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"Sears Camera Catalog - 1908 Product catalog
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- Sears
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- "Sears Camera Catalog - 1908
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- English
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- 117
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\ff\ www.butkus.us
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-F.UBI.ISHEN BY
SEARS3I.qSEtsEICK& eO,*View original page 1Page 4 · Read text
. E
www.butkus.us
COMPLETE INSTRUCTIONS
, I N
PHOTOGRAPHY
By F. M. NEEDHAM
A'GUIDE FOR THE BEGINNER AND BOOK OF REFERENCE
FOR THE EXPERIENCED PHOTOGRAPHER'
WITH THIRTY-SIX ILLUSTRATIONS
Published by
Sears, Roebuck 6&, Co.
Chicago, IllinoisView original page 4Page 8 · Read text
T I
F i www.butkus.us* .. F''
-SEARS, ROEBUCK & CO., CHICAG9, ILL.
INTRODUCTION
In this little volume we shall entirely avoid all the complicated
theories of the chemistry and optics of photograPhY, and confine our- ' selves simply to those lacts and principles which evefyone must be
familiar with in order to produce good pictures. There is plenty of; time to take ufi the scientific theories of photography when you have
learned the fundamental rules of exposure, development and printing.
Photography trndoubtedly ofiers a more attractive field, either
for pleasure or business, than anything else at present open to con-
sideration, and its great popularity is probably due, in no small meas-
ure, to the simplification of the various processes, the perfection
which has been attained in the manufacture of cameras, dry plates,
sensitized paper, and the various other materials and apparatus used,
all tending to make the production of photographs a simple and easy
matter.
In these days the lover of the beautiful secures in a few moments
exact likenesses of the choicest views of nature, which formerly
could be obtained only in a slow and laborious manner by those
favored few gifted with the ability to draw or paint. What could
be more treasured in after years than pictures of friends or family,
the old home, with al1 its fond memories and scenes of past
pleasures? I The modern photographic outfit places the ability to rnake such
pictures in the hands of everyone, and we believe that the time will
.oon "o-e when a person unable to operate a camera will be as
rare as one unable to read.
Before taking up the subject of photography in detail, the author
wishes to particularly impress upon his readers the irnportance, in
fact, the imperative necessity for the most careful and wA!9btql
attention to details. Success in photogr.
t@principles involved are simple and easily mas-
tered, but there is always a right way and a wrong way to do every-
thing. Photography is simply a branch of those great sciences,View original page 8Page 9 · Read text
G!;Fr 1%
6 COMPLETE INSTRUCTIONS IN PHOTOGRAPTIY
chemistry and optics, in which there is ao guesswork, no chance,
every result being in accordance with fundamental principles andF i laws which are inexorable. Like causes always produce fikJ results,
and when you make a negative which does- not prove successfui,
you may rest assured that in some detail, apparently unimportant
or perhaps entirely overlooked, you have transgressed these natural
laws, and a repetition of the same difficulty is o"nly avoiaed by care_
fully ferreting out the cause of the first failure.rjil
HOW TO SELECT AN OUTF'IT. iittil
liltil As this book may farl into the hands of some who have not yet
lrf purchased a camera, we have endeavored to give such information Itl
IT as shall make the selection of an outfit easier for those who have
lit had no experience in photography; so if you are about to invest in an outfit, we advise.you to caref.tliy read over the descriptions of the
rl carefullydifferent formswhat isof saidcamerasin regardas givento thein thekind folrowingof *or;t chapter,for which notingeach
t l style is suitable, and then after carefulry studying the description of
cameras and complete outfits as given in ou.-""ia1.gue, taking intcr
consideration, also, the amount of money which you wish to invest, tili t you should have no difficulty whatever in deciding which outfit to 'order.
,i Many who order cameras without fuly investigating the subject
beforehand, find, as soon as they becoml familia-r with the work,
that some other style, size or kind wourd have been more suitable
for their purpose' we believe, however, that anyone who makes
a selection with the aid of the suggestions given here, together,with
the very complete and carefut aescr;ptiorr. of the goods listed in our
catalogue, will be sure to get an outfit which wiil prove entirely
satisfactory and perfectly suited to the purpose contemplated.
t
t ._-*:-_View original page 9Page 10 · Read text
* f f i F www.butkus.us l SEARS, ROEBUCK & CO., CHICAGO, ILL
Digitally signed by
mike butkus
DN: cn=mike butkus, mike o=orphancameras,
ou=29,
CHAPTER I. email=mike@butkus.
org, c=US butkus Date: 2018.12.10
CAMERAS. 13:52:43 -05'00'
Essentially a camera is simply a light-tight box with a piece of
glass, called the lens, in one end and a means of supporting the sen-
sitive plate or film in the other end. Rays of light, reflected from
the object to be photographed, pass through the lens and are pro-E
jected against the plate rvhere they impress upon its sensitized surface
the likeness of the object.
