I need an indoor, low light lens and have been saving up for the nikon lens for the past couple months. However I have some other priorities that have come up and decided to try an alternative. I'm not yet settled on which of the following lens I should get so please chime in. Sigma 18-50 2.8 Tokina 16-50 2.8 Tamron 17-50 2.8 If there are any other lenses not mentioned above let me know. Thanks!