Nikon D3100 Optics
Nikon D3100 Optics
The Nikon D3100 ships in kit form with the same AF-S DX NIKKOR 18-55mm f/3.5-5.6G VR lens that's included in D3000 and D5000 kits. To better compete with models from brands such as Olympus, Pentax and Sony that have in-body image-stabilization, this kit lens comes with Nikon's excellent Vibration Reduction (VR) technology to help compensate for camera shake. We tested a sample of the AF-S DX NIKKOR 18-55mm f/3.5-5.6G VR on SLRgear.com. Optical performance is so-so wide open, but the lens is capable of very good sharpness if stopped down one or two f-stops, and the added image stabilization should come in handy in low-light situations. While sharpness wide-open is only average, this newer kit lens performs better overall than the original, non-VR 18-55mm, and is enormously better when it comes to flare: The previous version was subject to rather extreme veiling flare when shooting high-contrast subjects under bright conditions.
Kit lenses work well enough for most consumers, and serve their purpose, getting you started without breaking the bank; but a big part of the attraction with SLRs is that you can easily trade up to a better lens when your finances improve, and extend your reach to wider angle, telephoto, or macro photography just by adding to your lens collection. The 18-55mm VR lens that comes with the Nikon D3100 will do a fine job until such time as budget and desire lead you to start building a lens collection.
Like the Nikon D40, D40x, D60, D3000 and D5000 before it, the Nikon D3100 drops autofocus support for the older AF lenses whose focus mechanisms were driven from the camera. These lenses have what looks like a little screwdriver slot on their mounting flange that couples with a protruding, screwdriver-looking shaft on the camera body. A motor in the camera body is thus required to drive the lens mechanics to adjust focus.
More recent Nikkor lenses have AF motors built into the lens body, which tend to be both faster and quieter than the old-style drive system, as well as allowing the camera body to be lighter, smaller and cheaper. These newer lenses carry an AF-S or AF-I designation in their name, and are the only types of lenses the D3100 can autofocus with. CPU-equipped lenses lacking built-in focus motors can be used in manual focus mode, and type G or D lens types will also support full 3D color matrix metering for more accurate exposures, particularly when flash is being used. (You can tell CPU-equipped lenses by the set of five electrical contacts arrayed on the side of the lens flange.)
The tables below (courtesy Nikon Inc.) tell the full story of lens compatibility for the Nikon D3100.
Auto Distortion Control.
The Nikon D3100 includes the company's Automatic Distortion Control function, an interesting feature that was only recently introduced to its SLRs in last year's D5000. Enabled via the Shooting menu, this option automatically corrects for barrel and pincushion distortion in JPEG files, and works with most of the company's Nikkor D- and G-type lenses, except for PC, Fisheye and certain other lenses. We tried Automatic Distortion Control with the Nikkor 18-55mm VR lens that ships with the Nikon D3100, and it worked very well. See the Kit Lens Test Results section below for geometric distortion test results with this feature disabled and enabled. The Nikon D3100 also offers distortion correction as a post-processing function, available from the Retouch menu. The playback-mode function allows you to create a copy of an image after applying either an automatic correction with manual fine-tuning, or a manual correction with a coarser-grained adjustment whose effect is previewed on the camera's LCD display.
The Nikon D3100 shares the same Multi-CAM 1000 phase-detection autofocus sensor module that's previously appeared in the D3000 and D5000, among others. The Multi-CAM 1000 module offers 11 focusing points, of which the center point is a cross-type sensor. While the AF sensor itself is unchanged, Nikon has updated the viewfinder point display. In the D3000, the approximate AF point locations were indicated with dense black marks in the viewfinder. For the Nikon D3100, these have been replaced with much fainter markings, illuminated by single red LEDs. A further change to the viewfinder display, perhaps related to this change, is that the Nikon D3100 lacks the on-demand grid display function from the D3000. The new LED indications are quite bright, but very small, and several of them have a tendency to "bleed" into other points. The worst offender is the center point, which causes the top and bottom points to glow quite noticeably. It's a little distracting, but the glow isn't as bright as a properly illuminated point, so it's still easy enough to tell which points achieved a focus lock.
