Sunday, 13 January 2008

Blue Peter Extra Large Gridspot Part 3

The thing about experiments is that even the failures can be instructional, after finally getting my new camera and turning off Dynamic Range Optimisation. I took some shots of the light output.

24cm Grid Spot OutputWhat the camera sees is quite different from what the eye sees. What had looked like a big well defined circle by eye, turned out to be almost square with a circular hotspot. I added some diffusion in front of the flash head and some more behind the grid and was able to get a more even coverage but it cut a fair amount of light.

Drinking Straw Grid OutputThe other thing I realised was that the grid I had been comparing it to in part one, was quite a long one, but the 24cm grid is only one inch deep, consequently the light was able to spread more, so the comparison wan't entirely fair. I compared it instead, with a short grid made out of drinking straws.

The drinking straw grid produced a larger brighter circle which was very clearly circular, unlike the 24cm gridspot which was distinctly square. Why were the shapes so different? I think it is because the square section of the coroplast allowed the light to escape at a wider angle on the diagonals, but on the straw grid the angle is the same in every direction. I think it would be an interesting experiment to try different shaped grids to see what sort of pool of light they produce.

So far it wasn't looking very promising, the size, shape and power of the light wasn't very good. But did it do what it was designed to do? Did it soften the light?

24 CM Grid Spot output Using the 24cm Gridspot
Comparing the straw grid with the 24cm grid showed the that light was slightly softer, but the edge transition wasn't great and it wasn't a great deal softer. It was possible to tell the difference with a small object like my hand, but with something bigger, like my head, the difference between the two grids was negligable.

Drinking Straw Grid Output Using drinking straw grid.
One final observation was to do with handling, after a while the 24cm grid started to droop a bit as the duct tape heated up from repeated flashes. This didn't seem to affect the light quality particularly, but it affected positioning. The grid also started to lose its grip on the dish and needed a bit more tape to hold it together. It also doesn't fit conveniently in a kit bag.

So grudgingly, I have to conclude that the humble straw grid outperforms the gridspot in pretty much all areas. Its a great deal more convenient to take with you too. But I did learn a few things from this experiment.

1. The light source has to be a lot bigger to soften the light. 2. The shape of the holes in the grid affects the shape of the spot 3. The small straw snoot rocks

1 comment:

  1. So THAT is how you get that type of lighting. Thank you! I'll try the straw one for my speedlite but I don't know if I can make one big enough for my strobes!