Nikon D40 Exposure
The Nikon D40 gives you all the exposure options you'd expect in a high-end prosumer SLR, matching more or less identically the capabilities of the D50 in this area. Available exposure modes include Full Auto, Program AE, Manual, Aperture Priority, and Shutter Priority modes with shutter speeds from 1/4,000 to 30 seconds available in 1/3 EV steps, as well as a Bulb setting for longer exposures. The D40's x-sync speed for flash use is a very high 1/500 second, which makes it possible to take photos under fairly bright conditions that look as if the flash were the only light source. This exceptional x-sync speed might seem strange compared to the 1/200 second x-sync speed of the D80, a more expensive camera. What's up? It turns out that the D40, like the D70, D70S, and D50 before it, has a relatively slow mechanical shutter, but "gates" the CCD for its shortest shutter speeds. This mean that the CCD itself is actually exposed to incoming light for a longer period of time (perhaps 1/100 - 1/200 second), but the camera manipulates the chip's control voltages to only allow light collection for a much shorter period of time. This makes it easy to produce very brief exposures without the expense of a really high-speed mechanical shutter, and as a consequence also permits very high x-sync speeds. The downside is that large light overloads can cause streaking or smearing in its images. See our discussion of "Shutter Control vs CCD Gating" in our D80 review for more detail on this topic. Most users will never notice the effect of light overloads with the D40, as it generally takes something on the order having the sun itself in the frame to cause streaking with a gated CCD. We mention it, though, so you'll know what it is if or when you see it.
A very nice touch that's common to other Nikon DSLRs is that, while in Program AE mode, you can rotate the Command dial to select different combinations of aperture and shutter speed settings than those normally chosen by the autoexposure system. (That is, if the automatic program would have chosen 1/125 second and f/5.6, you could instead direct the camera to use 1/60 at f/8 or 1/30 at f/11, to get greater depth of field.) This is a very handy option for those times when you need some measure of increased control, but still want the camera to do most of the work for you. We personally use this capability more than Aperture- or Shutter-priority metering in our own shooting.
An interesting feature when using Manual exposure mode is the electronic analog exposure display visible in the optical viewfinder data readout. This shows the amount the camera thinks an image will be over- or underexposed, based on the settings you have selected, and helps you find the best exposure for the subject.
ISO sensitivity ranges from 200 to 3,200, adjustable through the Shooting display, or via the Shooting menu itself. Scrolling past the 1,600 setting offers a HI-1 setting, which is one full EV step above 1,600, equating to a value of 3200. ISO values are adjustable in one-EV increments (that is, changing by a factor of two between steps) across the full range, there's no option for the 1/3 EV steps offered by the D80. A High ISO / Long Exposure Noise Reduction mode in the settings menu lets you choose whether or not to increase the amount of anti-noise processing when shooting at the higher sensitivity settings (800 and above), or when you're shooting at shutter speeds of one second or longer.
White Balance Options
(Note: Since the camera is aimed at a less sophisticated group of users, Nikon doesn't specify the Kelvin temperature settings corresponding to the various white balance presets in the D40's manual. The numbers we reference below are taken from the D80: It seems like a pretty safe assumption that they'll hold true for the D40 as well.)
White balance modes on the Nikon D40 include Auto (usable from 3,500K to 8,000K), Incandescent (set to about 3,000K), Fluorescent (4,200K), Direct Sunlight (5,200K), Flash (5,400K), Cloudy (6,000K), Shade (8,000K), and Preset (which allows you to manually adjust the white value by using a white card or object as a reference point). All white balance settings are adjustable from -3 to +3 units on an arbitrary scale by use of the Multi-Selector arrows when you're in the White Balance menu screens (with the exception of the Preset option, which is not adjustable). While we called it arbitrary, in all but Fluorescent white balance mode, each step on the fine-tuning scale corresponds to 10 mired of color shift. The fluorescent setting provides a wider range of variation to accommodate the wide range of colors available in fluorescent lighting. You can also bracket white balance exposures (see the Autobracketing discussion below). Higher values correspond to a decrease in the camera's white point, in degrees Kelvin (meaning the images become "cooler" in appearance). This is a very nice feature, as we often wish we could use one of a camera's standard white-balance settings, but tweak it to be just a bit warmer or cooler than the default. To be sure, some experimentation would be required to familiarize yourself with the impact of these "tweaked" white balance settings, but having them available is a big plus. The table below shows approximate white point temperatures in degrees Kelvin for the various adjustments in each of the major white balance settings.
