I wanted to wrap up the week with a couple illustrations on speedlights vs real strobes. Specifically something I talk about a little bit in the Simulating Sunlight eBook but don't illustrate. One of the things that drives me a little nuts about using speedlights - at least when mixing them with ambient light conditions.
The shot at the top is just me setting up a quick illustration - this one happens to be using one of my uber-idiotically powerful studio heads on absolutely minimum power which was giving me f/11 or so. I just included it because it happened to illustrate on a micro scale of using bare speedlights or any bare hard light in a way that looks a bit more like sunlight than it does a bare light… Specifically smashing it into something before it hits the subject. Here it's just smashing into bits and pieces of the subject itself but it's illustrative and it also demonstrates how the distance of the stuff that the light is hitting projects different shadow edge effects. Obviously the the things the light is smashing into don't have to be included in the frame.
Moving on to color and the crazy factor with speedlights. I modified the setup a bit and used the closest semi-neutral thing I happened to have close by. A 45" Umbrella that would be a bit easier to match the speedlight and the studio head without a lot of care in terms of look - generic semi-directional. I fixed my camera exposure and the WB to daylight - at least Nikon's flavor of daylight. Here's the studio head with no color balance adjustments.
Here's the speedlight with a pretty close match of in camera exposure also with no color balance adjustments.
Let's not talk about what anyone likes better. Not the point. The studio head is at absolute minimum power but that actually doesn't matter at all with my particular heads because color temperature is stable across 7 stops of output levels. The speedlight on the other hand is really close to full power output - which is as warm as it's going to get generally. You probabably don't want to shoot your speedlights at full power most of the time - recycle times are too long, they chew through batteries, overheat, etc. As you turn the power levels down most of them get even cooler still. Significantly cooler than daylight at full power.
Hold that thought for a second while I chuck up a couple of pictures with a color checker. First the studio head.
My eye tells me it's a bit pink but the color temp is almost daylight - probably within a hundred or two hundred points of standard even though the sun isn't really standard. I would expect this as almost every daylight white balance camera setting always adds pink. Now let's take a look at the speedlight at about it's warmest.
Hmmmm, not even close to daylight. Now all this makes no difference at all if you are shooting at a consistent power level and the speelight happens to be your only light source. I can make both shots look exactly the same… Like this.
Okay so no big deal right? Right but here's where the pain comes in. In 99.9% of circumstances I have ever shot it the speelights are cooler than the ambient. Sometimes this can work and actually be attractive - maybe if it's soft light. Like simulating open shade. That circumstance in nature happens - and if there are things lit by the sun or reflected sun they will obviously be much warmer. Typically your subject won't be lit by both though - in a speedlight setup where you are blending with ambient your shadows will go crazy warm compared to the speedlight if you neutralize for that or your highlights will be really cool if you neutralize for the shadows. If you are trying to simulate a natural sunlight effect this just looks all wrong.
So let's fix it - enter some CTO or CTS gels. Typically 1/8 is a good starting point. Somewhere between 1/8 and 1/4 will give you a natural look that's not too too warm. When I want it to look like sunlight I typically use a 1/4 CTS. No big deal right? Well it's not if you have everything figured out and shoot at the same power level all the time. In most cases it's not super critical but if it is you definitely don't want to be changing up gel combinations every other shot. It's also quite a pain in the ass if you use multi-light setups and need color consistency between those. Speedlights - hmmmm no dice. At least not mine.
So there you have it. I am not at all telling anyone not to use speedlights. I use them all the time. More like be aware of the limitations and characteristics of what you use and have a thought process to how to deal with it to get the picture you want. One word of caution - I use the term "studio head" but I don't mean all of them - I mean specifically the ones I have. Some do not have color consistency across power levels. Some have options that trade one thing like flash duration off for color consistency. All lighting equipment is not created equal. I don't own the Einsteins but from what I see and have heard from people that do - they are a bargain. They give you somewhat the best of both worlds - super short duration if you need it and color consistency across output levels if you don't need super short durations. I wish these things were around when I bought my lights - dirt cheap and seem to be great.