The box constituting a camera may be constructed entirely of
wood or metal in a rigid manner, or it may be constructed partly of
leather, cloth or rubber, in such a
way as to permit its being folded
into a more compact form when not
in use, and it may be fitted with
various adjustments and accessories;
but no matter how complicated the
camera may appear at first sight, a
slight examination will demonstrate
the fact that essentially it it3!1gP$
*'ith a lens in one lig!!1!!g!|-$
end and a means for holding the
dry plate or film in the opposite end.
All cameras mav be divided into
THEcoNLEysENroR, ABoxCAllERA. four generalclasses, the simple hand
:ameras, frequently called Box Cameras' th" @
View Clameras and Portraii Cameras. There is an infinite variety of
;.ffi; "ttd sfftes of cameras, but they can all be classified
under one or the other of the above heads.
In taking up for consideration these different forms of camer?s,
it will be impossible for us to touch upon the details of manipula-
tion, such as the operation of shutters, methods of adjusting, etc.,F as these details vary in different makes and, moreover, small instruc-
tion sheets covering these particular points are always sent with each
camera.View original page 10Page 11 · Read text
COMPLETE INSTRUCTIONS IN PHOTOGRAPHY.
The simple Hand Camera or Box Camera is by far the
BOXcameras:"::X;ffil,f:#:'JJ:1";i::':l#:JJ:f "#;ff;,i1:;
secondly, to the low price at which such cameras can be purchased.
Although a box camera is capable of producing fine pictures
rvithin certain limits, there are many kinds of \\'ork beyond its
capacity, and many pictures rn'hich cannot be made at all \,\rith a
box camera are easily made with a camera more complete in its
adj ustments.
There are trvo principal forms of box cameras, knou.'n as plate
lrolder cameras and rnagazirre cameras. In the plateholder camera
the sensitive dty plate upon which the picture is mad.e is placed
in rvhat is known as a plate holder, and this plate holder, \vith the
plate in it, is inserted in the back of the camera when a picture is
to be made. Each plate holder holds trvo plates, and the plates
must be put into the holder in the dark room.
The Magazine Cam-
era is so constructed that
a large number of plates,
usually tu'elve, can be
put directly into the
camera itself and ex-
posed, one after theother,
thus doing &\\ro,1r with
the use of plate holders.
The most popular
and undoubtedly the
l-'est rnagazine camera is
the Conley Magazine,
an d our illustration shows
the manner in rvhich the
plates are held a n d
manipulated inside the CONLEY ITIACAZINE CAMERA, SHOWING
camera. INTERIOR ARRANCEMENT.
A Box Camera is about the best instrument for a beginner
who desires a simple, yet good camera at a very smatrl expense. Box
cameras are usualiy provided with universal or set focus lenses, that is.
lenses not requiring to be focused and therefore mounted immovably in
tire camera front" Such cameras offer special advantages to the begin-
ner, or to those \.'ho do not rvish to go too deeply into photography,
as it is not necessary to adjust the focus each time a picture is taken"View original page 11Page 13 · Read text
10 CONLEY'S MANUAL' OF PTTOTOGRAPHY.
The Fold-
i n g H a n d 'a
Cameras r e
designed to
be used either
with or with-
out a tripod,
and are suit-
able for any
class of work
which may be
done either with a simple
Box Camera or a complete
rofessional View Camera.
C a m e r a s d e -
VigW signed for use only
cameras Xjll-?,#Tj*"il:
and are almost always e'h-
ployed by professional pho-
tographers. Although they
do no betier work than a
good Folding Hand Camera,
they are more strongly and
substantially' constructed;
convenience in operating,
together with strength and
durability, being the points
kept most prominently
in vierv by the filalru-
facturers, rather than
mere elegance of frnish
or compactness.
The best example of
a thoroughly well made,
substantial, service-
able View Camera
is the Queen City
shown in our illus-
tration. A camera
like this one can beView original page 13Page 14 · Read text
www.butkus.us
SEARS, ROEBUCK & CO., CHICAGO, TLL. l l
used for any kind of work which either an amateur or professional
photographer would ever have occasion to do.
We cannot too strongly recommend the View Camera to both
amateur and professional for general photographic work. It combinesIease of operation, completeness of adjustment, strength and dura-F bility to a degree not reached in other styles of cameras. The bellorvs
is made amply long, the swings possess great latitude, the front has
a wide raflge of movement, all adjustments are easy to get at, and
therefore convenient to manipulate. The style of construction per-
mits the use of extreme wide angle lenses, or any kind of rapid recti-
linear or anastigmat lenses, even the largest sizes, and the ample size
and strength of the front even pernits the use of the smaller types
of portrait lenses. In a View Camera nothing that will add to its
convenience of operation, its accuracy and ease of adjustment, in short,
to its effectiveness as a picture taking machine, is sacrificed for mere
elegance of appearance or compactness.
