Understanding Flash Duration
Okay, we're to the point now where I feel like I can dive in just a little bit deeper into one of these concepts, and that is flash duration. Up until this point, we've used kind of a very oversimplified explanation of the speed in which a flash fires using my loop royalty one eighty I basically said when I fire this let's assume that it fires at one ten thousandth of a second it's, almost instantaneous for the purpose of just understanding how flash works in reality, it doesn't actually kind of work that way. When we see this light, when we see this flash, we see it as being either on we're off it's either flashing and his firing instantaneously or it's off in reality, if we were to slow it down, it doesn't quite work that way. Let me show you what a flash output graph looks like. If we look at this graph, ignore the numbers for right now, if we look at this graph, you'll see that starts at zero percent year, it goes up to a hundred percent no, one hundred percent is basically where t...
he flash fires where that output happens so what's happening is the flash is charging up at one hundred percent outputs, the power that you've said here, whatever that power might be, and then it trails off now when we watch this, when we look at it, it looks like that trail is instantaneous, like it just drops right out, but it actually doesn't the light. When it fires its slowly actually dissipates flash duration is measured by two times, and really one of them is the most important. They're called it the t five and the t one times or t point five point one what that essentially means that t point five times the amount of time it takes for fifty percent of the flash power to dissipate that time is actually the time that most manufacturers use. When they tell you what the flash duration is there's a problem with that? If only fifty percent of the power has dissipated, what about the other fifty percent? Well, the other fifty percent is still going to affect your image, so the flash duration is slow. That fifty percent is going likely affect something so whatmore adequate what's, a better measurement of the ability of a flash to freeze, or to know what the flash duration is is the t point one the team one time the t point one time is the time for ninety per cent of the light to dissipate, and that remaining ten percent that trails off it's really not going to affect much? Ok, that's, what really matters now in this graph I label this this is the world's slowest finish ok there's no flash that's actually this slow this is in milliseconds of the bottom so zero two hundred four hundred thousand milliseconds we're talking about one full second so the t five time for this sample flash is at one, five hundred of a second or one half second is the t five times at one full second is the t point one time meaning that if you actually own this flash it would basically be equivalent to turning on the light bulb in turning off that's how slow would be ok there's no flash that exists that's that slow this flash would have no ability to freeze a subject in motion because it's a terrible fashion doesn't exist but it does help to illustrate the point in reality every flash is actually different okay? So depending on the brand the make the model if the flash duration is gonna differ there's another interesting thing the teapot one time is the best measurement of the flash ability freezes subject but the higher the power that you use that point number three the higher the power the slower the flash duration so the slower that t point one time the lower the power setting on your flash the faster the t one time so the faster the flash duration apostrophe is generally gonna be faster than a studio stroke generally okay, so that's, why I often times when people are working with liquids when people are working with, like, kind of close up macro, dropping things into things of water, they're using pocket stroh's because they're convenient, they're easy to manipulate and so forth, and their flash durations are very quick. So to freeze the water, you need a very, very quick flash duration. One five thousandth of a second, one ten thousandth of a second to freeze water, and sometimes serious drugs can't quite get there. So if you want to get t one times for a specific flash, you can look online. A great resource is actually from andy gac, and he got at doc dot net and he's done some fantastic testing on flash durations. Oftentimes you confined the t one time for the manufacture themselves, but sometimes it's not available, so just look online and conf find the actual flash duration. I would highly recommend doing that before purchasing new flashes, because you might end up with flashes that might not have a fast enough laceration for whatever we use he might have. For most people, this generally is not an issue, but if you're wanting to use your flashes to freeze motion, this becomes a problem, so let me go over some sample times at one over one power, so at full power. A cannon five eighty yaks which we use in this tutorial siri's has a flash duration of one to pity the second meaning to get ninety percent dissipation of that light it takes one to with you a second to get there. That means that it might not fly and might not freeze to the effect that we talked about earlier, right? If we talk about this being one ten thousand of second one to be the second is kind of slow, so you're gonna get motion so if you flash expecting it to freeze and you see motion in there and you're like, wait there was no ambient light and my shutter speed was super high and I'm still getting motion it's because your power might be too high or the flash duration regardless of the power is too slow but look at this on a five eighty x if we slow down tto one half power immediately are flash duration goes toe one nine hundred nineteenth of a second okay, so almost one one thousandth of a second at one sixty fourth power so very low power settings were at one fourteen thousand of a second that's why I told you just to assume that this was one ten thousandth of a second because we're at like one sixteenth or one thirty second power right now on a nikon s p a t one over one is one two fifty eighth of a second one half is one eleven hundred of a second and one sixty fourth is one almost one sick eighty thousand a second on the einstein let me just grab the einstein so he's not just hidden down here let me grab this guy. All right, so here we have our einstein full studio stroke now this guy at full power one of one power this is putting out probably five, six, seven times amount of light of one of these pocket strobes it's actually still pretty decent at that much power. Getting downed power is still faster it's at one, four hundred a second as opposed to pakistan, which is around one two fiftieth of a second. So for full power and for the amount of light it puts out it's really quick, but you'll notice that they don't get as quick. This is actually a very fast studio strobe when it when we're talking about flash duration compared to other studio strobes look at this at one half power it goes to one one thousand of a second but at one sixty fourth power it on. Lee gets down to about one. Thirty seven hundred were still very fast it's still fast enough to freeze liquid, which is why this is often used for liquids and gases and those types of freezing applications but it doesn't compare to one fourteen thousand of a second or one sixteen thousand the second of that of a pocket strobe so pakistan has filled me quicker now we're gonna talk about with brand and flash quality and so forth not only can it affect things like color and power output and so forth it also affects your flash duration crappy generic ebay light okay, that one over one power it's one one forty of the second at one half power it's one one twenty six of us it's actually getting slower at one thirty second power it's at one one hundred of a second a flash like that has absolutely no ability to freeze. The falloff is too slow and as you know the light's falling off it's going to effect and create motion in a shot so quality of your strobes is actually a big deal look for reviews you khun yes take recommendations from us we use great stuff in this tutorial serious but always when you're looking to other stuff look for reviews before you gotta buy something because it might not fit the use that you might need it for. All right? So hopefully that makes sense hopefully understand flash duration speed in which that really matters is that t one time okay for ninety percent dissipation that's how you know how basically how good a flash is going to be at freezing motion