Lighting exercise HMI experements

This experiment was very interesting as this was the first time using an HMI light.

HMI: Hydrargyrum medium-arc iodide...The lamp operates by creating an electrical arc between two electrodes within the bulb that excites the pressurised mercury vapour and metal halides and provides a very high light output with greater efficiency than incandescent lighting unit.

With HMI bulbs, colour temperature varies significantly with lamp age. A new bulb generally will output at a colour temperature close to 15,000 K during its first few hours. As the bulb ages, the colour temperature reaches its nominal value of around 5600 K or 6000 K. 

The HMI light is very bright and has a colour temperature of 10,000ºK when new and 5600ºK after a period of time.

The HMI we used was between 5600º and 6000ºK so that is what we set the colour temperature at.

This light produced a very artificial looking light that we had to diffuse with silks and flags. After a while, we managed to start getting setups that were looking good. but I would only use a light like this while shooting in a green screen studio to replicate sunlight or positioned outside a house window on a cloudy day (or night time). Personally, I would rather use the natural sunlight and use diffs or flags to control it.















One thing I learnt was about exposing for the face: we used spot metering for this and that is a reflective based metering system. when exposing for the face using a reflective meting system expose exactly what the exposure is telling you to. however if using incidental metering the zone that the face should be (zone 6 for caucasian) should be exposed for one stop above what is read on the light meter.