So Part I was regarding the general choice between camera phone, P&S and dSLR. If you’re looking into the dSLR route, the next thing you need is a lens (or…multiple lenses). So let’s get to the lens questions!
Brand vs Off-Brand
If you own a Canon camera, the most obvious lens would be to buy a Canon lens. While it’s a good solution, it might not always be the best solution. Personally, I like to stay with the brand name for consistency and other details, but again, it’s not necessary. There are plenty of quality lenses from Sigma, Tamron, Tokina, etc. that fit on Canon/Nikon cameras. The off-brand lenses are generally cheaper, and sometimes you pay for that with the quality (build quality and/or image quality). I started out with a couple Sigma lenses before I switched to going all Canon. If the budget is an issue, I recommend looking into the off-brand lenses and getting reviews. Sometimes, you’ll find lenses that aren’t that much different in quality (be careful, though, as the image quality tradeoff might not be worth the lens cost difference).
Fixed vs Zoom Focal Lengths
A zoom lens allows you to stand in one place and change the depth/distance between yourself and the subject you are shooting. So in a matter of seconds, you can take a picture with a 24mm field of view and then take a close-up with a 70mm field of view. With a fixed lens, you have a 50mm field of view. And that’s it. If you want to get closer to the subject, you move your feet and get closer, or you switch your lens.
I started out with a set of zoom lenses because they are the most flexible (16-35, 24-70, 70-200). So with 3 lenses, I could go from very wide at 16mm to extremely tight at 200mm. As I started to build my gear, I started to invest in fixed focal lengths. The fixed lenses provide better image quality, force me to be more creative, and also give extreme apertures. What I mean is, with my 24-70, the widest I could be is 2.8. Now, I have a 50mm that can go to 1.2. The difference is huge in terms of low-light benefits or extreme depth of field. The trade-off, again, is that when I once carried 3 lenses, to cover the similar range of views, I now have a 24mm, 35mm, 50mm, 85mm, 100mm, and 135mm.
For a hobbyist/someone interested in the art of photography, I recommend going the fixed route because it challenges you to work harder and think differently and purposefully with your images a bit more than zooms. For the average person, I recommend zooms for flexibility and ease of use.
Not getting too technical, aperture can be looked at as a hole through which light travels through. The larger the hole, the wider the aperture (ie. f/1.8), the more light enters. This makes it useful for low-light situations. This also has a very small depth of field, which means one small portion is in focus and the rest out of focus. The camera lens will list the widest the lens will go (ie. f/1.4), but it can always stop down to smaller f-stops (ie. f/5.6, f/11,…).
A camera company will produce multiple lenses at the same focal length with different apertures, at different costs. The wider the aperture is capable of going, the more expensive. A Canon 50mm comes as a 1.2, 1.4 and 1.8 (Sigma makes a 50mm 2.8 for Canon). The f/1.2 lens can be about $1,600 while the f/1.8 goes for about $120. That’s a huge price difference. The build quality and image quality are also vastly difference. This is where budget comes to play to figure out what you can afford. Again, for the hobbyist, I recommend at least getting the 50mm 1.8 along with any other lens (fixed/zoom) that they find valuable.
One thing to note is that lenses are very valuable, and hold their value for a long time- it’s an investment. A camera body might get refreshed every year, but a new version of a lens takes a while. So I always say to invest more in quality lenses that multi-featured camera bodies, if you have to choose.
Fixed vs Variable Apertures
This is an area that it’s easy to miss initially that messes people up in the long run.
A fixed aperture is one that is constant the whole time. With fixed focal lengths (ie. 50mm 1.8), it is always a fixed aperture. With zoom focal lengths (ie. 24-70 2.8 or 24-135 3.5-5.6), the aperture could be variable or fixed. The 24-70 2.8 is fixed- it only has 1 aperture number listed (which is the widest the lens will go). A variable length generally has 2 numbers listed. The first number is the aperture at the widest focal length, and the second is the widest aperture at the longest focal length. This means that for the Canon 24-135 f/3.5-5.6, At 24mm, the widest aperture you can get is f/3.5. At 135mm, the widest you can get is f/5.6 (And it gradually decreases across the zoom). Most zoom lenses on kit packages with everything thrown in includes a lens like this. It’s highly flexible in terms of zoom range and is fine when you have a lot of light, but when you are indoors you will find yourself struggling. You might find that f/3.5 is what you need to be at to get proper exposure, but when you zoom in, the lens forces you to drop to f/5.6, and now all your images are too dark (underexposed). So I always recommend to finding a fixed aperture lens. These are more expensive, but totally worth it.
The other decision is what focal lengths to buy. Again, this is all dependent on what your wanting to use it for. The wider the lens (16mm), you get more scenery, but you also get distortion (subjects in the edges of the frame get stretched). The longer lens (200mm) also you to have a greater reach from far away, so it’s necessary for sports photographers on the sidelines taking images of the opposite end of the field. A 50mm lens (on a full-frame camera) is basically the natural perspective of the human eye.
So there you have it- pair this with Part I and you should be able to choose a decent camera/lens combo that fits in your budget and suits your needs. Any other questions on this? Hope it was helpful! :)