 So, we have the problem of measuring grain size in digital images. If you have a vectors graphic program that works okay, I've set it up so you can drag one of these circles over on top of grains and compare their size to those circles. And those circles are calibrated to the divisions between the phi scale that we're using for the grain size. However, I understand and appreciate that many of you can't run graphics programs. So, what I'm going to do is show you how you can measure them directly on a screen. So, it's much harder to do on a touchpad because touching the screen tends to move it. So, if you can lock the screen that'll work better. So, the first thing we're going to do is expand our scale to the point where we can easily measure grains. And then I'm going to calibrate a ruler to the size of grains to make it easier to manage. So, this big circle here is one millimeter or 1000 microns. And so, I have this grain size chart with millimeters marked on it. So, what I'm going to try to do is make it so that that circle is an even number of centimeters. And then I'll be able to divide easily. So, I'm going to make it really big. So, it's easier. I'm going to make it try to make it five centimeters. So, to do that, I'm going to increase the scale, which is different on your different programs until I get that being five millimeters. So, in mine, I can draw the box around it and it's still a little bit too small. So, the way my drawing program works, the box goes to the edge of the window. So, I'm going to draw just slightly smaller than the window that I have right now. Let's see. Let's see how that did. Okay. So, now I have five centimeters on my scale. My physical scale is equivalent to one millimeter. So, I'm going to write that down so that I don't forget it. And I will write it on the screen here. So, we have one millimeter equals five. I'll get rid of this panel so we can see that. Okay. So, then what I'm going to do is I'm going to measure with the ruler and I want to calculate how many millimeters that is on the photo. So, what I need to do is calculate what I would multiply times my ruler to get the millimeters on the photo. And so, in this particular case, one of the reasons I chose five is that is the equivalent of one over five, which is 20%. So, in other words, I multiply and my cell phone, which I'm using to film this, is in the way by one over five, my measurements, or I can take 20% of what I measure. Okay. And then I'm also, because I often mess things up a little bit, I'm also going to write down what the magnification on my screen is for that value. And it's 581%. 581% is the magnification it says in the screen, but that's okay. It's just notes for me. And you can see that I type is not so well. Okay. So, I want to keep this same magnification. So, I just turned the magnifier, which I definitely want to get rid of here. Okay. So, I don't actually change it. And now I'm going to scroll to the place that I want to measure. So, if I zoom out and zoom in, I have to get back to the 581 spot. So, I'm not going to do that. I'm just going to try to find it. And there it is. So, drag the scale bar. So, my box is here. Okay. So, now I am going to use my physical ruler and write down the numbers that I collect. So, it just occurred to me that you couldn't see my writing from before because of the location of the cell phone camera. We will just deal with that. Okay. So, I need to change the color. I'm going to change the color to white because that's easier to read. Forgot it wasn't capturing my whole screen. Okay. So, I am going to, I'm going to draw on this so that you can see a little bit what I'm doing here. So, let's see how big my cursor here. I'm going to make it really small as possible. That's as small as possible. Okay. So, let's see what grains you can see in your field of view. Okay. Let's do an easy one to start with. Okay. We'll start with this grain right here. So, what I'm doing is just holding my ruler up to it and I think you guys probably already know this but I will just show you in detail. So, I am actually in this dimension measuring two centimeters which is 20 millimeters. So, I need to go back and get some text here. So, two centimeters and that gets translated. If I won't get 20 percent of two centimeters that gets translated to one millimeter or 20 centimeters, 20 percent. Nope, that's not actually right. So, I want 20 percent of two centimeters is actually four is 0.4. So, one of the things that you can do and I recommend doing given how hard it is to actually calculate things. Let me turn this to white is just put your direct measurements what you actually measure into your spreadsheet and then multiply that whole column of numbers by the conversion factor and that will make it so you don't have to do the math directly in your head. Okay. So, another thing to note is that I measured the grain in this direction and it's a little bit different size in this direction. It's a little bit smaller and so for this grain I would measure the longest axis like I did and say maybe that it was moderately spherical or I could say moderately prismatic right. So, you could also measure both dimensions if you want it and keep that in your notes. All right. So, here's a grain right here again that has two different dimensions in it. Let me move my pencil out of the way here. All right. So, in this dimension I am getting we'll say eight millimeters on my ruler and in this dimension I am getting we'll say 15 millimeters. So, if I go back to the text this particular grain is eight millimeters by what did I say then that's in the dimensions on the image. So, this is basically the way you can go through and measure different grains. So, one of the things that you'll notice is that you can see the individual pixels and so we're measuring at the limit of the camera resolution which makes it really difficult but on the good side if you can't tell let me zoom in even more which will mess up my scale but you'll be able to see for sure what I mean here. So, let's zoom in really really high like right in here. All right. When you zoom in too much you can't actually tell where a grain ends. So, like I'm sure that this is a grain like all of this in here and I would say that this out here is not in the grain and we have maybe two pixels on either side that is difficult to tell. All right. And so, one of the things that's fine is what the data are and so one of the things to be careful of is if you can't tell within two pixels you don't have to measure more precisely than the size of two pixels. All right. So, there's error in your measurement because the data aren't as high resolution as we can measure in this digital image. So, I'm going to back out again okay and now my scale is messed up so I'm not going to actually measure anymore and maybe at this time you can say oh actually you know the edge of the green you know maybe maybe right here. So, if you're doing this in any sort of program that you can annotate you can you can sort of also mark the grains that you measure so you keep track of them because you don't want to measure the same ones again and if you're measuring 50 it'll be hard to keep track of right. So, you can just sort of like put a dot or something like that in the in the ones that you've measured. So, the other way is if you don't have a good enough screen to measure them on the screen like this you can print out the image and use it with a different with scale bars like you would with a map and then on when you do it on paper you don't get to make it easy to measure in terms of getting even numbers of millimeters relative to your specific number of microns. However, it could be physically easier for you and you're welcome to do it that way as well. Thanks for watching.