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Purma Guide Reference guide
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- Purma
- Model / document
- Purma Guide
- Document type
- Reference guide
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- English
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- 39
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- Film cameras
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WTTYWRITE A BOOK ABOUT IT?
There is no ideal att-round camera; every camera is the
result of a compromise between performanceand price-
whether you measurethe price in terms of speed, con-
venience,or simply pounds,shillingsand pence. The box
camera,the miniature, the reflex, and the stand camera,
offer certain characteristicadvantagesaccompaniedin each
case by equally characteristicdisadvantages.
In the PurmaSpecialwe havethe result of a new type of
compromise-a compromise between the desire to take
good photographs and a strong reluctance to go to any
trouble over them. lt ls, in fact, a lazy man's cahera, and
those who condemnit on that ground ignore the tremend-
ous contributlon to human progressmadeby men who were
too lazy to be happ)rdoing things the hard way.
The shutter speed is the only thing about the Purma
Specialwhich can be adjusted,and even this operation calls
for neither knobs nor levers, it is regulatedsimply by the
manner of holding the camera. Everythingelse is either
done for you or it cannot be done at all. The lens has not
only a fixed focus,but a fixed aperture, and it is neither luck
nor coincidencethat this combination of distanceand stop
ls the very one which the good photographer uses most
on four days out of five. The good photographer arrives
at this setting after some deliberation,consultation of an
exposure meter or guide, and finally, two separateadjust-
ments of focus and aperture. This cameradelivers it ready-
made.
In many ways the Purma Specialis the ideal camera for
novicesbut its utter simplicity is responsiblefor its frequent
appearancein more exalted company. More than one
Fleet Street ace carries the Purma Special as a sort of
insurance policy for the occasionswhen split secondscan
rob the Dailies of a scoop.
Naturally, this simplificationls a mixed blessing:there
- ar9 many things that the camerawill not do and as man),
{ others that it does indlfferently. No attempt is made toView original page 3Page 4 · Read text
www.orphancameras.com gloss over the very'lt obvlous llmltatlons of the camera In the iollowine pages. is, in fact, very necessaryfor these limitatio-ns't6be understood if consistentlygood results are to be expected. This is one answer to those who ask "lf the Purnia Specialis such a simple affair, why write a book about it ?" The other answer is-read the book and find out.View original page 4
Page 5 · Read text
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T}IE PT'RMJTSPECIAIJ
The Purma Speclalls a minlature camerataking l6 square
pictures lf x ii in. (3.2 x 3.2 cm.) on standari V.P.'film
(No.27 or 127). lt weighs l2 ozs. (340 grms.) and measures
6 x2[ xZt in. (15.3x 5.7 x 7 cm.).-at
The body of the camera is wlder the middle than at
the ends to accommodatethe special metal focal plane
shutter.
The top carries the built-ln optical dlrect-vlslon view-
finder,film-windingknob, shumerietting lever,and shutter-
releasebutton.
original Purma camera, known as the Purmo Speed,- Th"
f { q metal-bodyand six Instantaneousspeedsfrom | 125to
l/200 sec. lt is now obsolete.
The lrens
The lens is a Beck anastigmat with a fixed aperture of
f 6.3, and afocal length of 2d In. (5.7 cm.). All suifaceswtth
the exception of the outside of the front and back elements
are "bloomed" to reduce internal reflectlons.
When not in use,the lens in its cyllndricalplasticmount
retracts and is held down by a black plasticcap which screws
on to a threaded bosson the camerabody. Unscrewingthe
cap allows a spring to slide the lens out into the woiking
position.
This position is fixed.to give a sharp lmage of all objects -
from l0 ft. in front of the camerato the horizon.
Supplementar)rlenses described later are availablefor
photographingsubjectsat lessthan l0 ft. from the camera.
The Shutter
The shutter has no means of external adjustment. tts
speedis decidedsolely by the mannerof holdingthe camera.
