We have used photometric images of 10 barred galaxies in the B and I bands to infer geometric and dynamical parameters of their bars: their lengths, their strengths, and their corotation radii. The bar length, R_bar, is measured as the radius at which the odd Fourier components of the I image show a rise, accompanied by a blue peak in the B-I radial profile. The bar strength, S_bar, is defined as the integral of the amplitude ratio of the m = 2 component to the m = 0 component, over the radial range to the end of the bar. The corotation radius, R_CR, is determined as the first crossing point of the loci of the phase curves defining the radial dependence of the azimuthal maxima for the B and I images. With these definitions, we find that R_CR is in all cases slightly larger than R_bar, with a mean value close to 1.2R_bar. We find a weak dependence of the ratio R_CR/R_bar on morphological type, and a better correlated, though also shallow, dependence of this parameter on S_bar.