So I'm wondering if anyone can help me better understand the depth of field function.  My questions concern the nature of the options "focal length" and "lens radius".  What exactly do they mean?  Also, what does it mean by "set to current selection".  I assume this has to do with whatever object or objects are selected at the time.  Also, I'm trying to figure out how to make background objects blurred.

Please help if you can....

Depth of Field sets out to simulate camera focus effects. For instance in macro photography u'll see the photographer has its main subject (for instance an insect) quite sharp in view, yet the background has all blurred because its not in focus.

I think focal length is the distance from the camera to the point where the focus is perfectly sharp.

Lens radius would probably control how fast objects get blurry when they are further away from the point where objects are in perfect focus.

Set to current selection adapts the DOF settings to such extend that the currently selected objects in your bryce scene are in that perfect focus area.

Ive experimented with DOF only a few times. The main reason is because the render options only allow DOF to be ticked if you have "premium" render quality ticked, which makes render times VERY slow. So unless you get it right 1st time, its a nightmare tweaking it.

What I did is create a very basic scene 320x240 with a flat grey sky & delete the ground plane.
Then add about 20 cubes with default mats and just randomly placing all of them into the distance. (only about as far as the end of the ground plane would be).
Then make 1 cube in the foreground (make it a different colour if you want) and whilst its selected, click the "set to current selection" button.

you could put a few cubes in the foreground too, but i havent really tried that yet.

This way, the render times arent too painful and you can see reasonably fast results whilst experimenting. hope this helps.

I very much appreciate your help....however, there must be someone out there who knows a little more about this, or knows some of the tricks....I'm just trying to make the most distant objects in a picture blurry, while retaining the clarity of the other objects.  I tried choosing all objects save the ones I wanted blurry, then using the "set to current selection", but then everything became blurry.  Also, it seems once you change the numbers they stay that way....is there a way to reset them.  I'm having a bit of trouble explaining myself about this subject, but any information is helpful.

The bigger the lens radius number the smaller the depth of field. By this I mean things get out of focus faster the further you are from the current focal point. If you set the radius to 0.1 things will be more in focus than if the radius was 1.

Adding some more input to the knowledgeable ones above me.

I just put some quick on together. Rays Per Pixel effect the quality and render time. Lens Radius will also play into quality. It looks to me any thing over .50 starts to get destroyed. A setting of 10 will obliterate all except for Object selected. The rays per pixel set at 4 render time was 8 seconds. The rays per pixel set at 256 render time was up to 8:43 minutes and that was with ground material not casting shadows.

 

Resetting the numbers by typing in the box the number you would like. If you changed the lens Radius to ".15" "decimal point Fifteen" and didn’t get the decimal point the Lens Radius is way high "15" " fifteen" that would make everything blurry.

 

If a object "A" is to be in focus and Object "C" is to be out of focus this would be True.

If object "A" Is closer to the camera and you would like to include Object "B" too the In Focus. If object "B" is Farther away from the camera Than Object "A" Bryce will Give you a Average Focal length of the two Objects. Bryce will attempt to focal length on the space between "A"and "B" Giving a "False" Focal Length. The only way I can think that the work around would be is if Bryce had a Start and End Focal length.

You can always try Depth of Field Generator Pro by Richard Rosen man and Martin Vicanek . It will give a lot more control over the depth of field. http://www.dofpro.com/index.htm

I played with this a while ago as well, and after numerous attempts I was never really satisfied with the results that Bryce gave me. I found it much easier, faster, and got better results if I wanted to use DOF in a render  by rendering seperate masks in Bryce. I would them combine them in postwork using blur effects in an image editing program such as Paintshop Pro or Photoshop. Depth of field generator pro looks promising though, I've never seen that one before.

Attached Link: http://www.renderosity.com/mod/gallery/index.php?image_id=1402723

In real-world photography, depth of field refers to a "zone of sharpness" that extends in front of and behind the point you have focussed on and can be very narrow, where only your subject, or part of it, is in focus, or very wide where everything in the picture is sharp and in focus.  The closer you get to a subject the narrower this zone gets too.

The two most obvious controls you have over depth of field are lens focal length and aperture.

The focal length of the lens, briefly, can be termed the "size" of the lens, i.e. (say) 28mm or 500mm; 28mm is a wide angle lens, 500mm is a telephoto lens.  It refers to the distance behind the lens (in mm) at which the lens focuses the image it is being pointed at.  The longer the lens, the less depth of field you get, conversely, the wider the lens, the more depth of field you get..
The aperture is what you control with the aperture ring and is usually referred to by it's "f-stop"...an f-stop of 1.2 is wide open, and one of 64 is tiny.  The aperture's primary function is to control how much light gets through the lens.  The wider your f-stop, the less depth of field you have ; conversley, the smaller the f-stop, the greater the depth of field..
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Bryce attempts so simulate this with it's Lens Radius setting; the larger the number, the more blurred your background will become.

The picture on the left is an unretouched render done with Premium Antialiasing and depth of field (and soft shadows!) - link to the full-sized image is above.

The settings were:

Lens Radius 0.07
Focal Length 56.50

The one on the right has a lens radius of 1.0, just to show the effect (couldn't wait for it anti-alias, though!)

Hope this helps; I used to be a photographer and darkroom technician.

Quote - Ive experimented with DOF only a few times. The main reason is because the render options only allow DOF to be ticked if you have "premium" render quality ticked, which makes render times VERY slow.

Thats not entirely true.. premium settings arent slow per sé. If you want to just play around with DOF you will need to turn off all premium effects except DOF, which will avoid using processing power for unneeded effects.
Also you can easily lower the rpp to 4 to significantly speed up render times. the results are grainy but that doesnt matter for pre-view renders.
Once u have your DOF effect right, you can plop-render the blurriest area's for little pieces at 32rpp and see if its sufficiently noiseless. If it looks good, render ur image at 32rpp. If it doesnt look good, go to 64rpp with plop-render, and see if the noise has reduced enough then. usually you dont need to go further then 64rpp.
Ofcourse 32 and 64 rpp takes long but thats why u dont use them while setting up your DOF, and why u test with plop render 1st when trying to decide on the most effective rpp settings.
Bryce rendering is all about managing performance :-) The render might be slow, but there's loads of settings to speed up ur workflow untill ur at that final render.

very true Ray. One tripping point for most using DOF is for it to be too strong.In photography, you usually have a slight DOF unles you are shootng extreme closeups or have an object too close to the lens. Then the effect should be strong!

quick tip.. select all objects you want in  focus ..multi-select then go to the set current selection and it does it automatically. Groups or just multiple objects, yes there will be tweaking involved:-P It hasn't changed since this image: http://www.phase2.net/claygraphics/Marbles.html
Old school junk:-)

when you multiselect like that, doen't bryce use the geometric centre of the selected objects as the center of focus (focal length in this case). If so, then the objects are widely scattered in terms of distance from the camera, the outlying or close will still be blurred depending on the lens radius setting.

I use an invisible sphere to set the focal point where I want it to be.

I do that as well.

I generally apply DoF in post work .

I've used the bryce DoF using the select an object method and it's not bad, but to get good quality blur you need the higher rpp or to go up in res for the overall render. I just find it quicker to render the image, render an object mask and use the object mask to contol the blur in the GIMP.....

Thank you very much, everyone, for all your help.  You've helped me immensely.