All right, so we got shutter speed under our belt aperture. And now we're going to tackle ISO, and then put them all together. So first off, ISO was a standard for international standards organization, it's kind of boring. They do a lot more than just photography. But in case you were ever curious what ISO stands for, that's what it is. So I so comes to us from the film days, when films had certain speeds, there was ISO 100, ISO 200 400, and, and so on.

And the film speed meant how sensitive was that film to the light that comes in. And the lower that number, the less sensitive it was. So if we hold our shutter speed at a constant, one second, and we hold our aperture at a constant, f 2.8, just to pick some random values. And we load our camera with ISO 100 film, we're going to get a particular exposure. If we stuck in ISO 200 film with the same shutter speed and aperture parameters, we're going to get a brighter photograph, because that film is more sensitive to the light. Now the camera only held the shutter open for a certain amount of time that one second and it only open its aperture a certain amount f 2.8 in both scenarios, so the only variable with the film speed and the sensitivity to light.

So in the same way on a digital camera, the ISO kind of mimics the film speed. But what it's changing is the sensors sensitivity to light, but it's doing the same thing. So on our digital camera, if we have shutter speed, one second aperture f 2.8, ISO 100, we're going to get a particular exposure and if we bump our ISO the higher we go on the ISO, the brighter the exposure is going to get Now, this almost sounds too good to be true, because it is because we could just bump our exposure as high as we want, and take photographs in pitch black and get great looking photographs. But the problem with ISO is that the higher the ISO goes, the more digital noise we get. And the amount of noise we get varies on the level of camera quality. The better camera you have, the higher you can go.

And so before the noise degradation kicks in. But regardless of what camera you have, even if you have the best camera in the world, you're going to start seeing digital noise at some point. And it's kind of odd that we're talking about noise in a photograph because it's visual, and we usually hear noise with our ears. But in this case, it's digital noise and it manifests itself as pixels that are not quite the color they should be. The photograph starts to look grainy, and we actually start to lose dynamic range, which means how good the camera can express darks light in the same photograph. So then you might think, well, I always want to keep my ISO as low as possible, I'll always shoot an ISO 100, so that the quality of my photographs is better.

And that's perfect in a perfect world. But a lot of times, especially when you're shooting events and things that you can't control light, sometimes it's dark. And so you've got to make compromises. So sometimes you may say, hey, my lens only goes down to f 2.8. And I can't handhold this camera at less than one 60th of a shutter speed or else I'm going to have motion blur. So I've got nowhere else to go in my exposure except to adjust the ISO.

So you may end up at ISO 1000 with those other parameters and you have to take your photograph. When you are in good light, say for instance outdoors during the day, or in a very brightly lit room or whatever it may be. You do want to keep an RSO as low as possible. There's no benefit to having a higher ISO Besides brightening your exposure, and that's something you only do when necessary. So you wouldn't ever want to be outside in bright daylight ISO 1000 and then crank your shutter speed up to 130 2000. To compensate, you'd want to bring down your shutter speed and bring down your ISO because the camera is going to perform better at the lower ISO levels.

So now that we talked about how ISO controls the camera, aperture and shutter speed, let's put these things all together. As we just said, you want your ISO to be on the lower end of the spectrum whenever possible. Use shutter speed, pretty much has a floor, it's got a minimum that's going to be at if you're hand holding the camera or you're shooting things that are moving or both. So that is going to let we're going to know what we need to do for that. Say for instance 100th and we're shooting people standing still. So we're not gonna go lower than that.

And once we get to the point and I shut up Speed that we can achieve. No motion blur. All we have left is our aperture. And our aperture is controlling our depth of field, but also our exposure. So exposure wise, let's say at 100, for shutter speed, and ISO 100. We need f 4.5 to get the proper exposure.

Well, we also now need to consider what does that do to our depth of field. And it may be that we want a shallower depth of field for this photograph, maybe we're taking a portrait of one person and we really want to get that nice, blurry background and foreground and just have the subject be in focus. Well, we're going to want what what do we want to do that aperture we need to drop our aperture number so we can get a shallower depth of field so that F 4.5 is going to come down to let's say, f 1.4. What did we just do our exposure, we kept our shutter speed constant. We kept our eye So constant and we dropped our aperture. So our exposure is going to brighten up much more than we want it to.