A View Camera is a businesslike camera for real photographers
who are seriously interested in their work and who want an outfit
that is, above all other considerations, thoroughly practical in every
detail.
Portraits can be made with either a regular View
Camera or Folding Hand Camera, and in' a limited way POftfait
even with a simple Box Camera, but the camera designed CamgfaS
especially for the purpose has points of superiorityTofTtts
particular rvork, and in photographic studios or galleries regular
Portrait Cameras are usually employed. As these cameras are designed
only to be used in studios, no attempt at reducing them in size or
u'eight is made, so they are always large and heavy, and must be
supported on what is knorntn as a camera stand, a device so arranged
that the camera may be quickly raised, lowered or tilted to any
desired angle, and for convenience in moving the instrument aboutn the gallery,,the stand is usually furnished rn'ith sma1l wheels or casters.
As before stated, however, just as good portraits can be made
u'ith a View Camera as with a Portrait Camera. It is merely a
question of convenience in working, and many professional photog-
raphers who do both portrait rn'ork and outside work and who do not
care to invest in two cameras use a \riei,v Camera for both pur-
poses. While the Vielr Camera readily adapts itself to either
line of work, the Portrait Camera, orving to its size and weight, is
suita'ble for use only in the studio.View original page 14Page 15 · Read text
T -qaaF
"t 12 cor\,fpl-Etb' r Nsr Rucr I oNs N"'FHor'rc'cdKpnv.
T
CHAPTER II.
TENSES AND SIIUTTERS.
As previously explained, the lens is the piece of glass in the
frontofthecameraandisthemostexpensiveandthe@!!
of the outfit. The quality of u'ork done with a camera depends EI!
entirely upon the lens, and therefofe, in selecting your outfit care
should be exercised to secure one containing a good lens. As the
quality of the lens cannot be judged in any way by its appearance,
and as a beginner in photography is entirely incapable of judging
a lens, even by an actual trial, it is usually necessary to take the
dealer's word regarding this point and thus the advisability of dealing
vi'ith a house u'hose goods are known to be exactly as represented is
apparent.
Photographic lenses may be divided into five general classes,
single lenses, double or rapid rectilinear lenses, anastigmat lenses,
wide angle lenses and portrait lenses.
The cheapest photographic lens made is
NOn-AChfOmatiC a singie convex lens, just like a . common mag-
nifying glass or like the lenses in spectacles whiih Single LgnSeS
very old people wear. Such lenses are used only in
the very cheapest cameras and as they are not accurately ground and
not properly corrected, they distort the picture, and as they are not
achromatic they separate the rays of light into colors, thus blurrii!
the picture.
The Si"gl@
Achromatic
Single Lenses simple lenses' one d o u b le
convex, the other p1 an o
convex, cemented together, thus apparently
forming a single lens. Such a lens does not
separate the rays of light into colors and n'iil
therefore form a sharp, clear picture. Such
cameras as the Conley Sr. Bor, or the Conley LENSSINCLEWITHACHROMATICREVOLVTNO
Magazine Camera are prcvided with single DIAPTTRACM.
achromatic lenses.View original page 15Page 16 · Read text
www.butkus.us -& co;'cFrrcA@,rLL 13 SEARslwoesucK
A Rapid Rectilinear Lens, u'hich is a doubl" Rapid ReCtilineaf
lens, consists of two single achromatic lenses LenSgS
mounted in oppositeends of a brass tube' 'L?""["a rectilinear be-
cause they render the
straight lines of a picture
without distortion, the
word rectilinear being
derived from the Latin
words for straight and
{ line.
A rapid reetilineal -as lens, alreadY ex-
arev ofplained,two lensesconsistswhichreallY "combina- "p&il- of as
" the lens in the tions,
front of the tube being " known as the front
rni conlevlp.s pnRto REcTILINEARLENs' combination,'' the other
a s t h e . . . r e a r c o m b i n a t i o n . ' ' T h e b e t t e r g r a d e s o f r e c t i l i n e a r l e n s e s
are so designed and constructecl tirat the separate combinations may
be used alone, rn'hich is a desirable quality' as the single combina-
tions posser, t lno"h greater focal lengih than the complete lens' alrd
the efficiency of a phJtographic outfii is much increased by having
available lenses of different focal lengths'
E a c h c o m b i n a t i o n o f a d o u b l e l e n s c o n s i s t s o f t w o o f m o r e
piecesofglasswhicharefirmlycemented.togetherwithaninvis'lrle
lement (balsam), thus apparently forming a single lens'
I n a g e n e r a l r n ' a y , r a p i d r e c t i l i n e a r l e n s e s a r e d i v i d e d i n t o t r v o
"svmmetrical" and "convertible' " A symmetrica-l lens is lt classes,
1 one in which the front and rear combinations afe of thc same stvlc
of construction and the same focal length; in other worcis, the front
exactly alike, an''l it is fromF combination and rear combination are this fact that the lenses are spoken of as symmetrical. In a symmet- 1I
rical lens the single combinations usually have a focal length of about
double that of the comPlete lens'
convertible lenses are lenses in which thc front and rear combi-
nations are of different construction and consequently of difierent
i""rf lengths, and with a convertible lens thc user has at his com-
mand thlee different focal lengths, namely, the complete lens, theView original page 16Page 17 · Read text
