How can I test my lens??
Hope this don't sound like a stupid question but, How can I test my 3 lens? If I take a picture with all 3 of the same thing and the settings can I compare the 3 pictures. If so what is the best thing to take a picture of? Should I use a flash or go outside in the sun? I just want to see which is my best lens? I know I don't have any high end lens but i would like to know what would give me the best picture.
Shoot in daylight of something with color and details.
Shoot at maximum aperture (such as f4) f5.6 and f11 with each lens to see the difference there. Most lenses are best a couple stops down from maximum, and some will be better than others.
i use these formica samples..;)
It will be hard to come up with what is "your best lens" doing some simple shot comparisons of a stagnant object. One of your lenses may perform better at a certain focal length and then another one has a well defined sweet spot from an aperture perspective and so forth and so on. Each lens may perform better in their own varied and unique situations.
Just taking a stagnant shot at 30mm, f8.0, ISO 100 with each lens and then comparing the results I don't think will tell you very much as to which one is the best all around performer.
To me the best lens in my bag is the one I use the most.
While overall performance is a grand thing, indeed, as "bauerman" correctly points out, each lens will have its strengths. The only way you can determine "the best" lens is compare similar lenses, not lenses of different classes.
If you had, a SIGMA 70-300, a TAMRON 70-300mm and a SONY 70-300 to compare, then you could make this distinction.
Similarly, if you had a SIGMA 18-50 f/2.8, a TAMRON 17-50 f/2.8 and a SONY CZ 16-80mm f/3.5-4.5 ... once again, same class ... focus on something shoot away, changing the lenses after a "round-robin" at each setting.
Finding a common setting though, I had done with the SIGMA 10-20mm f/4.-5.6, TAMRON 17-50mm f/2.8 and the Tokina 20-35mm f/3.5-4.5 produced some really strange results. At a common 20mm, the TAMRON frankly shot the best, as I would have expected it to. But, then again, it cannot provide a 10mm shot, like the SIGMA UWA can.
The Tokina 20-35mm is a 35mm-film lens, and on a digital sensor ... it's kind of lame image-quality, but way cheap! You can get one for around $100, which is a far cry from the $400 TAMRON. You definitely pay for what you get.
I'm not really sure what you are trying to photography, Frank ... but if you can just set up some text (various font sizes) ... at about 5 feet away ... light it well and photograph it, you should be able to vary the focal length and reasonably determine sharpness and accuity.