There are three speeds-Slow (l125 sec.), Medium
(l/f 50 sec.)and Fast(11450sec.). When the camerais held
level, the shutter automaticallysets itself to work at l/150
sec.; with the camera on its left side, the shutter speedView original page 5Page 7 · Read text
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becomes, l45Osec.; and on its right side, l/25 sec. As the
picture is square,the shapeis.not altered by turning the
camerato set the shutter sPeed.
The shutter itself is of the focal-plane Pattern, -That is, it works close
to the actual film surface and admits light to the negative through. a
if it n friitt travels-with the camera in the level position-across the
oiitu."'-tt't" from right to left when the shutter release is pressed' slit is foimed in a curved metal plate which runs in guides..A
metal vane, attached tothis plate and linked to a pivotedtrass weight'
narrows or widens the slit'according to the position of the camera' varvins tlle width from about rk in. in the Fasi position to about { in. !p
in itre"stow. As the pivoted wiigtrt is attached to the main shutter
oi"to. it also helps to tontrol the iote at which the shutter travels. In
lttoitor,n positidn it acts ogoinst the shutter spring; in the Medium
Dosition'-A it'has no effect, andin the Fast position it acts with the.spring. rur"i aiic covers the back of the leni aperture to Prevent light from
reachingthe film when the shutter is be.ingset. This.disc is swung out ,'first pressure" on the shutter release button. of the r}ay by the
The shitt6r parts are'of rust-proof metal.
A moulded plastic lever, fitted flush with the uPPer
surfaceof the camerato the right of the view finder window,
sets the shutter. lt has a white arrow on toP to show the I
direction in which to set it. The method of settinSis the
h same for alt shutter speeds. Once the lever has been set
it can be returned to its original positiononly by releasing
the shutter with the press button. Any attemPt to force
it back will damagethe shutter.
The shutter rei-easebutton lies in a recesson the toP
surfaceof the camera.When the lensis held in the retracted
position by its cap, the shutter release button is auto-
hraticallyldckedto prevent accidentalexposure. The release
button must nevei be pressedunlessthe lens is in the
working position.
The Viewfinder
The viewfinder is of the oPtical direct'vision type Slvlng
a reduced-scaleimage of the field covered by the lens.
With the eye closetolhe finder and looking straightthrough
the centre, the view seen framed by the squareaPerture is
8 correct for all subjectsbeyond ten feet from the camera.View original page 7Page 8 · Read text
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When taklng photographs o{ subiects nearer than thls with the aid
of one of the iupplerneniary lenses, the finder is no longer accurate.
(See pp. 54 to 57.)
As a guide to the mannerof holding.thecamef to adjust
the shu-tter speed, FAST, and SLOW are m.arked to the
right and left'of the viewfinder,each word. being uPrisht
when the camerais held for the corresPondingspeed.
The Body
The body is made up of two black plastic mouldings.'9.ne
carrying the lens, shutter mechanism,viewfinder and film
wind, a-ndthe other forming a detachableback and carrying
the film pressureplate and number windows.
A curved steel plate acrossthe insideof the body Protects
the shutter mechanismand forms the film guide and aper-
ture. At each corner of the curved film aperture the metal
frame is raisedso that the film lies flat againstthe pressure
plate. Spring steel clips at each end of the back hold it in
iosition' when it is pressedhome.
The word TOP, stamped on the Pressureplate on the
detachableback indicateithe correct way round for replace-
ment, the top of the camera being the face carrying the
viewfinder, release,etc.
Red windows are normally fitted in the film-number apertures, but
if panchromaticfilm is to be'used, the green transParent discssupplied
with the camera must be fitted instead. To change the discs, the spring
retaining rings should be eased out with the point of a penknife.View original page 8Page 9 · Read text
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ITJTNDTINGTHE PIIRMA
Before you put a film into the camera,spend some time
pfactisingwith it until you are familiar with the operations
of holding and shooting.
How to toad the Purma
l. Free back at both ends.
