The power we now possess of fixing the transient impression of the rays
of light, and of retaining the beautiful images of the camera obscura,
is perhaps the most astonishing of the present age of wonders. Effects
similar to those of the electric telegraph, of steam navigation, of
dissolving views, and of other wondrous realizations of inventive
genius, had been anticipated in growing tales of Eastern romance
centuries ago; but the most fanciful imagination had not conceived the
possibility of making Nature her own artist, and of producing, in the
twinkling of an eye, a permanent representation of all the objects
comprehended within the range of vision.
Such an idea could scarcely have occurred until after the invention of
the camera obscura; but when looking at the beautiful pictures focused
on the screen of that instrument, it became an object of longing desire
to fix them there.
To trace the history of Photography from its earliest beginnings, we
must go back to the days of the alchemists, who were the discoverers
of the influence of light in darkening the salts of silver, on which
all photographic processes on paper depend. That property of light was
noticed in 1566, and it induced the speculative philosophers of that
day to conceive that luminous rays contained a sulphurous principle
which transmitted the forms of matter. Homberg, more than a century
afterwards, misled by this action of the sun's rays, supposed that they
insinuated themselves into the particles of bodies, and increased their
weight; and Sir Isaac Newton also entertained a similar opinion.
The influence of the solar rays in facilitating the crystallization of
saltpetre and sal ammoniac, was shown by Petit in 1722; and in 1777,
the distinguished chemist Scheele discovered that the violet rays of
the spectrum possess greater power in producing those changes than
any other. A solution of nitrate of silver, then called "the acid of
silver," was known to be peculiarly susceptible to the action of those
rays. The experiment by which it was illustrated consisted in pouring
the solution on chalk, which became blackened by exposure to light.
These discoveries were made by Scheele in his endeavours to find in
light the source of "phlogiston"--that _ignis fatuus_ of the chemists
of the last century. We thus perceive, in the first steps towards the
invention of Photography, one of the many instances of the discovery of
truth in the search after error.
At the beginning of the present century, Mr. Wedgwood, the celebrated
porcelain manufacturer, undertook a series of experiments to fix the
images of the camera, assisted by Mr. (afterwards Sir Humphry) Davy.
They so far succeeded as to impress the images on the screen, but
unfortunately they had not the power of preserving the paper from
being blackened all over when exposed for a short time to the light.
"Nothing," said Sir Humphry Davy, in his account of these experiments,
"but a method of preventing the unshaded parts of the delineation from
being coloured by exposure to light is wanting to render this process
as useful as it is elegant."
It was in June, 1802, that Mr. T. Wedgwood published "an account of a
method of copying paintings on glass, and of making profiles by the
agency of light; with observations by H. Davy." Mr. Wedgwood made use
of white paper or white leather, moistened with a solution of nitrate
of silver. The following description of the process, contributed to
the "Journals of the Royal Institution" by Davy, will be read with
interest, as showing how closely these experiments approximated to
the photogenic process, invented by Mr. Talbot thirty-six years
afterwards:--
"White paper or white leather moistened with a solution of nitrate
of silver undergoes no change in a dark place; but on being exposed
to daylight, it speedily changes colour, and after passing through
different shades of grey and brown, becomes at length nearly black;
the alterations of colour take place more speedily in proportion as
the light is more intense. In the direct rays of the sun, two or three
minutes are sufficient to produce the full effect. In the shade,
several hours are required; and light transmitted through different
coloured glasses acts on it with different degrees of intensity.
Thus it is found that red rays, or the common sunbeams passed through
red glass, have very little action on it. Yellow or green are more
efficacious; but blue and violet light produce the most decided and
powerful effects.