@F
14 COMPLETE INSTRUCTIONS IN PHOTOGRAPHY.
front combination alone, and the rear combination alone. Of course,
in different lenses the relative focal lengths differ, but taking the
lens furnished with the Conley Double Extension Camera in the 5x7
size, we have an example of a rectilinear lens of the convertible type
' in which the focus of the front combination is 18 inches, the rear
combination, 14 inches, and the complete lens, 8 inches.
Next to an anastigmat lens a good rapid rectilinear lens of the
symmetrical or convertible type is the best lens to use for general
all around photographic work.
Wide Angle Lenses are much the same as recti-
SIide Angle linear lenses in general construction, but the two
combinations are mounted more closely together and for LenSgS
this reason a wide angle lens is capable of including a
much wider extent of view, hence the name *i9ggla
These lenses are not very suitable for land-
scape or outside view work, although in certain
cases, such as the photographing of buildings,ttr
. s'here it is impossible to get far enough atvay to
include the whole of the building with a recti-
linear lens, the wide angle lens becomes a
necessity. IIIONARCH WIDE
Wide angle lenses are especially desirable ANCLE LENS.
for photographing interiors; in fact, they are practically indispens-
able for this work, as a single achromatic or rapid rectilinear lens
does not include a sufficiently wide angle of view to make a goodfi interior.
Anastigmat Lenses represent the highest degree of
AnaStigmat perfection in lenses and possess points of superioriiy over
the rapid rectilinear lenses rvhich make them very LenSeS
desirable. As compared with rapid rectilinear lenses,
the anastigmat lenses possess greater speed, better definition, and
entire freedom from astigrnatism. Definition is that property of a lffi lens rvhich enables it to make sharp, clean cut pictures, and while
fine definition may be obtained I'ith an ordinary rectilinear lens by
using a small diaphragm, which, of course, necessitates a longer
exposure, the anastigmat lens rvill give good definition even u'ith the
full opening. Anastigmat lenses are suitable for all kinds of photog-
"universal" raphy and may be described as lenses, as they are
adapted to landscape rvork, architectural subjects, interiors, groups,
portraits and copying. The large working aperture makes tbemffiparticularly suitable for very.rapid instantaneous exposures and for4View original page 17Page 18 · Read text
i- www.butkus.us
SEARS, ROEBUCK &'CO., CHICAGO, ILL t5
portrait work. A few years ago anastigmat lenses could only be
iurchased at very high prices, placing them beyond the reach of
tn.rry photographers, but during the last few years these lenses have
not orriy been still further improved in quality, but the competition
between different manufacturers has gradually brought the prices
lower and lorver until now it is possible to purchase a strictly high
grade genuine anastigmat lens rn'ith an eftective aperture as great as
n.O.S at prices for the 4x5 and 5x7 sizes ranging from $20.00 to
$35.00, including shutter. Lenses of this style and quality a few
t- years ago could not be purchased for less than $50.00 to $75.00. The
moderl anastigmat lens is in every way a triumph of opticat and
rnechanical skill.
Portrait Lenses arb also very similar in construction to
rectilinear lenses, but are so mads that they are -W-i$ Portrait.
that is, they require very short exposufes. Portrait lenses Lenses
usually have a long length of focus in proportion to the size
of tho plate and the great rapidity with which they work makes
them especially suitable for making portraits.
Portrait lenses are not to be recom-
mended for anything except actual portrait
work indoors. As before stated, all other
good qualities are sacrificed in order to
obtain great speed and they are not very.
rectilinear and do not possess much depth
of focus. 'Good portraits can be made
with rapid rectilinear or even with single
achromatic lenses, the only disadvantage being that a slightly longer
exposure must be given than would be necessary with a regular
portrait lens. -a
The focal length of lehs is the distance from the
ground glass to t-he optical center of the lens when F99al Length
focused on some distant object' The greater the Of LgnSeS
focal length, the narrower becomes the angle of view,
hence the single lens, which usually embraces a naltow angle of
view, has a long focal length, and the wide angle lens, which
embraces a large extent of view, has a very short focal length.
when the focal length of a double lens is mentioned, it is always
understood, unless otherrvise specified, to be the equivalent focus, by
which is meant the distance from the optical center of the lens to
the ground glass when it is focused on a distant object. The optical
""rrt", of the lens is not usually the same as the actual or mechanicalILView original page 18Page 19 · Read text
7
16 COMPLETE INSTRUCTIONS IN PHOTOGRAPHY.
_ centcr except with simple convex single lenses; . hence, the term "equivalent " focus as applied to double lenses, meaning that the lens
has a focal length equivalent to that of a single lens which rvould
proluce on the ground glass an image of a given object at a given
distance exactly the same size as rvould the double lens. In the case
of portrait lenses, which are very large and bulky, the back focus
is often stated so that purchasers can readily tell rvhether the camera
on which the lens is to be used has sufficient bellorvs capacitv to
accommodate the lens. The back focus is the distance from the back
of the lens to the ground glass l'hen focused on a distant object.