2. Remove back.
3. Insert gnpty,spool at winding end.
4. Insert full roll bf film.
5. Break papgr seal and pull off 5 in. of paper.
6. Attach en4 of paper td empty spool.
T. Wind until taut.
8. Replaceback.
9. Wind to first exposure.
l. Lever the back free by pressing your thumbnail Into the recesses
at each end of the bodi.
2. slide both ends of the back out at the same time: do not ooen it
like a book or you will damagethe body or the sDrins clios.'
3. Drop the plain end o.f the g.pty spool'into the holeippbsite the
winding knob and pull out the-knod to allow the srotted ind of the
spool to fall into place. Releasethe knob and turn it until it ensaees
with the slot. lf the knob does not go back flush with the top dr itre
camera the spool !.s not correctly fitted.
4. The ends of the full spool fit into the slots at each side of the recess.
When the spool is pressed down it is held in place by the plated
spring at the back of the recess. Blow out any dust fro'nr insije the
camera before you thread the film.
5. Do not break the seal before the film is in the camera, or it may slip
from your fingers and unroll.
5. Thread the tapered end of the backing paper into the wide side of
the slit In the windine-uaitingsoool.
7- Make sure that -the paper ties absolutery flat and runs
smoothly on to the winding Jp6oi while you give thl knob a couple
of turns.
8. Brush.awa)' sqe9k9 of.dusr or fluff from the edges of the right .anl
trap_where the back ioins the body. Look for the wor-d TOp stamied
o.n the film pressure plate, and piace this edge opposite the faci of
the camera which carries the viewfinder and shutter controls. push
.^ both ends of the back into place at the same time and make sure
lU that it is pressed well home.View original page 9Page 10 · Read text
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:r HOW TO IOAD THE PUR]'fA
www.orphancameras.com
r$
tft
l. Free the back at both ends.
2. Removeback.
3. tnsert an empty spool at winding end.it 1. Inserta roll of film at feedlngend.
5. Pull off 6 in. of backingpaper.
5. Pushend of backingpaperthrough wide side of slit.
l. Wind until taut.
8. Rcplaceback with TOP at top.
9. Wind flgure I into first wlndow.View original page 10Page 11 · Read text
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^ N.g,grpress on the shutter releose button with the lens coDIn Dloce. z. wl".n the cap is unscrewed,the lens slidesout into'trre ,fuortinq
positionand unlocksthe shutter mechanism.Do not;;t;ffi?
the slighlside play betweenthe lens mount and its housing';- th6 ia normal. Put the capin your pocket,or you ."v i"r" ii.
3. The shutter is s:t by pustringthe revei;b"ilii.,;;;.a punme in the direction of ths white airow.
Makea habit of setting-theshutter immedlatelybeforeyou want to
shoot. lf you set it ear-iler,you run the rlsk of ilt"r"inJit accidently,
think of the two acrions or Jttinf'anJ-r-;i;ilf;
Tl.:lt:r:.I::together,you will never be sure whether the shuttEri, s"t or not.
use.your right forefinger for setting the shutter and then ll*"I:
rr weil away.from the setting lever. The lever flies backto the lejp
sareposrtron-asthe shutter is released,and if your finger is in the - y.ay, you will spoil the picture.
4. Plant your feet-firmly od rhe ground, and make your body lnto a
steadysupporr for th-ecamera.-Hold the ."r"ta i"""1 il
!r!'Try agatnstyour nose and forehead. lf the horizon showj"nJ'orlii,r-rn ine
p!ctu1'e,.make sure that it is p^arallelto the top and bottom of ihi v-iewf,nder 9r y?:_yl!,y3l1t" p.tcrurespace.Ins,iuarinjii i,l i"iir."-
5"gp ygy-t forefinger bent w6[ over the rtruti"-r rei"Le or you wirl
flnd tt dtfficult to appry the flnar pressure. press aown .iJ;t,';; not jerk.
