Canon T3 Optics
Canon T3 Optics
Optical construction consists of 11 elements in 9 groups, with a 6-blade diaphragm for aperture control. Minimum focusing distance is 25cm or 9.8 inches for a maximum magnification ratio of 0.34x or 1:2.9 at 55mm. The lens accepts filters with 58mm thread and the front element does rotate during focusing. Maximum length is 84.5mm or 3.33 inches, while maximum diameter is 68.5mm or 2.7 inches. Weight is about 200 grams or 7.1 oz. As with many kit lenses these days, the mount is plastic to reduce cost and weight. The lens features an AF/MF focus switch to switch between autofocus via the built-in DC motor and manual focus (this lens does not have a more expensive Ultra-sonic Motor or USM). There's also a Stabilizer On/Off switch.
While we've yet to run this newer version through our testing process over at SLRgear.com, the preceding lens was quite impressive when compared to those bundled with Rebel cameras preceding the XS, yielding improved sharpness and reduced chromatic aberration.
Like other Canon DSLRs with sub-frame sensors (currently, the Canon Rebel XS, Rebel XSi, Rebel T1i, T2i, T3i, EOS 50D, 60D, and EOS 7D), the Canon Rebel T3 will work with pretty much any EF-mount lens ever made, as well as with the special EF-S lenses designed for cameras with APS-C size sensors. Designed with a smaller image circle (the area covered by the image on the film/sensor plane), EF-S lenses tend to be smaller and lighter than full-frame models with the same focal length and maximum aperture. EF-S lenses can't be used on full-frame Canon cameras, nor on their APS-H models with 1.3x crop factors, like the EOS-1D Mark III or Mark IV, but small-sensor cameras like the Canon T3 can use any full-frame lenses in Canon's arsenal.
The Canon T3 offers Lens Peripheral Illumination Correction, which corrects for lens shading (commonly called "vignetting"), producing uniform exposure across the frame by compensating for the light falloff seen with some lenses in the corners of the frame. Lens Peripheral Illumination Correction first appeared in the Canon 5D Mark II, and has since appeared across Canon's lineup, all the way from entry level to professional models. This setting is enabled by default, but can be disabled if desired.
As alluded to above, the "IS" in the new kit lens' name stands for "Image Stabilization." This is a handy and increasingly common feature of both lenses and some camera bodies. The idea is that a motion sensor, computer chip, and movable optical element are built into the lens barrel. The motion sensor detects camera movement that could lead to blurred images with long exposure times. This data is processed by the computer chip, which in turn moves the floating optical element in such a way as to counteract the motion of the lens, thereby keeping the image stationary on the camera's image sensor. The net result is that you can shoot at much slower shutter speeds than you'd otherwise be able to, without getting blurred images due to camera movement as a result.
Image stabilization technology generally works very well, and Canon has been making IS equipment longer than most competing manufacturers. The net result is that the Canon T3's IS-enabled kit lens does a great job of delivering sharp photos under dim lighting: In the case of the 18-55mm f/3.5-5.6 IS II lens, you should be able to shoot at shutter speeds up to 16x (4 stops) slower than you can normally hand-hold without IS.
Some manufacturers build sensor-shift image stabilization capability into their camera bodies, rather than their lenses. The advantage of this is obvious: Every lens you put on a camera with body-based stabilization becomes similar to an IS lens. A body-based IS system makes for a much less expensive lens collection, since you don't have to pay for IS technology in every lens you buy. There is a downside to body-based IS, though. Because their IS systems only affect the captured image, body-based systems don't stabilize the image seen in the optical viewfinder. (Of course, this limitation doesn't apply when using a Live View camera that captures its viewfinder image from the camera's main sensor.) In extreme cases, having a stabilized view through the viewfinder, like you get with the Canon T3, can be a great aid to accurate framing and improving your own stability for sharper pictures.
So neither IS technology (lens-based or body-based) wins over the other on all points. If you plan on assembling a large collection of lenses, body-based IS will save you money, but at some possible cost in performance, and without the benefit of a stabilized view through the viewfinder. Lens-based IS can work better (not all IS systems are created equal), but will cost you more if you end up buying a lot of lenses. For the casual user who doesn't plan on acquiring a large lens collection, either approach will work, now that IS-enabled kit lenses are appearing as part of consumer-level SLR bundles.
Canon T3 Autofocus
The T3 uses a similar AF sensor to that used in the Rebel XSi, T1i, T2i, and T3i, but lacks their enhanced precision at its cross-type center point. This AF sensor design hence doesn't provide any more precise focus when used with lenses with apertures of f/2.8 or larger, unlike those in its more expensive siblings. SLR autofocus accuracy is governed in part by how far apart you can space the sensor elements for a single AF point from each other. The wider this "baseline," the more accurately the AF point can determine focus. What limits the AF baseline spacing in a camera system is the lens aperture. You can build sensors with wider baselines, but that also restricts the range of lenses they can be used with. By and large, camera manufacturers have set f/5.6 as the minimum aperture their AF systems will work with. Lenses with wide-open apertures smaller than f/5.6 just won't focus. But once the baseline spacing is set, using a faster lens doesn't improve focus accuracy any, unless you add a larger baseline sensor. Across the board, the Canon T3's AF points are all conventional f/5.6 ones.
