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HMI Lighting for 35mm DSLR

V Janssen , Aug 11, 2003; 10:42 a.m.

What does "PAR" stand for in many of the HMI lighting designations ? What would be your recommendation for a start-up HMI kit. What type of head(s) ? wattage ? The application would essentially be : 35mm digital tabletop food photography . The goal is to supplement / simulate available daylight . Is the physical heat output something one should be concerned about ? Any disadvantages to using HMI lights despite cost ? Thank you for any additional information you can share in regards to this specific application. V.J

Responses

Brooks Short - Tampa, Florida , Aug 11, 2003; 11:04 a.m.

HMI's do produce some heat, not as much as tungsten but more than strobes. Balcar makes some very nice HMIs and has a pretty good selection of attachments and light modifiers.

But I'm curious as to why you would want to use HMIs rather than strobes ? You can simulate and augment daylight with strobes just as well as with HMIs, perhaps even more easily.

If it's shallow depth of field you're looking for, strobes that can be dialed down can help you achieve that. Whether you use HMIs or strobe you may need a ND filter as well for extremely shallow DOF.

HMI' also use a huge amount of electricity which might be something to consider.

Here's a sample food shot using strobes on a digital Pro Back. The goal was to produce a "morning" daylight look.


Sunbites Citrus

Brian Diaz , Aug 11, 2003; 11:50 a.m.

PAR stands for parabolic aluminized reflector. They have a curved reflector in back and a lens to focus the light in front. I don't know a lot about HMI lights, though I do know that their main use is for major motion pictures, where cost is less of an issue than having huge amounts of continuous, roughly 5600K light. Still photos do not need the continuousness, and DSLRs do not need daylight.

The heat may be somewhat of a factor, but not much more than if you have a few strobes with 250W modeling lights close to your food. The other thing is that your HMIs will need a ballast which controls the power supply by limiting currents, but by now, I have no idea what I'm talking about. That's why movie production companies pay electricians to plug in their lights for them.

Is there a particular reason you need HMIs?

Brooks Short - Tampa, Florida , Aug 11, 2003; 02:05 p.m.

I've been on film shoots where HMIs are being used and they're a good bit warmer than the 250 watt modelling lamps on strobes.

Here's what I do if I'm shooting food which is really sensitive to the heat from modelling lamps like frozen drinks or ice-cream etc..

I set up the lighting, composition and focus using stand-in food. This is a common procedure in the food photography world because set-up can take a while, hours sometimes.

When the "hero" food is ready I put it in position, checking focus and lighting briefly with the model lights on. Then I turn the model lights off and shoot my exposure brackets using just the strobes.

Of course, usually the client wants several different prop or point of view changes. Sometimes it's a small change which can be accomplished without using the model lights, just the room lights. Other times we have to start all over.

Using HMIs or tungsten, the lights are on for all the exposures, subjecting the food to a lot more heat.

But that's just the way I work. Use whatever you are comfortable with.

---- ---- , Aug 11, 2003; 03:53 p.m.

Yes, there is one big disadvantage of using HMIs: the CT of the bulbs are good for only about 500 hours after which the colour temperature starts to shift towards green. That is why HMIs have an hour-counter in them to help you keep track of the number of hours the bulbs have been burning.

PAR stands for parabolic aluminised reflector. PAR luminaires are usually employed in the movie industry for their punch; their highly reflective parabolic reflector makes them efficient. They are commonly diffused with silks or bounced off foam cores. Accessory lenses are used to shape the throw of the PARs somewhat. However, they are not adjustable finely like Fresnel HMIs.

I'd defer to Mr Brooks Short's advice and expertise to use studio flash instead (wonderful simulation of morning light, Mr Short, and great styling too). However, if you insist, for small set-ups there is a company out in California called North Light Products (www.northlightproducts.com ) which you may do well to look at; check out its Sunspots.

Oh yes, on the issue of ballasts: there are magnetic ballasts and electronic ballasts. Magnetic ballasts are far heavier and cheaper than electronic ballasts. Electronic ballasts are essentially flicker free which means that you can shoot at almost any speed. Magnetic ones cycle according to the AC frequency; you are limited to shooting no slower than 125th of a second in the USA.

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