The releasebutton movesfairly easilyforabout* in., andthen, when
about to refease,-?-u.pllt_:r-yeiymu'ch harder ;, il;;: latil;;; shake the iamera at the inGrla oi-exposure. e I3:T.:lr]I::-mayfirm, but not fierce, grip on the camera, and slow, steady squeezinq of the rereasebutton ii the answer.. gbcaudoiiti-*diinl;ii;:
shutter, there is a sharp impact at the oi ia; ;;;";i; d'ut tr,is occursofter exposure,ii dods no harm."nJ "s
5. lf the number is showingin the.first window, wind until you seethe
samenumber in the seiond wlndow. tf the numb"i ii tn.*i"q ii
the secondwindow (nearestto the windin!- kn;ti'*i;l"i"iiitril
next number shows in the first window. The-ippearanceof i
number in either window ls.precededby a line or four
dots. Always wind to a fresh frame.imriediateiy-aftei"ftr,."","[ing-.n
or,you may forget and spoil two picturLs. , f,|los,ure,
o. I ne snutter tock does not come into operition until the tens cao has been screwed right down. rf you tra'i" r"iir," itiiiti,,ii"ij'tnTfi
not made an exposure,you can-releasethe settiniiever uv un-
screwing the lens cap a {uarter of a turn and prJrrini-tr," ,;i.,'".ili releasebutton.
How to Unload the Purma
l . Wind end of paper to secondwindow.
14 2. Take ofr bacli of camera.View original page 11Page 12 · Read text
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HOW TO SHOOT WITH THE PURMA
l. Unscrewlens cap.
2. Push settint lever in
direction of arrow.
3. Sight subject In view-
flnder and pr€ss
shutter release.
lL Wlnd film to ncxt
frame.
HOW TO UNLOAD THE PURMA
l. Turn film wlnding
knob until end of
papershowsin second
wlndow.
a Remove camera back,
easing off both ends
together.
3. Stlck down paper seal
and remove roll.
4. Transfer empty spool
to winding end and
replaceback of camem,
TOP to top.View original page 12Page 13 · Read text
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3. Stick down seal and remove roll.
4. Transfer empty spool to winding end.
5. Replace back of camera.
3. Fold about half an Inch of the backing paper under, and turn the
winding knob until only the end of tlie-gummed paper seal is left
sticking out. Moisten the gum and presithe seal bri to the roll as
you continue to wind, then remove the sealed roll. In this way there
is no risk of letting the unsealed roll slip from your fingers. lf the
film is not going to be developed immedlateiy, retuin it to its
wrapping foil and carton.
16View original page 13Page 14 · Read text
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FIIMS AIVD FILTERS FOR THE PIIRMA
The Purma takes V.P. (Nos. 77 and 127) films with a
numbered paper backingwound on a metal.spool. Films
of this size' are maiufactured by most makers of
photographicmaterialsin two types-of emulsion-ortho-
ihrom"atii and panchromatic-aid in a range of speeds.
Without underitanding the effects of the type of film,
whether orthochromat-icor panchromatic,and its speed,
good photography is imPossible.
Orthochromatic Films
A photographicfilm does not resPondegually to all the
r.vs irf lishi-uponwhich fall on it when thd shutter is open. Some
r"yt the emulsion very strongly, while others are
".t*uik"r. Orthochromatiicor oitho film is highlymlch
sensitiveto blue light, less so to yellow, green and orange,
and oracticallynot-at all to red. For this reason'an ortho-
chromaticfilm may'hasbe developedby a red darkroom light.
Modern research produied fiims of this tyPe with
greatlyimprovedsensitivityto the yellow,greenand orange
i.vt. *hi.h eive a better 6lack anil white rendering of the
coioutt of 6ur photographic subiects. These films are 7'-chrome"senerallyindicatddby at,the end of the brand
i.r. und th.ir high ipeed and good photographicqualities
makethem probablythe most popularfllms tor amateuruse.