"When the shadow of any figure is thrown on the prepared surfaced, the
part concealed by it remains white, and the other parts speedily become
dark. For copying paintings on glass, the solution should be applied on
leather, and in this case it is more readily acted on than when paper
is used. When the colour has been once fixed on leather or paper, it
cannot be removed by the application of water, or water and soap, and
it is in a high degree permanent. The copy of a painting or a profile,
immediately after being taken, must be kept in a dark place. It may,
indeed, be examined in the shade, but in this case the exposure should
only be for a few minutes; by the light of candles or lamps, it is
not sensibly affected. No attempts that have been made to prevent the
uncoloured parts of the copy or profile from being acted upon by light,
have as yet been successful. They have been covered with a coating
of fine varnish, but this has not destroyed their susceptibility of
becoming coloured; and even after repeated washings, sufficient of the
active part of the saline matter will still adhere to the white parts
of the leather or paper, to cause them to become dark when exposed to
the rays of the sun.
"The woody fibres of leaves, and the wings of insects, may be pretty
accurately copied; and in this case it is only necessary to cause the
direct solar light to pass through them, and to receive the shadows
on prepared leather. Images formed by means of the camera obscura
have been found too faint to produce, in any moderate time, an effect
on nitrate of silver. To copy those images was the first object of
Mr. Wedgwood in his researches on this subject, and for this purpose
he first used the nitrate of silver, which was mentioned to him by a
friend as a substance very sensible to the influence of light; but all
his numerous experiments, as to their primary end, proved unsuccessful."
It will be seen, from the foregoing account of the results of their
experiments, that Mr. Wedgwood's process and the early processes
of Mr. Talbot were nearly alike; and if he had possessed the means
which the compound salt hyposulphite of soda afforded to subsequent
photographers, of destroying the sensibility of the prepared paper to
further impressions of the rays of light, there can be little doubt
that the invention would have attained a high degree of perfection at
the commencement of the present century. As it was, the failure of Mr.
Wedgwood to accomplish the object he was so nearly attaining appears to
have discouraged attempts by others, and twenty years elapsed without
any advance having been made towards its realization.
M. Niepce, of Chalons on the Saone, who was the first to succeed in
obtaining permanent representations of the images of the camera,
commenced experimenting on the subject in 1814, at least ten years
before M. Daguerre directed his attention to Photography. In 1826
these two gentlemen became acquainted, and conjointly prosecuted
the investigations which led to the beautiful result of the
Daguerreotype. M. Niepce having previously succeeded in obtaining
durable representations of the pictures focused in the camera, he
came to this country in 1827, and exhibited several of the results
of his process, and communicated to the Royal Society an account of
his experiments. These photographs, which may be considered the first
durable ones that had been obtained, were, with one exception, taken
on plates made of pewter. One of the largest was 5¼ inches long and 4
inches wide. It was taken from a print 2½ feet in length, representing
the ruins of an abbey. When seen in a proper light, the impression
appeared very distinct. Another one, which was stated to have been the
first successful attempt, was a view taken from nature, representing
a court-yard. Its size was 7½ inches by 6 inches, but it was not so
distinct as the preceding one. A third specimen was an impression on
paper, _printed from a photograph on metal_, the picture having been
etched into the plate by nitric acid, and then printed from. All these
specimens, though extremely curious as the first successful attempts
to preserve the images of the camera, were more or less imperfect,
and were far from presenting the beautiful results of Photography now
attained. It is remarkable, however, that the original process of
etching the picture on a metal plate, and printing from it, has now, in
the perfected state of the art, become the most recent improvement;
and the prints from photographic plates present some of the most
beautiful effects hitherto produced.[2]
M. Niepce communicated the particulars of his process to M. Daguerre
in December, 1829. They then entered into an agreement to pursue their
investigations jointly, but it was not until ten years afterwards that
the invention of the Daguerreotype by M. Daguerre was made known.
To M. Niepce must, therefore, be awarded the honour of having first
discovered the means of rendering permanent the transient images of
the camera obscura. The plan he adopted was to cover a plate of white
metal with asphalte varnish, and expose it to the action of light in
a camera, when the parts whereon the light was concentrated became
hardened, and the other parts remained unaltered, and could be washed
away.
