✱ Understanding Exposure in Maxwell Render

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Understanding basic camera exposure settings when using Maxwell Render is very important to getting the look you want and expect. Why? Maxwell Render mimics a real-world camera (YouTube video), and the default settings in the Maxwell camera are set up for typical exterior daylight shots. So what do you do when you want an interior or night shot with just emitter-based (artificial) lighting and no sun? This tutorial is all about exposure, and what you need to do to get the image you're expecting when you render your scene. Obviously not all renderings are exterior daylit shots. Ultimately you'll need to dive into the camera settings just like you would with a real world SLR or DSLR camera and get your hands dirty playing with the settings. Follow me...

There are no scene presets

Typical DSLR scene preset dial

Typical DSLR scene preset dial

Typical Point-and-shoot preset menu

Typical Point-and-shoot preset menu

One thing to realize is that when you're working with Maxwell, unlike a fancy real camera, is that there is no preset menu for different scenes (also known as automatic camera modes). You know - the ones for the little kids that move quickly when playing sports, the candlelight scene at dinner, snow/beach scene, etc.? All of those scenes change the settings in your camera for a very different combination of f-stop (aperture), shutter speed and sensitivity (ISO) to capture the scene based on the amount of light that is present.

You see, photography is ALL about light, and Maxwell Render is modeled after the real world and how light bounces off physical materials through the lens of the camera and ultimately onto the camera's sensor. You have to either learn or know a bit more about how these manual settings work together. I'm going to give you the short version here, and then you can dive in deeper to figure out what settings work for you in your particular scene, because every project is different. In other words, this guide won't cover every possible scenario, so don't treat it as such.

I don't mean to make this sound scarier than it is. In fact, it's not hard to understand once you understand the basics and begin playing with it. But unfortunately there are no shortcuts here so jump in a learn a little about photography and you'll be off and running with your newfound knowledge in a short amount of time. Once it clicks, you'll know what settings to tweak first and then you can fiddle with the smaller details later. Getting your starting point quickly will save you tons of time as you go through the rendering process.

Learning about camera settings

One website that I found extremely helpful when I was learning about manual camera settings was CameraSim. It's a great resource that not only shows you what adjusting the camera does (especially if you don't have your own to play with), but they also teach you why those adjustments change the outcome of the image. The interactive page allows you to make changes to those settings I was talking about and see the affects in real time, right in your web browser. They also have an iPhone app, and you can download their apps onto your computer for a small fee. Note: you need Flash to view the demos in your web browser.

Maxwell Render works just like a real-world camera, and that's why it's a good idea to learn about these settings. You'll see the settings that we use to control it are like a camera later in this tutorial. The good news is they both use the same terminology so if you're already used to using a DSLR or spend some time on CameraSim you'll see the direct correlation with the settings in Maxwell.

An example

Here is the simple scene I'm using for this tutorial. It's just a room-sized box with one side missing so we can see into it, and there are 3 large planes acting as light sources. Basically there is just an emitter material applied to the planes - they aren't actually "lights" at all. I love having the ability to create surfaces that act as soft boxes for lighting, and it doesn't get any simpler than just applying a material to the polygons to do this.

Click to enlarge

You can see I have turned on the polygon normals for those planes to make sure they are pointing the right direction because it is very important - light is only emitted from one side. Sometimes when these polygons are created they are facing the wrong direction, and it's up to you to make sure they point the right way. The only other thing worth pointing out is that the planes have been moved slightly away from the wall surfaces to make sure the light doesn't get blocked. Believe it or not, if a light is within a wall, it will not shine :)

Here are the palettes I will be modifying settings in to teach you about exposure:

FormZ's Display Options Palette showing the Maxwell Render camera settings.

FormZ's Materials Palette showing the Emitter material settings.

The Display Options palette controls the sensitivity of the sensor in the camera, and the Material Parameters allow me to adjust the intensity of the emitter light. You can see controls for f-stop, shutter speed, and ISO in the camera. The only thing worth talking about in this tutorial in the Material Parameters is the Power setting for the emitter.

Below are a series of images I made while changing the settings of the emitter material and/or camera settings for a simple scene in FormZ, but the settings would be the same in any application where you're using the Maxwell Render plugin. Each image has a description of what was changed to you can see what the progression was, and how each change affected the final outcome. As you'll see, small changes can make a big difference. Click through to see the progression.

The biggest difference that I'd like to point out is between the first and last image - the wattage of the emitter is exactly the same (100w), and the only difference is that the camera settings have been adjusted properly to compensate for the amount of light hitting the camera's sensor. Remember how I said earlier photography is all about light? As you can see, understanding these settings can be pretty important once you move beyond simple exterior sunlit scenes. The sun is very bright (a brilliant observation, I know), and the default settings are intended for that scenario. Interior lights are nowhere near the intensity of the sun, so the camera must be adjusted accordingly. It's also worth noting that the less light (artificial or natural) that you have in the scene, the more sensitive you'll need to make the settings. Like I said, there are no automatic scene modes in Maxwell (future feature maybe?) so in the mean time, it's a great thing to learn. With this knowledge, you are now worth more! 

I'd like to thanks Ben over at Pylon Technical for helping me learn this in the first place. Ben is also the guy who brought the Maxwell Render plugin to FormZ and Bonzai3d. Thanks Ben!

Bonus 

You can download the FormZ scene file here (v7), or the Maxwell Studio MXS file here if you'd like to play with it (right-click, download linked file...). You'll need the latest version of these programs (as of 2014-02-04) to use these files. 

I also have a three part series of quick tutorial videos that show you more about using emitter lights in FormZ/Bonzai3d and Maxwell.

Happy rendering!


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