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Photography is about creating images with light. For indoor, night, fill light, or certain special effects, using electronic flashes to generate light becomes an important component in modern photography. Nikon’s current flash technology is called i-TTL, and they offer five different external flash options. So far all of those i-TTL flashes have three-digit model numbers in the form of SB-n00 (e.g. SB-600, SB-900 and there is also an SB-R200) while the older, non-i-TTL flashes have two-digit model numbers (e.g. SB-28 and SB-80 DX). Therefore, it is very easy to determine which ones are i-TTL compatible. This article provides a brief history of the evolution of Nikon TTL flash technology and a guide to those five i-TTL flashes.
The intro image demonstrates the size differences amongst the SB-900, SB-800 and SB-600.
The Introduction of Digital and D-TTL
Nikon introduced the TTL (through-the-lens) flash technology to its film SLRs (Single-Lens Reflex Cameras) in the mid 1980’s. The major advantage of TTL flash is that flash exposure is measured during the actual exposure, as the amount of light reflected off the film is detected by sensors placed inside the mirror box. When a sufficient amount of light is detected, the flash is electronically shut off instantaneously.
In 1999, Nikon released its first digital SLR, the D1. The new problem then was that the digital sensor and the anti-aliasing filter in front of it did not reflect light the same way traditional film does. As a result, Nikon had to modify its TTL flash technology as it was no longer possible to measure the amount of reflected light during the actual exposure. Instead, Nikon used pre-flashes and measured their strength to determine how much flash power was needed.
The initial technology was called D-TTL. It is merely a slight modification from film TTL. Instead of measuring the light reflected off the film during actual exposure, D-TTL carries out a quick series of pre-flashes after the mirror has flipped up but before the shutter opens. On D-TTLDSLR bodies, the outward-facing side of the shutter blades is painted light gray to reflect more light so that it would be easier to measure the pre-flash. Flash metering is still carried out by sensors placed inside the mirror box as before.
Correspondingly, Nikon also made a slight modification to its last film flash, the SB-28, into the SB-28 DX. All three D-TTL flashes Nikon would eventually introduce all have the “DX” suffix. (Subsequently, there were also the SB-50 DX and SB-80 DX.)
The D-TTL era lasted four years and Nikon only introduced four DSLRs that use D-TTL exclusively: the D1 family: the D1, D1H and D1X and the subsequent D100 in 2002. However, the entire D2 family is also backwards compatible with D-TTL; in fact, they are the only cameras that are both D-TTL and i-TTL compatible.
i-TTL and the Creative Lighting System (CLS)
In July 2003, Nikon announced the D2H, the first of what would be four cameras from the D2 family, along with a new SB-800 flash. They were the first installment to Nikon’s iTTL and Creative Lighting System (CLS). The new triple-digit model number without the DX suffix indicated the new flash technology. The pre-flash is still required for digital, but it takes place slightly earlier in the exposure cycle, before the mirror flips up. Therefore, pre-flash exposure is measured inside the viewfinder instead of inside the mirror box.
In addition to TTL flash, CLS is a complex system of master and remote wireless flashes. There can be up to a total of three groups (A, B and C) of wireless remote flashes that can be controlled independently with different exposure compensations. There are also four separate channels (1 to 4) so that multiple photographers will not interfere with one another in the same room.
Nikon Flash Terminologies
TTL: Through-the-Lens flash metering
TTL-BL: Balanced fill flash between flash and ambient light
TTL-FP: Focal Plane flash: permits flash photography with a shutter speed faster than the camera sync speed, which is typically 1/250 sec or 1/200 sec on Nikon DSLRs. In the * TTL-FP mode: the flash uses a sequence of pulse flashes to get round the sync speed limitation so that it can sync with as fast as 1/8000 sec but at reduced flash power. The higher the shutter speed, the greater the flash power reduction.
A: Auto, instead of using TTL flash with a flash meter inside the camera to measure the amount of flash, use a flash metering sensor built inside the flash to control the flash level. Among iTTL flashes, this feature is only available on the SB-800 and SB-900
M: manual, control the flash level manually at full, 1/2, 1/4, 1/8…typically at 1/3-stop increments.