In M. Niepce's account of the process, after describing the preparation
of the asphalte varnish, he says:--"A tablet of _plated silver_, or
well-cleaned and warm _glass_, is to be highly polished, on which a
thin coating of varnish is to be applied cold, with a light roll of
very soft skin. This will impart to it a fine vermilion colour, and
cover it with a very thin and equal coating. The plate is then placed
on heated iron, which is wrapped round with several folds of paper,
from which, by this method, all moisture has been previously expelled.
When the varnish has ceased to simmer, the plate is withdrawn from the
heat and left to cool and dry in a gentle temperature, and protected
from a damp atmosphere. The plate, thus prepared, may be immediately
subjected to the action of the luminous fluid in the focus of the
camera; but even after having been thus exposed a length of time
sufficient for receiving the impressions of external objects, nothing
is apparent to show that these impressions exist. The forms of the
future picture remain still invisible. The next operation then is to
disengage the shrouded image, and this is accomplished by a solvent."
The solvent employed was a mixture of one part of oil of lavender, and
ten parts of oil of petroleum. The solvent was poured over the plate,
and allowed to remain. M. Niepce continues: "The operator, observing
it by reflected light, begins to perceive the images of the objects
to which it has been exposed gradually unfolding their forms, though
still veiled by the supernatant fluid, continually becoming darker from
saturation with the varnish."
The time required for the exposure of the plates in the camera was six
or eight hours. For the purpose of darkening the pictures, M. Niepce
used iodine, and it has been supposed that the use of iodine for that
purpose suggested the employment of it to his partner.
The process adopted by M. Daguerre was, to deposit a film of iodine on
a highly polished silver plate, by exposing the plate to the vapour
of iodine in a dark box. The prepared plate was then placed in the
camera, and after an exposure of ten minutes or more, according to the
brightness of the day, an impression was made on the iodised silver,
but too faint to be visible. To bring out the image thus invisibly
impressed, the plate was exposed to the vapour of mercury, in a closed
box. The mercury adhered to the parts on which the light had acted,
and left the other parts of the plate untouched; and by this means a
beautiful representation was produced, in which the deposited mercury
represented the lights of the picture, and the polished silver the
shadows. The iodised silver remaining on the plate not acted on by
light, was washed away by a solution of hyposulphite of soda, and the
picture could then be exposed without injury.
Nothing can exceed the delicacy of delineation by such a Daguerreotype;
for the fine surface of the highly polished silver seems to exhibit the
impressions of the smallest objects that emit rays of light. The length
of time required to produce an impression was, however, a serious
obstacle to the use of the process, as originally invented, for taking
portraits. Numerous attempts were consequently made to obtain a more
sensitive material. Bromine was tried, in addition to iodine, and with
such complete success, that a few seconds were sufficient to effect an
impression on the plate, which could be forcibly brought out by the
vapour of mercury.
It was in 1840 that portraits were first taken by the Daguerreotype
process in this country. In the first instance, a concave mirror was
employed to concentrate the rays of light on the plate, instead of a
lens; and the author has now in his possession a portrait taken in
this manner, by "Wolcott's reflecting apparatus." The object of using
a concave mirror was to be able to concentrate a greater number of the
rays of light than could be done by a lens, and thus to form a brighter
image. At the time that portrait was taken, the means had not been
discovered of making the mercury adhere to the plate, and a feather
would brush it away. Soon afterwards, however, M. Fizeau ingeniously
contrived to fix the images on the plate by gilding it. This was done
by pouring on to the plate a few drops of a diluted solution of muriate
of gold, and holding it horizontally over the flame of a spirit lamp;
by which means the gold was deposited and formed a thin, beautiful film
of the metal over the surface, and thus not only made the picture more
durable, but gave it increased effect.
