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mister3d
10-22-2012, 03:26 PM
So I'm trying to understand how I could easily use real-life settings for Vray camera.

ISO - 100-200 for daylight, 400 for overcast, 800-1600 inside, and 3200 in the night.

Shutter speed - like in still camera perhaps...

Film gate - 35 mm, 135 mm. I'm not sure if it affects the depth of field? What other types of common film could be used? Though in Vray it says horizontal length in milimeters, whereas here you get diagonals http://www.filmcentre.co.uk/image.html Anyway I guess the majority uses 35 mm.

Then realistic focal length for realistic field of view I think is important to get correct results (correct field of view) , so using real-world lenses focal length makes sense.

I'm not sure if realistic F-number is important, as it's barely perceivable if it's correct or not (if there's such a thing?). Though I might be wrong.

Then using exposure I'm not sure, as from one side it adds some more work to set, and your lights should have different crazy numbers. I mostly didn't use it, though I'm thinking about getting used to this for easier exposure control. I know in archviz they use real-life light units.

Exposure forces you to use the triangle of exposure. So I guess first you set your desired DOF if you need it, then you compensate it with shutter speed and ISO, which should be realistic for conditions. Or, you first set your motion blur if you need it, and compensate it with ISO and F-number (though in Vray you can turn off DOF effect, which is nice though not realistic... oh well, the times of time-free DOF and MB are yet to come). Though it should be easy, as in 3d your hands are not shaking.

FranciscoSCN
10-22-2012, 06:28 PM
Just had this conversation with a coleague that uses a physical camera and I told him that I don't really see the advantage of working with one. It's nice to deal with real photographic terms, but in a practical sense, I really don't like it. If a light is blowing up, then I change the value of that light, not the exposure of the camera. Of course, if people use fixed light values as you said, I can see why changing exposure would be used, but even then, I would rather render out different light passes and deal with it in comp rather than changing the look of the whole scene.

And for the DOF and MB effects, I can render a zdepth and vector passes, very fast. Having those "hardcoded" into the physical camera, would be a pain to render out for comp.

mister3d
10-22-2012, 06:34 PM
FranciscoSCN, thank you for the reply. I think you have a strong point on this. I do this the way you do, and I just thought how I could implement my knowledge of photography. But I was in situation, when having not realistic field of view caused not believable results, so I think sticking to correct film gate and focal length still may matter. Though there's a zoom, but still. Somehow I still managed to make it look wrong back then in this regard. I think I just did impossible field of view for macro shooting.
I think DOF also may be wrong if overdone sometimes, if you don't use the realistic settings. What do you think?

FranciscoSCN
10-22-2012, 06:52 PM
What do you mean by realistic field of view? Isn't that just an artistic choice? I work with Maya and I'd say the default cameras do a good job on displaying what I want, how I want it. They have a "Focal length" option as well as the "Field of view" one and they even match real life settings (50mm =~ 39,6 fov for 35mm film). If it's easier for you to understand things in photographic terms, then by all means, do it. Just don't let it justify loss of creative control over your work.

As for the exagerated use of lack of DOF effect, it does happen I guess. The point is, losing control to justify hardcore physical reality is not worth it in my book. Sure, maybe you don't have 100% accurate results if you do a zdepth pass and blur it in comp, but that doesn't matter. What matters is that you can make it believable enough to convince viewers.

mister3d
10-22-2012, 07:31 PM
What do you mean by realistic field of view? Isn't that just an artistic choice? I work with Maya and I'd say the default cameras do a good job on displaying what I want, how I want it. They have a "Focal length" option as well as the "Field of view" one and they even match real life settings (50mm =~ 39,6 fov for 35mm film). If it's easier for you to understand things in photographic terms, then by all means, do it. Just don't let it justify loss of creative control over your work.
3ds max camera has it too, but not Vray camera though. I think, sometimes it doesn't matter, but sometimes it does. Maybe in rare occasions. For example, if you use a 15 mm focal length and have a very big blur of depth of field, will it look correct? I think such things still may happen. Sometimes, I think you can and should consciously break those rules, but consciously is the key word here. Once again, you\re right it's not the most important tying definitely. But sometimes it does look wrong.


As for the exagerated use of lack of DOF effect, it does happen I guess. The point is, losing control to justify hardcore physical reality is not worth it in my book. Sure, maybe you don't have 100% accurate results if you do a zdepth pass and blur it in comp, but that doesn't matter. What matters is that you can make it believable enough to convince viewers.

I think sticking to more or less realistic settings is more safe, rather than doing insane settings, which are definitely not possible. I tstill have to think about this more, and thank you for those thoughts.

Panupat
10-23-2012, 06:42 AM
For Vray camera you have a lot of freedom. Usually there are only 2 attributes that you should think about

shutter speed - for the amount of motion blur you want
f stop - for the amount of dept of field you want.

That's assuming you want to do motion blur and DoF right in Vray.

After that you adjust ISO to get the exposure right. The advantage over real film is that, no matter what ISO you set, it won't give you film grains.

If you're doing neither motion blur or DoF, then it won't matter at all which attributes you adjust to get the right exposure.

What you need to be aware of, is that your shutter speed shouldn't be longer than your frame rate. For example, if your scene is 24 fps, setting your shutter speed to something like 1 second will give you weird results.

If you use movie camera mode, the shutter speed is taken care for you.

mister3d
10-24-2012, 10:37 AM
Thank you Panupat!

What you need to be aware of, is that your shutter speed shouldn't be longer than your frame rate. For example, if your scene is 24 fps, setting your shutter speed to something like 1 second will give you weird results.

I think you can make it longer if for a still image (not animation). And even for animation, you can make it longer as a special effect, though it won't be realistic. Then I also read you have a longer shutter open if shooting is in darkness, so more motion blur occurs.

CHRiTTeR
10-24-2012, 05:56 PM
What you need to be aware of, is that your shutter speed shouldn't be longer than your frame rate. For example, if your scene is 24 fps, setting your shutter speed to something like 1 second will give you weird results.

If you are talking about what i think you are talking about:
You can fix that by upping the motion blur's motion sampling in the render dialog's camera options

mister3d
10-25-2012, 06:46 AM
If you are talking about what i think you are talking about:
You can fix that by upping the motion blur's motion sampling in the render dialog's camera options
I think he means "shutter open for 1 second for a film camera means open all the time=impossible in real life". Or, that shutter speed should be minimum of the number of frames per second. Or, it'd be better 1\48 of a second for example if you want half the time. Damn, I'm slow with numbers.

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