Autofocus modes include One-shot (also known as single-shot), Predictive AI Servo AF (continuous), and AI Focus AF, which automatically selects between the One-shot and AI Servo modes. Of course, there is also a manual focus mode.
Like previous digital Rebels, the Canon T3 uses the built-in flash head as its AF-assist illuminator, rather than a bright light built into the camera's body. This works well because the flash is quite bright, and probably has a greater range than do typical on-body incandescent illuminator bulbs. Following the lead of the T1i, you can disable the internal flash, yet still have the benefit of the flash-based AF-assist illuminator. You do this via the Flash Control menu, but note that this AF-illuminator-only setting for the flash head means you lose flash exposure capability until you explicitly turn it back on. If you attach a 550EX external flash unit to the Rebel T3, its internal AF-assist illuminator can be used instead of the flash head itself, providing a useful working range of about 50 feet with a less obtrusive light source. For non-flash photography, Canon's ST-E2 wireless sync transmitter can also be used for AF assist, a handy trick. The ST-E2's AF-assist light has a useful range of about 25 feet. (Note though, that we haven't tested the ST-E2 ourselves, so we can't verify this performance independently.)
Dust Reduction Technology
The Rebel T3 digital SLR camera forgoes the EOS Integrated Cleaning System that's featured in Canon's SLRs since the Rebel XTi camera. Those models use an active approach to fighting the ill effects of dust in images, shaking dust particles off the low-pass filter in front of the sensor using a piezoelectric element, but the Rebel T3 instead relies solely--at least, in terms of hardware--on an antistatic coating that attempts to prevent dust adhering in the first place. In terms of software, the camera can be triggered to map any spots where dust has adhered to the sensor, saving it as Dust Delete Data and subsequently subtracting dust spots from the final image during post processing with a compatible personal computer and the supplied Digital Photo Professional software. The only provision for physically removing dust once it adheres to the sensor is a manual sensor cleaning function which raises the mirror, and allows users to clean dust that may have stuck to the low-pass filter.
We haven't yet seen an automatic system capable of removing all dust, but with the T3 lacking even a basic cleaning system, its users are even more likely to have to either learn how to clean their sensor, or send the camera in for cleaning.
Everyone understands that lenses sometimes get dust on them and need to be cleaned, and there are a lot of lens-cleaning cloths, solutions and other accessories on the market that work well. But what do you do when your sensor gets dusty? Dust specks on the sensor tend to show up when shooting at very small apertures, appearing as dark blobs on your images. They're distracting at best, a terrible nuisance at worst, if you end up having to retouch every image to be rid of them.
Most of us are naturally leery of the idea of poking around inside the delicate innards of our DSLRs to wrestle with recalcitrant dust specks. Gently blowing the sensor surface (actually, the surface of the anti-aliasing filter) with compressed air gets rid of some dust, but there's invariably a lot that just stays stuck, no matter what. So what do you do?
If you've got dust specks on your sensor (and sooner or later you will), you're going to need to clean it. There are a lot of products out there intended to address this need, but a distressing number of them work poorly (if at all), and many are grossly overpriced. Advertising hype is rampant, with bogus pseudo-scientific jargon and absurd product claims. And prices - Did we mention prices? How about $100 for a simple synthetic-bristle brush?
So how do you know which product to use?
We don't pretend to have used everything currently on the market, we but can tell you about one solution that worked very well for us. The "Copper Hill" cleaning method is straightforward and safe, and in our routine usage here at Imaging Resource, very effective. Better yet, the products sold by Copper Hill Imaging are very reasonably priced. Best of all, Nicholas R (proprietor of Copper Hill) has put together an amazingly detailed tutorial on sensor cleaning, free for all.
Sensor cleaning is one of the last things people think about when buying a DSLR, but it's vital to capturing the best possible images. Take our advice and order a cleaning kit from Copper Hill right along with your DSLR, so you'll have it close at hand when you need it: You'll be glad you did!
(While they've advertised on our sister site SLRgear.com from time to time, we receive no promotional consideration from Copper Hill for this note. We just think their sensor cleaning products are among the best on the market, and like their way of doing business. -- We think you will too. Check them out.)