The French government, fully appreciating the importance of the
invention, determined to purchase it from the patentee, and to throw it
open to the public. An account of the invention was published in June,
1839; and in the following month an arrangement was entered into, to
the effect that, in consideration of M. Daguerre making the process
fully known, a pension of 6,000 francs should be granted to him for
life, and a pension of 4,000 francs to M. Isidore Niepce, the nephew of
the original inventor of Photography, his uncle having died before the
final success was attained.
It was generally supposed at the time, that by the grant of those
pensions the invention was thrown open to the whole world, as
represented by the French Minister; but, nevertheless, M. Daguerre
patented the process in other countries, and France alone reaped the
benefit of a free use of the invention.
Whilst M. Daguerre was thus successfully working out to perfection the
plan of producing beautiful naturally-impressed pictures on iodised
silver surfaces, Mr. Fox Talbot was at the same time nearly attaining
the same results. The following is the account given by himself of his
researches:[3]--"Having in the year 1834 discovered the principles of
Photography on paper, I some time afterwards made some experiments on
metal plates; and in 1838 I discovered a method of rendering a silver
plate sensitive to light, by exposing it to iodine vapours. I was at
that time, therefore, treading in the footsteps of M. Daguerre, without
knowing that he, or indeed any other person, was pursuing, or had
commenced or thought of, the art which we now call Photography. But
as I was not aware of the power of mercurial vapour to bring out the
latent impressions, I found my plates of iodised silver deficient in
sensibility, and therefore continued to use in preference my photogenic
drawing paper. This was in 1838. Some time after--in August, 1839--M.
Daguerre published an account of his perfected process, which reached
us during the meeting of the British Association; and I took the
opportunity to lay before the Section the facts which I had myself
ascertained in Metallic Photography."
Whilst to M. Daguerre must be awarded the honour of having first
brought to perfection the method of rendering permanent the images of
the camera on metal plates, Mr. Fox Talbot may claim to be the first
who perfected similar images on paper, which the comparative roughness
of the surface alone prevented from being as delicately beautiful
as the pictures of the Daguerreotype. He commenced his experiments
in Photography in 1834; and on the 31st of January, 1839, he read a
paper before the Royal Society, entitled, "Some Account of the Art of
Photogenic Drawing; or, a process by which natural objects may be made
to delineate themselves without the aid of the artist's pencil."
Mr. Talbot had not then succeeded in obtaining the impressions of
images focused in the camera; what he had succeeded in doing was to fix
upon paper the shadows of objects placed upon it, and exposed to the
light of the sun. The paper was first dipped into a solution of common
salt, and then wiped dry, to diffuse the salt uniformly through the
substance of the paper. A solution of nitrate of silver was then spread
over one surface with a soft brush, and dried carefully before a fire
in a darkened room. The strength of the solution was regulated by first
obtaining a saturated solution of the nitrate of silver, and afterwards
diluting it with six or eight times its volume of water. The objects to
be copied, such as leaves, lace, or other flat surfaces, were pressed
against the prepared paper by a glass fixed in a frame, and exposure
to light quickly darkened all the parts of the paper, excepting those
shaded by the objects. The image thus impressed was what is termed a
"negative," the dark parts which excluded the light being left white on
the paper, and the parts through which the light passed being darkened.
To produce a picture corresponding with the natural lights and shades,
the process was repeated, substituting the picture first obtained, on
thin transparent paper, for the original object, by which means the
lights and shadows were reversed.
The chloride of silver, formed on the surface of the sensitive paper
by the combination of the common salt and nitrate of silver, being
insoluble in water, great difficulty was experienced in washing it
away, so as to prevent the whole surface from afterwards darkening
on exposure to light. The application of hyposulphite of soda, for
the purpose of making the pictures durable, was suggested by Sir John
Herschel, and it answers remarkably well, as it dissolves the chloride
of silver. A solution of ammonia is nearly equally efficacious in
removing the chloride.
