Wednesday, 30 September 2009

Flash and a slow shutter

The one unique thing about flash that distinguishes from any other kind of light is duration. Typically a small flash will have duration of 1/500s or less which is great for freezing motion when there isn't enough ambient light to register in the exposure. But what if you mix ambient light with flash and introduce some motion? If you keep the ambient light off the parts of the image that you want to keep sharp and put it where you want it to be blurred, you can create a feeling of motion in the picture.

Without Flash With Flash
Model Mayhem: Alex Marks

In this example taken at a recent strobist meetup, the flash didn't fire in the first exposure, which gives me the opportunity to show you what's happening. You can see in the unlit example that the majority of the image is very dark and the wall behind the model's head is well lit by sunlight. As I took the picture I moved the camera sideways to create some streaking of the image. You'll need to make sure that your sunlit portion of the image has some texture, in this case its a brick wall with graffiti, otherwise you won' get streaks. The shutter speed is 1/20s at f10 and ISO400

The flash is an Nikon SB28 in a softbox very close to the models head at about 1/4 power. I have also positioned it so that it casts a shadow over his face preventing the direct sunlight from contributing to the exposure. Its angled so that very little light hits the wall and what light does fall on the wall is very much reduced in power because the wall is much further from the light source than the subject.

The direction that the camera is moved is important because you don't want the flashlit area to merge with the bright ambient in this instance I'm moving the camera from left to right with rear curtain sync. Trying to figure out which direction to move the camera does my head in, so I just try both directions and then pick the one that works. Even though the shutter speed is 1/20s the flash fires for less than 1/1000s, superimposing a pin sharp image of his face on the dark area of the picture and the sunlit portion of the image gives him go-faster stripes.

Tuesday, 1 September 2009

Phottix Strato / YN16 Trigger modification

Ironically this post was scheduled to run a little while ago and I had forgotten about it, since I wrote it I have discovered that nobody seems to be stocking these any more. But I'll leave it up in case you already own one of these and this is useful to you.

Phottix Strato ButtonsI have solved the problem of accidentally pressing the button on these triggers. One of the problems with the triggers is that the button is not recessed. This makes it difficult to build a cover for the button. So my first step was to file down the top of the button until it was level with the case. Ideally you should open the unit and take the button out, but be careful, you should follow the instructions I gave you for changing the battery to open the case, or you could end up damaging your trigger. In the picture above you can see that you don't have to take a huge amount of plastic off it.

With the button safely out of the trigger you need to sand it down until it is flush with the case. I used a dremmel tool to do this, but you could just use sandpaper and patience. Don't overdo it though as when it is flush, the button will be transluscent. If you go too far you could end up with a hole in the top of the button, so frequently test it against the case.

Trigger coverNow that you have it flush, you have a variety of options. You could make a tube to transport it in. This has the disadvantage of taking up space in your bag when you don't need it. I made a flip-off cover for mine. I took a cd case and cut a square of plastic out of it big enough to cover the button and the recess it sits in. Then I used a strip of gaffa tape to attach the cover to the trigger, make sure you use the low residue tape and it should be reusable. You could even use velcro, but I found it less secure and awkward.

That concludes all my modifications of the strato triggers.