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Basic info on
lenses
/ Which lens should I buy?
Many people have asked, "which lens should I buy?" The simple answer is:
"I don't know; but I do know what I need" (emphasis on 'I'). If you're a beginner, a novice, or a hobbyist, then you really
don't need a high quality expensive lens just yet. Get to know what kind
of photography you're into and learn precisely what lens you do
need. But, before we talk about
types of lenses, let's look at terminology, to be sure you know what
we're talking about.
Below includes:
 | Lingo / Terminology |
| Common Lenses |
| Details and their meanings, for buying lenses |
| Which ones to buy? |
Lingo / Terminology:
|
Auto Focus (AF): |
> The lens has a little motor inside,
and is communicated to and controlled by the camera. These usually have a switch to allow you to change
to manual focus. |
|
Digital Lens: |
> (Also see Full Frame Sensor). These
lenses produce a smaller circle of light onto the sensor. Most
digital SLR cameras have a sensor which is smaller than 35mm film,
and so less lens and glass is required. These lenses don't work well
with film or with full frame sensors, but are cheaper. |
|
Focal length: |
> How long the focus range is. Eg: "I
have a 18 to 70 millimeter zoom lens" |
| F Stop: |
> The aperture setting. F2.8 gives a
very shallow field of view (everything else is blurred), and F22 or
more means more is in focus. See more on this at
DOF explained. |
| Fixed
Focal Length / Prime Lens: |
>
These lenses, you cannot zoom. You need to walk forward or backward, yourself. |
| Full Frame
Sensor / Camera: |
> This is usually a high-end (pro /
expensive) camera where the sensor is the same size as the old 35mm
film used in film cameras. These cameras need either new 'full
frame' lenses, or the older second hand lenses used on film cameras.
All new Sony cameras can take the old Minolta lenses, and the A900
will require either the full frame lenses or the old Auto Focus
Minolta film lenses. |
| Macro: |
> (1) The real meaning is, that the
size of the image is represented as a 1:1 ratio on your sensor or on
the film. So, an insect that is 2cm long at a minimum focus
distance, then is is 2cm long on your sensor
/ film. (2) Marketers now use macro to mean how close you can be to
the object (eg: insect) and still be able to focus on it. |
| Manual
Focus Lens: |
>
The older style where your hand moves the focus, and your eye /
brain makes the judgment. These lenses don't work on newer cameras,
except with an adaptor, which is just because the size and shape of
mounts are different, so you still need to manually focus them, and
manually work the aperture. |
| Prime
(lens): |
> Usually 'fixed focal length', where
it cannot zoom. If you want to zoom, then you need to step forward
or backwards. These lenses usually produce clearer and better
results. Many photographers might use 'prime' to mean their most
used lens, as well. |
| Zoom lens: |
> A lens that can vary it's focal
length. That is, you don't have to walk anywhere to have the subject
fill the image area, you just turn the thing on the lens to 'zoom
in' and 'zoom out' again. |
Some common lenses
|
Lens type / focal length |
Image of lens |
Possible usages |
Sample images |
|
11-20mm |
 |
Landscape, cityscape |
(no pictures planned) |
|
18-70mm* |
 |
General purpose, travel, landscape, simple portraits,
flowers... |
 |
|
35-70mm, Manual focus* |
 |
General purpose, travel, journalism, family, higher
risk of loss or damage (it's a cheapo) |
(waiting for the film to get
developed) |
|
24mm, 28mm, 50mm*, Manual focus (Prime Lense) |
 |
Portraiture, landscape, studio, product photography |
|
|
28-200mm |
|
Photojournalism, general purpose, family use, travel |
(no pictures planned) |
|
75-300mm zoom* |
 |
Portraiture, air shows, car rallies, cable cars,
parachuters, festivals, and carnivals |
 |
|
100mm 2.8 Macro* |
 |
Photographing insects, flowers, product photography |
Marbles captured with 100mm 2.8 Macro |
|
100mm 2.8, 200mm,
and 300mm primes. |
|
high quality
portraiture, sports, and wildlife |
(no pictures planned) |
* Pictured
** All lens lengths
given are approximations only, and based on the Minolta / Sony systemDetails and their meanings
| As you can see, we
describe a lens by its focal length. For instance, the second lens
above (Picture A) is a 35 to 70mm (zoom). If you go shopping for a
lens, you need to consider other details. Written on the front of
most lenses are the important details. This, is a 35-70mm (focal
length) zoom lens. The image ratio is 1:3½,
that is, the object is three and a half times smaller than
represented on the film / sensor. Compare this to the macro lens
above, which has a 1:1 ratio (the image appearing on the film /
sensor is the same as the object photographed (assuming you're at
minimum focus distance). |
Picture A. |
| Looking at the barrel of the lens
(Picture B), you can see
more details. At the top is the focus distance, here the current object is
about 2 meters from the lens. Also notice, this lens can focus on
object anywhere from one meter, (about 3 feet or so) to infinity;
not very 'general purpose'. In contrast, the macro lens can focus on
anything 35cm (about one foot) from the lens. Being able to focus so closely
gives you the great opportunity to zoom in on the eyes of a
dragonfly, and the stamens of a sunflower |
Picture B. |
In picture A, we can see it says "55mm diameter". This is for any
attachments you plan to add to the front, like
filters, which screw on
the front, and for replacing lost lens caps. Also consider aperture range. The lens pictured immediately above and
right, has a range from F3.5 to F22, which is great (see more on
DOF F-Stops at
this page), and F1.4 is great for 'low light' (usually indoor)
photography. However, you can't get such a sharp focus on all of the
object with
such shallow depth of focus as seen in the blue marbles (above).
One more thing, if you go buying lenses, I strongly recommend you to see
how it fits on your camera. There's nothing worse than assuming that
there won't be a problem, and then when you get your newest pride and
joy ever back home, your heart drops. See how it focuses in the store,
and how much you can see at various zoom lengths, and get the feel of
how close or far from an object you have to be to focus on it. If you
can, take some test pictures home and think about it; lenses are
expensive, and need some consideration. Which
ones to buy? Hmm... still a tough one. I bought the kit
lenses for my camera, and have found the general purpose abilities of
them good for most of the applications I needed. However, with knowledge and
experience I've found that sharpness, finer quality, and macro abilities were lacking
in my arsenal, and so I researched and found that the 100mm 2.8 Macro
(above) would be a great for smaller things. Though, I sing the praises of the 100mm 2.8 Macro, but these
lenses have brilliant focus on objects that are especially close, but
apparently macro lenses aren't so famous for objects that are further
away. I'll also be looking at getting either a 28mm, or a 50mm prime, or
a 28-70mm top quality lens (replacing the one of 'kit quality'). What do most people have in their kit? Well, they have the focal
range from about 18 or 28mm to about 300mm covered. Looking above, you can see
how that can be done in just two lenses. Why not have it done in one?
Well, to cover such a range, the images would be of much less quality
(lacking sharpness and perhaps colour),
but in fast action like a war zone... well... you can't go past a
28-200mm. Anyway, having at least two lenses
covering this range would
usually give you better results. Lenses are expensive, and so I
suggest you to go nosing in at the second hand section of your camera
store. You can pick up some good bargains, and ultimately have great
pictures to show for it. Though, do some research and ask questions of
other photographers (not the sales guy who probably doesn't know about
that particular lens anyway). More... Also, see "How to Take Photos"
to see some of these in action within specific uses.
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