The Calotype process, by which the images of the camera can be
fixed upon paper, was invented by Mr. Talbot, in 1840. It is thus
described:--Dissolve 100 grains of crystallized nitrate of silver in 6
ounces of distilled water. Procure some fine writing paper, and wash
one side of it with the solution, laid on with a soft brush; then dry
the paper cautiously, by holding it at a distance from the fire. When
dry, dip the paper into a solution of iodide of potassium, containing
500 grains dissolved in 1 pint of water, and let it remain in the
solution two or three minutes. Then dip it into a vessel of water;
remove the water on the surface by blotting paper, and dry it by a
fire, in the dark or by candle-light. The paper thus prepared is called
"iodised paper;" it is not very sensitive to light, and may be kept for
some time without spoiling. Next dissolve 100 grains of crystallized
nitrate of silver in 2 ounces of distilled water; add to the solution
one-sixth of its volume of strong acetic acid, and call that mixture
A. Then make a strong solution of crystallized gallic acid in cold
water, and let that solution be called B. Mix equal volumes of A and
B together in small quantities at a time. That mixture Mr. Talbot
calls gallo-nitrate of silver, and with it wash over the surface of
the iodised paper. Allow the paper to remain half a minute, and then
dip it into water, and again dry it lightly with blotting paper. The
paper thus prepared is very sensitive, and will receive an impression
in the camera in the shortest possible time. The impression is at first
invisible, but it may be brought out by laying the paper aside in the
dark, or by washing it once more in the gallo-nitrate of silver, and
holding it at a short distance from the fire. To fix the picture, the
paper is first washed in water and lightly dried, and then soaked in
a solution of hyposulphite of soda for a few minutes, by which means
the iodised silver is removed, and after being again washed in water
and dried, the process is completed. The picture thus produced is a
negative one, and requires to be transferred in the manner before
stated. The original Calotype may, by that means, serve to produce a
great number of pictures.
Mr. Talbot's patent was sealed on the 8th of February, 1841. In his
specification, he claimed the use of gallic acid, and he succeeded
in enforcing his claim in a Court of Law, though it appeared that on
the 10th of April, 1839, photographs of objects taken in the solar
microscope in five minutes, by the Rev. J. B. Reade, were shown at
the London institution, which were described to have been produced by
an infusion of galls, and fixed with hyposulphite of soda. It must be
mentioned, however, to Mr. Talbot's honour, that on a representation to
him by the President of the Royal Society that the art of Photography
was impeded in its progress in this country by patent monopolies,
he generously made a present to the public of all his inventions
and discoveries, reserving to himself only the privilege of taking
portraits.
The transfer from one paper to another of the picture obtained in
the camera, and the comparative roughness of the surface of the
paper itself, prevent Calotypes from exhibiting that sharpness and
delicacy of definition which are so admirable in a Daguerreotype.
Several attempts were therefore made to obtain a more smooth surface
for the reception of the image; but without much success, until glass
was adopted for the purpose. To make that material available, it is
necessary to coat it with some substance that will absorb the sensitive
solution. In the first instance, the white of eggs was employed
with considerable success. Albumen has, however, been supplanted by
collodion--a solution of gun-cotton in ether--which is found to be
peculiarly suitable for the reception of the sensitive preparation of
silver.
In conducting the collodion process, the collodion is first iodised by
adding to it iodide of potassium and iodide of silver, dissolved in
alcohol. The iodised collodion is then poured over a plate of glass
that has been carefully cleaned, and is moved about horizontally
until a perfectly uniform film is spread over the surface, to which
it adheres firmly. The plate is afterwards dipped into a solution of
nitrate of silver, which renders it so highly sensitive to impressions
of light, that it will receive an image in less than a second. The
image is latent, until it is developed by pouring over the plate a
mixture of pyro-gallic acid in distilled water, acetic acid, and
nitrate of silver. The impression is fixed with hyposulphite of soda.
