In a camera with a series combination of four similar thin convex lenses, the effective power and total magnification of this combination can be calculated as follows:

Effective Power: When lenses are in contact, their powers add up. Therefore, the effective power $ p_{\text{eff}} $ of the combination is the sum of the powers of each individual lens:

$ p_{\text{eff}} = p_1 + p_2 + p_3 + p_4 = 4p $

Total Magnification: The total magnification $ m_{\text{eff}} $ is the product of the magnifications of each lens in the series:

$ m_{\text{eff}} = m_1 \times m_2 \times m_3 \times m_4 = m^4 $

Thus, for a combination of four identical lenses, the effective power is four times the power of a single lens, and the effective magnification is the fourth power of the magnification of a single lens.