Some Observations on i-TTL

Summary

i-TTL Testing Image

The preview Forum on the Nikon 1 V1 had a comment entered today. The question is how accurate are the remarks? We will put them to the test, but first here is the unedited text from the thread:

The SB-5N operates is i-TTL compatible. That means it should operate in 2 different modes.

1. i-TTL BL mode that should be used for fill flash
2. i-TTL mode that is used when the flash is the main source of light.

On the Nikon SLR Cameras, If you set the camera to A, S or P mode with Matrix or centre weighted metering, the flash will operate in iTTL BL mode to give you balanced fill flash. You should use this mode when it is light and you could otherwise get a proper hand held exposure without flash. The flash will operate to simple fill in the shadows if you have back lighting or to stop “raccoon eyes” caused by shadows.

If you use M mode or set the camera to use the spot meter, the flash will operate in base i-TTL mode. The camera will meter the scene assuming that the flash is teh main source of light in the scene.

When you make a flash photograph, you are actually making 2 exposures at once. 1 is the flash exposure and the other is the ambient exposure. The flash with complete its entire cycle in less time than the shutter is open (between 1/1000 – 1/10000 sec depending on the output level setting of the flash) so the only controls you have to determine/adjust the power requirement of the flash is your aperture control and ISO setting (higher ISO will give your flash more reach). Adjusting the shutter speed is the control over the ambient light part of your exposure

I would suggest, If you are indoors in a dark room, that you try the camera in M mode, turn Auto ISO off, set Camera to ISO200 or 400 in a larger room to maximize image quality. Set the shutter say 1/60 and open the lens up wide and see how you go. The camera should automatically adjust the flash output to match the required exposure as set by the aperture/iso setting.

I understand that maximum shutter sync speed with flash is 1/60 with the electronic shutter but 1/250 sec with the mechanical shutter. Use the mechanical shutter if you are using i-TTL BL mode in daylight so you have more exposure leeway with the ambient light

Auto ISO can help if your aim is to use balanced fill flash in a lower light environment but becomes problematic if you are using the flash in a really dark room and that is your only source of light. The camera sets the Auto ISO level as though you are making an exposure without the flash.

You be the Judge

Nikon-1-V1 with SB-N5 Speedlight

Keep in mind that the aim of this exercise was to help those photographers who are part of the forum and are disgruntled about the lack of “stop action” available in low light level situations find solutions. The suggestions that flash be employed when in these kinds of situations where the subjects are active small children came as no surprise. The thread above was posted in an effort to explain how to enter something other than i-TTL BL mode with the SB-N5 Speedlight that is designed to work with the Nikon 1 V1.

I liked the images most which showed the least underexposure and were subtle in their information about the light source. If they looked too much like flash images they were not as much appreciated. The images made at A3200 which is essential the highest auto exposure mode available seemed to me to be the most authentic.

But you take a look for yourself. You might have different results than I did. It would be good to hear from you if these results don’t seem to bear out your own experience.

What I did like was the explanation of the way in which i-TTL exposure works on Nikon cameras. As with everyone else I think it necessary to find a way to produce images that are more or less free from blurriness if that is your desire.

I used the SB-N5 Speedlight for one entire evening at Christmas. The images made can be seen here. The ones that were the most blurred were ones where I panned the camera to reach a portion of the room and then made the exposure. But for the most part both the kids and the adults were reasonably exposed and sharp.

Unlike some of the forum participants on dpReview I did not come away from that experience thinking that I needed to sell my camera. In fact it was just the opposite. I like the smoothing effect of bounce flash with this camera and flash combination. I for once come out of a background of rangefinder use (Leica) and large format (Zone VI and Deardorff). If I could have had half the nifty features of these modern digital cameras “back in the day” I would have been a very happy camper. I just don’t understand the inability of today’s “serious enthusiasts” to deal with the luxury they have. Perhaps we are too spoiled for our own good?

I spent far too many hours in darkrooms trying to print negatives that I had made in conditions I had misjudged to be aggravated with a system like the one today where you can actually see the image you just made and modify your behavior on-the-spot. There really is no more need for missing an entire “shoot” provided you have thought through the workarounds needed to adjust to the problems at hand.

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