ut if we desire to bring the
indistinct objects in focus we must "stop down" our lens first by
trying the No. 8 stop, and if this does not accomplish the results the
No. 16, and so on until we get what we wish. As we look at the image
on the ground glass, it will be evident that as we stop down our lens,
the more remote objects are gradually brought into view with a sharp
outline, we shall discover that the image on the ground glass becomes
less and less distinct, which shows very clearly that we are
admitting less light, and the lesson to be learned is that when we
make the exposure we must give a corresponding increase in time as the
amount of light admitted decreases. An exposure that would give a
perfect picture at No. 8 may be very much under-exposed at No. 32
diaphragm.

Having focussed our camera and set the stop, we then close the
shutter, insert the plate-holder in the back of the camera and
carefully draw the slide. Omitting to pull the slide is a common
mistake with beginners. We are now ready to decide just what exposure
to give our plate. Rules for exposure are almost useless, but in
general it may be said that the modern plates are lightning fast and
that in bright sunlight at midday the average exposures will not be
over 1-25 of a second. An "exposure meter" will prove to be of great
assistance to a beginner, but such arrangements are not often used by
experts except in doubtful cases. We soon find that we can guess at
average exposures with considerable accuracy, especially if we adopt a
certain brand of plate and become accustomed to its working qualities.
Of course all of these speeds must be indicated on the shutter, and
all we can do is to set our shutter at this point and squeeze the
bulb. Correct judgment in exposure will only come after experience.
In taking interior views or making pictures on dark days we shall be
less likely to make a mistake than in bright sunlight. I have made two
interior views, to one of which I gave ten minutes and the other an
hour, with practically the same result in the negative. An
over-exposed plate is flat, which means that the print will lack
contrast and be unsatisfactory as a photograph.

After the bulb is squeezed and the exposure made we are ready to
develop our plate and to see what result we have obtained. Of course
in practice we make a number of exposures before we begin to develop.
Some photographers use numbered plate-holders and keep a record of the
pi