Panchromatic Films
Panchromaticor pan film is almost equally sensitiveto
all colours and for that reason it gives a better all-round
rendering of the averagephotograp-hicsubiect. Becauseof
their sen"sitiviryto lig6t 6f att iolours, panchro.maticfilms
should be opeired an-dprocessedin complete darknessor
by a very dim green safeiight.The high speed.panchromatic
fiims ..6 e*."fsively sens'itiveto red- light with the result
that red tones in th6 subjectmay comeout unnaturallypale. t7
PUR-8View original page 14Page 15 · Read text
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Film Speeds
The speed of the film is always stated on the carton in fisures which
may refer to any one of a numbir of different classifyingsyst-ems.These
s),stems.arebased on different methods of measuremen-tind while they
cannot be accurately compared, the table given below can be regardei
as a satisfactory practical guide.
COMPARISONOF FILM SPEEDRAI'N6S
B.S.ond B..S..LogWeston G.E. H. & D. EuropeonAmericon DrN
A.S.A. lndex Schiiner Scheiner
lndex
t 0 2lo I t 2 400 230 | g" t2lt0
t 6 230 , 2 t 8 660 250 21" t4lt0
20 240 t 6 24 800 26" 22 r5/r0
32 26 24 36 | 300 270 24 t7lt0
40 270 32 48 | 600 29" 25" r8/r0
64 29" 48 64 2400 300 27" relr0
80 300 64 96 3000 32" 2go 2t lt0 t25 32 96 130 4800 33" 300 221t0
160 330 t28 t90 6400 350 320 24lto
As the Purma has gnly three shutter speeds, it cannot take into
account small differences between one film speed and the next. This
allows^a much. simpler classificationof film sp'eeds.
All films below 24' Sch. (European) are too slow to be of much use
to the Purma which cannot give dn eiposure longer than l/25 sec. The
remaining speeds can be grouped intir three: Low speed'(24o Sch. to
26"-S:L.): Middle speed (27'Sch. to29o Sch.) and High speid (30. Sch.
to 32o Sch.).
Low speed films are roughly half as fast as the Middle speed films , ,The
(they the.refore.require twice the exposure) and the High sieed films
are roughly tqlcg as fast as the Middle speed films (t-hey'therefore
require only half the exposure).
Latitude
The film is.gpable of. responding tola very wide range of light varues, -
from very dull to very bright-a much widdr range thin is found in the
average subject. lt isthus generally possible to stray from the so-called
correct exposure-and still be within the range of the film's power to
reproduce the light and shade of the subject. Thanks to thi; latitude
the three shutterspeeds of the Purma wili usually include one which is
near enough tg the correct exposure for practi-cal purposes. As the
latitude of the film extends more-abovethan below thecoirect exposure,
it is a safe rule, when the correct exposure lies between two Shutter18 speeds, to choose the slower,-i.€., t6 over-expose.View original page 15Page 16 · Read text
www.orphancameras.com Grain The black parts of the negative are formed of microscopic grains of metallic silver. These grains are too small to show in contact prints or small enlargements, but in big enlargements they can appear as a general spottiness which breaks up the definition of sharp lines and destroys detail. The size of the grain usually varies with the specd of the film. Low speed films have a relatively fine grain and glve the best enlargements. High speed films have a much coarser grain which shows more when enlarged to the same degree. Some developers tend to leave the negative with a coansergrain than others. Ordinary developers, suitable for roll films larger than V.P., are unsatisfactory for negatives as small as those of the Purma. For all ordinary sizes of enlargement any of the proprietary fine grain developers will do, but for minimum grain size, one of the ultra fine grain formulae must be used. The disadvantageof the latter is that they may require up to three times as much exposure, which practically rules them out for Purma photography. When to Use Which The best film for eveq/day use is undoubtedlythe Middle speed panchromatickind. This is not too slow for bright winter days and not too fast for strong summer lighting. It hasa grain sizefine enoughfor all normal enlargementand its tone rendering of natural colours is the best possible. Its balanced colour sensitivity makes it excellent for portraiture, particularlyof children and youngwomen whose complexionswould be reproduced in unduly dark tones by, orthochromatic film. Disadvantages:lt must be handled in' complete darknessor by a veD/ weak green safelight,andj it costs more than orthochromatic film. Next in order of all-round usefulnesscomes the Middte speedorthochromaticfilm. lt has most of the good qualities of its panchromatic relative, but it has not the same balancedcolour sensitivity. However, averagesubjectsare sufficientlywell rendered. When used for portraiture, its lack of sensitivityto red meansthat it darkensflesh tones and sun tan, and is apt to emphasisefacialblemishes.On the, other hand, it costs less. The High speed panchromaticfilms should be reservedJ for such specialoccasionsas photographyin the dull winter months, indoor and artificial lighting work, and to allow the 19View original page 16
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fastest shutter speeds to be used for moving subfects.
