What is a Stop of Light
One of the terms that we've mentioned and that you're going to hear constantly throughout your photographic career is a full stop or, in short, a stop of light. What is a stop? You're going to be hearing this a ton, especially when we talk about exposure? Well, a stop is simply a relative measurement of light, it means either double or half the amount of light, but what is that relative to? What are we doubling? What are we having? Well, if I want to say a stop is relative to basically whatever we currently have and where we want to go and relative to everything, well, that makes absolutely no sense and it's a terrible explanation, and if I were to ask you a question will tell me this, how about you tell me how much light is actually in this scene? If you're starting on the photography, what would you say to that? If I were to say, tell me the exposure value of this scene, we're going to go, oh, there's, sixty five gallons of light in the scene where there's two hundred forty two leade...
rs of lightness in those terms make absolutely no sense, and there really aren't any specific terms of measurement for measuring the amount of lightness scene well, actually, you know what? I lied there are we can measure in terms of lumens, which is again kind of confusing. We can also measure in terms of tvs or exposure value, but if I were to tell you that this room has an e v of eight or far to say he's shooting outdoors and sunny weather has an e v of fifteen, what would that mean? That would mean absolutely nothing to someone just starting out in photography, so instead we use terms like a stop, so stop is simply going to be describing where we're at with our current exposure and where we need to go. So to show you all and hammer this point home, we're going to using our same exposure triangle rhea world analogy will this is our visual analogy, not real world, and what I want you to remember is that, well, stop is either double or half the amount of brightness, but we have three ways to control that. So let's talk about it, let's, go ahead first, and what I'm gonna do is just open up my faucet all the way to my widest open aperture. What we're going to say that this faucet is our lens and it has a maximum aperture of two point eight that's why does it go so this is as much light as we're going to get. Now we're going to do is go ahead and bring my eyes one hundred cup in and let's do this, I'm going to use my timer and I want let's go ahead and get back to that, okay, so what I want to do is I want a three second shutters, peter let's say that I'm at a three second shutter speed, and I'm at my after two point eight and one hundred s. Oh, well, far to start this and at three seconds, we know from before that basically we're only going to get halfway so that three seconds we fill the cup halfway up now filled halfway. This means that we're one stop underexposed or I need to brighten my image by one stop it's the same thing, so we have one stop under expose what I would need to do that three seconds instead of using a three second shutter speed, how would need to double or increase the heresy by one stop of brightness? And that would mean that I'd double it in six seconds, so let's, go ahead and reset that we're gonna go again six seconds and we're gonna double it. We're gonna get all the way filled up on their way, okay, so at six seconds we doubled the shutter speed we increase the shutter speed by one stop to get one stop brighter to get to our proper exposure well same thing with the after we can adjust the aperture to give us one stop brighter one stop darker one more thing I want to go for one last thing what if I leave it for a shutter speed of let's say twelve seconds well at twelve seconds at this was again in the same scenario what ends up happening? You guys can already guess we're gonna end up over filling the cup so if I over the fill the cup and this doesn't actually go up to this point but if I were to overfill I could say that I need to go with one stop darker so we can adjust the shutter speed and cut it in half to get back to that point so this is kind of our overexposed images now let's move on to our aperture okay so with the avatar let's go ahead and open the faucet up to I'm going to say this is full so this is that two point eight that's our widest open after let's say this is around f four so that's one stop darker or half the amount of light as two point eight okay so now let's go ahead and we're going to use the same cup and we're gonna do here is let use a six second shutter speed again and let's see where we get so has start we should get roughly around half that was indeed and we do we're at five point five seconds and we basically got half of our exploder so you can see here so it's not exactly going around a little bit but we got basically half so where we need to go so what we need do is again we need to increase the aperture by one stop in brightness and that means double it so again we would go back up to full life okay so you can see how these air two different control already controlling stop controlling our relative brightness now let's say this I'm going to give you guys another example and we're going to say that for compositional purposes I'm shooting water I'm trying to get that whiskey water effect and I find that out one point five seconds that gives me the perfect look in the water it's not showing too much motion it's not freezing it too much it's just right so I need to keep my shutter speed at one point five second let's also say that we're at f two point eight so we maximize the amount of light coming through we can't go on anymore now I need to go with one point five seconds for my shadow because that's for compositional purposes I don't want to change it but the problem is that well, and I saw one hundred if I go for one point five seconds, we get only a quarter of the cup filled up, so we're two stops underexposed well, same thing if I goto so two hundred, which is one stop brighter than the one hundred at one point, five seconds, we only get halfway, so we're one stop under exposed. So what I need to do is go up to stop and I goto four hundred and four hundred one point five seconds, get me filled up right to the top, so at one point, five seconds, we feel that we've got to the exact exposure while maintaining our shutters. I wanted to keep a shutter speed of one point, five seconds we used are so to increase by two stops and just one more time to reiterate, I'm going to put my phone down let's, take a look at this so I saw one hundred we have roughly a quarter of the cup filled up and I so two hundred we have roughly half the cup filled up, so we're one stop underexposed here were two stops underexposed and then at s o four hundred, we are correctly exposed with our desired exposure, so that is a stop it's, a relative measurement of light that incredibly useful for describing where we need to go with our exposure. And I want you all to remember what we discussed in the last video, which was when we go up and stops, we're doubling amount of light, so basically from one hundred, two hundred that's, twice as much as one hundred, four hundred is actually twice as much as two hundred, which becomes four times as much as it is a one hundred it's four times and it's not three times. Basically, a lot of people confuse it as each step up is three hundred percent, forty percent so forth. The easiest way to remember this that I didn't mention the last video is basically each step up, khun b indicated despite the number itself, so two hundred is twice as much as one hundred everything's in relation to one hundred. So four hundred is four times as much as one hundred, eight hundred is eight times as much as one hundred, sixty hundred sixteen times and so forth. Okay, so that's it for a stop of light. Hopefully, this video helps you all out let's, head on out to the next one.