Nikon D40 Metering Options
The D40 has three metering options: 3D Color Matrix II, Center-Weighted, and Spot. The 3D Color Matrix II setting integrates exposure information from a large number of areas across the frame (useful when brightly colored or very dark subjects occupy a significant portion of the frame) with distance information from the microchip in D- and G-series lenses. The result is much more accurate metering response than more conventional center-weighted metering would provide. Like the D80, the D40 uses a 420-segment RGB metering sensor for its 3D Color Matrix II metering, vs the 1,005-segment one in the D200 and D2Xs, but does still use the same 30,000-image database for judging exposure. Center-Weighted metering measures light from the entire frame but places the greatest emphasis on a circular area 8mm in diameter, corresponding to a bit less than 7% of the total frame area. Spot metering takes a reading from a 3.5mm circle centered on the active focus area only. The D40's spot metering sensor measures from a circle covering 2.5% of the frame.
The D40's Exposure Compensation adjustment increases or reduces the overall exposure from -5 to +5 exposure equivalents (EV) in one-third step increments, in all exposure modes. An Auto Bracketing feature captures multiple shots with different exposure or white balance values determined by either the photographer in Manual mode or by the camera in all other modes. (See below for details.).
When reviewing images on the LCD monitor, you can call up a histogram and a highlight function to give you a complete readout on the exposure. This is a useful tool to examine your exposure in the camera instead of waiting to download images and then deciding to reshoot. One change from the D80 though is that the D40 only shows a luminance (brightness) histogram, not separate red, green, and blue histograms.
Nikon D40 Continuous Shooting & Self-Timer Modes
The Nikon D40 offers a single continuous shooting mode, accessed via the Drive Mode option on the Shooting display and Shooting menu screens. Only a single drive mode is offered (vs the separate low and high-speed modes on the D200), with a frame rate of 2.5 frames/second. This matches the performance of the original D50. The D40 also sports the obligatory self-timer mode, with delay options of 2, 5, 10, and 20 seconds.
No Automatic Exposure Bracketing?
Bracketing is the practice of taking shots above or below the indicated exposure for a given subject, a way to make sure that you get at least one properly-exposed image of difficult subjects. Most digital cameras these days offer some sort of automatic exposure bracketing, and all prior Nikon DSLRs did as well. We were thus rather surprised to find no option for bracketing on the D40. In our own shooting, we find ourselves using the auto-bracketing feature quite frequently. While it does give you three times as many shots to deal with on the computer later, it's a great hedge against lost detail due to blown exposures on tricky subjects. We recognize that Nikon was aiming for dead-simple usage on the D40, but auto exposure bracketing is a feature we think even relatively novice shooters could use and benefit from.
Nikon D40 "Image Optimization" Options
The Nikon D40 also offers the by-now-familiar Optimize Image menu, accessed through the Shooting menu, which lets you choose various presets for softer, vivid, and more vivid colors, special color and sharpness settings for portraits, plus an option for snapping black-and-white images.
The custom option lets you adjust sharpening, contrast (tone compensation), color mode (normal or vivid modes in sRGB color space, or Adobe RGB for people working in color-managed computer environments), color saturation, and overall color hue. All of these go quite a bit beyond the capabilities you'd normally expect to find in an entry-level DSLR.
One area where the D40 is more limited than the D80 is in its black-and-white shooting mode. The D80 lets you apply color filters when shooting in black and white mode, mimicking the effect of color contrast-enhancing filters on a black-and-white film camera. The D40 offers only a single color-to-monochrome rendering.