The SB-400 Does Something Useful, Part 2

I presented the theory in my last post that when (some) Nikon cameras are set to manual exposure, the Exposure Compensation Dial can be used to adjust a shoe-mounted iTTL speedlight. The goal was to provide a level of control over the speedlight when used as a fill light.

The Two Exposure Theory: Before proceeding, I'd like to present a model often used to explain the difference between ambient exposure and flash exposure. The ambient exposure, or the "available light", is set using a combination of exposure duration (shutter speed) and aperture size (F-Stop).  The Flash exposure is determined by the F-Stop only, assuming that the shutter speed you are using is within the normal synchronization range of the camera. In most Nikon DSLRS, it is 1/200 or 1/250 of a second. On the Nikon D50, D70/D70s, and D40, it is 1/500 of a second. However, the P7700 has a leaf shutter mounted inside of the non-removable lens, and can therefore synchronize at any speed, theoretically. There is a caveat to that, as we shall see.

Exposure 1 - Ambient : To test the theory presented in my last post, I mounted the P7700 on a tripod and positioned it in the shadow of a tree.With the ISO set to 200 and the aperture set to F 5.6, four exposures were made.

• Top left: 1/250 of a second
• Top right: 1/500 of a second
• Lower left: 1/1000 of a second
• Lower right: 1/2000 of a second

Exposure 2 - Flash : The shoe mounted SB-400 speedlight does not have a built-in exposure compensation dial. Instead, I'll be using the dial on the top of the P7700, as shown in my last post. 

In this series, the Exposure Compensation Dial was set to, form left to right, -3 stops, -2 stops, and -1 stop of underexposure. Notice the the sky stays the same, and the flash only illuminates the tree.

Now this is all TTL stuff, so the exposure represents the camera's best guess at what you want. It makes a judgement based on the relative brightness of the regions identified by the Nikon Matrix Metering algorithm, and it's usually pretty close.

In this next sequence, the Exposure (flash) Compensation was set, from left to right: 0 stops, +1 stop, and +2 stops. You may notice that the difference between the +1 exposure and the +2 is not as pronounced as one might guess. This may (emphasize the word "may") be cause by the flash exposure getting clipped at the exposure time of 1/2000 of a second. This is something that must be considered when using leaf shutters in these super-sync situations.

Depth Of Flash - Again: Remember that distance plays a part in the intensity of the flash. Nearer objects are "brighter" than those more distant. The shot above was made at 1/250 at 5.6, ISO 200, without flash. The concrete sidewalk is obviously darker than the vertical retaining wall.

For this shot, the flash was engaged. You can see that the shadows nearest the camera (lower left) are brighter than those farther away (upper right). Distance decreases intensity, as you can plainly see here.

What this proves is that there are some controls available when using the Nikon P7700/SB400 combination. Not that this is an ideal combination, but I think this may come in handy someday.

Finally: The SB-400 Does Something Useful

From www.nikonusa.com

I'm a little ashamed to admit that I own a Nikon SB-400 speedlight. From a feature point of view, it's has only one setting TTL, one control (on/off), and nothing else. It head can be tilted to the vertical position, but not rotated. No manual, no Aperture Automation, no nothing.

To my surprise, Stoffen actually makes a diffusion dome for the tiny unit. I can't imagine how this would contribute to improved light quality, but obviously somebody did.

 I bought it for two reasons: I was curious to see how it would perform with my Nikon D40, and being the ultimate Nikon Fan Man, I thought it was cute. Count on it, I'll buy something that I want, and will spend a lifetime justifying the purchase.

Ken Rockwell puts great stock in the unit, firmly believing that it's the only on-camera flash a photographer really needs. I would agree with him, if my needs coincided with his, which they don't. After all, he probably created the  "Cute Photos Of My Kids" genre of blog photography. And while the photos are technically fine, they're just not to my tastes. 

Normally, I would use the SB-400 only as a fill light for my Tokina 10-17mm fisheye. In this sample made on an overcast Halloween celebration, the fill just barely provides enough light for a decent catchlight, which is about all I wanted or needed. This shot, taken in 2008, was probably the last time I actually used the lens.

From http://forum.xcitefun.net

New Playdate: I have a Nikon P7700 which I've used as an emergency, shoot-flash-in-sunlight camera. Because the lens is not removable, it can utilized a leaf shutter, allowing it to synchronize at some very high speeds. While its pixel count exceeds my D70 bodies, the small sensor yields images with high noise potential and excessive depth of field. But it is what it is, and used only in extreme circumstances when its unique capabilities make possible to use an on-camera flash to wrestle with impossibly bright sunlight.

I noticed the placement of the Exposure Compensation Dial (see down arrow, above), is conveniently placed for manipulation by my right thumb. I didn't give much thought to its usefulness because I seldom make adjustments in either of the two automated exposure modes (aperture and shutter). When used in Aperture Priority, rotating the dial can increase or decrease the exposure by lengthening or reducing the exposure time, respectively. (I have no idea how the camera would respond the the Program or Fully Auto exposure modes, as I never use them). However, when the camera is in the Manual Mode, the shutter and aperture are set by the user and not the camera. Rotating the Exposure Compensation Dial will have no effect on the exposure duration or aperture size. Unless...

There's A SB-400 In My Hotshoe! That's right! I can use the dial to adjust the output of a shoe-mounted SB-400. I suspect this is the only speedlight that can be so adjusted because exposure compensation in the iTTL Nikon Speedlight is controlled with the + and - control buttons at the 3:00 and 9:00 positions of the Multi Selector. The SB-400 has no Multi Selector, but this might actually work.

I tried it out on a Nikon D70 and it appears to also work. It did NOT work on a D600. But the SB-400 could be the ideal pairing for the P7700, since the flash exposure compensation would be right under my thumb, providing I remember to shoot in the Manual Mode, and confine myself to using the flash as a fill light.

 When I have a chance, I'll try it out on something real.

More to follow...