Against the very high speed of such films must be set
coarsergrain, need for greater care in handling,palenessof
red tones, and last but not least, higher cost than of ortho-
chromaticfilm.
Low speedfilms give the finest grain, but they limlt the
use of the Purmato a narrow rangeof subjectsand lighting.
FILfiISFORTHE PURMA
Groin
Ensign:
Ultrachrome Middle speed ortho Medium
Gevaert:
Panchromosa Middle speed pan Fine
Superchrome Middle speed ortho Fine
llford:
Selochrome Middle speed ortho Fine
Selo H.P.3 High speed pan Medium
Kodak:
Plus X Middte speed pan Fine
Verichrome Middle speed ortho Fine
Super XX High speed pan Medium
Panatomic X Low speed pan Very fine
What is a Filter
A filter is a coloured glassdisc which is fitted in frcnt oi
the cameralens to prevent some of the light from reaching
the film. lt is used to correct the tendency of the film to
:seesome colours duller than we do, and some brighter.
A filter tends to brighten its own colour. lt tends to
darken all other colours.
Nine times out of ten you will want to use a colour filter
to darken the blue of the sky and make white clouds,and
the yellow, green and brown of the landscape,stand out in
their true natural brilliance.
This can be done by a yellow or green filter; the particular
colour and depth of tint dependinguPon the sort of film
20 you are using ind how dark you want the blue sky to look.View original page 17Page 18 · Read text
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TAIffNG THE PHOTOGRAPH
Knowlng how to use the three shutter speeds of the
Purma will not help you to take photographsunlessyou
know whento use ttrdm.
lf you.shootbeachsceneswith a High speedfilm in your
camerain strong sunlightwith slow shuttbr speedyou'will
pro.dqcean almosr black negative,while if you shoot on a
dull December morning with a Low speed film ar Fast
speed you will get an almost clear negative. Both wiil be
q.ulte useless:what is wanted, is a ndgative which shows
the b.rightestparrs of the subject as ndt quite opaque and
the darkest as not quite transparent, with all the Inter_
mediate tones re-producedin propoftion-i.e., a negatiye
wtri..l has been given the correcr exposure.
What is the correct exposure? ilefore we can answer
thisquestion we must firsd know two things: the speedof
the film, and the srrength of the light.
The Effect of Film Speed
producethe samedegreeof blackeningof the negative, .. fo
light must act for a longer time on a slower film than on a
faster one-i.e., the slower film needs a longer exposure
under the same lighting conditions.
grouped.for the Purma user (see p. lB) Low speed^.As
films need twice as much exposure as Miaatd speed hlms
and four times as much as High speedfilms.
The Strengrth of the light
The strength of daylight varies accordingto the month
and the time of d^y. In-winter the light is-weakerthan in
summer; at mid-dayit is stronger thin in the morning or
evening.
The photographicvalueof the sunlightalsodependsupon.
how. much of it gets through the clouls and haze. lf there
are heavy.clouds.obscuringthe sun, the light at mid-dayin
July can be weaker than on a clear December morning.View original page 18Page 19 · Read text
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So the weather must be taken Into account In deciding
what exposureto give.