And now we need to compensate. We've already got our ISO at 100. So that's where we need to be and we can't go any lower. We have shutter speed, we're at 100. Well, if we go down in our aperture, let's go up in our shutter speed, because that's going to bring our exposure back in. And like we said in the shutter speed module, there's really no disadvantage to having a faster shutter speed than you need.

At that point, we're only controlling our exposure, it's not going to affect the quality photograph. So we can bump our shutter speed up to say one 400 to compensate for the aperture dropping. shutter speed and aperture can go opposite ways and keep your exposure the same. So if you think of it like that, where they can play off each other, and then ISO is almost like an independent control. So they all control shutter speed, lower shutter speed burnin exposure aperture, lower aperture bright exposure ISO, higher ISO brighter exposure, so we got two lowers make it brighter and ISO makes it darker. And then we have the opposite where aperture and shutter speed as they increase, it gets darker and as the ISO decreases it gets darker.

So to summarize ISO, the lower it is the more dynamic range your camera will have the better quality photograph and the less digital noise. It's also going to make your exposure darker. The higher you go with ISO, the brighter your exposures gonna get. But the trade off is digital noise and dynamic range decrease. Neither of those are desirable effects. So whenever you can you want to keep your ISO as low as possible while your other parameters are where they need to be.

So I'm going to give some examples of shooting situations and talk about through what three parameters would probably be. And these are just rough estimations, just to illustrate the point. So I'm shooting one person outdoors, on a pretty bright day, I'm going to take my ISO down to 100. That's the lowest my camera will go. And then I'm going to take my shutter speed, and I'm gonna put it up one 200. And then I'm going to take my aperture, and I'm going to put it somewhere down f 2.8.

So I want a pretty shallow depth of field. And I may take a test shot and say, well, it's way too bright. But I want to keep my aperture where it is because I want the depth of field. I want to keep my ISO where it is because I want to clean photograph. So all I have left is shutter speed. So I'm going to increase my shutter speed to darken down the exposure.

And then my photograph looks the way I want. Now let's say I'm shooting a group of people, and I've got layers of people. So I have maybe four layers deep. So now I've got a lot of depth that I want to have in focus. So let's say for instance, I get out There are my cameras on one 400th of a second, ISO 200 and my aperture is F two. And I take the photograph, and it's right where I want it, except my depth of field is too shallow, the exposure looks good.

So I need to increase my aperture from F two to maybe, let's say f 6.3 and I bring it up, I increase my depth of field but now my photos can be too dark. Now I've got my shutter speed currently set to one 400. So I'm going to drop that down because I brought my aperture up whenever my shutter speed down and I'm going to go down to maybe one 100 and take the photograph and maybe it's brighter but it's still a touch too dark. I don't want to bring my shutter speed down anymore, because I want to make sure I don't get motion blur. So my ISO, I'm going to give it a couple bumps up and that's gonna break my photograph. Now I've got the exposure where I want it.

I've got a safe shutter speed. I've got the depth of field I need for my increased aperture. Okay, one more example. We're inside in a dimly lit room. And we have a lens that can only go down to f 2.8. And we're already there.

So we've got our aperture set to 2.8. And then we've got our shutter speed down to 180 s, which is say the lowest I can go with this lens handholding without getting blurry. And now our ISO is on 200 and take a shot and it's way dark. Well, the only thing I can mess around with in this situation besides adding flash, which we're not getting into now is increasing my ISO. So I go all the way up to 800 and I shoot it's still too dark. And I go to 1250 and I shoot and there it is, looks good.

And while it's not awesome for us to have our ISO up in that realm of really high in that situation is the only thing we can do to get the photograph. We need to get it So, a properly exposed photograph is better than no photograph. And you may be tempted to just keep decreasing your shutter speed to get your exposure where you want it to be. But once you get down into that dangerous territory of shutter speed, we're going to get motion blur, you're going to start to have a blurry photo, and a blurry photo is not as good as a noisy photo. I any day of the week would rather have a photo of digital noise from high ISO than a blurry photo from motion blur. It's much more acceptable to have a noisy photo, and it's also something that you can manipulate and edit and post production.

To minimize the effects of but a blurry 40. You can never edit away the blurriness once blurry, always blurry, you're stuck with a blurry photo. So make sure to always keep your shutter speed in a safe zone and use the other parameters to get the exposure that you need. I hope that explains things. There could be more examples but I think those illustrate the relationship between shutter speed aperture and ISO. If you're still confused about it, please let me know in the comments and questions.

I'd be happy to get back to you and explain other examples.