Canon T3 Optical Test Results
Kit Lens Test Results
Good performance with the Canon 18-55mm IS II (Image Stabilized) kit lens.
|18mm @ f/8||55mm @ f/8|
As mentioned above, the Canon T3 is offered with an EF-S 18-55mm f/3.5-5.6 IS II kit lens, possessing a typical optical zoom range of about 3x. The 35mm equivalent range is about 29-88mm, because of the T3's 1.6x "crop factor". Sharpness is quite good at 18mm, however there's moderate chromatic aberration visible in the corners. We can't really comment on corner sharpness because of the proximity of the trees in this shot, though, so we've added a Multi Target shot at f/8 below. Results at full telephoto are quite good too, with good sharpness across the frame and lower levels of chromatic aberration.
A small macro area (for an SLR kit lens), with very good but somewhat soft detail. Flash throttled down well.
|Macro with 18-55mm IS Kit Lens
55mm @ f/5.6
|Macro with Flash
55mm @ f/5.6
The Canon T3's macro performance will of course depend entirely on the lens in use. With the 18-55mm IS II kit lens set to 55mm, the Canon T3 captured a small (for a non-macro SLR lens) minimum area measuring just 2.23 x 1.48 inches (57 x 38 millimeters). Resolution was pretty good, but details were a bit soft, and corners had a small amount of additional softening. (Most lenses have some softening in the corners at macro distances, but this lens performed better than average in the corners.) The Canon T3's flash also throttled down for the macro area very well. There was no detectable shadow from the lens barrel, resulting in a good exposure with the flash.
Slightly higher than average barrel distortion at wide-angle, but low pincushion distortion at telephoto from the 18-55mm IS II kit lens.
|Barrel distortion at 18mm is 0.9 percent|
|Pincushion distortion at 55mm is <0.1 percent|
The Canon EF-S 18-55mm IS II lens produced about 0.9 percent barrel distortion at wide-angle, which is slightly above average and noticeable in some of its images. At the telephoto end, there's just under 0.1% pincushion distortion, which is lower than average and hardly noticeable. Geometric Distortion is the tendency for the lens to bend straight lines outward (like a barrel -- usually at wide-angle) or inward (like a pincushion -- usually at telephoto). The Canon T3 does not apply any geometric distortion correction to its JPEGs, as uncorrected RAW files have the same amount.
Chromatic Aberration and Corner Sharpness
Moderately high chromatic aberration at wide-angle, moderate at telephoto telephoto. Slight to moderate softening in the corners wide-open. Sharper in the corners when stopped-down.
Chromatic Aberration. Chromatic aberration in the corners with the Canon T3's 18-55mm kit lens is pretty evident (we'd call it on the high side of "moderate") at both wide-angle (18mm) and telephoto (55mm) settings. At wide-angle, it's brighter and therefore more noticeable than at full telephoto. Color fringing is still somewhat evident in the center at wide-angle, but very low in the center at full telephoto.
Corner Softness. The Canon T3's 18-55mm IS II kit lens produced some soft corners in a few shots when shot wide-open (maximum aperture). At full wide-angle, corners were only slightly soft compared to the center, with the upper left showing the most softness, which wasn't much. The center of the image was quite sharp. At full telephoto all the corners were soft with the lower right the softest, but the center was also a bit soft.
Shading. Vignetting or corner shading was very low, but that's because the Canon T3 corrects for it by default. See the Peripheral Illumination Correction section below for a comparison between corrected and uncorrected JPEGs.
"Stopped-down" to f/8, performance at wide-angle was similar to wide-open with perhaps slightly lower levels of C.A. Sharpness improved in both the center and corners at telephoto, as one would expect.
Overall, a pretty good performance for a kit lens.
Peripheral Illumination Correction
Like other recent Canon DSLRs, the T3 features Peripheral Illumination Correction feature to reduce vignetting or lens shading with Canon lenses.
|18mm @ f/3.5|
The Canon T3 provides what the company calls Lens Peripheral Illumination Correction, which corrects for lens shading (commonly called "vignetting"), producing more uniform exposure across the frame by compensating for the light fall-off seen with some lenses in the corners of the frame. Mouse over the Disable and Enable links above to see the effect with the 18-55mm kit lens at wide-angle at maximum aperture. Notice how the corners and edges brighten up with the center remaining roughly the same brightness. The default setting is Enable.
Peripheral Illumination Correction works with over 85 different Canon lens models, in both RAW and JPEG workflows. For JPEG shooting, the correction is made at capture time, while RAW shooters can access the function in Canon's Digital Photo Professional software, although Canon shooters should note that the latter approach offers the highest degree of correction. In-camera correction of JPEGs operates with somewhat reduced strength, especially when shooting at higher ISO sensitivities, given that the correction can make image noise more pronounced. From the factory, the T3 body ships with correction data for about 25 lens models. Canon's EOS Utility software allows correction data for lenses (including models as-yet unreleased) to be uploaded to the Canon T3.
The images above were taken from our standardized test shots. For a collection of more pictorial photos, see our Canon EOS Rebel T3 (EOS 1100D) Photo Gallery .
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