View Full Version : DOF settings?

04-03-2008, 03:51 PM
Just curious what I'm doing wrong. Granted, I know little about how real cameras work, but specifically for LW, how do the grid size, camera focal length, DOF focal distance and F stop relate to each other?

I'm trying to get a table in focus in a room, but I'd like the far wall and the things against it to be more blurry. I can get the table in focus, but if there's any blurriness in the background it's hardly noticeable. I'd like a more pronounced effect. Either that or I can get the background blur I want, but then my table is blurred too, even though it's very much closer to the camera.

04-03-2008, 04:11 PM
I did read what the manual has to say about it (all 7 or so short paragraphs 8~ ), and reading that you'd think it's no big deal, but it doesn't seem to be working as they describe it.
And then there's the question of how to get perfect antialiasing for it, but I'll get to that later....

04-03-2008, 09:39 PM
No, please, don't everybody reply at once, I need time to take this all in. ;)

I've done a bunch of experimenting over the last several hours and have had reasonable, albeit probably not accurate, results.
One thing I can say is I don't think the focus circle thing is particularly intuitive. It increases diameter as the focal distance increases, but there doesn't seem to be a way to gauge "falloff" within it or without.
I mean, according to the manual the focus circle is the part of the render which will be in perfect focus, but it's not like focus just ends at the edge of the sphere of influence. There's a falloff. Is that what the f-stop determines?
Is there a way to calculate a specific effect knowing your grid size, object size, focal length, and distances between the camera and everything else, or is it just guesswork and test rendering?
The OGL preview is pretty cool, but doesn't seem to be very accurate.

04-03-2008, 10:12 PM

what version of lightwave are you using?

The first thing, make sure that your models are to scale, because the dof is on a real world scale, ie if you model is say 10 mm high you will probably get a higher amount of the dof effect, or you model is say 900 metres you get less of a dof afect, also the distance of the object to the cam is going to determin how much dof you are going to get, realy close more dof, realy far away less dof.

If you use your zoom with your cam your going to get more dof aswel.

The way I work is that I adjust the focal first and then adjust the fstop, and and watch the area that I wont focus on until the pixels become sharp, so that they look realy pixelated.

I genraly don't use a fstop value less than one, if you have to use more than that then the model scale could be incorect.

I Hope this helps.

04-03-2008, 10:34 PM
Thank you Mat, I'll check into that. I figured scale should be all relative, but you're saying the best way to predictable results is to build to real world scale?
I really hadn't thought of that, but I guess it makes sense.
LW 9.3.1, btw.

3D Kiwi
04-03-2008, 10:52 PM
Dont forget to use the ogl dof display, that way you cant set up your dof in realtime.

04-03-2008, 11:13 PM
Dont forget to use the ogl dof display, that way you cant set up your dof in realtime.

Yeah, I see that now. I had already posted earlier that it doesn't seem to be very accurate, but what it is, is very subtle.
Comparing the OGL DOF preview to what I end up with, in retrospect is actually fairly accurate. It seems it just takes some getting used to, being that it's so easy to miss subtle changes.

04-08-2008, 05:21 PM
The scale thing is spot on. Lightwave works best when everything is to scale. Plus, as you build/accumulate models, they can easily interchange in and out of different scenes. If you are in top view, you can adjust the Focal Distance and see a dotted circle that expands/contracts based on your FD setting. Also, I have found that I have to go below 1.0 to start seeing the effect I want - depending on the scene. Requires some nice antialiasing to smooth it out.

04-08-2008, 10:11 PM
Have a read (http://www.lightwiki.com/Interactive_Depth_of_Field)


04-11-2008, 05:37 PM
Very cool, BeeVee, thanks. :)