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Canon ef-s 18-55mm f3.5-5.6 is ii lens đánh giá

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Canon EF-S 18-55mm f/3.5-5.6 IS - Review / Test Report - Analysis

Lens Reviews - Canon EOS [APS-C]

Article Index Introduction Analysis Sample Images & Verdict

Page 2 of 3

Distortion

Typical for many APS-C standard zooms the EF-S 18-55mm f/3.5-5.6 IS produces very strong barrel distortion at 18mm [~3.2%] changing to very mild [~0.2%] pincushion distortion at 55mm. Move the mouse cursor over the focal length text marks below to observe the respective distortions 18mm 28mm 55mm

The chart above has a real-world size of about 120x80cm.

Vignetting

The Canon EF-S 18-55mm f/3.5-5.6 IS is a dedicated APS-C lens and these lenses tend to produce a comparatively high degree of vignetting. At 18mm @ f/3.5 we're talking about ~1.35EV here which is quite easily visible in many field images. The problem eases towards the long end of the zoom range and it's generally not all that bad anymore at f/5.6 and a non-issue beyond.

MTF [resolution]

Usually I'm doing the lab tests straight at the beginning of the testing procedure but the weather was fine at the time [November tends to miserable here in Central Europe] so I took it into the field first. I had to raise an eyebrow or two during the image browsing thereafter. In fact I rechecked the EXIF data in order to make sure that the [very sharp] images were taken with this lens - a member of the dreaded "kit" lens league after all. Well, enough chatting - let's have a look at the resolution data obtained under lab conditions now ...

The center resolution of the lens is extremely high throughout the tested zoom and aperture range and at its sweet spots it matches or exceeds the sensor resolution of the 8mp base DSLR used for testing. Normally you would expect a severe drop off beyond the inner image portion but this is not the case. The border and even the extreme corners remain on a very good level especially at 18mm. This is not unprecedented - the Nikkor AF-S 18-55mm f/3.5-5.6 ED is also darn good - but it's certainly something new for a budget Canon standard zoom lens. Rest assured that you may not be the only one reading this in disbelief.

Please note that the MTF results are not directly comparable across the different systems!

Below is a simplified summary of the formal findings. The chart shows line widths per picture height [LW/PH] which can be taken as a measure for sharpness. If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations

Compact and affordable, the EF-S 18-55mm f/3.5-5.6 IS II is an ideal general-purpose standard zoom for users of Canon's APS-C format DSLRs, covering an effective focal range of 28.8-88mm. Its four-stop Image Stabilizer is useful for keeping images sharp in low-light conditions.

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Canon has once again updated its kit lens for consumer digital SLR cameras, the 18-55mm ƒ/3.5-5.6 IS II lens shipping with the Canon T3 and T3i cameras. There's not a lot changed under the hood, with no change in weight, size or lens element configuration, but Canon indicates the image stabilization system has been improved, and there is a new color scheme to boot.

The EF-S mount lens will only mount to Canon digital SLR cameras with sub-frame [APS-C] sensors. Thus, for this particular lens, it will exhibit an effective focal length of 29-88mm. The lens takes 58mm filters, and a lens hood is indicated as an optional accessory.

This lens isn't a ''constant'' lens, in that as you increase the focal length, both the maximum and minimum aperture sizes decrease. The following table reflects the changes as you zoom:

Focal length18mm24mm35mm55mmMax. apertureƒ/3.5ƒ/4ƒ/4.5ƒ/5.6Min. apertureƒ/22ƒ/25ƒ/29ƒ/36

The Canon 18-55mm ƒ/3.5-5.6 IS II lens is available now with a petal-shaped lens hood, takes 58mm filters, and retails for around $200.

Sharpness The Canon kit lens is remarkably good, considering its economical price point; there's not much of an improvement between this lens and the previous [second] version of the 18-55mm.

The 18-55mm ƒ/3.5-5.6 IS II shows excellent sharpness at 18mm wide-open at ƒ/3.5, a focal length/aperture combination which typically shows off the weakness of most consumer-grade lenses. If you were looking very closely, you would see that this performance isn't completely ''flat'' across the frame, but in our view it's not noticeable enough to be a problem. Stopping the lens down to ƒ/5.6 will provide optimal performance at 18mm - not tack-sharp, but very, very good. For a lens of this price point, this is amazing performance.

The sharpness performance improves at ƒ/3.5 as you zoom out the focal range and stop down, achieving its optimum sharpness at 35mm and ƒ/5.6. Diffraction starts to set in around ƒ/8, but you don't really start to see mediocre performance until the aperture is stopped down to ƒ/16. Beyond that point, with the lens fully stopped-down, images produced are quite soft indeed.

The lens' telephoto performance at 55mm is less exceptional; the variable aperture starts at ƒ/5.6, where we note fair to good sharpness [though in our copy, a little soft on the left side]. Stopping down to ƒ/8 provides better sharpness at 55mm.

Chromatic Aberration Something's got to give when you're creating an economical lens, and in this case, it comes in the form of prominent chromatic aberration. Typically we see some form of chromatic aberration in wide-angle lenses, but usually only in the corners; in the Canon 18-55mm IS II, it's even visible throughout the middle of the frame. CA in this lens shows up as magenta fringing in areas of high contrast, and it is possible to correct in post processing. It's most prominent in the wider angles than zoomed in, but it's always present in the corners. The only exception is when you use apertures that produce less-than-sharp results: in this case, you don't notice the chromatic aberration because it's blurred.

Shading [''Vignetting''] Corner shading isn't overly problematic in this lens - there is some, but it's only notable when the lens is used in its widest angle [18mm] and with its widest aperture [ƒ/3.5]. At this setting, the extreme corners are 2/3 of a stop darker than the center of the frame. This improves to almost being negligible by ƒ/8. At other focal lengths, the only time corner shading is even slightly noticeable is when the lens is used wide open, and then the shading is almost unremarkable.

