BrickHouse Photo School

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Posts Tagged ‘f value

Trip Through the Canon Store: Ultra-Wide Zoom Lenses

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A lens is a tool. Most people forget that for some reason but simply enough, a lens is a tool that we use to make an image. Like all tools, at the risk of overextending the analogy, the better the tool, the better the finished project. I hear from people asking about lenses and I spend some time trying to explain them. I will go into great detail about lenses in future posts but for the sake of time, let’s make a few things clear:

  • Lenses are Measured in Focal Length: The focal length is the definition of how strongly an optic system focuses (converges) or diffuses (diverges) light. The focal length is measured, as a rule, in millimeters and it is the measurement from the optical center of the lens to the focal point on the image sensor (or film).
  • Focal Lengths Based on 35mm Film Standards: With the popularity of 35mm cameras, the focal length is based on that measurement. IF you have a camera that has a image sensor smaller than a 35mm camera’s film surface, which most digital camera image sensors ARE smaller than film, there is a multiplier you must use. For instance, the image sensor on a Canon EOS Rebel XS is 22.2mm x 14.8mm. The dimensions of 35mm film is 35mm wide (actually, it’s 36mm wide but you have to take in consideration spacing between the frames and room for the perforations). So, the EOS Rebel XS in our scenario has a magnification rate of about 1.6x.
  • Do the Math: So if you purchase a 20mm lens, it would be at 20mm on a film camera or 20mm x 1.6 or 32mm – in case you don’t want to do the math – on a digital camera.
  • This is Photography, Not Math. Why is it Important?: Well, simply put, if your camera has a magnification ratio, then you’re not getting as wide of an angle as you want. Let’s say you really want a 14mm lens because you’re shooting wide landscapes or large groups. OK, but your camera has a 1.5x magnification factor. So, you’re really getting a 21mm lens.
  • What are the Alternatives: Camera and lens manufacturers have settled the problem for the most part. They have made “full-frame” sensors that are close enough to the size of 35mm film that the magnification ratio has little impact. Secondly, these companies have also made “digital specific” lenses that already calculate the magnification ratio into the millimeter measurement. For instance, the Canon 5D Mark II is full frame, so if you buy a lens, you’re going to get the focal length as measured for film. Also, Nikon makes full-frame cameras (called FX format), which includes the D3 and D700 plus they make DX format (digital specific) lenses, which already account for the magnification.

Enough with the math, right? Just remember, unless you’re buying a digital-specific lens or your camera is full frame, the focal length of you lens is multiplied by the magnification factor.

Aperture Settings
Professional grade cameras, for the most part, have a fixed aperture value versus a variable aperture. Fixed aperture lenses have a constant maximum aperture throughout the zoom range. A variable aperture lens changes its maximum aperture in regards to the zoom. For instance, a 28-70mm f/4-f/5.6 lens means at 28mms, the maximum aperture is f/4 whereas at the high-end of the zoom range (70mm) the maximum aperture has reduced to f/5.6.

Variable aperture lenses are not normally as well constructed as the fixed aperture counterparts. The advantages, however, tend to be less weight and lower cost. Remember, the aperture value effects the depth-of-field you can achieve.

Canon’s Ultra-Wide Lenses
Canon makes three ultra-wide lenses: the EF 16-35mm f/2.8L II USM; the EF-S 10-22mm f/3.5-4.5 USM; and the EF 17-40mm f/4L USM.


The Canon EF 16-35mm f/2.8L II USM


The Canon EF-S 10-22mm f/3.5-4.5 USM


The Canon EF 17-40mm f/4L USM

EF 16-35mm f/2.8L II USM
This pro-level lens (Canon’s professional lenses typically have the “L” designation) is perfect for those who need wide angle capabilities and a big maximum aperture. On any Canon digital that does not have full frame, this lens will give you the focal length equivalent of a 26-56mm lens while still retaining the f/2.8 aperture value. This lens is ideal for photojournalists, landscape photographers and wedding photographers who shoot big groups in often poorly lit churches. It’s a relatively heavy lens (640 grams) mainly because it needs big glass for the fast shutter. The ultrasonic motor (that’s the USM designation) delivers fast and silent autofocusing. This isn’t a cheap lens, either. Expect to pay nearly $1500-$1900 US for this piece of glass. Is it worth it? Depends. If you’re interested in photojournalism or documentary photography or have a goal of becoming a wedding photographer, then yes. This piece of glass will be around to stay.

EF-S 10-22mm f/3.5-4.5 USM
This consumer-grade lens is designed specifically for Canon digital cameras that LACK full frame sensors, so basically most Canon cameras (You can tell by the EF-S designation that it’s for digital specific cameras). This lens is the equivalent to a 16-35mm zoom lens. This is also a variable aperture lens, meaning the biggest aperture setting is f/3.5 at 10mm and at 22mm it’s f/4.5. It’s a little more than half the weight of the EF 16-35mm f/2.8L II USM (385 grams). This lens will not, however, cost as much. You can find this lens for about $750-$850 US.

EF 17-40mm f/4L USM
The last lens on our ultra-wide zoom lens list is the EF 17-40mm f/4L USM. Think of this lens as the compromise lens between the high-priced EF 16-35mm f/2.8L II USM and the consumer-grade EF-S 10-22mm f/3.5-4.5 USM. This is still a pro series (L series) lens and still offers a great wide angle zoom range. For cameras that are not full framed, this is the focal length equivalent of a 27-64mm lens while still retaining the fast (but not real fast) f/4 maximum aperture. I like this lens and use it often. I find it to be a high-quality lens for a relatively low price. You can purchase this lens for about $700-$850 US. While not as wide as the 10-22mm lens mentioned above, I’ve never found myself too limited by its focal length. I highly recommend this lens as a good “walking around lens” because its range is going to work for a variety of assignments.

In the next installment, we’ll discuss Canon’s wide angle prime lenses.

Good luck and keep shooting!