Depth of field

[minimar]

I have been trying to do the depth of field efect and it works nicely, well done. But when i switch to meters from inches i just cant get any efect at all can you explain me the aperture number? i have been putting even 8000 and it did nothing. One again when i switch it to inches everithing ok even with number 25. I am not overriding the focal distance. In the manual it is said that
bigger number means more efect. What to change and how to calculate in metersunits the aperture number?

many thanx
martin

[dalomar_cg]

Re: Depth of field

well the aperture value in the camera settings is the physical size of the aperture in scene units. Meaning that when you change units the size of the aperture will change even though the value stays the same (this is what your experiencing). The main issue is that most people typically set the size of their aperture via the F-Stop value, which is not the same as the actual size of the aperture. The formula is actually pretty simple just the focal length (I don't know what the SU default value is, but probably around 50mm) divided by the desired aperture (so that would be whatever you would normally set in the camera; i.e. 4,5.6,8,12,16,22). Once you convert the focal length to whatever units your in, just do the calculations and you should get the proper size for the aperture in your scene units.

I know this is a little long winded, but its not too bad. There was a post that had a bunch of info on DOF set up. I can't remember if it was from Jorge (the guy who wrote the SU specific parts of the manual) or someone else, but if I remember correctly it closely resembled whats in the manual. I'll see if I can dig it up and put up the link

[minimar]

Re: Depth of field

sorry may be i am a completly an .....
but it is not working that you said. I show on the example
1. there is a file which have been provided together with the manual its name is chairs_dof.skp
2. the scene is set up in the inches units, distance between object and camera is 67' and something== 800 inch
parameters are: physical camera on
shutter speed 125
OFL 200mm == 7,87 inch
F-number 12
ISO 125
DOF on
aperture 25
OFD 800

you say that usual number for aperture in camera is 7,87 / 25 = 0,318 is that correct?
if it is correct then what should be the aperture number if i change units to mm
then for the same scene is the distane between object and camera 20500 mm
parametrs for the physical camera same (?)
DOF on
aperture 200 / 0,318 = 628 (?)
OFD 20 500

This setting is not giving out the same picture as the scene with inch. I am doing something wrong but what???

thanx
Martin

[minimar]

Re: Depth of field

and another one

is the f-stop in physical camera the same parameter (i know the value is not) by meaning as aperture??
if yes. Which is stronger when they are both on?

martin

[dalomar_cg]

Re: Depth of field

Well...Depth of Field is not supported when using the physical camera, so thats probably why your not seeing any DOF while using the physical camera. So if you switch back to the standard camera then you should see DOF. As far as the f-stop/aperture settings and math I think you might be a little confused, so here's some clarification.

First off the focal length is basically the field of view of the camera. So smaller numbers like 18mm-28mm have a very wide field of view(like a wide angle lense), where 90mm and above are going to have a very narrow field of view (like a telephoto lense). Although this is almost always measured in millimeters, for the purpose of finding the correct DOF it is necessary that this number be in scene units.

The Focal distance is the actual point of focus of the camera. So that would be the distance from the camera to the object that you want to be in focus. Although this is important, the aperture/f-stop settings do not reference this value.

F-Stop is the value that is familiar to photographers, and certain f-stops are associated with different DOF affects. Lower F-Stop numbers (from 1 to ~6 or 7) have a shallow DOF, thus leading to allot of blurriness. Higher F-stop numbers (from ~14-32) will give a wider depth of field which allows alot of objects to be in focus.

The Aperture is the physical size of the opening of the camera. This is the value that has to be in real world units. Since most people are more comfortable setting the F-stop value to choose the amount of DOF, the f-stop value needs to be translated into the correct aperture value. This is done through the formula that I told you before, with the Focal Length(in scene units) being divided by the desired f-stop value. This will give you the size of the aperture in scene units.

Currently you will have to set the aperture value in the DOF settings. Once the DOF is enabled for the physical camera, it will produce the correct depth of field based on the f-stop value in the Physical camera settings. Hope this clarifies things for you.

[Free Agent_cg]

Re: Depth of field

is there any way of relating sketchups field of view to vray's focal length, like a ratio or something, like if i set vray's focal length to 20 what would set in sketchup's field of view to see what vray will render... sorry if this is a stupid question, its kinda bothering me...

[dalomar_cg]

Re: Depth of field

If you look really closely, when ever you adjust your field of view, in the corner there will be the numeric value of the focal length. You can keep an eye on that to make sure they match.

[paulj]

Re: Depth of field

Quote Dalomar:

Well...Depth of Field is not supported when using the physical camera, so thats probably why your not seeing any DOF while using the physical camera. So if you switch back to the standard camera then you should see DOF.

I'd like to add depth of field to some of my exterior renderings with vray sun and sky on....any way to do this???? I'm using a physical camera to mangage the brightness but this conflicts with DOF???

Any help please....thanks!

[howardhong_cg]

Re: Depth of field

there's certain kind of bug in DOF.

METERs can not be apply to DOF.

[Toams]

Re: Depth of field

Quote Dalomar:

I'd like to add depth of field to some of my exterior renderings with vray sun and sky on....any way to do this???? I'm using a physical camera to mangage the brightness but this conflicts with DOF???

I do the same, but have problems (no DOF even by F-numb. 1. as well, so please, small help would be useful...

[dalomar_cg]

Re: Depth of field

Well if you'd like DOF and the Sun, then you'll have to decrease the intensity of the sun. With the regular camera the intensity of the sun is like 380, so 1/380 or about .003 should be a good sun intensity to work with the regular camera.

Once you've got the sun working, then you'll have to worry about setting the aperture value and the focal distance. There was a post by Jorge (here it is) a while back about setting up DOF and I recommend you take a look over it (I believe it is in the VFSU training manual as well). After you've found the focal distance for where you want to be sharp then you'll need to find the right aperture settings (this is not the F-stop number, but the physical size of the opening (with bigger being more blurring)). For aperture at least, I'd recommend doing tests at a small resolution starting with a small aperture value and increase it til you get what you're after.

[paulj]

Re: Depth of field

dalomar,

I've been trying to decrease the intensity of the sun by manipulating the multiplier...but I haven't been successful. Is this the correct way to decrease sun intensity???

[dalomar_cg]

Re: Depth of field

Make sure you are doing this in the sun intensity multiplier in the Sky settings, not the Texture multiplier.

Beyond that, the approximate multiplier setting should be around 1/380, so about .002 to .003

[paulj]

Re: Depth of field

you were right i was changing the wrong multipliers. I was changing the one next to the gi(skylight) color swatch and the one under the "common" bracket where i selected "sky". When I used the sun intensity multiplier, it worked beautifully! I ended up with a setting of .00006

could you explain what the other multipliers are for?

thanks for your help dalomar!

[dalomar_cg]

Re: Depth of field

I'm not sure exactly what you mean, so I'll just answer both of the possible questions...

The multiplier out in the Environment rollout is really only active when you don't have anything mapped (ie just a color). The Texture Editor multiplier multiplies the texture as a whole, so this would be used for small adjustments to lighten or darken a texture, or in the case of an HDR, increase its brightness to work with the physical camera. The issue that you came to before was that the sky itself was being decreased as the texture, but the intensity that the sun references remained the same, thus keeping everything just as bright.

As far as all the other sun parameters a good place to look would be on Spot3d...You also might want to look at the examples too

http://www.spot3d.com/vray/help/150R...parameters_sun