Nikon D90 Flash

Like the D80 and D300, built into the D90 is an unusually capable pop-up flash unit, which operates in one of five main modes: Front-Curtain Sync, Red-Eye Reduction, Red-Eye Reduction with Slow Sync, Slow Sync, and Rear-Curtain Sync. Front-Curtain Sync fires the flash at the beginning of the exposure, with every shot. Red-Eye Reduction mode fires the (very bright) AF-assist light before the main flash exposure, to reduce the Red-Eye Effect in shots of people. Red-Eye Reduction with Slow Sync works in a similar fashion, but combines the flash with a slower shutter speed for night portraits. (This reduces the harsh effect of nighttime flash shots, allowing more of the ambient illumination into the picture.) Slow Sync mode works with shutter speeds as slow as 30 seconds to preserve color in night shots. Finally, Rear-Curtain Sync fires the flash at the end of the exposure, producing light trails that appear to follow (rather than precede) moving subjects. In all flash modes, the flash fires with every exposure. Closing the flash disables it completely. Holding down the Flash Mode button while turning the Sub-command dial adjusts the overall brightness of the flash from -3 to +1 EV in one-third-step increments.

Besides the main flash modes listed above, the D90's onboard speedlight can also be used in manual mode, as a repeating flash, or as a commander in Nikon's Creative Lighting System. (See below for more on that last item.) The D90's internal flash is fairly powerful, with a guide number of 12 meters or 39 feet at ISO 100 in auto mode, extending slightly to 13 meters (43 feet) in manual mode. (The greater range in manual mode is because it doesn't have to expend energy on the metering pre-flash.)

The built-in flash's normal X-Sync speed is 1/200s, but FP flash sync speeds as high as 1/4000s are available with optional SB-800, SB-600 or SB-R200 external flash units.

While we've never personally felt a need for a stroboscopic flash on a camera, we can imagine it being used for a variety of creative effects, as well as being highly useful for scientific applications. The D90's onboard speedlight can be used as a stroboscope, using the Repeating Flash option on custom setting menu e3. Through this menu, you can set the power level from 1/128 to 1/4 power, the number of flashes from 2-35, and the frequency of flash pops from 1 to 50 Hz (1-50 pops/second). As you might expect, the number of times you can have the flash fire varies inversely with the power of each pop: At the maximum 1/4 power, you can only get two pops in rapid succession. The maximum of 35 pops in sequence is only possible at the 1/128 power setting, moving up to 1/64 power decreases the maximum number to 25, and so on. Also note that you'll of course have to have a long enough shutter time to accommodate your flash series, so you'll likely have to visit custom setting menu e2, to change the maximum shutter time permitted with the flash.

Also included on the D90 is an external flash hot shoe, just behind the pop-up flash compartment. The hot shoe accommodates Nikon accessory flash units, as well as a wide range of third party flashes. The full range of flash sync modes remains available for compatible flash units, but third-party models may not support all modes. Unlike the D300, the D90 does not provide a PC sync terminal.

3D Color Matrix II Flash Metering
The "3D" aspect of the Nikon metering system is that it uses subject distance information from the lens (only available with lenses that contain CPUs) to guide its exposure decisions. This is particularly key with flash exposures, because flash illumination falls off quite strongly as the subject gets further from the camera. We at IR are huge fans of Nikon's flash technology, it's really a case of technology working perfectly in the service of creativity. The camera just quietly does its job, so you can focus on composition, color, interacting with your subjects, etc. It doesn't remove the creative decisions of how you want to light your subject, it simply removes the technical legerdemain from the equation. It won't by any means turn a duffer into a pro photographer, but it'll certainly take an average shooter a long way in that direction.

The D90 with Nikon's Creative Lighting System
Nikon has long been a leader in flash technology, but in late 2003, they significantly upped the ante, by announcing their Creative Lighting System. This system of flashes and supporting camera bodies lets the photographer control up to three separate groups of remote flash units, with an essentially unlimited number of individual strobes in each group. The exposure and operating mode of each group of flashes can be controlled independently, and exposure is metered through the lens (TTL) for all units.

On the D90, the internal strobe can both act as a controller and also contribute to the exposure, it can control two groups of remote strobes, and can use any of the four available channels to communicate on. The screenshots above give some idea of the options available. The built-in flash can operate in either TTL or Manual exposure mode. In TTL mode, you can vary its exposure over a range of -3 to +3 EV. In Manual mode, you can vary its power from full power (1/1) to 1/128 power. Each of the two groups of remote flash units can be operated in either TTL, AA (Auto Aperture), or Manual mode. Auto Aperture mode is the exposure mode that will be familiar to users of non-TTL metered autoexposure flash units, in which you set the camera at a given aperture setting, and then the flash measures the light reflecting back at it and adjusts its output to produce a given level of reflected light. The remote flash groups can be adjusted over the same +/- 3EV exposure level or 1/1 - 1/128 power levels as the built-in flash unit.

This degree of control directly from the camera is really remarkable, and can save you some serious money if you're planning on taking advantage of Nikon's Creative Lighting System. If you don't need to control more than two groups of external strobes, you won't need to buy an SB-800, saving you at least $300 at retail. If you're interested in macro flash photography, you won't need the SU-800 controller that comes as part of Nikon's R1C1, going with the simpler R1 kit instead. - That'll save you a good $200-250 at retail. Likewise, compared to Canon's wireless flash system, there's no need for a separate controller with the D90, again saving you several hundred dollars.

A full treatment of this system is beyond the scope of this review of the D90, but we have a bit more detail on it posted as a separate article: See our Nikon Creative Lighting System review for more info.