 feet down, 13.10 feet east, and 3.43 feet north.You see I am exact.I have to be.In one minute it moved 0.080 feet upward, 0.053 feet to the right, and 0.096 feet in its apparent path.It passes the width of a weatherboard, 0.37 foot, in four minutes and thirty-seven seconds."Kennedy was talking rapidly of data which he had derived from his metric photograph, from plumb line, level, compass, and tape, astronomical triangle, vertices, zenith, pole and sun, declination, azimuth, solar time, parallactic angles, refraction, and a dozen bewildering terms.
"In spherical trigonometry," he concluded, "to solve the problem three elements must be known.I knew four.Therefore I could take each of the known, treat it as unknown, and have four ways to check my result.I find that the time might have been either three o'clock, twenty-one minutes and twelve seconds, in the afternoon, or 3:21 :31, or 3 :21 :29, or 3:21 :33.The average is 3 :21 :26, and there can therefore be no appreciable error except for a few seconds.
For that date must have been one of two days, either May 22 or July 22.Between these two dates we must decide on evidence other than the shadow.It must have been in May, as the immature condition of the foliage shows.But even if it had been in July, that is far from being September.The matter of the year I have also settled.
Weather conditions, I find, were favourable on all=20these dates except that in September.I can really answer, with an assurance and accuracy superior to that of the photographer himself - even if he were honest - as to the real date.The real picture, aside from being doctored, was actually taken last May.Science is not fallible, but exact in this matter."Kennedy had scored a palpable hit.McLaughlin and Hanford were speechless.Still Craig hurried on.
"But, you may ask, how about the automobile picture? That also is an unblushing fake.Of course I must prove that.In the first place, you know that the general public has come to recognise the distortion of a photograph as denoting speed.A picture of a car in a race that doesn't lean is rejected - people demand to see speed, speed, more speed even in pictures.Distortion does indeed show speed, but that, too, can be faked.
"Hanford knows that the image is projected upside down by the lens on the plate, and that the bottom of the picture is taken before the top.The camera mechanism admits light, which makes the picture, in the manner of a roller blind curtain.The slit travels from the top to the bottom and the image on the plate being projected upside down, the bottom of the object appears on the top of the plate.For instance, the wheels are taken before the head of the driver.If the car is moving quickly the image moves on the plate and each successive part is taken a little in advance of the last.The whole leans forward.By widening the slit and slowing the speed of the shutter, there is more distortion.