Bearidgin mind-the limited range of the Purma shutter,tr only three very broad types of lighting need be considered
at any time of year:-
Bright:Sunshiningin a clearskY.
Goid: Normal fine weather with thg sun iust strong enough to
Droduce' faintly visible shadows.
Dult:-Sky dompletely covered with cloud through which the sun
cannot be seen.
Good light needsthree times as much exPosureas Bright
light. Dull light needsthree to six times as much exPosure
as Good light.lffi
i The Type of Subject
A photograph'light is made by light reflected from the sub.iect.
The ieflected from'a whitewashed cottage will act
upon t-hefilm much more strongly than the weaker reflec-
tibn from a dark-timbered barn,-aithoughthe samedaylight
may be illuminatlngboth sublectsequally. The barn, there-
for'e,will needa longer exposlre than the cottage. Similarly,
an open landscapeor seascapewill need a much shofter
exposurethan one with heavy massesof buildings,trees,
or groups of people in it, particularly if they form the
interest of the picture.
Here again,dhree groups are sufiicientfor the simplified
technique of Purma photography:-
Light:Open landscapeswithout important foreground. Snow scenes.
Normoli Open landscapeswith important foreground figures or
objects. Wide streets and squares.
Dork: Figuresand buildingsin narrow streets' under trees or in very
well-lit interiors. Portraits in shade.
Normal subiects need two to three tlmes the exposure
for Llght. Dark subjects three to six timesthe exposure for
Normal.
Controlling Exposure with the Shutter
The right exposurefor any photographdependsuponthe
factorsalreadydiscussed: 4I'View original page 19Page 20 · Read text
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l. The FllmSpeed(Low,Mlddleor High).
2. The Daylight(Bright,Good,Dull) for the particulartime of day
and year.
3. TheSubject(Light,Normal,Dark).
In practice, once the film has been chosen,exposure ls
controlled by varyingthe size of the lens aperturi and the
shutter speed. Most camerasallow control of both lens
aperture.andshutter speed,but the Purma lens aperture is
fix:d and exposureis controlledby the shutter speed olone.
The three shutter speedsare: Slow-l125 sei., Medium-
l/150 sec., and Fast-l/450 sec.
Another way of putting this makesit easierto understand
what_happensw_|rena change is made from one speed to
another, i.e.: Slow-18145:0 sec., Medium-31450 sec.,
fast-1i450 sec.
In changingover from Medium to Slow, therefore, the
exposure becomessix times slower-i.e. from 3 to lg-and
in going from Medium to Fast,the exposure becomesthree
times foster-i.e. from 3 to l.
Practical Exposure Guide
lf you cannot be botheredwith technicalities,or have no
time to be exact, following rule will give- you a veD/ -the
high proportion of satisfactorynegatives:
. .-i!.4tu._lPpy_a__r!ry_! Good Light+ NormotSubject- MEDIUMSHUTTERSPEED.
For other films,lightingand subjects,step up the shutter
speed to Fastwhen at least two of the othei factorsgo up a
steP:
_-A!cI.l.PgZa_fil1_+_BrightLisht+ NormolSubject- FASTSHUTTERSPEED.
Step down to Slow when at least two of the other factors
go down a step:
-.\i.d.dt-9Lp_.:_a_FltgJ Dull Light* Dork Subject:42 SIOWSHUITERSPEED.View original page 20Page 22 · Read text
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, A step up in one factor cancelsout the effect of a steo
down in one or both of the others and reavesthe ttirti"', speedunaltered:
Light+ Lightsubject=o ii F,lp,i r}tt.t "HiJ,fitl"
The classificationof .daylightinto Bright, Good, and Dull--" should be usedwith some thought tolhe time of"Jiy ;;J y";;.
The above exposuresappry to the middre of the day rn summer.
A more accurate guide to exposure is given below.
