Guide to Nikon TTL Flashes

by Shun Cheung

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-TTL DSLR 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.

Nikon Flash Specifications

	SB-900	SB-800	SB-600	SB-400
Guide Number at ISO 200	157.5 (feet)	174	138	98
Weight (w/out batteries)	15.1oz, 427g	12.4oz, 350g	10.8oz, 306g	4.5oz, 128g
Battery Type	4 AA	4 AA, 5 AA	4 AA	2 AA
Recycle Time with NiMH AA Batteries	2.3 sec	4 sec, 2.9 sec with 5 AA	2.5 sec	2.5 sec
High-voltage Input	yes	yes	—	—
Swivel Head for Bounce Flash	yes	yes	yes	horizontal only
CLS Master	yes	yes	—	—
CLS Slave	yes	yes	yes	—
Zoom Head	24-200mm FX/DX adjustment	24-105mm FX coverage	24-85mm FX coverage	fixed at 27mm FX (18mm DX)
Flip-out Diffuser Coverage	17mm FX 11mmDX	17mm	14mm	—
Add-on Diffuser Dome Coverage	17mm FX 11mm DX	14mm	not supplied	not supplied
D-TTL	—	yes	yes	—
Film TTL	—	yes	yes	—
A Mode (non-TTL auto flash)	yes	yes	—	—

Nikon SB-800 Flash with SD-8A Power Pack

Conclusion

For those who own current Nikon DSLRs (as well as the F6 film SLR), i-TTL and CLS is simply a wonderful flash system that can be as simple as just the built-in pop-up flash, one external flash, or it could be a complex, multi-flash system that works in a coordinated manner.

If you are a more casual digital photographer taking the typical family and travel images and would like something a bit stronger than the camera’s built-in flash, the SB-400 would be a good, affordable choice without any advanced features.

For the more intermediate to advanced photographers, the SB-600 is still quite affordable but is packed with useful features such as horizontal and vertical bounce flash as well as serving as a wireless remote.

For serious amateurs to professional photographers, especially those who are into wedding, wildlife, news, and certain types of sports photography, the SB-800 and SB-900 should be the best tools because of their power and fast recycle times. Additionally, for a lot of indoor, controlled settings, multiple Nikon CLS flashes can work together to produce beautiful results. At this point the SB-900 is certainly state of the art, but some may find its large size to be somewhat inconvenient.

Additonal Learning

Shortly after I had written this article, I bought a copy of Nikon School’s new DVD: A Hands-on Guide to Creative Lighting, featuring professional photographers Bob Krist and Joe McNally. I watched the entire DVD immediately and then repeated some selected sections. The DVD is a bit pricy but provides an excellent presentation on the entire Creative Lighting System. The DVD has two main sections. First Bob Krist reviews the basics about the quality of light and then builds a three-flash set up for a typical portrait session, one flash at a time. He also describes how to operate the SB-900, 800, 600, and R200.

The second part of the DVD features Joe McNally with Bob Krist assisting him at three locations: (1) the Boston Ballet photographing several dancers in both action and group portrait settings, (2) a bridal portrait session at a country inn, and (3) a fisherman portrait set up in a New England harbor where McNally eventually uses a total of a dozen i-TTL flashes working in coordination. They demonstrated many different CLS setups under many different real-life settings.

If you would like to learn more about lighting with Nikon i-TTL flashes and how the system works together in actual settings, this DVD is a really good way to go.