In the first two parts (Part I, Part II) of the Nikon CLS Advanced Wireless Lighting series, I have showed many examples of the pulse communication sequences but didn’t go into details about them. In part III, I will discuss the detailed coding scheme used by Nikon CLS Advanced Wireless Lighting system.

From the previous examples we know that there are several command types the master flash unit emits to control the remote flash units. To avoid interference, the optical pulse sequences start with a channel indicator so only remote flash units belong to the specified channel react to the commands. This channel indicator always contains 3 pulses. After examining the distances between pulses, I found that all the distances are results of a unit distance multiplied by integers, except for the channel indicator pulses, which contains 1x, 1.5x, and 2.5x unit distances between pulses. It appears that the optical wireless communication uses a hybrid coding scheme. After the channel indicator, the pulses confirm to simple binary format, pulse for “1”, no pulse for “0”. So it is quite easy to figure out what’s going on. ūüėČ Read More…

Posted in Photography Lighting on November 10th, 2009. 10 Comments.

In the Part I of the Nikon CLS Advanced Wireless Lighting series, I described the very simple and inexpensive setup I used to capture Nikon CLS wireless flash sequences and showed you some captures of the simplest form of wireless flash communication. I then detoured to talk about some trivias about the Nikon non-wireless i-TTL flash process. Going back to the series again, I will talk about the flash sequences with remote flash(s) set to TTL mode.

All the tests below were conducted using the built-in flash on a Nikon D200 in Commander Mode. The flash sync mode was set to Front Curtain. The exposure mode doesn’t really affect the results if the shutter speed stays within the sync speed limit of the camera, which is 1/250s. The sequences are slightly different in Rear Curtain flash sync mode with shutter speed slower than 1/2 second. I will get to it later. Read More…

Posted in Photography Lighting on November 9th, 2009. 2 Comments.

I started the series of posts about Nikon Advanced Wireless Lighting (see Nikon CLS Advanced Wireless Lighting, Part I) but quickly realized that there are some interesting aspects of the non-wireless intelligent through-the-lens (i-TTL) system as well.

The i-TTL system typically works like this: immediately before firing the main flash, the flash fires a series of pre-flashes. The reflected light from the scene is detected by the camera. Combined with other information from the camera’s 3D Color Matrix metering system, the camera determines a proper flash output and fires the flash.

Nikon’s i-TTL has two modes: Balanced Fill-Flash mode and Standard mode. The Balanced Fill-Flash mode automatically balances the output of the Nikon Speedlight and the scene’s ambient light while the standard mode ignores the background and tries to bring the scene to a standard level. The standard mode is automatically activated when spot metering is selected. Read More…

Posted in Photography Lighting on November 9th, 2009. 3 Comments.

Nikon Creative Lighting System (CLS) is a complete lighting solution with the latest Nikon Speedlight flashes. The system consists of the following core functions: i-TTL Balanced Fill-Flash, Flash Value Lock, Auto FP High-Speed Sync, Advanced Wireless Lighting, Multi-Area AF-Assist Illuminator, and Flash Color Information Communication. For a quick descriptions of each functions and CLS basic capabilities, please check out this Nikon support link.

Advanced Wireless Lighting allows photographers to control their Nikon Speedlight flashes from a distance without wires. Compared to other wireless trigger or optical slaves, the Nikon system make it very easy to control up to three remote flash groups that can have unlimited number of flashes per group. For each group, you can remotely setup the flash in TTL, Auto Aperture (AA), Manual modes, or turn it off completely without the need of walking up to the flash or running any wires. Read More…

Posted in Digital photography, Photography Lighting on November 8th, 2009. 4 Comments.

If you are not limiting yourself to natural light photography, at some point you may start to consider flashes or strobes and various light modifiers for them. Umbrella and softbox are two of the most commonly used light modifiers for portrait photography. People are quick to notice that umbrellas are typically much cheaper than softboxes. Does it mean you get what you paid for? Read More…

Posted in Photography Lighting on October 28th, 2009. 3 Comments.

The mysterious smoke fascinates many photographers. If you are one of them, you may be tempted to take your own smoke photos. It is not difficult at all. The following video tutorial shows you how to setup the equipments, take the photos, then edit them in Adobe Photoshop to achieve some cool effects.

Posted in Tips and Techniques on October 13th, 2009. No Comments.

People who are familiar with flash photography know the inverse square law, which states that illumination from any light source falls off with distance. For a point light source, the intensity of light is inversely proportional to the square of the distance from the source.

This is a law based on physics principles, specifically in this case, energy conservation. As energy radiates from a point source, it spreads out to an area that is proportional to the square of the distance from the source. Hence, the radiation passing through any unit area is inversely proportional to the square of the distance from the source.

Like any physics law, there is a specific set of conditions the inverse square law can be applied. One of the key phase here is “point light source”, which typically means something infinitesimally small in mathematical term.

The flash head cannot be a point light source, right? Well, the bare flash head is quite small. It can be a good approximation if the subject is far away from the flash. If you put the flash behind a softbox or umbrella, the light source is essentially the entire surface of the softbox or umbrella. We typically do not use the softbox or umbrella very far away from the subject. So you cannot consider the softbox or umbrella as a point source. Will the inverse square law fail then?

Yes and No. If you blindly apply the inverse square law using the distance between the subject and the softbox (or umbrella), the law fails especially when the distance to the subject is short compared to the dimension of the softbox. However if you think the surface of the softbox as a collection of tiny point light sources, the law continue to apply and the intensity of the light at the subject is result of being illuminated by the collection of point light sources that have various distances from the subject.

Someone tried to bust the inverse square law myth and failed. The tests contained numerous errors, such as measuring the light intensity off the axis, using the pixel values as intensities, ignoring the gamma correction done by the camera, etc. When the experiment was done right, the myth was un-busted.

Posted in Photography Lighting, Tips and Techniques on October 4th, 2009. No Comments.

Perhaps one of the first tips you learned about flash photography is to use bounce flash indoors. The reason is quite simple: direct on-camera flash produces unflattering photo and it also creates a hard¬†shadow¬†on a wall behind the subject. By bouncing the flash light off the ceiling or walls, you can create a natural-looking photo with soft shadow. Bouncing the flash effectively creates a much larger light source that can wrap the light around the subject. Bouncing also changes the direction of the light so the shadow is thrown down behind the subject instead of directly behind the subject. Read More…

Posted in Photography Lighting, Tips and Techniques on September 27th, 2009. 3 Comments.