Question about Focus Distance Guide



  • I have a technical question about how Poser's Focus Distance Guide,
    which is ambiguous in user's guide.

    Suppose that the cross hair of the guide is set to a point of distance 10,
    then which of following points are in focus?

    1. Like real world photography, points whose distance from camera lens is 10.

      In this case, if cross hair is set to the waist of a standing person,
      then face of the person can be out of focus (depending on F-stop value).

    2. Points whose distance (length of normal) to the screen plane (which has camera lens) is 10.



  • what might help you visualize where it will focus is by loading up a cube and parenting this to the camera. Make sure it is rotated so one face is directly facing the camera. Once you have the cube rotated and parented to the camera you can use ZTran on it to move the cube closer or further from the camera and have the face intersect with the object you want in focus. Just unchech visibility for the cube when you want to render.



  • Case 1. DoF works like a real world camera so far as blur goes, but is independent of light intensity (unlike a real world camera).
    I'd attach a tutorial I did for Poser DoF but I don't have the privileges. I gave it to someone else either on this forum or at rendo, but I can't find it on either. Marvelous search engines.

    It seems we are condemned to ever re-invent the wheel...



  • Thank you for replies.

    Two pictures below shows what I set the guide to a point I guessed to have the same distance
    from camera as the figures eyes, and actual rendered image with 50mm F 1.8.

    As you can see eyes are out of focus.

    In order to focus the eyes, isn't there any ways to directly measure distance between average point of eyes and camera, or should I introduce a similar approach as ghostship's one such as placing a globe (centered to the camera), change its radius gradually so that it touches the point to be focused?

    0_1494939057802_Portrait_D_preview.jpg

    0_1494939067804_Portrait_D_half.png



  • You could try this script by Structure from Renderosity. It lets you select the actor to be in focus. That's what I use.

    https://www.renderosity.com/mod/freestuff/easy-dof-for-poser-updated-for-p11-/76709


  • Poser Ambassadors

    @golgo17
    It looks to me like you went out of your way to pick the wrong depth. You turned the torso, creating a situation where the figure's right armpit is clearly behind the face, and then you set the depth on the armpit. Turn your own head to the left and then ask yourself where your chin is. It's over your left armpit, not your right.

    But in any case, assuming the situation is such that I'm not able to mentally project the face onto the torso, I do this:

    1. I use Dolly camera, not one that orbits.
    2. I tilt the dolly camera up to point to the face
    3. I use the DoF distance guide directly on the eye
    4. I tilt the dolly camera back down to the torso

    Tilting the dolly camera doesn't move it, so the measured distance to the eye is not altered.
    0_1494944259281_upload-e3c75bae-ddda-4249-9c54-48176675c34c

    However, now that you have me looking, I'm beginning to think the focal plane is actually a plane.

    I will have to do some more experiments.

    When i changed the fstop to .1, creating an extremely shallow in-focus field, the face is not in focus after tilting back down.
    0_1494944532852_upload-5e887d35-abe5-4a5b-995d-0db466ad74aa

    0_1494944462774_upload-2b3f93b8-713a-4807-8b88-d8fdfac26e00


  • Poser Ambassadors

    So I believe this is evidence that disproves the theory (if anybody had it) that the in-focus region is a sphere around the camera, based on the distance to the camera.

    I literally made a sphere around the camera, and placed a tile pattern on it. All points on this sphere have the same distance to the camera.

    Only the center of the render is in focus, no matter where I point the camera. Therefore the in-focus field is not shaped like a sphere.

    0_1494945038829_Sphere.jpg


  • Poser Ambassadors

    Aha - so I very precisely (using Python) built a plane and placed it 50 inches from the dolly camera. I set the focus distance to 50 inches (not using the guide at all) and rendered to get this image, where everything is perfectly in focus.

    0_1494945739555_Plane50.jpg

    Now to ensure I didn't make a rendering mistake, I changed the focus distance to 50.2 inches, and rendered again. Everything is now out of focus, and equally so at all points.
    0_1494945781237_Plane50.2.jpg

    From this I can conclude that Poser's focal plane is, in fact, a plane.

    Now as a result, attempts to measure the distance from camera to object will FAIL. You must measure the Z-depth from camera to object and then you will have the right distance.


  • Poser Ambassadors

    So I took my "focal plane" prop and parented it to the Dolly Camera, while the Dolly Camera was at 0, 0, 0.

    This gives me a new focus distance guide that's better than the built-in one.

