Depth of Field Question

[Paul Forwood]

Hi I am still trying to get my mechanical model into a pleasing composition and at the moment I am working on the terrain. I have been playing with different camera angles and depth of field. I particularly wanted to use D.O.F to help give some atmospheric perspective but my results are less than satisfactory.

 

Here is an example with depth of field with just 4 passes:

[higginsdj]

The more passes you do the better the look. Each pass moves the fov slightly - its the same for motion blur. 9 passes seems to be a reasonable minimum.

 

Cheers

[Paul Forwood]

Here is another example with no D.O.F and a different point of view.

It has just occured to me that fog might be what I need to use for the aerial perspective. Advice required. Please!

[KenH]

Yes! Fog! It's built into the renderer, but I've never tried it. Looking good. I think you need at least 25 passes for good DoF.

[Paul Forwood]

Thanks, Ken.

I've got one rendering at the moment with 16 passes and fog. So far the preview is pitch black after 10 passes. Hmmm, somethings not right.

[JTalbotski]

Fog doesn't work, at least not on the Mac with v11.

 

Jim

 

Edit: I take that back, fog does work on the Mac. I was assuming the setting that I gave the camera would transfer to the final render panel, but it didn't. If I set fog in both places, it works. (Double check before posting, Jim!)

[Paul Forwood]

Okay, I've had some success after playing with the settings.

I didn't realise that fog takes it's colour from the camera's background colour. I also had the start and end settings far too close to the camera. The blend was so short that the fog was very close and dense.

Here are a couple of renders that are closer to what I was trying to achieve:

[Paul Forwood]

I'd like to see the camera's background colour available in the final render options to act as a reminder and to give you the option of setting it without having to abandon the filename that you may have just setup.

 

The previous fog was a pale blue and this one pushes it towards the red end of the spectrum. Violet.

[Paul Forwood]

Great! Now that I know how to play with fog I can get back to the landscape.

Thanks for your input, guys!

[JoshB]

http://www.hash.com/forums/index.php?showtopic=12070

 

Discussion about DOF. What I do is just set the camera to DOF. Set the back focus pane (anything behind this pane will be out of focus), the middle pane (anything in this pane is in focus), then the forward pane (anything in front of this pane will be out of focus). Select the camera, shitf click force keyframe, for all channels, and be sure to check the drivers to make sure it took. The other thing is if you turn multipass on you override the camera keys--therefore, have to set the distance by hand. If I'm not mistaken as you move the forward, middle, and back panes the numbers change for the camera DOF. Just, make sure that your render to file window has the same settings and you should be golden.

 

J

[Paul Forwood]

Thanks, Josh. I hope I can retain that until the next time I use DOF.

[steve392]

Thats a good looking image ,using the dof thing seems to give it an extra dimension ,I will have to learn that ,.Nice job Paul

[Paul Forwood]

Thanks, Steve, but just to put you straight about the effect ...

 

Although this thread started out as a question about depth of field I suddenly realised that I was using the wrong tool for the job. Depth of field is for creating those shots where you want to keep the subject of interest in sharp focus but throw everything else out of focus, just like with a real camera. (The first example above shows a render using DOF with just 4 passes.Not enough to do it justice.)

 

What I was actually trying to achieve was aerial perspective, where objects in the distance tend to fade and look more blue. In the real world it is caused by lower frequency light being lost over greater distances, leaving only the higher frequencies to reach the eyes. That is why when the sun goes down we get a sunset. The sun's rays are passing through more atmosphere, before reaching our eyes, than when the sun is directly above us, thus filtering out the colours at the lower end of the spectrum. I think i got that right.

 

Anyway, if you want to get that aerial perspective into your images try FOG. This thread should be called FOG.

 

Cheers

 

Edit: I just wanted to correct something that I stated earlier concerning the water looking transparent where the fog is. It turns out that when I turn Fog off the transparency remains so I think I must have altered a light or the water properties since that earlier render. So that's GOOD! Fog works well!

[jesshmusic]

Yeah, the water thing is weird.

Looks much better, though!

 

I believe that some fog should be in any scene (where there is atmosphere) because that is the way of the world. Even indoors, the air is not perfectly clear. The trick is how much fog to apply and what color to make it.

 

Keep up the good work and if you find a solutio to the water, do tell.

[jesshmusic]

I have a thought... if you are just wanting an atmospheric feel, not an actual fog, you could set your sky background to "Ignore Fog" and then blend the color and falloff so it looks ok.

 

This is the kind of look I have in the image in this post of a project i am working on:

 

http://www.hash.com/forums/index.php?showt...indpost&p=85248

[JoshB]

The way this effect was relayed to me is the following:

 

Air has water within it--humidity. Therefore, the further away an object is from you the more water is in between you and the object--therefore, it will tend to look blue--at noon. Further, depending on the level of humidity the level of this effect changes. That why painters will add blue to their pain the further back something is. Therefore, the more humidity the more the effect--with true fog being the steam like result.

 

As the sun rises and sets it is a prism effect. The atmosphere is the prism. As the sun is lower you get the reds and orange--as the sun goes up (well not really up but it's easier to explain this way)--the angle between the sun, the atmosphere, and our eye changes--which is why I said at noon. Because, depending on the time of day the blue may have purple, red, orange and for very short periods green and yellow.

 

DOF is a combination of the apeture within a camera and of course the actual focus mechanism. With a regular camera you can turn the apeture setting to fully open and more things in the background will be in focus (Ansel Adams loved open apeture settings). If you decrease the apeture opening you will get more contrast with the background (if you go to my site and look at the lilys image or the floating leaf you will see the results of a closed apeture).

 

As far as actual focus each lens has a range of focus where something is in or out of focus--which can be compensated for or adjusted with the apeture. But enough of that...

 

The image is coming along nicely. You might want to add some turbulance to the fog though since it looks like you are going more for true fog than just a depth effect given the distance between the windmills. And right now there is no variation instead it looks like a gel between the windmills.

 

J

[Paul Forwood]

you could set your sky background to "Ignore Fog" and then blend the color and falloff so it looks ok.

 

You've got some really cool stuff going on there, Jessmusic. I'm not sure how to do what you are suggesting with colour and falloff but I'll have a play and see what I can learn. Keep up the great work with your project. Bet you can hardly wait for that new G5!

 

You might want to add some turbulance to the fog though since it looks like you are going more for true fog than just a depth effect given the distance between the windmills

 

Josh, these images are just the results of experiments. I was actually looking for the aerial perspective affect but couldn't help playing with fog as fog to see how effective it is. Yes, that's a good suggestion for fog. For my current purposes I just need an almost imperseptible interpolation from crystal clarity to haze. I think I can use FOG happily enough now to achieve the results I'm looking for. Just need more time playing with it under various lighting conditions.

 

Cheers