486 THE GARDENING WORLD 
Darjc Blue Iris and Light Yellow Daisy, taken with an 
ordinary plate. 
Photography for Garden hovers. 
By the Rev. F. C. Lambert, M.A., F.R.P.S. 
(Continued from page 410.J 
III.—Ortho Chromatic Plates for Flower Work. 
Suppose the sun to be shining directly 
into a room. We now close the shutters 
so as to leave only a very narrow slit or 
chink through which we get a narrow 
streak of bright light. Holding a bit of 
white paper in this line of light, we get a 
bright line of white sunlight. Now let us 
borrow a three-cornered glass drop from 
a chandelier, or a glass prism, and hold 
it over the small slit. We shall then 
get a “spectrum” band of bright colours, 
'viz., blue, green, yellow, orange, and red. 
In this way we learn that white light is 
really composed of light of various 
colours. Suppose now that sunlight falls 
on a vellow flower, for example, a Butter¬ 
cup. Dandelion, Sunflower, etc. Some of 
the light rays pass into the petals, and 
other rays are reflected and enter our eye. 
In this case the blue ravs enter the flower 
and are lost to sight, but the yellow rays 
are reflected. Similarly a red Rose re¬ 
flects red rays, so we say the flower is red. 
But if that same red Rose be illuminated 
bv blue rays only it Would appear black, 
because it can reflect only red rays to our 
eye. The photographer, when dealing 
with coloured objects of any kind, has to 
remember that what he calls the colour 
of the object is due to its power of select¬ 
ing and reflecting certain rays, while 
other rays are absorbed. 
Now while the absorbed rays are lost to 
sight they are not entirely lost, for they 
enter the cells of the plant and enable 
them to store up its secretion (such as 
starch, cellulose, and so on), but these 
thoughts, interesting as they may be, are 
taking us away from the camera. 
The next point is that some colours 
strike our eve as light, while others ap¬ 
pear relatively dark. In the' example 
chosen for this chanter we have a blue 
Iris and a yellow Daisy. Ninety-nine 
people out of a hundred would at once 
sav that the Daisy attracted the eyes be¬ 
fore the Iris, because the yellow colour 
whs brighter than the blue colour. 
T,et us now'-set up these flowers against 
a brown paper background and photo¬ 
graph them with an ordinary plate. We 
shall get such a result as is shown in 
Fig. 1. Here the dark blue Iris comes 
out light and the light yellow Daisy comes 
out dark. Obviously this is not true to 
nature. Why is this? The answer is that 
July 25, 1908. 
the ordinary photographic plate does not 
see colours as our eyes see tnem. In other 
words, the blue rays act on the plate more 
energetically than all the other rays, so 
that blue part comes out darkest m the 
negative and lightest in the print. On 
the other hand red rays have least action, 
hence we light (or ought to light i our 
dark rooms by red rays only. But as a 
matter of fact a good deal of the so-called 
red glass of our dark room lamps does 
permit some blue light to get through, so 
that an ordinary plate if exposed too 
much in the red lamp-light will be 
fogged. 
in order to get over the false light and 
shade rendering of the ordinary plate two 
things are done. In tne first place cer¬ 
tain dyes are added to the coating of the 
plate, in small yet sufficient quantity to 
make the pi ate more sensitive to the green 
and yellow rays of light. But even when 
this is done still the plate is relatively too 
sensitive to the blue rays. Therefore we 
must- cut out some, but not all, of the 
blue rays by placing a yellow glass or 
gelatine screen in front of the lens. This 
yellow “ray filter” or “colour screen 
nandicaps the blue rays and gives the 
other colours a chance in the race. It 
is now easy to see that if we cut out too 
many of the blue rays we shall pass from 
one extreme to the other and make the 
blue come too dark. So that not only 
must we have a colour sensitive or ortho- 
chromatic plate, but also a colour screen 
of the right shade of yellow. This matter 
of the colour screen is of great import¬ 
ance. I have known economically- 
minded photographers try to save a shil¬ 
ling or two by using a bit of common yel¬ 
low glass, wdth resulting failure, of 
course. The plate manufacturer will 
supply at a quite small cost a colour 
screen of the right kind to suit his plates. 
This, with reasonable care against break¬ 
age, will last a lifetime, but as strong 
light may cause its colour to fade or 
change it should be kept in the dark when 
not in use. 
Now we have seen that under ordinary- 
conditions the blue constituent rays of or¬ 
dinary daylight are the most photo¬ 
graphically or chemically active. There¬ 
fore if we cut out a lot of these blue rays 
with our yellow colour screen we must 
compensate by giving a longer exposure. 
Both plates and colour screens vary a good 
deal of course, but speaking in a broad 
and general way, we shall find a yellow- 
colour screen that increases the ordinary- 
exposure by something like five to ten 
times, unscreeijed exposure will prove 
most useful in the maority of cases 
for flower and fruit photography'. 
Another point to notice now' is the im¬ 
portance of not exposing the “ortho” 
plate to any kind of light in the dark 
room any more than can be possibly- 
avoided. With a very little practice it 
w'ill be oossible to put the plates direct 
from the plate maker’s card box into the 
dark slide in absolute darkness. Again 
when developing, the plate should .be 
transferred from the dark slide to the de¬ 
veloping dish quickly', and wdth as little : 
dark room light as possible, the developer 
poured oyer it, and then the dish at once 
covered with a piece of card or thin w'ood, 
then gently rocked and kept covered for a 
minute or tw'o before it is examined. A . 
glance of half a second is enough to tell 
one how matters are going on. Protect¬ 
ing the plate from any kind of dark room 
