Clearly it is the relations 
within the picture that are 
similar to those within the 
image of the scene, not 
absolute properties. The actual 
size of the picture and 
everything in it are immaterial 
as long as all the objects and 
distances are drawn to scale 
from the point of view of the 
artist and they are drawn in 
perspective. Although the use of 
color is important in achieving 
a realistic likeness to a scene 
rich in color, its absence, as 
drawings, woodcuts, and black-
and-white photographs show, 
does not prevent recognition of 
the things depicted. 
 
    I must confess, however, that 
I have oversimplified the 
problem. Although a photograph 
of a scene will yield an image 
very similar to that directly 
yielded by the scene itself, 
paintings and drawings will not 
necessarily do so. Even 
photographs entail some 
important differences. The 
maximum reflectance 
difference between the lightest 
and darkest region in a 
photograph is no more than a 
factor of around 30, for 
example, whereas regions in 
the scene itself can differ by a 
factor of 100,000 or more. 
Drawings and paintings are 
limited in the same way, and 
these limitations present 
artists with a challenge when 
they want to represent very 
light or strongly illuminated 
regions.