Why can't you use high absorbances to determine bacterial growth?

Question

When you use a spectophotometer? Or if you can why not so accurately?

Answer 1

Absorbances are based on the passage of light.  Technically bacteria growth is turbidity or "cloudiness" of the solution.  Bacterial cells in solution are not the same as a solute in a solvent since their distribution is "clumped" in cells. Bacterial growth is more accurately measured by a colorimeter.

Answer 2

You can use absorbance to follow bacterial growth, but it isn't very accurate.  If the absorbance is too high, you may saturate the spec and get very inaccurate results.