The SB-800 is essentially the same flash as the SB-80 DX, which was the last D-TTL flash, with a different pre-flash and exposure measurement technology. In fact, the two look very similar. From the back side, other than the model number, they look identical.
As the very first in the i-TTL/CLS series, the SB-800 can either be a stand-alone flash, a CLS master that is mounted onto the camera and controls other remote flashes, or a CLS wireless remote slave. As either a CLS master or slave, the SB-800 can use all three groups and all four channels.
For four years since its 2004 introduction, the SB-800 was Nikon’s best flash that has a lot of advanced features:
A 270-degree rotating flash head
TTL, TTL-BL, A, GN, M and RPT options
Manual mode from full power down to 1/128 power, in 1/3 stop increments
AF assist LED
Built-in bounce card and flip-out diffuser, supplied removable diffuser dome
LCD brightness control
The SB-800 has a unique 5th battery option. It comes with an add-on compartment that can hold one AA battery. You can replace the regular battery chamber door with that compartment so that the SB-800 can use 5 AA batteries simultaneously, thus getting a slightly faster recycle time. Additionally, the SB-800 has an external high-voltage power input to use an external power supply for even faster recycle time.
The FP (focal plane) sync feature allows flash photography at any shutter speed, including faster than the typical maximum sync speed at 1/250 second. Under the FP Sync mode, the SB-800 will fire a number of flashes to cover the entire frame as the focal plane shutter moves across the frame. However, flash power is greatly reduced.
The SB-800 also has the best compatibility going forward and backward. It can work with film TTL and D-TTL bodies.
A minor downside for the SB-800 is that it has a somewhat cryptic menu system. The key to remember is that you need to hold down the center multi-selection pad for two seconds and the menu on the back LCD will switch to a different mode for master/remote selection as well as several optional settings. One example of the somewhat problematic menu system is the lock feature: on the SB-800, if you hold down both the Select (SEL) button and the on/off button for two seconds, the flash will enter the lock mode with a lock icon appearing on the LCD. All of a sudden, the controls on the SB-800 “will not work” any more. You need to hold down those two same buttons for two seconds to unlock the flash. I have seen people entering the lock mode accidentally and got stuck.
While the SB-800 is still widely available at various camera stores at the present time (December, 2008), it is quite clear that the new SB-900 is its replacement so that the SB-800 will unlikely to stay in the market for too much longer.
The SB-900 was introduced in July 2008 along with the D700 DSLR. It has a similar amount of flash power and the same CLS master/slave capabilities as the SB-800, but the SB-900 has a much improved menu system as well as a lot of new options. In particular, the SB-900 has a huge zoom head that can focus its flash beam to the 200mm angle of view, thus making it an excellent choice for long telephoto work. As a result, the SB-900 is much bigger in size than its predecessor and can be a little unstable when it is mounted on top of a small DSLR.
Concerning features, the SB-900 retains essentially all capabilities the SB-800 has and then some:
Nikon SB-900 on a D300
The flash head can now rotate a full 360 degrees
The 5th battery option is gone, but with 4 AA batteries, the SB-900 still has improved recycle time and the option to use an external high-voltage battery pack remains.
FX/DX coverage with auto detection: Given the popularity of DX DSLRs, this is an obvious improvement that was clearly missing in the last several years. In previous Nikon flashes, the angle of coverage only corresponds to the angle of view for FX for each focal length. The SB-900 can cover either the FX or DX angle of view, thus conserving some flash power on DX DSLRs.
Built-in thermostat with auto shut off for overheat prevention. While this is a good feature to have, I have read a number of complaints that the flash shuts off after only a dozen or so full-power flashes, thus causing problems to some wedding photographers as their SB-900 shuts off at critical moments. However, keep in mind that this feature can be switched off.
Center Weighted, Standard and Even flash coverage selection
Gel filters with auto white balance control
However, Nikon has removed backward compatibilities with D-TTL and film TTL from the SB-900 as those old cameras are no longer popular any more.
The SB-900 also has the lock feature, but they have apparently learned from the SB-800 experience so that the SB-900 has clear markings on the back of the flash about which two buttons to press simultaneously to engage and disengage the lock. There are many of these little improvements that make the SB-900 much easier to use than its predecessor.