DOF control

[Lupaz]

Hi everyone,

Does someone knows if its possible to control the "zone" of the image that blures with DOF near the focal point (I believe it's called distance range or something like that)?
I've attached 2 images. The first image is the original render directly from Max. The second one is edited in Photoshop; it is the first image with a layer over it with an image without DOF for the column on the front.
What I wanted was to keep that bluring on the column on the back while no bluring at all on the column on the front.





Thanks.

[Morbid Angel]

I believe the paramiter you need to adjust would be aparture width in vray camera. The lesser the value the more distance is in focus between your camera and your focal target distance.

[Lupaz]

The lesser the value the more distance is in focus between your camera and your focal target distance.

yes, but with a smaller number the bluring on the column on the back would be also smaller. I want to keep the aperture the way it is (same bluring for the column on the back).

[Da_elf]

thats the nature of a camera. if you increase the that focal range then the background pillar would naturally be less blured unless you moved it further away

[Ruairi]

Re: DOF control

Hi everyone,

Does someone knows if its possible to control the "zone" of the image that blures with DOF near the focal point (I believe it's called distance range or something like that)?
I've attached 2 images. The first image is the original render directly from Max. The second one is edited in Photoshop; it is the first image with a layer over it with an image without DOF for the column on the front.
What I wanted was to keep that bluring on the column on the back while no bluring at all on the column on the front.





Thanks.

the only way to do what you are asking is to do a render with and without DOF and do a masked blend between the 2 images in post, since it's not the way a real camera behaves...

[flipside]

Yeah but since the power of 3d is that it can overcome many real life limitations, I would also like to be able to control a zone where the image stays sharp.

[vlado]

Yeah but since the power of 3d is that it can overcome many real life limitations, I would also like to be able to control a zone where the image stays sharp.

Unfortunately, this cannot be done by raytracing. The effect that you want would mean that light rays do not travel in a straight line... which is the basic assumption behind raytracing If you want non-physical DOF effect, do it in post - there are many options in that regard.

Best regards,
Vlado

[Lupaz]

If you want non-physical DOF effect, do it in post - there are many options in that regard.

the only way to do what you are asking is to do a render with and without DOF and do a masked blend between the 2 images in post, since it's not the way a real camera behaves...

Ok, so what I did was the way to go.

thanks!

[Lupaz]

Drilling further down the problem

First of all late me state that I am a coworker of the person who started this thread.
Reading the responses on this thread, and the confusion generated, I just can't seem to avoid jumping in....


Depth of field is the range (not a point) along the lens distance axis where objects are in focus. It is a factor of the lens' focal distance (mm), and aperture.
The lower the focal distance (wide angle) the larger the depth of field. Also, the smaller the aperture (i.e. FStop 32), also the larger the depth of field.
Hence, we usually don't see out-of-focus objects in wide-angle shots. Also, if we use a larger aperture (i.e. FStop 2. we get more out of focus. Every photorapher nows that if you want to blurr the background of a portrait, use at least a 100mm lens.

Let me make clear that this is not only about "how much blurred" an object is, but also how wide, or long, the range is where everything is in focus.

I know that vRay lets you set the "how much blurr" (aperture), and the distance from the camera (focal dist.) where an object appears in focus.

The question still remains, then:
How do I control, based on the focal dist. as the center, how deep the range is (towards and moving away from the camera), where all objects are in focus?

It is my humble opinion that vRay does not seem to simulate a real camera correctly.
First, the aperture value is inverted, as i should get more depth of field with a lower apperture (an open diafragm) than with a bigger one (a closed diafragm).
Second, if vRay would simulate a real camera correctly, I should not be able to tell vRay "how much blurr i want". That would be computed based on the lens' focal range (mm, or field of view as it usually mentioned in CG), and the diafragm's aperture.
For those who like to tweak real-life things, let me say that at least, i should be given the option to let vRay compute this correctly, which I don't seem to have.

I have rendered images with vRay's DOF with wide-angle and telephoto cameras, and the range of objects in focus appears to be the same. this is simply not possible in real life.

regarding to vlado's comment, I am not a programmer, but I've certainly seen raytracers who could simmulate real cameras correctly.

The botom line is, I guess the problem was not well understood from the beginning.... and I just wanted to clarify the idea. I hope it helped.

Cristian.-

[RErender]

In the next release

the vray physical camera plugin,

What are the differences with the max camera ?

It simulates a real-world camera complete with a lens system. You can specify dimensions of the film, focal length of the lens, IOR and shape of the lens, f-stop etc. The main difference is that you can the image distortions that you get with a normal camera, complete with the accurate depth-of-field effect (e.g. the image is less blurred in the center than it is at the edges etc). V-Ray actually goes on to simulate the rays being refracted through the lens.

Best regards,
Vlado

[Da_elf]

and with vray camera we should have vray lensflare hehee. the rebirth of 3d lensflares!!!! whoo hooo

[Dynedain]

It is my humble opinion that vRay does not seem to simulate a real camera correctly.

That's because Vray is relying on Max's use of a Pinhole camera, instead of a camera with a lense.

Vlado has demoed a "real camera" for Vray that does have the features you're looking for. Hopefully we'll see a build including it soon.

[Buck]

Re: Drilling further down the problem

First, the aperture value is inverted, as i should get more depth of field with a lower apperture (an open diafragm) than with a bigger one (a closed diafragm).

I think Vray is using that parameter to say how large (in whatever units you are working in) the aperture opening is? If this is the case, then it's not inverted.

[Dschaga]

I have rendered images with vRay's DOF with wide-angle and telephoto cameras, and the range of objects in focus appears to be the same. this is simply not possible in real life.

this is not true... it'S somehow like a visible illusion because a telephoto will emphasise only DoF ..here some samples:
http://www.luminous-landscape.com/tutorials/dof2.shtml

or a thread on this forum:
( http://www.chaosgroup.com/forum/phpB...&highlight=dof )


maybe this thread about the doftoy script can help you find all the values for vray you would need:
http://www.chaosgroup.com/forum/phpB...&highlight=dof

i also think it should be possible to define the range(start /end distance) of the sharp area instead the focuspoint and fstop. ..its only a question of math.