There are lots of criteria to select a lens. Here are some ideas about what you can do.
What are the typical questions, dilemmas ?
- fixed focal length (prime) or zoom ?
- which focal length ?
- how wide or how long ?
- which minimal aperture ? how fast ?
- manual or auto-focus ?
- normal AF or fast/silent AF ?
- cheap or expensive ?
- original manufacturer or third party ?
- new or used ?
- pro or consumer grade ?
- stabilized or not ?
I'll try to answer all those questions step by step... and at the end, decision will be yours.
1. fixed focal length or zoom
Normally prime lenses (fixed focal length) are optically much better than their zoom equivalent. This is because they can be optimized for that particular focal length, they consist of less elements and hence are optically better (less degradation or side effects). Other advantages of primes: they are lighter than a zoom, more compact, sometimes less expensive and most of the time much faster (you will not find a 1.4 or 1.8 zoom) - important for low light photography, action or to control DOF. So, when you need speed, compactness, and picture quality, go for a prime. BUT a zoom gives you incredible flexibility because of the variable focal length and recent design are optically very close the quality you can get from a prime. The difference might not be worth the investment in expensive primes for the normal amateur user.
2. which focal length
this all depends on the application. These
are typical
applications for the typical focal lengths:
first of all, on a Nikon digital SLR, you have to take a crop factor
into
account. This has to do with the fact that a DSLR sensor is not the
same size as
film. The focal length is a physical property of the lens but on a
Nikon DSLR, a
100mm lens will give you the same field of view (or zoom factor) as a
150mm lens
on film. The focal lengths mentioned hereunder are the actual lens
focal length,
not the equivalent in the film world.
8 mm is the shortest length (Sigma
fisheye) for a commercially
available lens
10.5mm the current focal length for the DX Nikkor rectangular
fisheye
special effects with distortion - fun - super-wide shots after de-fishing
10-20, 12-24, 11-18 - typical ranges for super-wide angle zoom
architecture
street photography
wide landscapes
special effects (distorted foreground)
18-70, 17-55 - normal range zooms
normal
range zooms, allround - basically for
everything
landscape
city life
portrait
28, 35, 50 primes
general
purpose lenses, typical allround
lenses if you like primes.
This is the easiest way to get quality
shots at a reasonable
price.
60 macro
object
photography
portrait or general purpose
85, 105, 135 primes
portrait
with nice blurred backgrounds (those
lenses usually have a large aperture)
indoor sports
28-70, 35-70 zooms
general
purpose on a film camera, became a
bit long for digital camera's
ideal high quality portrait zooms
70-200, 80-200 zooms
normal long
zoom range
portrait from a distance (non obtrusive)
ideal "zoo" lens
indoor or outdoor sports (tennis,
basketball)
80-400, 200-400 zooms
general
purpose long zooms
nature photography
birding
200, 300, 400, 500, 600 primes
animal
photography
birding
sports (football, tennis)
50-500, 300-800 super-zoom
birding
air shows
tele-converters 1.4, 1.7, 2.0, 3.0
to add
flexibility and increase the focal
length. They work with most long lenses.
Check compatibility for instance using
the chart published on
www.nikonians.org
3. fast or not (maximum aperture)
The fast lenses (with a larger maximum
aperture, typically 1.4
or 1.8) are usually more expensive but allow to shoot in low light
and/or to
play with DOF (see www.dofmaster.com)
to
get nicely blurred backgrounds for instance. Faster lenses also perform
better
under normal circumstances (all lenses typically have their "sweet
spot" a few apertures down)
Fast lenses are a must to shoot sports for instance because you'll need
a fast
shutter speed, and if you want to catch enough light, there is no other
solution
than a fast lens with a decent performance fully open. For instance, I
shot
indoor tennis with an 80-200 2.8 (200mm needed to get into the action),
your
shutter speed will be between 1/320 and 1/400 @ISO800-1600 depending on
the
light. Another example: indoor basketball; my experience is that a 2.8
zoom
might be a bit slow. I recommend an 85mm 1.8 for instance. You get the
speed to
freeze movement and that lens is still reasonably priced.
