Video Transcript
Find your lens Nodal Point easily for better Virtual Production results!
Greg Corson · 9,018 views 14 Aug 2022 #unrealengine #virtualproduction · Duration 6:20 · youtu.be/_ZD_iMlowFs
No tracking hardware needed! Fastest and simplest way to do it with a mount costing as little as $10 (if you don't already have it!) 00:00 Intro, why do it? 00:46 This is NOT it! 01:00 It's here! 01:13 Measuring Rigs 02:06 Two Sticks Method 02:40 Too far back 03:00 Too far forward 03:25 Found it! 03:37 Measure it 04:33 Important points 05:38 In Closing To see a lot of the tools and gadgets I use all in one place, check out my page on Amazon. Check back often as I'm still building the page. As an amazon affiliate I earn a little money to support the channel if you order from these amazon links, there is no extra cost to you. Some things may be cheaper in local stores. https://www.amazon.com/s
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hi everyone this is greg corson i've been getting a lot of questions about nodal offsets tracking offsets and the like so i want to go over it again and show you the easiest method for finding the entrance people of your lens this is important because if your offset is wrong the talent and the cg background won't stay aligned their feet may appear to slide or just not stay in the right spot you don't have to get this perfect but if you plan to use moving cameras having an accurate measurement will avoid the kind of stuff that makes a shot look fake technically the term for what we're going to measure is called the entrance people or no parallax point but most people just say nodal point or nodal offset so that's the term i'll use here too it's shorter first things first
a lot of people think that this mark on your camera is the nodal point that they should measure from sorry but that's not right this is the position of the sensor in the camera the nodal point is actually inside the lens just to be clear in this shot the white line is what we call the lens axis a line that goes right down the center of the lens your nodal point will be somewhere on that white line between the two red markers the rig you're seeing here is what i'm going to be using to measure my nodal this may look a little complicated because i built it from some large parts i had laying around just so that it would be easier to take pictures of and for you to see what's happening on it the only thing your rig really needs to have is a clear pivot point here it's the white line and it also needs the ability to slide the camera forward and back of that pivot point along the red line as you
see here here's a close-up of the bar i'm using but you don't have to use one of these a lot of tripods have the ability to slide the camera back and forth around the pivot like this one and you can also get ones like this that have a knob that lets you slide the camera forward and back if your tripod has a quick release plate you can just get one of these which is a longer version of the mounting plate you can just slide back and forth in the quick release or if you want to keep it really inexpensive you can use one of these double brackets that usually only cost about ten dollars the method we're going to use is called the two sticks method because you can do it with any two vertical lines two pencils stuck in clay on a desk or a couple of light stands any two vertical lines one near to the camera
and one farther away the way i'm getting my two reference points is by putting a piece of tape on the window and then setting up the camera so that the tape lands in the center of the frame and is just touching the edge of a vertical reference in the distance in this case a building now all i have to do to see if my pivot point is under the nodal point of the lens is to pan it you'll notice if i pan it to the right the red mark ends up to the left of the building edge and if i pan it to the left the mark ends up on the right side this means that the pivot point is behind the nodal point or too far back so we have to move it now i've slid the camera on its rig so the pivot point is under the front part
of the lens and we'll do the same test we'll pan to the right and you'll see that the mark is now to the right of the building and we'll pan to the left and the mark is now to the left this means that i've slid it a little too far and we need to come back so after a few more adjustments of sliding the camera back and forth now i pretty much got it right on you notice when i pan that mark stays stuck right to the edge of the building this is what my rig looks like after that successful alignment the pivot point marked by the white line is pointing right up to the y in the word sony on the lens this is my nodal point
now all i need is a measurement from the nodal point to zero point on my tracker for the vive that's right where the tripod screw goes in so as you can see here i measure up from the lens axis that's the red line and then back that's the green line till i get to the tripod screw and i've got the right number remember every lens is going to be a little different and if you change the zoom and focus it may move the nodal point so you want to check that just change the lens settings and then redo the two sticks test after zooming my lens from 24 to 70 millimeters and redoing the test you can see that now the nodal point has landed on the word s in sony or back about a centimeter from where it was for each lens setting you test be sure
to make a note of where the nodal point actually ended up on the lens measure from some fixed point like the edge of the focus ring or from a logo on the lens this way if you ever need to change where your tracker is mounted on your camera rig you can just re-measure it you don't have to redo all these tests again remember when you're measuring that you must measure the offset from the nodal point on your lens to the tracking origin of your tracker on the vive this is at the tripod screw but for some other types of trackers it's not always there it could be forward or back of the tripod screw or even to one side of it be sure to look at the manual to find out where it actually is so you can measure to the right spot if you're using something like a vive tracker unreal's camera calibrator can
find your nodal and tracker offsets automatically for you these results are usually pretty precise but still a good idea to measure your nodal position using this technique just so you can compare the results of the automatic tracker to this one in a future tutorial i'll show you how to adapt unreal's nodal point calibrator to work with other kinds of tracking systems i'm still working on the process remember that this rig i've shown you is just for measuring the nodal point once you've got the measurements you can take your camera and put it on a normal tripod again the important thing here is to know where that nodal point is so anytime that you need to know the offset from your tracker to the nodal point you know where to measure to if you found this tutorial helpful please remember to hit the like button
and if you can subscribe to the channel as well if you have any questions leave them in the comments section and i'll try to answer as soon as i can in the meantime happy filming see you next time
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