The Nikon D3100 lets you choose either auto or manual focus, but it doesn't have the small AF mode dial on the front of the camera as found on higher-end Nikon DSLRs. Instead, the switch on the lens must be used. Setting the switch to "M" puts the lens into manual focus mode, while "A" places it in autofocus mode. Single-servo AF (AF-S), Continuous-servo AF (AF-C), Auto-servo AF (AF-A) and Manual focus (MF) options can be selected via the menu system. (For Live View or movie shooting, there's no AF-A mode, and the AF-C mode is replaced by a similarly-functioning mode named Full-time servo AF.)
Single-servo AF is best for stationary objects, as the camera sets focus only once when the Shutter button is first pressed halfway (or if the AF-ON function is set, when the AE-L / AF-L button is pressed). Continuous-servo AF and the Live View / movie Full-time servo AF both mean that the camera continuously adjusts the focus, as long as the Shutter button is halfway pressed, suitable for moving objects. In Auto-servo AF mode, the camera begins focus operations in Single-servo mode, but switches to Continuous-servo AF if it detects motion within the active AF area.
In higher-end Nikon SLRs, there's an important difference between Single and Continuous Servo modes: In Single-servo mode, the shutter won't release unless the lens is focused, or the lens itself is set to manual focus -- what's known as Focus Priority. In Continuous-servo mode however, the camera operates in Release Priority -- the shutter will fire regardless of the state of focus. The Nikon D3100's AF system is however always in Focus Priority mode, regardless of the servo mode selected (except of course when using Manual focus).
The AF-Area Mode option is on page two of the Shooting Menu, and duplicated in the information display (see right) lets you select between Single-point, Dynamic Area, Auto Area AF and 3D Tracking modes. Single Area AF simply means that the camera judges focus based on one part of the subject, and the user can manually select the AF point by pressing the arrow keys. Dynamic Area AF employs all of the autofocus points, though you can still manually select the main point. When Dynamic Area focusing is enabled, the camera first focuses on the subject in the selected focus area. When the subject moves to a different AF area, the camera shifts the focus to "follow" the subject. This is great for irregularly moving subjects. (Sports and kids come to mind.) The Auto Area AF option means that the camera automatically detects the subject and selects the focus point(s). The 3D Tracking mode uses the 420-element RGB exposure/white balance sensor to aid in subject tracking.
In any of the AF modes other than Auto Area, you can select the focus area by using the up, down, right, or left arrow directions on the multi-selector. There are two methods by which you can lock focus on the Nikon D3100. The first is to half-press the Shutter button to lock the focus, placing your subject in the selected focus area, halfway pressing the Shutter button, then realigning the composition and firing the shutter. (This is the default behavior of the Shutter button, but if the AE-L/AF-L button is set to AF Lock, it will override the shutter button as long as it's held down.) Alternatively, when using Single Servo AF, you can press the AF-L/AE-L button to lock focus (and exposure, unless that button is set for focus only in the Setup menu). Keeping this button pressed will lock focus and/or exposure, even if the Shutter button is released. This lets you recompose the photograph without keeping your finger on the Shutter button, but on the AE-L/AF-L button instead. (Reducing the chance that you'll accidentally trip the shutter when you don't intend to.)
There are several options available for the AE-L/AF-L button, which can be set via the Setup menu. You can program it to lock either focus or exposure separately, or both together (the default). You can also change its operation so a single press locks and holds the exposure setting. (No need to keep the button pressed down.) Finally, you can set the AE/AF lock button so it alone controls the autofocus system, meaning the autofocus won't actuate when the shutter button is half-pressed, only when the AE/AF lock button is pressed instead. (Except when using full-time AF-F mode in Live View mode or while recording movies.)
