Effect of varying the internal extinction. Top panel: comparison of log(ΣF_Hα/Σf_λFUV) in our catalog vs. the assumed . The dashed curve shows the logarithm of the minimum predicted ΣF_Hα/Σf_λFUV among our steep IMF models that are capable of producing clusters with as high a maximum F_Hα/f_λFUV as the maximum F_Hα/f_λFUV observed (southwest to northeast hatches) for each . The dot-dashed curve shows the same for our truncated IMF models (northwest to southeast hatches). The curve for the steep IMF models levels out beyond because at that assumed internal extinction and higher, all of our steep IMF models are capable of producing clusters with a maximum F_Hα/f_λFUV higher than the maximum observed, so the log(ΣF_Hα/Σf_λFUV) value for α = 3.3 is given for all . Bottom panel: comparison of N_Hα/N_blue in our mass-selected catalogs assuming a Salpeter IMF (red curve) and steep IMFs (blue and purple curves) vs. assumed . The values predicted by our steep IMF models are shown by the gray shaded area. The darker shaded area is between the highest and lowest value predicted by our steep IMF models, and the lighter shaded area is ±0.01 around the darker shaded area, corresponding to the typical errors for N_Hα/N_blue in our analysis. Observations agree with steep IMF models when 0.10 <  < 0.15 mag is assumed.