'The Diaphragm or Stop is the means of regulating the
Diaphfagns amount of light which passes through the lens during
an exposure; Usually in the oid stvle single lenses or Of StOpS
'.
'! number of holes of different sizes in it, so placed that any one of
these holes or openings may be revolved to the center of the lens
and the size of the opening regulates the amount of light admitted. 'Il' Such stops are known as revolving diaphragms, because they are
revolved to bring the desired opening into position.
Rectilinear lenses of the old style were usually provided with a
set of loose diaphragms or stops, that is, separate pieces .of metal,
each with a hole in the center, which rvere inserted in a slot in the : lens tube. Loose diaphragms are knorvn as waterhouse diaphragms.
Another style, known as the Iris diaphragm, is an ingenious
device of thin metal or hard rubber leaves inside the lens tube, so
arranged that a round opening is left in the center, the size of which
can be varied as desired by turning a lever on the outside. The
Iris diaphragrn is, of course, the most convenient and satisfactory
style, as there are no loose pieces to lose or mislay, and it can belIt instantly adjusted to any desired size The efiects produced by the
different styles of diaphragms, Revolving, waterhouse or rris, are,
of course, identical, and the only differences are matters of conven-iiI
ience in operating or elegance of design and finish
The use of diaphragms can best be illustiated by USe Of
Diaphrasms jl".,,lil'";i" il*:X,o}#:::*"J i3,.:l$"Jtil?;
upon some object about 20 or 25 feet arvay. Upon carefully observing
the image upon the ground glass, you will note that objects quite
close to the camera, and probably, also, otrjects at a considerTlG
distance away, are blurred, that is, not sharpry focused. No.v, put
ffi;r sil;Tl stop in the lens and probably tle first thing you willView original page 19Page 20 · Read text
www.butkus.us
SEARS, ROEBUCK & CO., CHICAGO. ILL. t7
observe is that the image is not nearly as briglrt T it was' There
is less light comi"g lfrtJ"gh the lens. Buffiok closer and yorr will
find another "harr!e: those portions of the view that were before
out of focus or fuzzy are now sharp and distinctTl Alittleexperimentingherewillshowyouthatthesmallerthe
stopis,the sharper, cle"rer-and rnore distinct the picture is, and this
may lead you to ".k, *hy not use the smallest stop a1l the time? In
;;iy, ;" witt catt yoo, ,tt"rrtion to the fact that the image, although
sharp, grows correspondingly darker and dimmer as the stop is made
smaller, and as it requires a certain invariable arllgunt 9f actio-n.'F'Y
lisht in order to produce th;li"t"teJ""ian readily understand that
tr;alqti" .top is, the Sitg theexposure mustbe' It therefore
;;"ffi-*ctically i-poffi except under very unusual con-
ditions to make " .tttp ,hot o, instantaneous exposure with a small
stop or diaphragm
The size or diameter of the stop is usually desig- SiZe Of
nated by its felation to the focal length of the lens. Diaphragms
For example, if the 1oca1length of the lens is 8 in<
and the diameter of the largest stop is 1 inch, the focal length diyfld
by the diameter of the stop gives us eight and the stop is called F'8;
F. staflcling for focal length. In a lens having the largest stop F'8,
the next size is F.11, that is, equal in diameter to one-eleventh of
the focal length, and the next size is F'16, etc'
There is another system of designating the stops, known as the
U. S. system, in which a stop equal in value to F'8 is called No' 4'
F.11 equals No. 8, etc.
The tollowing table gives the relative values of the F. sYstem
and the U. S. sYstemof making stoPs:
F.4 equals - - No. I F'22 equals - - N o . 3 2 64 No. equals F'32 2 - - No. equals F.5.6 No. 128 equals - - F'45 4 No. equals - - F.8
F.11 equals - - No. 8 F'64 equals No. 256
F.16 equals - - No' 16I The size of each successive stop is such that it wirl require just
twice as long an exposure as the one preceding it; fo-r-example' if for
the No. 4 stop the c-orrectexposure is 2 seconds,the No. 8 will require
4 seconds; No. t6, 8 seconds; No. 32, 16 seconds; No' 64, 32 seconds;
I No. 128, 64 seconds,etc.
stops and their rela-h A knowledge of the values of the difierent
tion to each other is necessary in determining correct exposures
and should be carefully studied by anyone using a camera' I
F.I .-,-,--;.- . -d-View original page 20Page 21 · Read text
g a - -
Itl COMPLETE INSTRUCTIONS IN PHOTOGRAPHY.
