Good average exposure settings for moblur vraycam - archviz

[Morne]

Hi all

Whats a good average setting for vraycam exposure on a sunny day for vraycam that could work both for a flyover, as well as walking speed on the ground?

[maxedesa]

I'm interested in learning this as well for movie cam.
I understand traditional 35mm SLRs but never used a "real" movie camera. Looking out the window I know I could go outside and get a good exposure with f/11 @ 250. Not sure where to start for the Movie Cam settings (shutter angle, etc.).

Caleb

[kriscabrera15]

Well I think when u are working in 3d or in any case it's just a matter of what settings look good so maybe just jump in a mess around with some settings every scene will be different depending on lights and all

[tashko.zashev]

As far as i know, with real movie cameras its very tricky to adapt the desired motion blur effect with the available F-stop range supported by the camera lens.
This could be very well controlled by using the V-Ray physical camera settings. Depending on the on the look you want to achieve, slow shutter speed for more smoothed motion with less details or very fast shutter speed for sharp images.
When you are happy with the result, you can use the camera ISO parameter to adjust/animate the exposure, for cases when the camera path crosses between outdoor and indoor area. Probably someone can share some other thoughts.

[Morne]

I've been getting some good results with a heli animation flying low over terrain. In this case for the rotor I had to push F number to 45, shutter 500 and ISO 1000 Looks great

This settings however suck on another exterior (this time archviz) with many trees and grass, almost asif to moblur is a bit much. F 22, shutter 250, ISO 400 seems ok for this render, although it sounds a bit whack for "real world" values...

[Rens]

There's only one setting that controls motion blur in film cameras, and that's the shutter angle. Everything else is for DOF, brightness and noise level.

Standard motion blur is 180 degrees. Smaller/shorter is more shuttery, wider/longer is smoother.

The shutter angle controls the amount of time the frame is lit for. 180 degrees is half of the time, so for 24 fps film that would be 1/48th of a second. The other 1/48th of a second the film isn't lit. Basically this means that you only see objects travel half the distance they actually cover each frame.

[maxedesa]

Thanks, that helps.

As to the What Looks Good vs. Real issue - On one hand I agree, we are just making pictures, and it isn't real. But as far as I know Vray is based in real physics. If you understand the presumptions underlining the application I think you'll have a better grasp of it's usefulness and more ease in use.

[joconnell]

Exposure is far too subjective really and with movie cameras they have lenses that smoothly change from one aperture to another so if you go from an open, brightly lit area to a shadowy area you can open up or close down the lens so that your exposure looks good at all stages.

One thing that I have a habit of doing is making my colour values too bright or too dark. This image has a rough scale showing what brightness / luminance values a few different materials hover about (https://www.fxguide.com/wp-content/u...edo_values.jpg) and you can see that the blacks and whites are a bit further off the extremes we might normally go for. We could be using white values that are a bit too bright and thus reflecting too much GI, likewise our darks are sucking out a lot of light. Vlado's mentioned this a few times.

There's kind of no good average exposure, as it depends on how dark your ground is, how bright your sky is, are you in a shadowed / sun sheltered area or right out in the open?

[Morne]

There's kind of no good average exposure, as it depends on how dark your ground is, how bright your sky is, are you in a shadowed / sun sheltered area or right out in the open?

I'm out in the open in sun and I'm NOT using movie cam

[joconnell]

That's all fine, but are you on dark grass? On white concrete, on bright sand? Your exposure is largely to do with the colour and brightness of the objects around you and what you want to draw attention to so there's no right answer, or even a good setting as such, it's totally scene dependant.

There was an old rule that photographers used in the film days called the sunny 16 rule. You'd set your lens to f/16 and then whatever iso speed your film was, you'd also set your shutter speed to that so if you were using iso 200 film, you'd end up using f16 and 1/200 of a second as your shutter. In cg however there's a few other variables since you can control the brightness of the sky. For photography you can't control the brightness of the sky or the brightness of the object you're trying to photograph so you've to use your camera settings to control everything - in some ways having the other two factors out of your control is slightly freeing since there're less factors.

With vray bits you've control over everything so you can either lock your camera settings and then use your lights to control your end exposure, or you could rather stupidly change all your materials to control your end exposure, or use any of the three camera controls that'll control brightness. The main decision is if you want to use in camera depth of field or motion blur as if so, it'll mean one of the controls has to be at an exact value to get the look you want. If you want shallow focus then you might find that you have to use a specific f number which will in turn over cook your render so you'll have to lower your shutter speed. Likewise if you want to match the motion blur of shot footage, you'll likely need to use a specific shutter speed which might under or over expose your scene. If there's no creative / look aspect to what you're doing, then it doesn't matter which of those controls you decided to tweak. For the least destructive of them though perhaps stick with iso? It won't change the look of your render in focus or motion blur so perhaps it's the safest to go with?

As with Bobby / glorybound, get yourself a cheap canon dslr and start shooting stuff yourself to see what differences your aperture and shutter speed are making.

[Rens]

Just to explain my previous comment a bit better; if you're looking for a standard film look motion blur you'll have to set your shutter angle to 180 degrees for the movie cam. If you're using the photo cam set your shutter speed to 1/48th for 24 fps and 1/60th for 30 fps. Which is also half the time of one frame.

Then adjust your f-stop so you get the depth of field you want.

Only then change the ISO to get the correct image brightness you want.

With real cameras you'll obviously run into constraints pretty quickly, but of course this is CG and the ISO speed doesn't affect noise level, render speed does.

As joconnell mentioned, setting your material to correct colour values is very, very important if you're going for realism.
In reality only lights and cameras are variable, material properties are constant.