BEYOND THE KIT LENS
So you've been enjoying your first DSLR for a few months now and are looking to expand your lens collection beyond just the kits lens. With so many options out there it's confusing what to get and where to begin. Hopefully the following will help steer you in the right direction and give you something to consider when making your next purchase.
First things first, ask yourself what type(s) of photography you are interested in doing? I will tell you now that the beginner faces the temptation to buy every piece of equipment and focal length lens imaginable to cover all photographic scenarios. While that might sound like a good idea, you're most likely wasting your money. Some glass will inevitably end up sitting in your camera bag, rarely making it onto your camera. I'm speaking from personal experience here.
The second thing I will point out is that better lenses will give you better image quality, not better photos - that is something you have to deliver yourself! You could opt for something that's an all purpose lens like an 18-200mm or 18-300mm but, I'm not really in favour of these lenses.
Don't get me wrong, they are great for what they are, and the convenience they offer. Ideal for a family day trip out with the kids when you don't want to hump all your gear with you. I fully understand that but, essentially they're just kit lenses with a broader focal range.
For my mind you should ideally look for genre specific lenses that are going to benefit you the most. If you're into landscapes, naturally wide angle lenses (35mm and below) are going to be of interest to you. Portraiture, you're looking at the 70-200mm range. If its wildlife (birds, animals etc), 300mm+ lenses are going to be the weapons of choice. Of course these are traditional focal lengths for these genres but there is nothing to say you can't use an ultra wide angle or even a fish eye lens to take a portrait with, if that's the effect you want, or using a telephoto lens for lanscapes. Conformity stifles creativity!
PRIMES VS ZOOMS
In case you are unaware, a prime is a fixed focal length lens (28mm, 50mm, 85mm, 105mm, etc.). A zoom is a lens that can change it's focal length. Your kit lens for example will be a zoom lens (18-55mm, 18-70, 18-105mm, etc). Both have their advantages and disadvantages and are favoured by different photographers for different reasons.
Primes tend to offer superior optical quality in terms of sharpness, reduced aberrations and distortion, since they only have to cater to a single focal length. For this reason portrait photographers like myself tend to prefer fixed lenses. Zooms on the other hand are highly beneficial for their ability to crop closer, bringing you nearer to the action when you need to be and going wider when you don't. Photojournalists and wedding photographers often opt for zoom lenses for this reason. This feature does come at the expense of image quality, unless you're buying expensive glass, which although often not as sharp as primes, are still very good nonetheless.
I LIKE PHOTOGRAPHING PEOPLE
Lets say you really enjoy portraiture and are wondering what lenses are suitable for "the classic portrait"? Now other things factor in. These are available space, compression and of course price.
Available space is the amount of room you have to shoot in. With a long focal length lens you'll have to step back in order to get your subject in the frame. If you plan on or end up photographing indoors frequently and you don't have enough room to backup or move your subject further back, then you're going to have a problem getting the shot. Your sensor will also play a big part in this. If you have a 4/3rds sensor found in Olympus and Panasonic cameras then your focal length is effectively doubled. A 50mm lens will behave similar (in some respects) to a 100mm lens. APS-C sensors which are found in entry-level to "prosumer" bodies, give a 1.5x to 1.6x magnification effect. On full frame the focal length behaves as is stated - 50mm is 50mm.
Compression is also something else to consider and frequently overlooked. Sure, if you don't have a lot of room, you just use a wider angle lens, right? Well it's true you can fit your subject in the frame with a wider angle lens but, what that lens does to the facial features is often not flattering. The wider the angle of the lens, the more distorting its effect on facial features. Noses and foreheads are more bulbous and the face just looks warped. For this reason longer focal lengths are employed to give a more attractive look to a model's face. 85mm to 135mm are regarded as classic portrait focal lengths, although I enjoy using 180mm too, especially for its ability to defocus the background quickly. You can read more about compression here and how you can quickly make your gorgeous model look quite ugly.
Price is obviously going to be a deciding factor in any purchase. For example on Nikon cameras the 105mm f/2.8 VR Micro-Nikkor is a great macro and portrait lens but, its over £600. The 85mm f/1.4 is almost double that and the 70-200 f/2.8 VRII £1000 more than the 105mm. While they are great lenses, there are cheaper alternatives which still offer fantastic results. Remember, its not about the gear but what you do with it that is far more important.
The 85mm f/1.8D or G are much more pocket friendly and the Samyang 85mm f/1.4 offers real value for money with great optics and its ability to meter with the camera. It does lack autofocus though, which might be off-putting to some shooters. It's also worth mentioning that on the Nikon entry level cameras, there is often a lack of a focus motor. Older AF-D type lenses won't auto focus, so be aware of this if AF is crucial to you.
On APS-C I found the 50mm f/1.8 quite acceptable for portraits but on the full frame D800, the distorting effects were much too unflattering on features and so I opt for the longer lenses now. For environmental portraiture, where your subject and their surroundings are in the shot, the person is smaller in the frame and distortion much less apparent and I have no qualms using the 50mm for this purpose. It's just when you get up close and personal with head shots that you can warp the subject's face.
TAKE YOUR TIME
Before you make any decision, make sure you do the research on any lens you intend to buy and make sure it fits your needs. Is the focal length suitable? Do you require image stabilization to minimize hand held blur? Is the focus speed sufficient? Do you buy the cheaper option or the best that you can afford? Are there third party alternatives?
For example, portraiture is the hub of my photography but I also love macro photography of insects etc. (although I rarely get out enough to shoot these). Rather than going for an 85mm f/1.8D lens, I opted for the 105mm f/2.8VR, which is primarily for macro work but fantastic for portraiture too - a dual purpose optic, awesome!! Its a full frame lens but I bought it when I had the Nikon D90 - an APS-C sensor.
I could have saved myself a few hundred pounds and bought the 85mm f/3.5 VR which is a DX macro lens. Since I planned on upgrading to an full frame sensor, I future-proofed myself by getting the 105mm. Had I not of thought about the long term, I would have had to sell the 85mm at a loss to fund the 105mm. This would have cost me more in the long run and highlights the need to plan your equipment progression.
There is certainly enough to think about above and no right or wrong answer, just what is going to meet your photographic and financial needs the best. I urge you not to put too much emphasis on the camera and lens to deliver great photographs. This is your job. Equally though, don't cheap out and expect to have the same latitude that professional equipment will offer you. There is a reason why professionals use professional gear.
Kit lenses are a great way for the beginner to find their way around the camera. I was always impressed by the 18-105mm VR that came with my Nikon D90. Stopped down to f/11 it was razor sharp but, therein lies a problem. F/11 is quite a small aperture and professional glass generally offers that same degree of sharpness at 2-3 stops wider than f/11. In short, that's a lot of light to sacrifice for a sharp photo and if shooting indoors where its not that bright, your pictures will suffer with blur, or you have to raise your ISO up to the point where image quality begins to decline.
On the flip side of that coin, if you shoot landscapes and are tripod mounted, then this isn't such a problem. After selecting the optimal aperture and hyperfocal length, its not uncommon for a photographer to take a 10 second or longer exposure with the use of ND filters. So fast aperture glass isn't such a prerequisite. A good optical performer is. So again, consider what is best for your photography. There is no one size fits all cap. They are tools for a specific job. Just as a screwdriver isn't the best device to carve out a notch, nor is a chisel for undoing a screw.