Depth Of The experiment of focusing on a certain object
with the largest diaphragm in the lens and finding otherFO|US
objects which are closer to or farther from the camera,
out of focus, will also illustrate another qualification of lenses, knorvn
as depth of focus, or the extent to which both near and far objects
can be brought into focus sharply at the same time.
Depth of focus depends entireiy on the size of the diaphragm and
the focal length of the lens. The smaller the diaphragm is, the
greater will be the depth of focus, and the shorter the focal length of
the lens is, the greater the depth of focus will be. conversely, the
larger the diaphragm or the longer the focal length, the less depth of
focus the lens will possess. An increase in the focal length or in the
size of the diaphragm is necessarily accompanied by a corresponding
decrease in the depth of focus. Lenses, even of entirely different
styles of construction, always possess depth of focus to exactly the
same extent if they are of the same focal length when used with
stops of the same size. For instance, if we take an ordinary rapid
rectilinear lens with a focal length of 8 inches and make a nega-
tive rn'ith it, using, for example, stop F.32, and at the same time we
make another negative with a fine anastigmat lens of 8 inches
focal length, again using stop F.32, both negatives vr.ill show
depth of focus to exactly the same extent. rf we take two lenses of
unequal focal lengths and use them both with stops of the same
value, say for example, F.16, the lens having the shorter focal length
will show the greatest depth of focus. If rve take two lenses of the
same focal length and use one with a large stop and the other with a
small stop, the picture made with the small stop will show the great-
est depth of focus.
Depth of focus, which is the capacity of a iens to give sharp
images of objects situated at different distances from the camera,
must not be confused with definition. Depth of focus depends
only bn focal length and size of stop, and is the same with all lenses
where these two factors are the same. Definition, which is the ability
of a lens to produce sharp, clear, crisp detail, is a test of quality ano
is possessed to a much greater degree by fine lenses than by cheap
lenses. The finest definition is yielded by the modern anastigmat
lenses. Rapid rectilinear lenses give good definition, but not as good
as does the anastigmat lens.
From consideration of the foregoing statements, it is apparent
that any increase in the working aperture of a lens must ngcessarily
be accompanied by a corresponding decrease in depth of focus, or, inView original page 21Page 22 · Read text
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SEARS, ROEBUCK & CO., qHICAGO, ILL. lg
other hord., the larger the stop, the less the depth of focus will be-
It is also evident that great depth of focus is easily obtained with
any lens by using a very small diaphragm; but this, as explained in
the next paragraph regarding speed of lenses, means a corresponding
increase in the length of exposure.
It must also be borne in mind that great depth of focus is not
always desirable. For example, rvhen photographing a group, it is
much better if the background is not sharp. only the figures them-
selves in the group should be in sharp focus, and the backgrou'nd and
other non-essential details should be made as inconspicuous as pos-
sible by having them out of focus. Many landscape pictures are
much more artistic if only the important or interesting portion of the
picture is sharply defined, and other parts, possibly the'extreme
iirt"r,"", are slightly out of focus, thus giving greater prominence to, f
and emphasizing the essential or important parts of the picture.
The lensth of exposure, light and other conditions Thg Speed
being .q@y upon the size of the of Lerises 'with the focal le'gth, op"rrirrg ln the lens as compared
"tra tti. naturally brings qs to the consideration of one of the most
important qualifitations of a lens, viz., its speqd or rapidity. It will
be readily understood that the lens with the largest opening in pro-
portion tt its focal length rvil1 be the most rapid, that is, will make
pi"tor". with the shortest exposures, and speed is a very desirable
feature. The largest opening, sometimes called the aperture, of a
single achromati" l"ttr is usua)ly from F.12 to F.15, u'hile a good
douUte or rectilinear lens usually has its largest opening about F.8;
so it is very apparent that a rectilinear lens is much faster, that is,
requires much-rhort"r exposure than a single lens' To put it into * ptain figures, a lens rvorking at !-.8 $,i11 require less than one-third as
long an exposure as one working at F.15, all other conditions being
"qrr-"l. Thls, of course, applies only when working with the largest
sttp. If both le'ses are stopped dorn'n to the same. size opening;
.ry F.32, for exarnple, then the same exposure is required with each.
The largest opening of a wide angie lens is usually about F.15,
and sometimes as small as F.22; so wide angle lenses are necessarily
slow.
Anastigmat lenses are much faster than rectilinear lenses, the
most popular t-vpes usually working at F.6.8, which makes them about
30 per cent faster than the ordinary rectilinear lens working at F.8.
In actual practice they make an even better showing than this as
FView original page 22Page 23 · Read text
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20 COMPLETE INSTRUCTIONS IN PITOTO'CRAPIIY.