In Live View mode, the Nikon D3100 offers only contrast-detection autofocus (some Nikon SLRs give you a choice between phase-detection and contrast-detection in Live View, but not the D3100). There are three focus modes in Live View: Single-servo AF (AF-S), Full-time servo AF (AF-F) and manual focus (MF). Of note is AF-F mode which is similar to AF-C mode when using the optical viewfinder (though you don't have to half-press the shutter button), as it is the first time a Nikon SLR offers continuous full-time autofocus in Live View and Movie modes. There are four AF-area modes in Live View mode: Face-priority AF, Wide-area AF, Normal-area AF and Subject-tracking AF. Face-priority is useful for portraits. Up to 35 faces can be detected and when more than one face is present, the D3100 will select the closest one. You can also manually select which face to focus on using the multi-selector. Wide-area is recommended for landscapes and other non-portrait shots. Normal-area offers a smaller focusing area, and is useful for focusing on a small area of the frame. With either Wide- or Normal-area, you can move the active focus area with the multi-selector. Using a tripod is recommended. Subject-tracking attempts to track a selected subject as it moves through the frame. You position the focus point over your intended subject and press the OK button to begin tracking. To end tracking, press the OK button again. Note that Subject-tracking AF may be unable to track a subject if it's too small, moves too quickly, is similar in color to the background, changes sizes, or if the subject and background are very bright or dark, etc.
Like past Nikon DSLRs with built-in flashes, the D3100's AF-assist light is a bright incandescent bulb that emits from the body near the handgrip. We thought to call particular attention to it, because some DSLRs use the flash as an AF-assist light. That would be fine, were it not for the fact that some such cameras also require that the flash be used in the exposure, so there's no way to have AF assist for available-light shots. The Nikon D3100 doesn't have this limitation. AF assist is however not available in Live View mode.
The Nikon D3100 includes a two-pronged approach to fighting dust. The dust reduction system previously seen on the D3000 and D5000 digital SLRs has been adopted for the D3100, where the optical low pass filter over the sensor is vibrated to shake off dust. In addition, Nikon has coupled this with what it is calling the "Airflow Control System". In essence, the camera's internals have been designed so as to control the flow of air -- along with the dust the air is carrying -- when the shutter is triggered, channelling dust particles away from the sensor.
The Nikon D3100 lets you choose when the sensor is ultrasonically cleaned. Selections available in the Setup Menu are Clean at Startup, Clean at Shutdown, Clean at Startup & Shutdown, or Cleaning Off. You can also lock-up the mirror for manual cleaning (see below). It's important to check that you have sufficient power available while cleaning the sensor though. When the camera is switched off or the power runs out, the mirror and shutter will return to their normal positions- potentially causing damage if there's something blocking their path. Helpfully, the Nikon D3100 will attempt to give a warning roughly two minutes before the power runs out, by flashing the self-timer lamp and emitting a beeping sound -- a good warning to get your cleaning supplies out of the camera pronto!
Despite the new dust cleaning features, we haven't seen an automatic system yet that's capable of removing all dust. So while this is a nice feature to have, don't be fooled into thinking that you won't have to either learn how to clean your 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 rid of them.
Most of us are naturally leery about 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 run rampant. And prices -- Did I mention prices? How about $100 for a simple synthetic-bristle brush?
So how do you know what product to use?
We don't pretend to have used everything currently on the market, 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, highly 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 d-SLR, 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 d-SLR, 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.)
Kit Lens Test Results
Good performance with the 18-55mm VR kit lens.
|18mm, f/8||55mm, f/8|
The Nikon D3100 comes with a Nikkor AF-S DX 18-55mm f/3.5-5.6G VR (Vibration Reduction) kit lens, which has a typical optical zoom ratio of about 3x. Details are pretty good across the frame at full wide-angle, with minimal corner blurring, though images are a touch soft overall. There are low levels of coma distortion in the leaves at the corners, and chromatic aberration isn't an issue because most of it is removed by the D3100's image processor (see below). Results at full telephoto are quite good, with good detail across the frame and very little corner softness. (These shots were both taken at f/8. See below for how the lens performs at maximum aperture.) Overall, a good performance for an inexpensive kit lens, and the built-in Vibration Reduction (Nikon's term for optical image stabilization) will come in handy for hand-held shots in low light.
