WHAT IS STROBE POWER AND HOW MUCH DO I NEED?
Photographers love to get overly technical sometimes when talking about strobes. How to measure light output, guide numbers, falloff etc. Although that can be interesting and useful, what most people care about when buying strobes is Power, Features, and Price.
UNDERSTANDING WATT SECONDS
If you’re new to studio lighting, your first question is likely; how much power (watt seconds) do I need? Well it’s a good question because the answer will have the greatest impact on price and what you can photograph with your strobes. To answer the question we need to understand a little more about what the heck watt seconds are. In simple terms watt seconds are the unit of measure used for power output in strobes. The maximum watts that can be output over a 1 second duration. Kind of like lightbulbs in your house. The 10W bulb in the nightlight, the 60W bulb in the living room, the 100W bulb in the lamp, all with different maximum outputs.
WHAT DO THE STROBE’S NUMBERS MEAN?
Pretty much 99% of the other strobes on the market rate their strobes this way. A __-400 strobe model means 400 watt seconds, a 600 in the brand name means 600 watt seconds. Alien Bee’s are one strobe company that uses a different way of rating output called true watt seconds instead of nominal watt seconds like everyone else. That means an Alien Bee’s B800 strobe is actually only 320 watt seconds. Just so you don’t get too confused when you’re shopping around.
HOW MANY STOPS SHOULD MY STROBES HAVE?
New photographers often think that you can just turn your camera to a desired aperture (f-stop) and a matching aperture setting on the strobe. Camera f8, turn strobe to f8, done. It doesn’t work that way. Strobes are adjusted in power increments. 1.0 to 6.0 representing 6 stops or 1/1 (full power) to 1/32 power. It does not match your camera f-stop setting of f 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 45, 64. The reason for this is that every time you add a reflector, softbox, or umbrella to your strobe, that f-stop is changed. Also you should note that these are FULL STOPS mentioned not the 1/3rd stops that are quite common in today’s DSLRs.
You have two identical 400W strobes in the studio in the exact same position, both powered to 6.0 or full power. You put a reflector on one and take a shot. The light meter says f22. The other strobe you put on a softbox and it measures f11. That’s a full 2 stops less with the strobe at exactly the same power. It’s all in the modifier. Starting to get the picture? Every modifier, light position, tilt, turn, or ambient light makes all the difference. This is why you can never just set you strobe to match your camera.
SOMEONE TOLD TO GET AT LEAST A 1200 WATT STROBE?
Well that person is just following what they’ve heard somewhere or they happened to buy themselves. As photographers we like to brag about equipment. My camera is full frame, yours is only a crop sensor. It only matters if it helps or hinders the way you shoot. A 1200w strobe might be great for them but not be at all practical for you. You need to seriously identify what and where you typically shoot. If you shoot newborn and the occasional portrait, a 300W is plenty of power. 600W or 800W would be way too much.
IS THERE SUCH A THING AS TOO MUCH FLASH POWER?
Yes, here’s why. Many pros have 800W or 1200W strobes but if you ask them, you’ll find that they rarely use them at more than half power. To shoot your fastest lens like your 50mm f1.8 wide open for those blurry background, cute newborn shots you’ll need flash but not too much. An 800W strobe turned to its lowest setting is still way too much power to shoot your lens at f1.8. You’re likely only going to get the lens to shoot at f5.6 because of all the flash power. Now you’re limited because of too much power. If you shoot corporate machinery on location in big dark warehouses with 30 foot ceilings, then 300 watts won’t be enough. You’ll likely need 600 watts per head. So where’s the happy medium? Here’s where it lies for most customers.
- 300W- Hobbyist, Home studio, pictures of the kids, newborn, small product photography, groups of 2
- 400W- Home studio, portrait, larger product photography, groups of 6
- 600W- Studio, vehicles, outdoor, groups of 20
- 800W- Pro, full size studio, location sets.
Of course there are exceptions to every rule. You’ll often find pro studios with 300W strobes as well as 600W strobes depending on the shoot. Or you’ll see pros with extremely expensive strobes that dial way, way down to 1/128 power. For myself 400W strobes are perfect for me which provide a great balance.
Starting out with a basic 400W two light strobe kit is a fantastic way to start. The truth is that most photographers end up with 4 lights at some point anyway. Background, main, fill, hair light. The nice thing is that they will all work together, so don’t stress out too much. There really isn’t a wrong decision. Get what’s right for you and forget all the noise from others and the internet. The important thing is just to start shooting!