,compared with rectilinear lenses, because, owing to their better defin-
ing power and flatter field, they can be used at full aperture in casesll
where the rectilinear lens would be still further stopped down.
Portrait lenses are the fastest of atl lenses, all other qualities
being sacrificed for the sake of speed,andusually work at from F.3rl
to F.5rl, which is from trvo to six times as fast as rectilinear lenses,
from ten to fifteen times as fast as single achromatic lenses, and
fully twenty times as rapid as the average u'ide angle lens.
Speed in a lens is especially important rvhen making snap shot
or instantaneous exposures, as the extreme shortness of the exposure
must be made up or compensated for by an ability to admit a large
volume of light, owing to the short time in which the light is allowed
to act upon the plate.
Bearing in. mind the extremely short time in which light is
allowed to act upon the plate in an instantaneous or snap shot exposure
(only a small fraction of a second), and remembering that a certai!
amount of action by light is absolutely necessary in order to IillG
@, the necessity of using a rapid lens, that is,
one with a large opening, thus admitting lots of light, will be apparent.
The fact that a shorter exposure is necessary N'ith a lens which admits
a large volume of light may be illustrated in a crude way by the
operation of filiing a vessel with water through a pipe. The vessel
can be filled entirely full with a small pipe, but it will take a much
longer time to do it than rvould be required with a large pipe. In
other words, the pressure of water being the same, the larger pipe
n'ill fill the vessel much more quickly than the smaller pipe. In the
same way a picture can be made in a very much shorter time rn'ith a
lens having a large aperture than it can rvith a lens having a smaller
aperture.
Single achromatic lenses are rapid enough for ordinarv snap
sbot rvork u'hen the light is brilliant, but a double or rectilinear lens
is, of course, better, and there are many occasions when the light
is not quite bright enough to make a good snap shot r,r'ith an achromatic
le--:s and yet bright enough to make good negatives with a recti-
linear lens. The still greater rapidity of the anastigmat lens makes it
possible to secure fully timed negatives on dark,cloudy days rvhen snap.
shots would be impossible, even rvith the best rapid rectilinear lenses.
With a wide angle lens snap shots can only be made under the
; most favorable circumstances. In spite of the fact that the wide
angle lens is slow, it is a very valuable addition to an outfit, beingView original page 23Page 24 · Read text
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SEARS,ROEgUCK&.CO.,'CffiiAGU, 21
espeeially suited' to photographing interiors' As time exposures
rnust be made urry*.y, whln'photogt"phing interiors, the slowrress
of the wicle angl" i";.: i' "o disadvantage' and the wide extent of the
view embraced is a great ad-vantage, as single achromatic and rectilinear
lenses do not e-brl"" a wide enough angle to show all that is usually
desired in an interior view" Owing' Ito*tt"" to the wide anglel embraced, these lenses, to a certaii extent' distort and spoil the
perspective of -the vieu''
In the preceding paragraphs we have ex- ACtUal Diaphfagm
pla.ined that the speed pf a lens depend.s.upon ValUgS
ih" si"e of the aperture as compared with the
focal length, but we cannot measure th" gQ|!114: aperture and focal
length direcily with a rule except in the ""tf "'tmple lenses, consist-
i n g o f o n l y o n e p i e c e o f g l a s s o r o n e c o m b i n a t i o n . w i t h a p e r f e c t l y of the the diameter that assume will l"is we single convex sirnple is the camera when and that' 1 jnch is diipllragrn--riry stop or largest
focused or, ,o-" Ei.trr,t object, the distance from the optical
center of the lens to ih" groorrd glass is 16 inches. we then say that
the value of the largest Jtop, that is, the full aperture of the lens, is
F.16; in other *orir, the diameter of full aperture is equal to one-
sixteenth of the focal length and, therefore, this lens is said to have'a
speed of F.16.
Now, this same principle holds true when we come to double
lenses of the ,""t1irr"ffi angle, anastigmat and porrrait types'
b u t w i t h d o u b l e l e n s e s t h e F . v a l u e o f t h e o p e n i n g c a n n o t b e d e t e r -
minedcorrectlybydirectmeasurementrvitharuleininchesorfrac.
tions of an inch. To appreciate this fact' we must remember that
the speed of a doubl" l"rr. depends upon the amount .or volqryg.of
licrhr which it transmits. A single lens transmits a volume of light
i"- diameter, but a double lens trans-
@t"* mits a volume of light that is r"t.i-gr*ter in di1-"1"t, 11.1 llt!
d i a p h r a g m t h r o u g h - w h i c h i t p a s s e s . T h i s i s d u e t o t h e f a c t t h a t t h e
rays of light, ". ih"y enter ih" 1"rrr, are refracted, causing them to
convefge'andthediaphragm,whichislocatedbetrn'eenthefrontand
rear combinations of trr" lens, a110ws a cone of light to pass through,
which, before its refraction, was gr-rt"r in diameter than the
diaphragm itself'
With single lenses the diaphragm is placed in- front of the lens
and only the actual volume of light which passes through the
airptttug* can. be transmitted by the lens' but in double lenses theView original page 24Page 25 · Read text
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?) COMPLETE INSTRUCTIO}IS IN PHOTOGRAPHY.
diaphragm is placed insi4e the lens. betw-een the front and rear
combinations, and the light passes througtrffiion
ffiEFhE' refraction Jorrrr"rg"* it before it reaches the diaphragm
and enables it to pass through an opening of less than its orvn
original diameter.
