8 Points To Understanding ISO And Image Quality

Photography - 101 Understanding Exposure
15 minutes
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Transcript

In this video we're gonna be talking about eight key points I don't know why I held up five, that's five, this is eight see I can count very well a key points to better understanding ISO and in particular how ISO relates to image quality. So let's start from the top key point number one and this is going to be review for everybody because I expect that you've already understood and mastered this concept. Your ISO is the cameras sensitivity to light, okay, so you raise the ISO, your sensitivity increases. Now we basically use ISO in situations where well the combination of shutter speed and your aperture doesn't yield the correct exposure, you don't get enough light it could be because you need a closed down aperture so that you get better depth of field. It could be because you need a faster shutter speed or combination of both.

Either way, you're not getting enough light. So we bumped up the ISO to compensate to increase that sensitivity to light. Now More specifically, it's not actually the cameras sensitivity To light it's actually the cameras sensor if we're talking about a digital SLR, like this one. Okay, so we're talking about the actual sensors, sensitivity to light. But if we're talking about a film camera, then we're talking about the film's sensitivity to light. So when you go out and purchase film, you're looking at the film's ISO rating, not the cameras, cameras don't have an ISO rating, just the sensor or just the film.

Okay, so we know this ISO is the digital or is the sensitivity to light either for a digital SLR sensor or for film. Great. Let's go on to Key Point number two. Number two is to understand that every bump up in ISO is going to basically introduce grain into your image and it's going to do a couple other things as far as image quality, which we're going to talk about and key point three as well. But that grain that it introduces is going to reduce image detail. Now I have a perfect little example here set up for you.

So we're here in Lightroom. And what I want to show you basically is that we took this exact same image with a Canon 60 mounted on the tripod and We shot these cupcakes with different ISO settings. So let's look at these fullscreen just so we can see each one of them. I'm going to hit ISO, we can see our information, we have our first image here at ISO 400. And then we go up to ISO 1600. And then we go up to ISO 6400.

And then we go up to ISO 12,800. Now the differences between these images is actually relatively difficult to see. But what we do notice if we zoom in, is that we're starting to introduce a little bit of grain and that grain is actually removing image details. So let's say for example, if I were to select these two, and I'm going to compare them side by side, so we have ISO 400 on the left, and we have ISO 12,800. On the right, take a look at this, we have a lot more smooth and consistent detail within this image, whereas in the one on the right we can see we kind of have this little blotchiness we have reduced overall detail in the image with that increase in ISO. Now the great thing about cameras today is that you can step them up to 60 412,800 ISO and even Beyond that on a seven s goes up to like 400,000 is not necessarily usable.

But at 12,800 I'd still say that this image is usable if you have to shoot with that ISO setting, it's usable I mean cameras are getting to the point where they can see in the dark basically, but just realize that every step up is going to introduce grain and that grain is going to reduce detail. I have another extreme example I want to show you guys actually this is on an AE seven s and here you can see that there's been ISO 1600 where we bait we don't even see hardly any noise it's which is really incredible because back on film and on the early days of digital slrs ISO 1600 was actually quite a bit and you would get a lot of noise. But look at this. It's it's almost perfectly it looks fantastic. But look at ISO 102,000 we can see a lot of that detail being destroyed and then ISO 400,000.

Again, this yields basically at this point ISO 100,400 thousand, those are still unusable ISO is at least in my opinion, those really aren't good enough quality, but on the a seven so it's only seven as you can Go up to very high ISO numbers and still yield completely usable images, which is absolutely fantastic. Okay, so moving on to key point number three is that raising your ISO is going to reduce overall color and dynamic range within your image as well. This is another effect that it has over image quality. Now what exactly does that mean? Well, here's one of the images that we captured actually during our shoots, and I'm going to reset this out back to the original. This is one of those scenes where we talk about often maximizing dynamic range within a single RAW file.

And to do that, to really maximize dynamic range. You need to shoot in RAW and you need to shoot at your lowest possible native ISO and we'll talk about Native ISO in just a moment as well. But what this does is what we're trying to do here is if you look at the histogram, we've captured as much detail as possible from the shadows, all the way up to the highlights. we've captured everything, at least everything that the sensor can possibly capture within that range. If we raise the ISO, let's take a look at what this was shot at. So this was shot at 100 ISO.

