Skip to main content

ISO and Noise

Lesson 20 from: Mastering Your Digital Camera

Chris Weston

buy this class


Sale Ends Soon!

starting under


Unlock this classplus 2200+ more >

Lesson Info

20. ISO and Noise

ISO has a trade-off -- the higher the ISO is, the more noise or grain the image will have. See how aperture affects image quality in this lesson.
Next Lesson: An Acceptable ISO


Lesson Info

ISO and Noise

remember This all camera film has a film speed, which is referred to by its rating. This one is also 200. Now, the higher so on your digital camera is effectively the same thing, but it works in a very different way. Film is made up of several layers. One of those layers contained silver Halide crystals, and it's these crystals that react a light. A slowest films such as this one uses small crystals, which have the benefit. You can't see them in an average sized print to make films faster. Manufacturers use bigger crystals, but at some point the crystals are so big they become visible, which results in grainy film images. Now the Holy Grail for manufacturers is grayness film, and a digital camera gives us that there are no silver Halide crystals on a digital sensor, so there is no grain. So why can't you simply set the very highest Aiso value you've gotten shoot away because digital introduces a new problem. Noise digital eso works using the process of amplification when you increase t...

he so you are amplifying the light signal in exactly the same way when you increase the volume on your TV or hi fi, you are amplifying the sound signal. If you raise the volume too much, you start to hear background Aziz reduce amplifications. You turn down the volume, his goes away and the same thing happens with a digital camera. When you amplify the light signal too much, that is when you increase so too much you introduce the visual equivalent of hiss, which is noise. Now, to explain why this happens, I'm going to visit a vineyard. We see digital noise as brightly colored, random, unrelated pixels on because they're random and unrelated, they degrade image quality, so we need to avoid them now. Digital I s O noise relates to something that we call the signal to noise ratio. And to demonstrate that I'm going to use the three glasses of water on this glass of red wine. The water represents light and the red wine represents noise. So imagine that we have a low iron, so rating set on the camera 100 I s O because the I so is so low. The camera needs a lot of light in order to make the exposure that's represented by the four glass of water. Now let's imagine increasing the I s 02 200 IRS. So So we've doubled the I S O. Which half the amount of light signal required by the camera to make the same exposure half the amount of water. Let's say we double the I so again to 400 IRS. So this time we're having the amount of light yet again. So 1/4 of the amount of the original exposure. Now let's add some noise into the picture. We're going to do that by taking a teaspoonful of red wine and adding it Initially into this glass of 100 eyes. I water. We mix it up a little bit, we'll see that there's so much water in the glass. The red wine becomes diluted to the extent that you can't see it. And this is exactly what happened in the camera. There's so much light signal that what noises their inherent in the light disappears and is diluted by the light signals. But what happens if we add the same amount of noise at 200 eyesight? Well, it still gets very diluted, but now we start to be able to see it a little bit more easily. And if we do the same thing again adding the same amount of noise to 400 I s o. Now we start to see quite clearly that the noise of becoming more visible because there's far less light signal to dilute it. Now let's up the ante. We're going to set the I S 0 to 1600 s o. And at 1600 hours, so we only have 1/16 of the amount of the original light signal. I'm gonna do the same thing again. I'm going to add the same amount of noise, mix it up a little bit. Now we can see that at IRS. So because there's so little light signal available were starting to really see the noise appear. So the higher the I S O rating, the more noise is visible in the image. If you're shooting J pegs whenever I eso is set above the base value, that is the lowest value Turn on the high I s O noise reduction function, which you'll find in the shooting. Manu. This will tell the camera to identify and rectify noisy pixels while it's processing the image. Hi, I s O noise reduction in camera only works on J peg files. So if you're shooting in raw mode, you can use computer based off where to achieve the same thing. In all cases, remember the mantra. The best way to keep noise to a minimum is always suit the lowest. So you need to get the lens aperture and shutter speed you want.

Class Materials

Bonus Materials with Purchase

Bonus PDFs

Ratings and Reviews

mark jacobson

What a marvelous course! What a marvelous teacher! When I went to college, my father would always ask me about my professors, more than the courses themselves. He was passionate about learning and although too busy with earning an income to go beyond an undergrad degree, continued to read 50 books a year. I still remember how he'd get almost visibly excited when I'd tell him about some special professor who taught with such enthusiasm and, more than just passion, evident delight and joy in the subject. 'Ah they're the best, son. How wonderful you have such a teacher." Well, he passed away decades ago but if he were still around I'd get a kick out of telling him about Chris Weston, the 'Prof' of this course. He's one of the very special ones: a teacher who's loved and lived his vocation--his avocation--since he was a boy--and still is as excited about it now as he was then. The result: a course that seems to be more a labor of love--of pouring far more energy and thought into the details then one typically finds in these courses--than anything else. Bravo Chris! I'm already on to your next one.


Chris is an amazing instructor who dissects theory giving amazing analogies that bring concepts to life. I have rarely been able to sit through most video course for more than a half-hour but watched this one from beginning to end. A good refresher course if you've been away from the camera for awhile or there are some concepts that still illude you. I highly recommend this course and look forward to watching his others. Thank you for the clarity and great explanations.

Sky Bergman

This was an amazing class. I have looked at a number of basic photography classes. This one was by far the best I have seen. Chris is an exceptional teacher. He breaks things down into digestible information and then inspires you to be creative. Thank you!

Student Work