Now, to determine the speed of a lens, we must have these two
factors: first, the exact equivalent focus of the lens; second, not the
exact diameter of the diaphragm itself, but the diameter of the cone
of light which it will transmit. The "qoivrl"ffi
the distance from the optical center of the lens to the ground glass
when the lens is focused upon a distant object. with simple lenses
we, can measure this directly with a rule, because the optical center
and the mechanical center coincide, but in a double lens the optical
center and the mechanical center do not, as a rule,'coincide, and
while the actual optical center can be determined by a complicated
mathematical computation, it is unnecessary to do so, as there is an
easy and simple n'ay to determine the equivalent focus of a double
lens and also the actual F. value of the opening, u'hich u,e will now
explain.
. To measure the speed of a double lens, in other
TO Measure the u'ords, to determine the true F. value of the largest
Speed Of LenSeS opening, we proceed as follows: 4rst, focus .t1.y
carefully and accurately otr . .rr"rf?-irtant object
and mark on the bed of the camera the exact point to which the
bellows is extended; second, focus on some small article at a distance
rvhich will enable you to make the image on the grounrl glass exactly
the same size as the object itself, and perfectly sharp, with full
aperture. A strip of white paper or a rule forms a handy object for ,
tbis purpose, and great care must be exercised to make tie image on
- the ground glass absolutely the same size as the object itself u.rJp"r-
fectly sharp. Norv, again, mark on the bed of the camera the plirrt
to which the bellou's is extended, and the clistance betrveen this point
and the point to which it rn'as extended previously when focuseld on
the distant object, is the exact equivalent focus of the lens.
rt will readily be understood that this work requires a long
bellows camera, such as the No. I conley view, or the conley Double
Extension camera, and to insure accuracy in marking the points to
u'hich the bellou,'s is extended, some point on the bed of the camera
must be selected u'here a small mark or scratch can be made on the
movable portion to exactly coincide .vvith the immovable part. ThenView original page 25Page 27 · Read text
-FF
24 COI\{PLETE INSTRUCTIONS IN PHOTOGRAPHY.
bubbles, but as these air bubbles have no influence upon the optical
qualities of the lens, they are not regarded as faults.
rn considering the matter of bubbles in lenses, we must bear in
mind these facts: first, in making anastigmat lenses it is absolutely
necessary to use these special and peculiar grades of lens glass;
second, these special varieties of glass always contain at least a few
small air bubbles; third, these bubbles have no practical efiect upon ' the working quality of the lens. From a consideration of these three
facts, it is evident that the presence of air bubbles in a lens is of no
importance rvhatever and may be entirely ignored by the user of (
the lens.
In the manufacture of ordinary rapid rectilinear lenses, single
achromatic lenses, wide ang-le'lenses, etc., it is possible to'use tlre
commoner varieties of crorvn and flint optical glass, the making of
which is a more srmple matter than the production of the special
glass for anastigmat lenses, and no difficulty is found in producing
these cheaper glasses without bubbles.
\\rhile occasional pieces of the special Jena lens glass are foul.rd
free from bubbles, such pieces are rare, and a complete lens entirely
free from air bubbles (if sold as an anastigmat lens) might well be
regarded with suspicion, as complete freedom frorn bubbles would
indicate tllat a cheaper glass had been used in its construction and
that it was not a genuine anastigmat lens.
Kindof Lens rens,f'"ir,"liT::t1*'lJ:"ri'.*,1ffT"'*:fr:
tigmat, unless such a lens costs more than you care totO PUfChaSe
invest, in which event a gooC rapid rectilinear should
' be selected. A wide angle lens makes a very valuable addition to an
outfit, but is, of course, suitable for only certain "l"ss"Effirk, and,
although it will enable you to make many pictures which your regular
lens would not make in a satisfactory manner, it could not be de-
, pended upon for all around work.
Portrait lenses,being suitable only for portrait work, are seldom
used by any but professional photographers, and then oniy in the studio.
The Shutter is the mechanism or devicq, by means ofThe
which the opening to admit light through the lens is openedShUttef or closed in making an exposure. There is an infinite
variety of shutters on the market, almost every manufacturer having
a different style, but the object attained in all cases is the same;View original page 27Related documents and language editions
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