Best lens for a T3

Question

I bought a T3 a few years ago.  It has served it's purpose for basic pictures but I want to buy a better lense that will work for action shots, outdoors and low light settings.  I realize I might have to buy more than one lense but I am starting to get into photography more and my budget is very tight right now.  

Answer 1

The point of a camera having a "removeable" lens is that no single lens is ever "best"... but you can swap in the lens which is most opimal for the situation at-hand.
I have an EF 135mm f/2L USM --  a fantastic lens, great for low-light and subjects at a moderate distance.  It's also one of the least expensive of the L series lenses (the L series lenses are Canon's top-end glass).   But as this is a prime (non-zoom) lens, it doesn't have the versatility if your subject shooting distance and framing need to keep changing... which is why just about everyone makes a 70-200mm zoom.  Further, most manufacturers make that 70-200mm zoom in a version that can provide f/2.8 at any focal length in the range.
By using the lower focal ratio versions of the lens, the lens gathers more light while the shutter is open.  The f-stop (focal ratio) is the ratio of the focal length divided by the diameter of the lens (clear aperture).  The bigger that diameter, the more light it collects.  The ratios happen to use even powers of the square root of 2.  f/5.6, for example, is √2^5, f/4 is √2^4.  f/2.8 is √2^3, f/2 is √2^2, and so on.  Notice how each square root of 2 is being raised to one power less each time we move down to a lower stop.  The reason the square root of 2 is the all-important base value is because each time you change the diameter of a circle by a factor of the square root of 2 (approximately 1.4) you will either DOUBLE or HALVE the area of that circle (depending on whether you are making the circle larger or smaller of course). 
This means an f/4 lens litterally is collecting twice as much light as an f/5.6 lens (allowing you to either reduce the ISO or halve the amount of time that the shutter needs to remain open to capture the same exposure.)  An f/2.8 lens is double the f/4 lens... or four times the f/5.6 lens.  An f/2 lens is double again (or 8 times more light than the f/5.6 lens).   A couple of stops makes a huge difference.
But there are two trade-offs... as the aperture increases in size, you also make the "depth of field" (the range of distances at which subjects nearer or farther than your intended focus distance will also appear to be in reasonable/acceptable focus.  This means if you need subjects both near and far to be focused nicely then a low focal ratio is working against you (but these are laws of physics so we just have to put up with them. )
The second trade-off is physical and economic.  When you increase the diameter of the glass so that you can collect more light, the glass also gets thicker and thus heavier.  But also, the dispersion increases as well.  Dispersion is the property that causes light to split into it's different wavelengths (like the rainbow that you get when you shine a "white" light through a prism.)  This causes the images to go soft (especially near the edges).  When you zoom in to the corners to inspect the image, you may notice that edges of objects have a "purple fringe" on one edge and a "red fringe" on the opposite edge.  That's the light starting to split into a rainbow spectrum due to dispersion (the name for this is "chromatic aberration").   It turns out you can correct for this -- not perfectly, but mostly.  To do this, you'd need to add more corrective elements of different shapes to reverse the dispersion problem.  Different materials can be used to make the "glass" and some recipies with exotic substances (translation:  expensive) will greatly improve the situation.  Canon sometimes uses fluorite.  Fluorite is a crystal that has low-dipsersion properties.  It occurs in nature but only in small sizes and always cloudy/impure (not suitable for making a lens).  So they "grow" their own fluorite crystals in a kiln.  But to "grow" these crystals without impurities means it has to be grown slowly... it can take months to grow the crystals to a point where they are large enough to be ground into lenses.  
This means you are using more expensive glass which is harder to produce and it also means you are adding even more glass (more weight) and of course this drives up the cost of the lens even further.
This is why you tend to not find lenses which are versatile, good in low light (low focal ratio), with high image quality, AND inexpensive.  What you need to do to the lens to make it good in low light and still maintain a high image quality definitely drives up the price tag.
You can find budget lenses but you always have to ask... what compromises are being made in order to keep the costs low?  
Lenses are always a game of trade-offs.  There's a continuum of price ranges, capabilities, and qualities.  The good stuff is also the expensive stuff.    If it were possible to make a "good", "cheap", "low-light" zoom... then we'd all own it and manufacturers wouldn't even bother to make the expensive versions because there would be no market for it.
Tim Campbell
5D II, 5D III, 60Da