If we raise the ISO to say 200 ISO, maybe the camera sensor is capturing 12 or 13 stops of dynamic range in this image and we get all those shadows, we get all the highlights in that image. And we can take it and we do basically this to it. Where we make our final adjustment where we pull up the shadows, we pull down the highlights and get a nice balanced and tone mapped image. But if I raise the ISO to say 200, then we're going to leave off a little bit of that histogram, we might be clipping shadows we might be clipping more highlights because the camera may not be able to capture say 13 stops of dynamic range, it may be only capturing 12.7 stops. When we go to ISO 400, we reduce it again, maybe now it's at 12 stops ISO 800. Now it's at 10 stops ISO 1600.

Now it's at eight stops. Every step up we're reducing the amount of dynamic range that can possibly captured within one single image. That means that if we're trying to create a nice beautiful landscape with an amazing range of color and tone Well, we need to keep it at the lowest possible ISO. It's also the reason why if you look at nighttime shots where you raise it up to say ISO 3200, ISO 6400, you kind of notice that the colors look a little bit dingy, they kind of look a little bit, well they just don't pop the same way that they would an image like this shot at ISO 100. Okay, so just remember that again, stepping up not only increases grain sticking to the ISO will also decrease overall dynamic range. All this talk about raising the ISO decreasing dynamic range, introducing grain and so forth, kind of might dissuade you guys from increasing your ISO but it is absolutely necessary in many situations and this is what I would say four key Tip number four might be point number four.

That is that raising the ISO and getting your shutter speed up high enough where you get a sharp image is much much better than keeping the ISO lower and getting a blurry image. So for example, this image right here this was shot at one one 60th of a second which you gives us just enough sharpness to keep our couple sharp and in the shot, while also introducing a tiny bit of motion in like kind of the these little pedals that they're throwing across the frame. We can even slow it down a little more if we want to get more than motion. But let's say if I kept this at ISO 800. That would mean that how to reduce the shutter speed down to something like Well, let's see, if we go from 3200 to 1600, down to 800. We'd be going from shutter speed of 160 down to one ADF down to 140.

At 140 of a second. Yes, we might get better color Yes, we might get better detail, but then we yield a blurry image a blurry image that would be unusable. So this is my point is that our digital cameras, they're fantastic. You can raise the ISO up pretty high going up to 1600 3200. It's totally fine. Getting a sharp image.

Getting a usable image is always going to be more important than making sure that you have perfect detail and absolutely perfect color and dynamic range and so forth. So understand the situation. know when it's totally appropriate and when you need to bump up the ISO. Now Key Point number five that I wanted to bring up is that a lot of you will think that well, maybe it's better for me to shoot at a lower ISO, and then basically get a slightly darker image and raise it up in post rather than raising the ISO in camera. That's definitely a bad idea. I'm going to show you exactly why.

In general, let's go back to just this whole view right here. I have two images right here that I wanted to demonstrate with. So you can see here, that one was shot at 30 seconds f four ISO 430 seconds, f four and ISO 1600. Now this is a two stop difference. So going from 400 to 800 to 1600. That's two stops.

Yes, that is two stops. So what if I shoot a darker over here like because I want to yield better dynamic range and better detail and so forth and brighten it up and post to get a better look? Well, let's try that. You're going to find out that basically by doing this, you will actually get worse dynamic range worse color will end especially worse detail by raising the exposure significant In post Okay, so on the left we have our image shot at 1600 ISO and on the right we have our image shot up 400 ISO, and we raise the exposure by two stops to match it in post production. Let's go lights out by hitting l if you're in Lightroom. What we're going to do is zoom in now to this image and check this out.

The image on the left at the higher ISO in camera yielded a better image than the one on the right where we shot it at a lower ISO and then raised it digitally in post. So we have more green over here I see more color noise where basically we have these kind of variations in color that don't look good going into the shadow we can see that we have more banding more noise inside of the shadows we have all these issues, whereas the left shooting at the higher native ISO in this camera gave us a much better image than basically just trying to raise it in post. So that is key. Tip number five Do not shoot at a lower ISO expecting to adjust it in post and get a better image. By raising your exposure in post production. You're always better off raising camera to the next native ISO level that gives you a correct exposure than trying to do it in post and that leads me perfectly in the key point number six which is what the heck is native ISO?

