The sun. [volume] (New York [N.Y.]) 1833-1916, 1891-07-29
PIN HOLE PHOTOGRAPHY.
Why Too Small an Aperture Makes DEM,
zion Worse Iustead of better

LECTURE BEFORE THE ROYAL INSTITUTION ~
LORD RALEIGH. PROFESSOR OF NATURAL
PHILOSOPHY IN CAMBRIDGE UNIVERSITY.
From Mature
/, now pass on to another subject with which
s nave lately at, been engaged namely. tho con.
op lcal Images; II has long Teen known 10 ~.
,ronomers md TO those VINO study o.,ics that
r.ortional to the aper,ui 70 employee. Why ist
that We cannot get as high II definition as we
In accordance With tue historical develor.
ment OF the science OF ortics. tho student i,
to1t 10 focus ut another. but when he he has
made inr;her advance In the science he nds
ss' ssf sss hns On
siderable extension: light coming from Que
pon as be ee hs
diffusion. and the rea on is not ha, d 10 see in
a. s ,Ss ma Hay GsIsdsT wins, IsSpn
sssss%sss,sa 'N a., t$ $.s .h Hsns
point arrive in the same phase In. dii Se'sas
paths 81 the rays are oil rendered OFT lily
Of them have 70 travel being cont eusated for
H. the case OF these which ,ome throush tie
saSst,Ston glass or AIR. So t ths, inc
rays arrive at the same time. II We take q
not 2ne At the focus but
any dmnn,ion n at the seGon point lies IN the
s5a sS S 81" GSr ssss Z si
, to-, l, g q, Ths Images Of the com:
/ and II the distance between The centres do / OF
exceed the diameter Of the Representative
her esn be no
the Aperture. and thus the resolving poW or is
I'll, sctly us the aperture
examples that this is SO. have prepared
series 81 photograrhs Of q g, atins consisting
equal 10 their own diameter. and such that The
distance from centre to centre Is 10 inch.
ami large condensing lens. and the photo.
Ernnhs we're taken In the usual way; except
sass and was stopiei By perior Sti
ne w'T ss.,.lia each 81; ss.e shs ssOo.u5s
Sosed Ss Ts. Throws upS "s s
;,h picture done 81 by an aperture Of
a sSs worse f IN s s
is deterioratine: that WINS done by an aperture
OF four hundredlhs of an inch. The neAtis
Of an Inch aud You can see that the ues are
getting washed ont IN focusing the plate
Gf es ana
developing the plate. to find hem still visible.
T. a. was In virtue Of the shorter wave length
aperture was only two and-a.h half hundre1ths
Sas been SI TO IVA wash away y image a!tasshsr.
although. so far as ordinary optical imperf.c-
favorabIy with the smaller aperture than with
the larger ones.
THIS experiment may be essily made with
that each one Of M audience may be
sSS to by ssad which h
disIributed me piese OF sauze Should b,
placed against the window 80 rs to be backed
l. al n n NJ n d,d ut h
ss f Glass or opal sobe You then look az
the Gauze through the pin holes Using tho
asant;ion and ultimately AZ sight Of tie wires
feet rom the vauze. H. whoa looking through
tho smaller hole you have lust lost the wi es.
into operation. You viii see the wires again A'''
That is one SIDE u the question. However
the os
-tricted. On the other hand. IL the aperture 10
much restricted. then The lens IL OF no use.
ami you Will get as good an image without 1t
have not time to deal with this matter as I
formed y narrow aperture parallel TO one
tween, the cauze and the sc Screen. IESpe ns
ment.l there is tn tmaEe-il We can dignity
safa ns ss
s shs .so. S5n Ina M
aud now il Looks ,SlerabIs good. but vi! =
% a r.i bs VIII S that the deno D
are getting washed out. Again. "a i:
il the isln:%ess of the light. We SsnnSt avoid
traction Of aperture but t". .! owe that he res
suit Is not s 20 TO be explained vi now put IN
View nnd T' Ss't s hSs
light to enable US t" see the first set II the den
milton had been good enough; Too email an
and il the aperture. is sufficiently small tho
Image is no worse without a lens tina" with one;
That is the imp rtnnt question 10 dealing wi
pin hole photography: 1t was first consoles ed
tile result indicated BY the formula. 2rs- A.
where 2r is the diameter OF the aperture. tho
r.her lien
ture and the screen upon which the image is
Ills reasoning however though ingenious.
is not souni regarded as An attempt ut an ac-
cnra 9 solution OF the question. In fact. it is
been sufficiently worked out 70 enable re
whom we owe this achievement is Prof L"m-
mel. have adapted his results TO the problem
noo rebSnry 1871
shown. exhibiting TO The eye The as rlhut On On
n hs bs n
ibeSond that ri1sn y feszsals rule. sui. able
radius isr=> IA.
will not detnin you further than Just to
show You one application OF pin hole photog-
raphy on n different scnle from the usual.
The definition imrr ives MS tue aperture In
creas es: but In the absence OF lens the aug.
menttd aperture entails n GreRly extended
focal length. The limits OF an Ordinary port-
able "a nera are thus soon nhsSed. The orig
jgnal OF the Transparency now 20, be thrown
room. carefully dnrkened. me aperture III;
the shutter was O.07 inch and the distance ~
the l2xl0 plate from tho aperture was teet.
The resulting picture OF II group Q! cadars
shows nearly as much detail as could be seen
direct from the place in question.
Frenchmen In u s. tate or Exaitntion.
A ato