Week 1

Power Pack Revision

"In simple terms a power pack is a big capacitor that discharges electricity to make a flash"

-Ionizing means to give something an electrical charge

We need to control:
1. Duration (how long the flash lasts) which effects synchronisation and motion blur
2. Power (the intensity of the light) which effects exposure
3. Colour (white balance) we need a uniform white balance

Asymmetrical Verso A2 and A4 (how they distribute power)
1 plugged in = 2400 J
2 plugged in = 1200 J in each
3 plugged in = one 1200 J light and two 600 J lights.

However, this system may not apply to other brands of power packs. Different power packs have different circuitry. 

In macro photography you can have 'too much light' so you can plug another light into the power back to reduce joules on the light your using.

Lighting in the Studio: "always look for alternatives!"

Flash Duration

Flash doesn't just "turn on then off" - it works up like a slope and then slowly drops off (refer to diagram in workbook 17/2/11).

How do we measure the duration of the flash?
If we take the maximum intensity on a graph and then come down to 0.5 (half way) that will be the t0.5 duration (refer to diagram 2 in workbook 17/2/11. So, there is still some light that will effect the image on either side working up to the maximum intensity that will effect motion blur.

t0.1 is a more useful measure of duration because it measures allot more light (about 90%) so the 10% left over is barley even a problem (refer to diagram 3 in workbook 17/2/11)


the 't' represents time on the graph.

- Flash duration is important to freeze motion properly.

- Verso claims to have the ideal packs for fashion photography.

- Reducing power output effects duration

Colour Temperature Considerations

When you reduce the power output the color temperature will change;
Flash color at its peak intensity is blue
Flash color at its least intensity is red 

So reducing the power of one head and halving that again for another head is bad because it results in 2 colors. LUCKILY this is fixed automatically by the power packs. Broncolour has a very sophisticated way of doing this but less sophisticated systems are acceptable too.

Clear flash tube means you need a tinted cover glass
Tinted flash tube means you need a clear cover glass.