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How can I get accurate DOF calculation?

nickalamannickalaman Posts: 196
in Daz Studio Discussion

Any one knw how to get accuaret DOF in studio with Iray, As a photographer, I'm quite famiiar with what for exmaple a 70mm lens looks like at an aperature of 2.8. at  focal distance of 5ft on  a full frame camera.. When I dial those number in studio, I'm not even close, the back ground is blown way out of focus, An aperature of about 20 is closer to what really is 2.8. Octane does this pretty well, is there a scriot or somethihng that can help figure this out.

 

thanks

 

 

Comments

  • SickleYieldSickleYield Posts: 7,644

    The easiest way is to select the camera, go to the camera settings, and turn DOF to "ON."  You need to  look through a different camera such as the Perspective view (and you must have created a new camera, not be using one of the default loading directional cams).  Now you should see the two DOF planes in the scene.  When you drag the Focal Distance value it will move the two planes, and whatever is between those planes will be in focus.  Changing the F-stop changes the distance between the planes.  It's still probably not accurate to a camera, but it does let you control the focus.

  • Richard HaseltineRichard Haseltine Posts: 102,424

    This may give sime insight into what is happening with camera values http://docs.daz3d.com/doku.php/public/software/dazstudio/4/referenceguide/scripting/api_reference/samples/rendering/calculate_fov/start

  • nickalamannickalaman Posts: 196

    Thanks SickleYield for the exlanation, but how to focus the camera I figured out with a bit of work, I've actually gotten quite proficent with it, I found a script that autofocus the camera, I installed it on my toolbar, and now the camera focus almost as fast as Octane's camera system. (it works by creating null object and pareting it to the head, it then calculates the distance, between the null and the camera, if any one would like it just google Set Focal Distance By cwichura.)

     

    Back to my original topic, Thanks Richard I did look at the comments, and now I'm pretty sure it's a bug.

     

    Here are a few examples that demonstrate it, in all cases the frame wifth is 35mm, and a focal length of 70mm. the only thing that changes is the fstop. The first image at fstop 2.8 has way too much bokeh, i wish my camer could do that at an aperature of 2.8, the second image at an fstop of 28 looks closer to what it should be, and the last one at fstop 99 is infinite focus. 

    It would be nice to figure out who to calulate the real fstop. if fstop 28 is equal to a real fstop 2.8 then I know i just have to multiply by 10. When you are looking for reality in your images, getting the camera to behave like a real camera should make our renders even more believable.

     

    Nick

     

    f stop 2.8.jpg
    773 x 1163 - 607K
    f stop 28.jpg
    773 x 1163 - 627K
  • nickalamannickalaman Posts: 196

    seond image

    fstop 99.jpg
    773 x 1163 - 664K
  • ToborTobor Posts: 2,300

    Be aware that as implemented in D|S, Iray itself has no DOF controls. The tone mapping tab in the render panel is for manipulating the lighting curves in a scene. Even the shutter speed dial has no photographically-applied effect (e.g. camera blur), even though Iray itself supports blur. Some Iray things just aren't implemented in D|S.

    While the D|S DOF camera controls are mathematically based, they are not based on real-life lenses. So while Iray may be a physically-based renderer, Iray is not involved in these calculations.

    Whether or not you can apply a simple factor to calculate DOF I'm not sure. It would be great is f/2.8->f/28, but I've never found it to be that simple. So instead I've always just done it visually, typically with a "focus set" camera that is parented at 90 degrees to the main camera.. 

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