Oh Wall, Oh Sweet, Oh Lovely Wall!*

Warning: Much of what is done in with speedlights in the field is only made possible by the instant preview feature available with digital cameras. There will be exposure adjustments made on the fly, resulting in some unexpected and disappointing first tries.  iTTL will get you to third base. With some fine tuning, you'll score a home run.

When I'm on assignment, I generally try to make two photos with two different viewpoints: A visually interesting shot for possible placement on the front page, and one with lots of local participants for the Community section on Page 18. For the former, I usually follow the old rule of the Four B's: Babes, Babies, Beasts, or Blood. Include one or more in a photo and you have it made.

I was at the Obon festival in the Buddhist Temple here in San Mateo, hoping to find an interesting shot that might make page 18, or with some luck, the front page. In the first shot, I found two sister dressed in beautiful kimonos. After introducing myself to their mother, I had to decide where to place them. You see, the Buddhist Temple courtyard has walls on three sides, so the prevailing light would be high overhead blue sky. However, since it was late in the afternoon, one white west-facing wall was acting like a giant reflector, so I positioned my subjects in front of this convenient, soft, light source. 

ISO 640, 1/2500, F 2.8

It took three shots to coax a smile from the younger sister, but the results, minus the fellow in the background, made for a nice shot. Incidentally, if you look closely at the fans, you'll find them slightly out of focus. Blame that on too much "shallow depth of field" enthusiasm!

ISO 800, 1/800 @ F 2.8

Ambient Light With Fill: It was twilight when the Bon-Odori, the dance done at the conclusion of the ceremony, started. I decided to use the wall behind me as  a bounce surface for a shoe-mounted SB-900 with a converted SD-8 battery pack attached for additional juice, as a lot of power (light) is diverted when bounce flash is used, especially outdoors. And when using High Speed Sync (HSS), there's even less. There was just enough light to add some twinkle in my subject's eyes, but not much else.

1/320, F 2.8, ISO 800

As the ambient light began to fall, I increased my exposure time. Same flash fill as before. When compared to the previous shot, you can see that the lighting is less directional because the ambient had dropped to a level  closer to that of the frontal flash fill. Remember that when using HSS, the rules on exposure aren't the same as those with conventional flash. While I had increased the ambient by a factor of slightly more than (1 1/3 stops), the longer exposure time actually increased the the flash output slightly. I doesn't make sense, so just trust me.

1/10, F 5.6, ISO 800

Dragging Shutter: The evening had grown darker still, and the decorative lanterns were finally lit. Since my shutter speed had dropped below the 1/200 of a second conventional flash sync ceiling, I was getting much more power from the shoe-mounted flash, so it behaved more like a key light and less like a fill. In a moment of whimsey I rotated the camera, giving me the arc-shaped streaks in place of the lanterns. It was a fun experiment, but I'm not sure I'd do it again, should these same circumstances present themselves in the future.

1/5, F 8.0, ISO 800

These shots are starting to get closer to what I had in mind. The darkened sky is now truly blue, and the background details are minimized by the decreased ambient. The lanterns look more like lanterns, and the overexposed windows and doorways in the background keeps the viewer within the courtyard. The wall bounce is now a very dominant key light, and in spite of the smaller (F 8.0) aperture, seems to provide enough light. I went with the small aperture for the increased depth of field, a concession necessary due to the difficulties my camera had finding focus in the waning light.

1/10, 5.6, ISO 800

I'm usually much more careful about "cutting off" my subject's feet, but it couldn't be helped. The shortest length on my zoom lens on my camera was 24mm, and it just wasn't quite wide enough. I find that wide lenses force me to get close to my subjects. But because of some obstacles behind me, I couldn't back up any farther.

1/10, 5.6, ISO 800

If your wondering why these photos a lacking in "eye contact" the reason is simple: They are dancing while walking in a circle, stopping only occasionally to turn around to face me. It seem that they were always facing towards camera right so they wouldn't trip, or facing the middle to get their instructions, so there a very few faces in these shots.

Lest you think there is some sort of magic afoot, all these images needed some post-production adjustment, but surprisingly, not much.


*Shakespeare, William. A Midsummer Night's Dream. Act 5, Scene 1

Correcting Back Focus

I really liked this image when I made it on July 3. The lens, a Nikon 20-35mm 2.8 D, was purchased for under $300.00 from Fireside Camera in San Francisco. I was warned that one of the glass elements in the lens had a small scratch on it. It turned out to be a tiny and could only be seen if a flashlight was used to light it.

On this day, my goal for the day's shooting was to experiment with large shooting aperture settings using my formula for flash-fill. To limit the depth of field, I set the ISO to an equivalent of 100 and installed a 3-stop neutral density filter. The lead shot was made at F 3.5, which for all intents and purposes was wide open. Again, I was happy with the shot, until I took a closer look.
 
You can see that the foreground subject is very soft, while the spectators in the background are noticeably sharper. Now I KNOW I had focus properly, but obviously something was amiss. This condition, where there is a disagreement between the actual plane of focus and the locked autofocus setting is called Back Focus, or Front Focus if you prefer. In my case, there was clearly a problem, exacerbated by my nearly wide-open shooting aperture. Photographers who shoot with fast prime lenses will do well to check their lenses, since these large aperture wonders leave the shooter with a very, very narrow margin of focusing error.
 

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To test the lens, I used a Datacolor SpyderLensCal Autofocus Calibration Aid, a relatively inexpensive device that gives a photographer a convenient way to easily check for back or front focus. First, you'll need to set the device the Calibration Aid at the proper distance from the film plane of the camera. I found that the website of a similar device suggested that the distance between the file plane and the focusing spot should be 25 times the focal length of the lens. In my case, the 20mm short setting suggested a distance of 500 mm, or about 20 inches. Once the distance is set, you photograph the high-contrast focusing spot in the center of the device and check the inclined ruler on the side. By examining the sharpness of increments, you could see exactly where you camera was locking focus. 

  
When set up, you'll get a photo that looks something like this. Incidentally, I used a Nikon speedlight for illumination. After making the photo, you can check the offset by simply zooming in during the image preview. I've found that it's pretty easy to see where the plane of critical focus is. Once you've established how a particular lens responds during autofocus, you can save a custom focus setting in the camera body for up to 12 individual lenses.


This sample image shows the 20-35 lens with the focus locked on the focusing spot. It was alarming to see an out-of-focus reference point, and discovering a plane of sharp focus was behind the zero setting. Notice that the numbers between 2 and 6, located behind the focusing spot, are in sharp focus, while the 1 and the 0 are not.

You can see a short YouTube video here. Don't be discouraged, as making the adjustments gets easier each time you do it. The focus offset for my 20-35mm lens was set to -20, the most offset I could dial in. When I assigned it to Custom Setting #3, I was surprised to find that the camera was able to extract the aperture and zoom range directly from the lens itself and include those specifications in the custom setting. 

You can see the improvement it made. Just so that you know, there will always be a bit more depth of field behind the critical focal point than in front. At any rate, this would allow me to establish critical focus on my subjects eyes, exactly what one needs to do when photographing people.  


The proof came when I photographed this woman during International Night here at the Adult School. While the settings were different from those in the lead photos, the focusing problems appear to have been addressed. The eyes are sharp, and there is plenty of detail in the rest of the photo.

These before and after back-focus comparison shots are very much an apples and oranges affair. But the improvement is there to see, even though the shooting conditions of the two sample shots weren't identical.
Some final caveats: You have to remember to turn the back focus setting "off" when you change to another lens. Also, this feature is only available on the "prosumer" level cameras, which means the D300 series, the D7000 series, and all of the full frame bodies.