- Treeline at 200 mm
New Users Corner
Lens types and terms
There are a confusing number of different lens types available for DSLR cameras along with equally confusing terminology.
- Zoom lenses
- Ultra-zoom lenses
- Prime lenses
- Macro Lenses
- Focal Length and aps-c
- Wide Angle lenses
- Ultra Wide Angle lenses
- Telephoto lenses
- Oddball lenses
Zoom lenses
If you come from the point and shoot camera world then you are familiar with zoom lenses. They are lenses that have a variable focal length range. The kit lens that comes with most DSLR bodies is always a zoom. Often a 18mm to 55mm.
Zooms are versatile lenses and are relative new comers on the photography scene. Twenty five years ago they were rare and expensive. Computer lens design software combined with computer controlled lens grinding equipment has made them ubiquitous. These lenses in the less expensive versions tend to be on the slow side.
Things to watch out for are: does the lens change length when it is zoomed. Lenses with internal focusing do not and are more desirable than the ones which do change length. Does the front of the lens rotate when the lens is focused or the focal length is changed? This can cause problems with certain filters since some, like polarizing filters, need a a certain position to work as you want them to do. That means you have to readjust the filter everytime you focus.
Prime Lenses
Treeline at 50mm
Before there were zooms there were primes. These are lenses with a single fixed focal length. Some people prefer to called these fixed focal length lenses rather than primes.
Prime lenses are often faster, meaning they let more light into the camera. They can be lighter weight than zooms. And they are usually considered to be optically superior in many cases. The sharpest lenses are are almost always primes. This is because the lens design is simplified for a prime lens over a zoom lens which has to physically move lens elements around in the lens barrel as the focal length is changed.
Of course with a prime lens you have to use the two footed zoom, you will need to move closer and further away from the subject with your feet instead of twisting the zoom ring.
Some extremely fast primes are made like the Canon f/1.2 lenses in 50m and 85mm. Canon has even made a 50mm f/1.0 lens. These ultrafast lenses are specialist lenses and tend not to be as sharp as normally fast versions. That f/1.0 lens is four stops faster than a kit lens at f/4 which means that if you shot at 1/25th of a second with the f/4 lens you could have shot the same scene at 1/500th of second with the f/1.0 lens or 1/250th of a second with a f/1.2 lens.
The longest telephoto lenses also are primes. Canon has made a 1200mm f/5.6 lens and the rumor is that they would still make one if someone was willing to pay for it. They do have a 800mm f/5.6 lens currently available as does Sigma. Sigma also has some very long telephoto zoom lenses.
Macro lenses
Macro lenses are one area where you cannot believe what you are told by the manufacturers. Strictly speaking a macro lens is a lens which which can focus down to 1:1. That means the image size on the camera sensor is the exact same size as the real object. Something one centimeter wide at 1:1 will create a one centimeter wide image on the camera sensor.
However manufacturers advertise some of their zoom lenses as being macro lenses. This is always a pure and simple lie. All macro true macro lenses are prime lenses, although I suppose a manufacturer could design a zoom macro, none do so. Besides focusing very closely macro lenses are very sharp as a rule. They are also commonly used as portrait lenses. Primes are commonly made at a f/2.8 aperture which means they are moderately fast lenses.
Owning a macro lens will open a whole new world to you as you can zoom in on bugs, slugs and flowers along with anything else that you fancy shooting. A macro around 100mm in focal length is often recommended as a good starting prime since it will let you get a little further away from the subject than a 50 or 60mm lens will and is lighter and cheaper than the 150mm or 180mm lenses.
Lens Focal Length
What makes a lens a wide angle or a telephoto? The 35mm camera industry has adopted the 50mm lens as the normal or standard lens. There are all sorts of mythology attached to how this came about but the truth of the matter seems to be that Oskar Barnack the designer of the Leica 35mm camera back in the 1930’s seems to have settled on the 50mm as lens on that could be produced for a good price with excellent optical properties.
The normal focal length range for a 35mm format camera extends from about 45mm to 55mm and lenses with less than those focal lengths are known as wide angle lenses. And lenses with greater than those focal lengths are known as telephoto lenses.
Complicating the situation for DSLR cameras is the fact that most DSLR bodies use some form of the aps-c sensor size rather than a full frame 35mm sensor. These are commonly called cropped frame sensors. Olympus uses another even smaller sensor called the four thirds sensor.