The pictures produced by the collodion process are negatives, which
serve admirably for transferring positive pictures on to sensitive
paper. But, if required, the negative picture can be readily changed
into a positive one, by converting the darkened silver into white
metallic silver, by a mixture of protosulphate of iron and pyro-gallic
acid. In a short time a white metallic image is obtained, which, when
relieved by a background of black velvet or black varnish, equals in
delicacy of finish the most beautiful Daguerreotypes.
Many attempts have been made, but hitherto without success, to obtain
photographs coloured, as well as shaded, by nature. The opinions of
those who have most studied the subject differ as to the possibility
of ever attaining that desired object. Sir John Herschel has so far
shown that it is not impossible, as to have impressed the colours of
the solar spectrum on paper, by the mere action of light; and parts
of the images of objects fixed on the screen of the camera are also
sometimes coloured. These facts induce us to hope that in the progress
of discovery some means may be found of obtaining naturally-coloured
photographs, notwithstanding it has been pronounced, by good
authorities, to be an absolute impossibility.
Specimens of coloured photographs were exhibited by Mr. Mercer at the
recent meeting of the British Association, which showed that by the
use of various chemical preparations that are sensitive to light,
photographs may be shaded in colours. The principal re-agents employed
were salts of iron, and by immersing the paper in suitable menstrua,
after the image had been impressed in the camera, the picture was
developed in any colour required; the same tint being spread over the
whole. One purpose to which it was suggested this coloured photographic
process is applicable, is printing on woven fabrics, the action of
light serving as a mordant to fix the colours.
Photography has been already applied to various uses, and it is capable
of being rendered much more valuable. To the meteorologist it affords
the means of registering the rise and fall of the mercury in the
barometer and thermometer, and, by a self-registering apparatus, the
changes of temperature and of atmospheric pressure are marked upon
paper that records the time at which the changes occur. It may also be
applied, in the same manner, to register the directions of the wind,
and the times of its changes. The sun impresses his own image upon
paper; and the spots on his surface, thus correctly delineated, can be
compared with those seen in pictures of the sun at other times; and
the foundation is laid for more correct knowledge of the nature of
those appearances, and of the motion of the sun himself. Photographs of
the moon and planets present exact representations of those heavenly
bodies, as seen through the most powerful telescope; and, with the
assistance of the stereoscope, the figure of the moon is shown in its
true globular form, as it can be seen by no other means. It has been
proposed, indeed, by the aid of Photography, to extend our knowledge
of the stars far beyond the reach of telescopic vision; for as the
image focused on the screen of the camera is composed of rays from
every object on the body of a star, it might be possible to see those
objects by greatly magnifying the image. It remains, however, for the
further progress of discovery and invention, to arrive at so delicate a
delineation by photographic processes, as to obtain landscapes of the
moon, and portraits of the inhabitants of Jupiter!
One of the latest advances in the art of Photography has been the
engraving on steel-plates by the action of light, by which means more
forcible effects have been obtained than by the impressions of light
upon paper. Mr. Fox Talbot has distinguished himself in thus fixing the
images on steel, as he was the first to impress them upon paper. In
his method of doing so, he covers the steel plate with a solution of
isinglass and bichromate of potass, and placing a collodion negative
picture upon it, he exposes it to the action of light. When the picture
is sufficiently impressed, he etches it into the plate by means of
bichloride of platinum. M. Niepce, the nephew of the original inventor
of Photography, has produced the same effect by reviving the first
processes adopted by his uncle; using, as he did, bitumen, dissolved
in essential oil of lavender, to cover the plates. Two other foreign
photographers, M. Poitevin and M. Pretschi, have also successfully
directed their attention to engraving the images of the camera, which
has now obtained a high degree of perfection.
It is well worth notice that these most recent improvements in
Photography are but further developments of the original designs of M.
Niepce, who not only succeeded in etching the pictures impressed by the
light of the sun on his metal tablets, but made use of a glass surface,
on which the now generally adopted collodion process depends.