The Canon 24-105L lens is a wide angle to telephoto zoom lens with a fixed maximum aperture of f/4. Canon designated it as an “L” lens which indicates that it is one of their professional grade lenses. I originally bought this lens to serve as a general purpose zoom for travel photography. In addition to having a very nice focal range, the lens has image stabilization which comes in handy when setting up a tripod is simply not feasible.
If you are used to shooting primes or variable aperture zooms, the 24-105L will seem physically quite large. In fact, my initial impressions of the lens were dominated by it’s large size and heft. The lens weighs 1.5lbs (670 gr) and is roughly 4.2″ x 3.3″ in length and diameter. I know that some people recommend this lens over its f/2.8 counterpart because of size, but in my opinion the lens is not that much smaller (it is still a big lens).
To evaluate the sharpness of the lens, I selected the north entrance of Stanford University’s Quad (Figure 2) as a test subject and took photos at varying aperture and focal length. I used a Canon 5D camera, tripod, and remote release. Image stabilization was turned off and the camera was leveled with a hotshoe bubble level.
Figure 3 shows pixel level detail for a crop near the center of the image as one varies f-stop and focal length. Examining these crops, we can see that the image is sharp wide open at f/4 and stopping down to f/8 only improves the image minimally (because f/4 is quite good). Performance is good at all focal lengths.
Figure 4 shows the detail for a crop on the middle right of the image. Note that because of the changing focal length, the crop is taken from slightly different positions in images from different focal lengths. At 24 and 50mm the picture is sharp at f/4 and improves slightly by stopping down. At 105mm and f/4 the picture is significantly blurry but becomes sharp by f/8. Both the wide and tele images exhibit slight chromatic aberation and one can see a slight blue fringe at 24mm and a red fringe at 105mm on left edge of the pillar.
Figure 5 shows detail from the edge of the frame. In this case, the 24-105L lens is best at middle focal lengths (50mm) and becomes slightly softer as we go both wider or longer. Again, stopping down to f/8 improves the image.
|Figure 3. Pixel level detail from center crops shown at 100% magnification.|
|Figure 4. Pixel level detail from middle right crops shown at 100% magnification.|
|Figure 5. Pixel level detail from edge crops shown at 100% magnification.|
Vignetting is easily dealt with in today’s RAW processors and generally I feel that it should not be a primary criteria when evaluating lenses. Figure 4, shows the worst case scenario for the lens at 24mm and f/4 (which is quite bad) but by rolling the mouse over the image, you can see a version corrected by Lightroom. Stopping down the lens also reduces vignetting.
Image stabilization is one of the primary reasons to get this lens and it works extremely well. Normally, I use IS to obtain sharp images at shutter speeds that would be marginal for hand holding (see example pictures in Figure 7). In travel photography this often occurs indoors especially when you cannot setup a tripod.
|Figure 7. Example images where image stabilization helped to ensure a sharp picture.|
Figure 8 shows the distortion in the 24-105L at varying focal lengths. Each image is a full-width crop of the top portion of the picture (about the top third). As we zoom from wide to tele, the lens exhibits strong barrel distortion at 24mm, becomes almost neutral at 35mm and then shows mild pincushion at 105mm.
|Figure 8. The top portion of images taken at 24mm, 35mm, and 105mm showing the distortion present in the 24-105L.|
- The lens comes with a rubber gasket to keep water and dust from entering in the gap where the lens is mounted to the camera body.
- I took this lens to the Grand Canyon and on a windy day I managed to get sand in the focussing ring. This has no effect on quality, but I can tell there is grit in the lens and manual focusing has a grating feeling (to me this is like fingernails on a chalkboard).
- The lens telescopes outward as one zooms toward 105mm (Figure 9). This increases the size of the lens considerably.
|Figure 9. The lens extends physically as one zooms from 24mm to 105mm.|
This is a a fantastic general purpose lens well suited for travel photography. Although there is slight softness towards the edges when the lens is shot wide open at f/4, the image is very good. With image stabilization, using the smaller f-stops is feasible with good hand-holding technique in less than optimal lighting conditions.
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