Effectively what this means for owners of aps-c cameras is that they need to multiply the stated focal legth of their camera lens by a crop factor to get the effective focal length. Now this doesn’t explain what the real situation is but for everyday use you can think of it that way. So for Canon cameras you would multiply by 1.6 which would mean that a 50mm lens is actually a 80mm lens. No longer a normal lens but now a short telephoto. Nikon uses a 1.5 crop factor making the 50mm lens an effective 75mm and Olympus uses 2X making a 50mm effectively a 100mm lens.
Perhaps a better way to think of the situation is this, imagine you take a photo with a 50mm lens on a full frame camera and print out a 8X12 inch print from the image. If you take a pair of scissors and cut out the center 62.5 percent of the print that would be what the Canon aps-c sensor sees and what you would get in your image file. The percentages for Nikon’s and Olympus’s would vary but the situation is the same. You can see from this where the term crop sensor comes from.
Now this as a practical matter has some consequences for you. Lenses tend to be the sharpest and have the least amount of distortion in the center of the frame. Crop sensors only use that central part of the image and thus make some marginal lenses work better than they would on full frame sensors. That is good. Since you effectively multiply the focal length that 300mm lens is now a 420mm lens. That is good. But what you win on the telephoto end you lose on the wide angle end. That 30mm wide angle is now a 48mm normal lens.
The normal lenses are considered to have about a 45 degree Field of View (FOV) which is the angle that they ’see’. If you look at that image I placed in the prime lens section, it was taken with a Sigma 50mm f/2.8 Macro lens. Since that lens is effectively a 80mm lens is has a 25 degree or so FOV. Look at the trees in the center of the skyline, now look at the shot on the top of the post taken with a Canon 70-200mm f/4L IS set at 200mm and the same trees are much larger, the lens FOV is smaller, efectively about 7 degrees. The shot down in the ultra wide section was shot at 11mm with a Tokina 11-16mm f/2.8 lens. It has an effective FOV of 100 degrees and the trees are just visible but you get to see a much wider view of the grass flats.
Wide Angle lenses
Traditionally wide angle lenses ran from 40mm down to 28mm or so. With a rare and expensive 24mm occasionally seen. With the crop sensor effect this means that you need a range of 25mm to 16mm or so to give you the same effective (FOV). And on the Olympus you need 20mm to 14mm.
Wide angle lenses let you take a wider shot of the scene. You can squeeze more people in on a group photo and you can get a wider panorama view of landscapes. Kit lenses (18mm to 55mm) cover a wide angle to short telephoto range.
Ultra Wide Angle Lenses
Treeline at 11mm
Because of the crop sensor effect a lens that would be considered to be very wide angle on a full frame camera, is not so on a crop sensor body. To get the same FOV on those bodies you need a very wide angle lens, and these are called ultra wide angles. They generally range from 10 to 12mm at their widest end and go up into the 22mm range at the top. A 10mm lens on a crop sensor body give the same FOV as a 16mm on a full frame body.
The Canon system has lenses that are designated as EF-S mount and those lenses protrude into the mirror box of the camera at the back end. The smaller aps-c mirrors clear that end of the lens when the camera shutter fires, but the larger mirror on a full frame body would slam into the lens with disastrous effects. Thus those lenses are designed not to fit on full frame bodies. Lenses with the EF mount fit on all Canon bodies and most canon lenses are EF mount.
Other systems, so far as I know, don’t have this problem. But they still have lenses that are designated for aps-c use only. The lenses will physically work on full frame bodies but they are optically designed for aps-c sized sensors and will not illuminate the full sized sensor. This is called vignetting. The Tokina lens I used above only works at 15-16mm on full frame bodies for example.
These ultrawide angle lenses will produce distortion. This not because the lens is defective it is because you are squashing the very wide angle image onto a flat surface. The distortion can be dealt with in editing software like Photoshop if it bothers you. I rarely bother since I just accept it as a part of the ultra wide lens use.
You can minimize distortion by good camera technique. You need to hold the lens parallel to the ground. Tilting it up or down will increase the perceived distortion.
Fisheye lenses.
The lenses we have been talking about so far in the wide angle category are rectilinear lenses. That is they produce a image that fills the sensor from edge to edge and while they are distorted the distortion is not extreme. There is another type of wide angle lens called a Fisheye that makes no attempt to minimize distortion. They produce round image circles with a LOT of distortion. Julie K has a gallery with some of these shots that you can look at.
Peleng lenses are a cheap way into the fisheye world. I believe they only work in manual mode which probably isn’t a major problem with this type of lens. And you may need an adapter to use it on your camera. Sigma, Canon and Nikon all make higher quality fisheyes.