A slightly large macro area with the kit lens, with soft detail overall. Flash throttles down pretty well.
|Macro with 18-55mm Kit Lens
|Macro with Flash
The Nikon D3100 captured a slightly larger than average macro area with the standard 18-55mm kit lens, measuring 2.75 x 1.83 inches (70 x 47 millimeters). Detail was somewhat soft, though there was hardly any additional softening in the corners. (Most lenses have some softening in the corners at macro distances.) The Nikon D3100's flash throttled down for the macro area pretty well, though the resulting image is a bit dim (easily fixed by applying some positive flash exposure compensation).
High barrel distortion at wide-angle with the 18-55mm kit lens, though hardly any distortion at telephoto.
|Barrel distortion is 1.0 percent at 18mm|
|Almost no pincushion distortion at 55mm|
The Nikon D3100's 18-55mm kit lens produced about one percent barrel distortion at wide-angle, which is higher than average and noticeable in its images. At the telephoto end, there was only about two pixels worth of pincushion distortion which is negligible. This 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).
Auto Distortion Control
Low geometric distortion when Auto Distortion Control is enabled.
|Barrel distortion at 18mm is 0.2 percent|
|Barrel distortion at 55mm is less than 0.1 percent|
The Nikon D3100 offers an Auto Distortion Control feature to reduce geometric distortion automatically. As you can see it worked quite well with the 18-55mm lens, reducing barrel distortion at wide-angle significantly, but it overcorrected the pincushion distortion at full telephoto ever so slightly. Since this option is database driven, it's only available for Nikkor D and G-type lenses with certain optics such as Fisheye and Perspective Control lenses excepted. Auto Distortion Control is Off by default. You can also apply Auto or Manual Distortion Control to JPEGs after the fact, in the Retouch menu. Manual mode works with images from any lens.
Chromatic Aberration and Corner Sharpness
Low C.A. in JPEGs, higher in uncorrected RAW files. Some blurring in the corners of the frame at wide-angle and telephoto with the kit lens wide-open.
Chromatic Aberration. Chromatic aberration is moderately low at the full wide-angle setting of the Nikon D3100's 18-55mm VR kit lens. At telephoto, chromatic aberration is even lower and hardly detectable. (This distortion is visible as a slight colored fringe around the objects at the edges of the field of view on the resolution target.) The Nikon D3100's image processor does a good job at automatically removing most C.A. from JPEGs, and it works with any lens. (See below for crops from uncorrected RAW files.)
Corner Sharpness. The Nikon D3100's 18-55mm VR kit lens produced soft corners of the frame at full wide-angle, noticeable in a few shots. The upper left corner was only a touch softer than the other corners, and the softness didn't extend very far into the frame. The center was fairly sharp. At full telephoto, the left hand side corners were also soft, with the lower left being the softest, but the lens is softer overall at telephoto than at wide-angle. There's also a little bit of vignetting (corner shading) at both ends of the zoom, as indicated by the darker corner crops. These are typical results for a kit lens, considering the aperture was wide-open for these shots. (Corner sharpness and vignetting typically improve as the lens is stopped-down from maximum aperture.)
Higher levels of C.A. at wide-angle and telephoto in RAW files.
|Wide: Upper left
C.A.: Moderately high
Softness: Moderate blurring
C.A.: Very low
Softness: Fairly Sharp
|Tele: Lower left
Softness: Moderate blurring
C.A.: Very low
Softness: Slightly soft
As you can see from the crops above, levels of chromatic aberration are higher in uncorrected RAW files. Nikon has been reducing C.A. in its JPEGs for a while now in their mid-range and high-end DSLRs. It's nice to see the feature come to the entry-level D3100. It looks like the Nikon D3100 may also be doing some corner shading correction as there is more corner light falloff in uncorrected RAW files than can be seen in JPEGs, but there is no mention of corner shading correction in the user manual.
The images above were taken from our standardized test shots. For a collection of more pictorial photos, see our Nikon D3100 Photo Gallery .