We perform a cosmological parameter analysis of the 75 square degree CTIO lensing survey in conjunction with CMB and Type Ia supernovae data .
For \Lambda CDM cosmologies , we find that the amplitude of the power spectrum at low redshift is given by \sigma _ { 8 } = 0.81 ^ { +0.15 } _ { -0.10 } ( 95 \% { c . l . } ) , where the error bar includes both statistical and systematic errors .
The total of all systematic errors is smaller than the statistical errors , but they do make up a significant fraction of the error budget .
We find that weak lensing improves the constraints on dark energy as well .
The ( constant ) dark energy equation of state parameter , w , is measured to be -0.89 ^ { +0.16 } _ { -0.21 } ( 95 \% { c . l . } ) .
Marginalizing over a constant w slightly changes the estimate of \sigma _ { 8 } to 0.79 ^ { +0.17 } _ { -0.14 } ( 95 \% { c . l . } ) .
We also investigate variable w cosmologies , but find that the constraints weaken considerably ; the next generation surveys are needed to obtain meaningful constraints on the possible time evolution of dark energy .