I’ve never felt attracted to this type of lens and have never owned one. These lenses may not produce a full circle image on aps-c sensors. And there is software called defishing software that attempts to convert the images into rectilinear form.
Telephoto Lenses
Telephoto lenses have focal lengths greater than the normal lens. The provide narrower FOV, all the way down to 2 degrees or so with a 800mm lenses on an aps-c sensor.
Short telephotos are popular as portrait lenses since they tend to have a pleasing perspective. Look at Ken Rockwells site linked above for some of his ideas on the subject.
Longer telephotos are needed for nature and critter photography. Many people think you need at least a 300mm lens for most bird photography and many people use 400mm lenses. Lens prices for prime telephotos tends to skyrocket at the 300-400mm range. A very high quality 300mm f/4L IS lenses runs around $1200 at this time. The 400mm f/5.6 is about the same but doesn’t have IS and is slower too. But the 500mm f/4L IS is $5800. So for most people a 300 or 400mm will be the absolute end of their lens buying possibilities.
Zoom telephotos exist in three types for Canon lenses. There are the cheap low quality lenses sold to new users in the 70-300mm range. These junk consumer grade lenses are slow and have really poor optical quality. I think they lead many new users to give up in frustration since they will blame their inability to duplicate high quality images on their lack of skills when a large part of the problem is the lens that they are using.
There is a perennial argument in photography circles over what is the most important factor in making excellent images. Some people claim that a highly skilled photographer can take great shots using poor equipment. That may be true, tho I have my doubts, but the truth of the matter is that most photographers are not at that level of skill. On the other hand buying expensive gear will not help you make great images if you lack the skills to use it. I know of people who have sunk ten of thousands of dollars into gear and still make mediocre photos.
So in my opinion having equipment that is suited to your skill level is important. Poor equipment matched with not so great skills is going to lead to poor photography.
Canon has an intermediate level of lenses. The Canon 70-300mm f4-5.6 IS lens is a pretty good lens with IS. It runs about $550. For slightly more you can get the very excellent Canon 70-200mm f/4L lens without IS but it is a very sharp lens with very good autofocus speed. It is a good way to get started with L glass. And there is a little known but good quality lens available if you can find a used copy. The Canon 100-300mm f/4.5-5.6 EF lens. Not the macro version which is firmly in the junk category. You can often pick up one of these gems for $250 or so from Keh.com. It is sharp and has good autofocus speed. The one defect is that the lens runs out to its longest length when allowed to hang down. A minor irritation.
Again I don’t know enough about Nikon lenses to make recommendations. They have at least two grades of lenses, the consumer grade junk and the excellent top grade. I don’t know if they have a mid grade range of lenses.
Lens Speed
Lens speed is related to the widest aperture of the lens. The lower that number the more light it allows to hit the camera sensor. And that means that you can use it in darker environments. Indoors for example without flash use.
Your kit lens will be a slow lens with an aperture range in the f/3.5-5.6 range. That makes these lenses very hard to use in low light. Happily both Canon and Nikon sell excellent low price 50mm f/1.8 lenses. The Canon runs around $85 and I think the Nikon is slightly more. These lenses are called plastic fantasticks since they have cheap plastic construction but good optics. These lenses will let you do low light photography.
Canon makes a whole series of fast prime lenses starting with the 50mm f/1.8. There is also a better quality 50mm f/1.4. There series continues with the 85mm f/1.8, 100mm f/2, 135mm f/2 and 200mm f/2.8 lenses. The prices start around $300 and get up to $600 when you get to the 200mm lens. These are not L lenses but they have very sharp optics and fast autofocus. And of course they are all ‘fast’ lenses meaning they have a wide maximum aperture. If you can break your reliance on zoom lenses these are an excellent way to expand your lens collection.
Oddball Lenses
Lens manufacturers make all sorts of odd special use lenses. Some portrait photographer like a soft look so Canon makes a 135mm soft focus lens. I’m not sure how much value it has in the era of Photoshop.
There are lenses that produce intentionally distorted images, LensBaby. They make no sense to me but someone is buying them.
There are lenses with swing and tilt adjustments for architectural and product shooters. The Canon TS-E series. These lenses are so important to some photographers that they have switched camera systems so they can use them. Nikon finally came out with one in 2008.
And I’m sure you can find other oddball lenses if you look hard enough.
Summing Up
Well so much for my 1000 word goal, this post is almost 3000 words. A lot of the opinions above are my opinions and there are people who will not agree with them. They can get their own blog I guess, heh. Next up in the New User Corner will be a post on what new users should do next once they have that DSLR in their hands.
I’m planning a post of CF card speed in between tho.