Distortion Distortion is typical for a wide-angle zoom lens; lots of barrel distortion when zoomed to wide [18mm], approaches no distortion in the middle, and gets a bit of pincushion distortion at the telephoto end. At its worst, distortion is almost one percent. With the 18-55mm IS, the distortion is fairly linear, and meets at the zero-distortion level at around 40mm. You can turn your curves back into straight lines easily with most image processing software.

Autofocus Operation The Canon 18-55mm ƒ/3.5-5.6 IS II isn't a USM lens, but it does still employ a lens-based motor: the lens focuses fairly fast, but is noticeably slower than a USM lens. As well, the lens makes a slight, low frequency whiz as it focuses. Manual focus override is unavailable while the lens is set to autofocus operation: in order to focus manually, autofocus must be overridden with the ''AF/MF'' switch.

Macro With a reproduction ratio of 1:2.9 [0.34x], the 18-55mm has decent macro capability, but it still won't replace a macro lens. Its minimum close focusing distance is 25mm [just under 9 inches].

Build Quality and Handling At 7.1 ounces, the Canon 18-55mm ƒ/3.5-5.6 IS II is very light, and to accomplish this it is largely plastic, though it is of a high-quality construction. There are no fundamental changes to the design of the lens from its immediate predecessor, with the exception of the use of rounded aperture blades as opposed to straight. Both the lens mount and 58mm filter threads are plastic. There is no flexing or rattling when using the lens: the exterior of the lens has a stippled black matte appearance, while the lens barrel, visible when the lens extends towards 55mm, is smooth. The only information available on the lens are marked focal lengths: there are no distance scales or depth-of-field indicators.

The lens only has two switches to speak of: one to enable or disable autofocus [''AF/MF''] and one to activate or deactivate image stabilization [''Stabilizer ON/OFF'']. Image stabilization works as advertised, providing several stops of steadiness in our hands, though as always the actual usefulness is going to depend largely on the capability of the individual camera user. There is a very slight sound when image stabilization is active, but mostly only audible when your ear is next to the lens. [See our IS Test page for more details].

The zoom ring is the prominent feature of the lens, at an inch in width. The rubber texture is a series of raised ribs that provide an easy grip. The zoom action is smooth, going from 18mm to 55mm in a ninety-degree turn, with only a minor amount of force required to transition between focal lengths. The lens extends as it is zoomed out, adding an extra half-inch to its overall length. Zoom creep was not a factor in our testing with this lens.

The focusing ring is mounted near the front of the lens, with a rubber ridged knurl that is easy to turn. The lens is not built well for manual focus: the ring is only an eighth of an inch in width, and doesn't offer much in the way of travel for manual focus operations [less than ninety degrees of turning action]. The ring turns during autofocus operation, and can't be overridden in this mode: you must specifically disable autofocus to override the focus clutch. Note that while the focusing ring turns, the front element does not, so attached filters will stay in place during focusing operations. The focusing ring ends in hard stops at the close-focusing and infinity ends, and we cannot tell if it can focus past infinity. You can also manually focus the lens if you turn the optional lens hood.

The optional EW-60C lens hood is bowl-shaped with a bayonet-mount. The hood lens reverses onto the lens for easy storage, and has a smooth black finish on the interior. Attaching the hood adds about a half-inch to the overall length of the lens.

Alternatives

Canon 18-55mm ƒ/3.5-5.6 IS ~$160 There's not a lot different between these versions of the lens; some slight improvement in sharpness, perhaps a little worse in the CA department.

Sigma 18-50mm ƒ/2.8-4.5 DC OS HSM ~$200 Sigma produces a worthy competitor at around the same price point, offering an improved HSM focusing system and slightly faster aperture. It's slightly sharper [except when used wide open] and has less tendency to chromatic aberration.

Tamron 17-50mm ƒ/2.8 XR Di II VC LD Aspherical IF SP AF ~$600 You'd pay a little more, but it's a bit more than a kit lens; the Tamron 17-50mm offers a wider angle, and a faster aperture. It's not as consistent for sharpness, with our review copy showing some interesting corner softness results when used at ƒ/2.8, but stopped down, it was quite decent.

Canon 18-135mm ƒ/3.5-5.6 IS ~$320 Another option would be to get a more dedicated all-in-one lens such as the 18-135mm, which costs only a little bit more but offers much more telephoto performance, with about the same optical results.

Conclusion With the legions of Canon T3i cameras sold in a given season, it's reassuring to know that the kit lens that ships with it actually performs decently well. It's decently sharp when stopped down and there is a nice sweet spot around the 35mm point where you will get sharp, undistorted photographs. It shows a bit more chromatic aberration than we would like, but of course if that is a problem for a given user, there are dozens of other lenses to upgrade towards.

Product Photos

Sample Photos

The VFA target should give you a good idea of sharpness in the center and corners, as well as some idea of the extent of barrel or pincushion distortion and chromatic aberration, while the Still Life subject may help in judging contrast and color. We shoot both images using the default JPEG settings and manual white balance of our test bodies, so the images should be quite consistent from lens to lens.

As appropriate, we shoot these with both full-frame and sub-frame bodies, at a range of focal lengths, and at both maximum aperture and ƒ/8. For the ''VFA'' target [the viewfinder accuracy target from Imaging Resource], we also provide sample crops from the center and upper-left corner of each shot, so you can quickly get a sense of relative sharpness, without having to download and inspect the full-res images. To avoid space limitations with the layout of our review pages, indexes to the test shots launch in separate windows.