jeudi 22 novembre 2012

Linear light from a flash

This post is an entry to the "How I took it" contest at

Recently I found an article on how to make a DIY honeycomb snoot from drinking straws and cardboard. The effect on the resulting pictures got me thinking : why only guide the light to one circular spot, and not a line ?
Maybe I didn't search the web enough, but I couldn't find a way to make a line of light from a flash without using gobos or other light-suppressing devices. Anyway, let's see the modifier I'm talking about !

Here's a photo to demonstrate the effect you can get with a light guided this way (JPEG straight from the camera, no post-processing) :

This pic was taken with a single flash and natural light (window, clouds), the modifier discussed here, and a gel filter to get a red light. More technical details on this shot are at the bottom of this post.

Now, how to make a flash modifier that creates this effect ?
You'll need :
- a piece of cardboard (25x10cm for my flash)
- scissors and a sharp knife (or hobby knife)
- white paper (or you can go the cheapskate way like me and use old paper to recycle, as long as it's white and without too much ink/toner on it so it won't hinder the power of the flash, or worse, change the color tone)
- paper glue
- sewing thread and needle
- adhesive tape
- color gel filters (optional)

The main body is just cardboard, take a piece about 25x10cm (I scavenged an Amazon parcel).

 Fold it around the head of your flash, and tape it/sew it on the first 4-5cm, to make it stay on the flash head.
Then, just after those 4-5cm, cut the flaps open, to obtain this result (you don't have to make it as ugly as I did) :

 Now we have the skeleton, it fits on the flash head. It's time to make the reflective part of the flash modifier.

The first thing to do is to glue some paper on the cardboard in front of the head, in order to reflect the whole white light, and not only its brown component.

Once this is done, you already have a linearly guided flash, but it produces a very thick line (about 1m thick on a wall located 1m from the flash).
If you want to control the thickness of the line or just reduce it a lot, you'll want sliding reflective flaps inside the modifier.

Here's my take on those flaps (I suggest you try to find a better solution, this one is a bit awkward to use) :

 What I did was simply cut more paper the size of the reflective zone, and use thread as sliding rails for the flaps.
You just attach the thread on one corner of the modifier, pass the needle on the opposite panel after passing through the flaps, and pass this way on the 4 corners of the panels and flaps. Then, once you're sure the panels are parallel (or the way you want them, like tighter for a tighter flash line), you can secure the thread to the last corner.

And here we go, the modifier is ready.
Use a tripod or another trick to get the flash in the position you want, and trigger it flash the way you want (eBay cheap wireless transmitter in my case, doesn't always work perfectly, but hey, that was cheap and I get to tinker with electronics to find out what I can improve).

Here's the setup of the shot I took with this flash modifier :
- The camera was on the tripod on the left (and in my hands for this shot), with a cheap timer remote.
- Flash on the tripod on the left (with wireless receptor), to get it at the right height and the right angle.
Now let's look at the line of light itself : the three shots are taken at the same manual settings as the demonstration shot :
You can see the result of having the flaps parked on one panel on the right, the middle shot is with the same setting as the demonstration shot.

Here's a photo of how I arranged the flaps to tighten the line of light, and the Rosco filter between the modifier and the flash head.

More technical data :

Flash : Yongnuo YN 460-II, power to 3 bars (1/16 I believe)
Color filter : "light red" Rosco Gel filter
Camera : Panasonic FZ200,
EXIF : f/2.8, 100 ISO, 1/15s, f=9,4mm (31mm equiv. full frame), 3MPixel JPEG
Gun : Airsoft (Tokyo Marui Glock 17)

Any input on this quick and dirty prototype ?

Aucun commentaire:

Enregistrer un commentaire