I've said native ISO many times and I will probably say it many more times so what is native ISO? Well every camera and this is a Canon find the mark three whether you're on a rebel whether you're on a five D Mark three whether you're on a D 100 whether you're on a Sony camera every single camera has what's known is as a native ISO for this camera for the canopy new Mark three the native ISO when shooting stills is ISO 100 This means that basically every stop every full stop from that native ISO is a another native ISO number. So what does that mean? Okay, so if we go from 100 to 200, that's a native ISO 200 to 400, that's native ISO 400 to 800, that native ISO 800 to 600, and so forth. The in between numbers are not native ISO numbers. So firstly, ISO 160, ISO 320 ISO for whatever those in between numbers are not native ISOs.

And so what's essentially happening is that if you shoot out a number like that, the camera is actually shooting at ISO 100. And it is digitally modifying it to bump it up to ISO 160 or whatever you're shooting at. So the cameras actually digitally brightening these images which will yield worse results than if you step it up to the next higher ISO. So for example, I would actually get a cleaner image shooting at ISO 200 and darkening it down a little bit versus ISO 160. Okay, so keep the camera well at least we'd recommend keeping the camera at the native ISO. For every camera it's going to differ.

For example, on a lot of Nikon cameras, they start natively ISO 200. So ISO 200 400 800. Some cameras are ISO 160 native, so it'd be ISO 163 2640, and so forth. Just learn your particular camera and we'd recommend Sticking with those native ISO numbers, just for best image quality now is it gonna be a huge massive difference? Well, no, but it will give a little bit of a difference in image quality. And when you're actually looking in and pixel peeping, it's actually quite noticeable.

Okay, now moving on to Key Point Number seven is that I would recommend leaving your eyes though adjustment as the last step in the exposure equation. So for example, you go into a scene and you choose a shutter speed that fits the type of action and whatever it is that you're shooting, or you pick an aperture that matches the type of compositional field that you want to have. At that point, then decide what you need your ISO to be. So don't rely on ISO don't just set the ISO at 400 and then go out anywhere and start shooting because you really aren't kind of reducing image quality in a lot of situations that aren't necessary. For example, I know a lot of shooters that they'll leave their cameras on ISO 400 and they'll shoot outdoors the entire time just with a left on ISO 400 because they're worried about when they go in the shade.

They might not have enough light But then when they go back into daylight, they'll have you know, too much and they figured it doesn't really matter, you're better off just adjusting in each scene that you need to. So leave that as the last part of your equation because why would you want to reduce image quality just directly from the camera. Finally, Key Point Number eight is that you can use ISO for creative effect. But my guidance would be to be extremely careful. Okay, now, let me show you exactly what I mean. Let's go back to Lightroom.

And I have two example images right here, we're just gonna bring them up in survey mode. Now, these images were shot on our rebel they're shot during the course of this workshop. And a lot of photographers when they go out in this kind of situation, and more experienced photographer, photographer will go in and say I'm going to shoot this ISO 400 ISO 800 because it's going to yield a less digital image, digital cameras at 100 ISO I mean, they can capture so much detail, so much dynamic range that it almost looks digital in a sort of way and an hour to 100% agree with that. So what they'll do is they'll step it up to ISO 400, ISO 800. And they'll shoot a scene like this at a higher ISO which is going to decrease the dynamic range and add a little bit of grain and noise and kind of reduce a little bit of color and it makes it look kind of like it did back on film.

And that's great. It makes her very natural filmic effect. But what I would say is if you are an advanced photographer, and you have a grasp of everything, and you understand this, then fine, by all means go out and do it. But there is a giant warning with that because when you go out and you shoot images like this in daylight, if at a later point in time you say that Oh man, I really wish I had more detail in these shots. I really wish I had more color in these shots. You can never go back if you shot these ISO 400 whether you shot raw or JPEG, that's not something that you can undo.

It's always going to be at ISO 400. And the detail that you capture is the detail that you have. If I want to introduce a grain and kind of a filmic look in post, I can do that I can do that with Lightroom. I could do it with Capture One I could do with Photoshop. I can do it. It's fairly simple to do.

And there's also presets It's out there that help you to do it as well. But if you do it in camera, and you further enhance and post, well whatever you've done in camera cannot be undone. So that's my warning there and that's kind of why I'd say I would recommend against using it as a creative effect in camera because you can always add filmic effects later but you can't take it away if you did it in camera. So if you absolutely 100% know that this is what you want and you're okay with those images being that way forever, then by all means, use ISO for creative effect. Otherwise, again, leave ISO is the last step in your creative exposure equation and use it simply to just get to the correct exposure. That's it for this video on ISO.

Hopefully this has helped you all to better understand ISO and how it relates to image quality. And well I'll see you all in the next video.

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