Shoot four rolls of film

Bracket by shutter speed 1/1000, 1/500, 1/250, all at f/8 or so on a
cloudless day. Use a scene that has full range of colors from open
shade to white surfaces. A street with houses will suffice. Develoop
the four rolls at normal, -10%, -20%, and -30%.

Make prints.

Start with grade 3 paper if you are using roll film. The best one to
use is Ilford Galerie. DO NOT use VC paper, because you have no idea
what the actual grade is. Print the most promising negatives on grade 3
paper, switching around the various rolls until you get a good print
with a full range of tones and detail in the highlight and shadow
areas. I find that 1/500 @ f/8 is usually the best at my latitude (40
N) in the summer (mid-morning). Because various camera lenses,
enlraging lenses and enlarger illumination systems affect the contrast,
you must determine the contrast FIRST. When you havve done this, the
speed will be easy to determine.

Simply compare the meter reading with the exposure used for the best
negative. If you find, as most do, that adding 1/2 to 1 stop improves
the image quality, then simply subtract 1/2 to 1 stop from the EI. If
the ISO is 400 and you find that 1/2 stop more is best, then use EI
250/320. Id 1 stop more is best, use EI 200. You will NOT find that
your speed is higher than ISO.

 The usual ring around requires 9 exposures. One each of
three strips there are three exposures, one at one stop
under the rated speed, one at the rated speed, one at one
stop over the rated speed. Three such strips are shot and
developed to get three contrast grades, one at the
manufacturer's recommended amount of time, one for about 33%
less and one for about 33% more. For tabular grain films the
variation will be around 20% to 25% for a one grade contrast
change.
 Remember that exposure controls overall density but has
little effect on contrast once the exposure is above a
certain minimum. Development time affects both contrast and
overall density but mostly contrast.
  Print on "normal" grade paper and choose the print with
best tone rendition.
  In general, once the exposure is above the point where
shadow detail is well up on the toe of the film curve
increased exposure will make little difference in tone
reproduction, at least until very high values are reached.
There is some advantage to keeping exposure on the minimum
side, especially for small format film. Grain and effects
which limit sharpness increase with density so the least
dense negative which yeilds good tone rendition is desirable
to maximize sharpness and minimize grain.
  For their own films Kodak and Ilford have somewhat
different contrast aim points in their development charts.
Kodak speeds and development times are based on a contrast
which is right for diffusion enlargers and contact printing.
Ilford bases its speed and development recommendations on a
compromise value of contrast midway between that needed for
diffusion enlargers and that needed for condenser enlargers,
on average about a one grade difference. Negatives which are
right for one type of enlarger will print fine on the other
with a one grade change in paper contrast.
  While condenser enlargers tend to pick up blemishes more
than diffusion enlargers, for the same negative printed on
both the lower contrast paper needed for the condenser
enlarger tends to knock them down again.