    Now I loaded James as a test figure, turning his torso and head like the OP. Then I z-translated my focus plane until it intersected his eyes.
    0_1494946214302_Focus James Setup.jpg

    I read the focus plane z-trans value which was -106.2 inches. I typed 106.2 into the focus distance guide and rendered.

    Voila - perfect focus on the eyes.
    0_1494946255577_Focus James Render.jpg


  • Poser Ambassadors

    @ghostship said in Question about Focus Distance Guide:

    what might help you visualize where it will focus is by loading up a cube and parenting this to the camera. Make sure it is rotated so one face is directly facing the camera. Once you have the cube rotated and parented to the camera you can use ZTran on it to move the cube closer or further from the camera and have the face intersect with the object you want in focus. Just unchech visibility for the cube when you want to render.

    This was the right answer. But on the face of it you could not tell as it was given with the same conviction as the wrong answer.

    I prefer to test how the program actually works and now I've proved that the focal plane is a plane.


  • Poser Ambassadors

    How can we move that focus gizmo (apart from zooming with the slider)?
    Cause sometimes the center of it can't be seen in my composition.


  • Poser Ambassadors

    @Biscuits said in Question about Focus Distance Guide:

    How can we move that focus gizmo (apart from zooming with the slider)?
    Cause sometimes the center of it can't be seen in my composition.

    By gizmo, you're referring to the built-in focus distance guide? But I just showed you how that is not even what you want to do. The guide has no visible geometry to intersect with the face unless you rotate the camera, which will make the guide wrong.

    Use a plane like I did or a box like ghostship suggested.


  • Poser Ambassadors

    Wanted to edit to add, but timed out:

    When you use the focus prop as I did, you can even use a different camera to see what it intersects. You can move some other camera into any position to observe the focus plane prop. Move the prop with the z-trans dial and you have the exact value you need to type into the focus distance for your rendering camera.

    Using the prop frees you from having to do the measurement with your rendering camera, where the composition is such that it is impossible to view the intersection you care about.


  • Poser Ambassadors

    The way I set focus distance is: use Main Camera, centre whatever needs to be in focus using DollyX & DollyY dials, change focus_Distance as required, move DollyX & DollyY back to original position, render.

    Once I start this process I don't touch any other dial & so far I've never had a problem setting focus where I want it.

    Oh, changing display modes can make it easier to judge sometimes too - I use hidden line a lot.



  • Results of experiments by bagginsbill was beyond expectation, but now I focus the scene as I want.

    Thanks.

    0_1495016928312_Portrait_E_DollyY_Half.png



  • Corvas has a replacement for the camera focus prop that helps focus in a similar fashion to baginsbills example - ** I would back up your default poser file before replacing it with this one first though - - - - https://www.renderosity.com/mod/freestuff/focus-for-poser/77187

    I use Semidieu (ShaderWorks) 'Advanced lights and camera guides', which is a set of python scripts that displays grids and wireframes for the focal distance, f stop, lights etc. and it's great but it was sold at Runtime dna and is sadly no longer available as Semidieu left the Poserverse.

    I think runtime dna also had a lighting set with a camera focus replacement in, I spent ages trying to find it at daz but I couldn't remember which set it was included in lol.

    There were also other camera replacements made over the years that showed wireframe quides, but my memory is so foggy these days - possibly by PhilC or Netherworks but I can't be sure

    couple of tips...

    1. When trying to get the focus just right in poser 11 remember that you can turn on the focus guide permanently by going to - Menu - Display - Guides - Focus Distance Guides.

    2. Once you're working up close - on the camera Parameters - left mouse click on the arrow next to focus_Distance - mouse click settings - and temporarily change the sensitivity to 0.001000 this will allow for finer adjustment, change it back to 0.010000 for greater distances.


  • Poser Ambassadors

    Oh that Focus for Poser freebie is amazing!!!

    https://www.renderosity.com/mod/freestuff/focus-for-poser/77187



  • @Biscuits I never knew it existed. Downloaded, and will definitely be trying it out. ~smile~


  • Poser Ambassadors

    Aha, the geometry for the focus guide is called camtarget.obz (zipped obj file) & is in the default Runtime/Geometries/Camera folder. I had no idea until I looked at Covas' freebie & started poking around ;)

    I might try making my own version, always thought a grid would be more useful.


  • Poser Ambassadors

    I didn't know you could replace the guide geometry. Great! I made a grid - it's way more useful.

    I tried attaching it here but I'm not permitted. Why not? This is dumb.


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