EXPOSUREGUIDE FORTHE PURI4|A
f . Find the Subject-Weother Facar
Subject Weather
Bright Good Dult
3 4
4 5
5 6
2. Add the Light Factor
Month Time of Day-2
9 a.m.- ll a.m.- p.m.- 4 o.m.-
ll a.m. 2 p.m. a b.m. 6 b;.
3. Add the Film Foctor
Film Factor
Low speed 3
Middle speed 2
High speed I{4
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1. Add the Fllter Foctor
Filter Factoi'
No. I Yellow
No. 2 Orange
No. 5 Light Green
5. f the lotol is:
I or 2: Use Fast shutter speed
3 or 4: Use Medium shutter speed
5 or 6: Use Slow shutter speed
"In Between" Shutter Speeds
lf you use a meter or chart, showing a range of shutter
speedsand lens apertures,you will have to usethe shutter
speedshown oppositethe lensaperture,f 6.3 of the Purma
lens. This speedwill not alwaysbe an exact Purma speed.
For ordinarysnapshootingyou will be safein usingthe Purma
speed below-i.e., slower than the one indicatedby your
meter or chart.
To get a more accurateadjustment of exposure you can
use a suitablefilter, or adaptyour viewpointto the lighting.
Whenyou usea xZ filter in front of the lens, it halvesthe
amount of light reachingthe film. This automaticallyhalves
the exposureand is thus a usefuladjustingdevice,always
providedthat the effectof the filter is acceptable.
lf, for example, your mecer gives the correct exposure as l/50 sec.,
you can use the Slow shutter speed ( l/25 sec.) arrd add a x 2 filter. The
same filter would enable you to use Medium shutter speed when the
subject needs l/300 sec., and so on. Remember that although you are
shortening the exposure,the shutter speed has not been altered, so that
you cannot use this trick to help you to photograph fast-moving subjects.
The whole range of "in between" speeds given by filters is shown in
the table on page 46. 45View original page 23Page 24 · Read text
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ADlUSflNG EXPOSURESW|TH F'rrERS
Exposure Shutter With Ortho Films With Pon Fitms
Reguired Speed odd Filter add Filter
I lzs Slow None None
riso-ri60 Slow Yellow Yellow or
l/r00-t/ t2s Slow OrangeLight Green
l / r s 0 Medium None None
r/300 Medium Yellow Yellow or
r/s00-| /7s0 M e d i u m OrangeLight Green
r/4s0-t/s00 Fast None None
r/e0Gt/t000 Fast Yellow Yellow or
Light Green
Tl" exposure dep.endson the proportionsof light ond .exact ,
shodein the picture, and therefore on ihe direction-ofthe
lighting. lf you stand with your back to rhe sun so rhar
your subject liglited from the front, you can .is .strongly
give two-thirds the.expo:jrrethat you wourd use for d subject
lighted from the side. lf you sh6ot towards the sun,mosr
of your subjectwill be in shadowand wiil need at leasttwice
asrnuchexposureas the samesubjectlightedfrom the side.
This is another way of tlie subfectfit the exposure .making when you cannotmakethe exposurefit the light.
the,exposure.givenby your meterfor a subjectlighted ,_!oIpl":,lf from,the.side is l/100..sec.,by choosin-gyour viewpoint so that th-esun
you' you wiil be abteto useMediumspeed. (213of l/100 sec. !s ?g.nllo is l/l50.sec.)- 9t.uy shootingagainstthe rightyou can'givesrdw rplud
ar tne risk ot stightover-exposure.(l/100 sec.doubledis lTsoset.;
However, most films allow so much latitude in exposure
that you will be safe, nine times out of ten, in rnorliing to I the nearest Purma shutter speed.
tighting Angles
How the light fallson the subjectdoesnot onryaffectthe
46 exposure,it decisivelycontrolsthe oppeoronceof tie subject:View original page 24From the M. Butkus archive. Original publisher and archive notices are retained.
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