4. VR/OS or not - vibration reduction or optical stabilization
I cannot be objective about VR/OS. Some
people don't like it,
some people love it. I am in that latter category.
The principle is that motion sensors determine your own movement, and
some
lenses are moved in real time in the opposite direction to compensate
your
movement to get a steady picture. That technique allows you to shoot at
lower
speeds than usual, avoiding motion blur due to camera/lens shake.
Usually, those
systems allow you to win 2-3 stops (up to a factor 8), the most recent
VR-II
from Nikon, up to 4 stops or a factor 16 (the factor is depending on
the focal
length, you might win a factor 10 at 50mm for instance but only a
factor 3 or 4
at 18mm). OS is the Sigma version of the VR (Nikon system).
In practice, this allows to shoot handheld in poorly lit environments,
for
instance I could take concert pictures with the 80-400OS lens at 400mm
1/60sec
handheld, this is approximately 10 times too slow to avoid camera shake.
What are the problems with the VR/OS lenses: first of all, the system
works
after a fraction of a second, inducing a kind of shutter delay (you
have to
press first on the shutter button to activate, this takes 1/3 sec, and
press a
second time to take a picture, that means in practice that you have to
pre-activate when almost ready to shoot). Another problem is price, the
VR
equivalent of lenses are much more expensive than the standard version.
Depending on the VR/OS implementation, you have to be careful when
using a
monopod or tripod, this could increase the blur... just carefully read
the
documentation. And last but not least, the VR as the name indicates,
reduces
vibration, and does not freeze motion... that means that VR will not
help you to
shoot action in low lit environments. Only one solution: fast lenses.
5. Original manufacturer or third party
There again some people will only buy
Nikon, some other people
will recommend third party lenses. What are the biggest differences:
Nikon
lenses are typically better built, with a better quality control, but
more
(sometimes much more) expensive. Third party lenses are usually
cheaper, but
with some issues (not always on par optically speaking, build quality
not that
good). This should be looked at on a case by case basis.
There are a few third party lenses I can recommend, and a few you
should not
look at. Consult the photography forums, ask questions about practical
experiences and make your own decisions.
Personally, I am very happy with a few third party lenses like the
Tokina 12-24
and the Sigma 80-400OS.
Until now, I have avoided all cheap Tamron and Sigma lenses because of
build
quality, but some of those lenses are excellent optically speaking and
are a
nice opportunity to the cost conscious amateur to get very good results.
6. Used or new ?
I would say both. If you need an invoice for the insurance company, for instance, then just buy new equipment. If you want to buy very recent equipment, I would also buy new. But there are lots of very interesting bargains on the internet. You can find extraordinary old manual lenses at no cost... for instance an 85mm 1.4 AIS for 300EUR/USD while the recent AF version will cost 5 times more money. Check the resource sites I recommend to see if a used lens is worth the investment but you can get pro-lenses at a very reasonable cost if you are patient enough.
7. Manual or auto-focus ?
This is a difficult choice. 30 years ago, all lenses were manual lenses and nobody had a problem with it. We now have the luxury of being able to shoot with autofocus lenses. Older Nikkor lenses (AI or AIS according to Nikon terminology) are still compatible with prosumer and professional Nikon camera bodies. There are used lenses available at reasonable prices and with excellent optical quality. If you like the feeling of the oldfashioned metal build, smooth mechanics and if you can focus manually, there are quite some possibilities there. It is possible to find superfast manual lenses with no AF equivalent (35 f1.4, 24f2, etc...) allowing to shoot in low light environments with very good quality. Up to you to determine if you can cope with the burden of manual focusing. Don't forget that the focusing screens (with split screen) we had in the past in MF cameras are not there anymore and that you'll have to rely on your eyes or the assistance of the focus indicator (a green circle in the viewfinder typically) to determine if the picture is in focus. Separate screens are available as accessories but those should be mounted by professionals and if you do so, you'll probably lose some brightness in the viewfinder. Anyway, I am a big fan of old AIS lenses because of the price/performance ratio. See for instance my review here.