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Question about camera moving vs. focal length

XoechZXoechZ Posts: 1,102
edited December 1969 in Daz Studio Discussion

Hello!

One thing that always confuses me a bit when working with cameras in DAZ Studio is the correct setting of placement and focal length.

So, when I set up a cam and it is too far away from the main object in the scene I can either move the cam closer to the object or adjust the focal length until I get a good frame.
Same in the opposite direction. When the cam is too close I can either move it away or, again, adjust focal length.

My problem is that I never really know when to do what. I have searched the web about it and the only thing I found are descriptions what focal length is, but not how to use it, or which values are good for different needs.

Maybe some of you can give me some advices about it. How do I set focal length correctly (for different needs like portraits or full environment scenes)? And when is it better to move the cam closer or away from the main object?

Thanks,

XoechZ

Comments

  • RoguePilotRoguePilot Posts: 239
    edited January 2013

    Nice question.

    This is a standard photoraphy response.

    A focal length of 50mm on a standard 35mm film camera gives a matching perspective to the human eye.

    A shorter focal length (say 27mm) zooms out but give a greater sense of perspective, things appear even further away as distance increases. If you moved the camera forward to fill the frame on Vickys face you'll see her nose bulge out.

    A longer focal length (100mm) zooms in and flattens the perspective. Backing the camera up to put Vickys face in frame will shorten her nose.

    As to what you would use it for, for figure work a longer lense is seen as more flattering where a shorter lense is seen as more characterful.

    To be deliberately 70s non reconstructed male here;
    Character (usually men) = short lens.
    Glamour (usually women) = long lens.

    It's also a useful trick in scene setup to indicate all sorts of emotional states.

    The best use of this ever in film is in Jaws. The scene on the beach when Chief Brody realises that there's been another shark attack.
    A really tricky move is pulled off as the camera lens is zoomed out at the same time that the whole camera is pushed in with perfect synchronistion. This gives the same emotional impact that you feel when you realise you've just made a huge mistake. (The world rushes away just leaving you on your own).

    Post edited by RoguePilot on
  • Richard HaseltineRichard Haseltine Posts: 97,233
    edited December 1969

    RoguePilot said:
    The best use of this ever in film is in Jaws. The scene on the beach when Chief Brody realises that there's been another shark attack.
    A really tricky move is pulled off as the camera lens is zoomed out at the same time that the whole camera is pushed it in with perfect synchronistion. This gives the same emotional impact that you feel when you realise you've just made a huge mistake. (The world rushes away just leaving you on your own).

    I believe Hitchcock made extensive use of the technique.

  • XoechZXoechZ Posts: 1,102
    edited December 1969

    Thank you very much for your detailed answer. I think I understand the concept now.

    So,

    1. moving the camera towars the target and zooming out creates more perspective and depth (but if you overdo it you get that " fish-bowl" effect, right?)

    2. moving the camera away and zooming in flattens the image.

    If that is true, I say thanks again :-)

    But I have another question:
    Number 1 is logical to me - perspective and depth is always a good thing in digital images. But when do you need number 2? Is there a reason why I should flatten an image (besides shorten a nose in a portrait)?

  • SzarkSzark Posts: 10,634
    edited December 1969

    Using a Higher (longer) lens will narrow the field of view which help when focusing on a particular figure without as lot of the background visable.

  • RoguePilotRoguePilot Posts: 239
    edited December 1969

    Richard Haseltine said:
    RoguePilot said:
    The best use of this ever in film is in Jaws. The scene on the beach when Chief Brody realises that there's been another shark attack.
    A really tricky move is pulled off as the camera lens is zoomed out at the same time that the whole camera is pushed it in with perfect synchronistion. This gives the same emotional impact that you feel when you realise you've just made a huge mistake. (The world rushes away just leaving you on your own).

    I believe Hitchcock made extensive use of the technique.

    Hitchcock did everything first : DISCUSS ;)

  • RoguePilotRoguePilot Posts: 239
    edited January 2013

    Szark said:
    Using a Higher (longer) lens will narrow the field of view which help when focusing on a particular figure without as lot of the background visable.

    I think you mean depth of field.

    Is that a camera dependent setting in Studio? I thought it was a seperate setting.

    Actually field of view is also a valid point too. Sorry.

    Post edited by RoguePilot on
  • RoguePilotRoguePilot Posts: 239
    edited December 1969

    XoechZ said:
    Thank you very much for your detailed answer. I think I understand the concept now.

    So,

    1. moving the camera towars the target and zooming out creates more perspective and depth (but if you overdo it you get that " fish-bowl" effect, right?)

    2. moving the camera away and zooming in flattens the image.

    If that is true, I say thanks again :-)

    But I have another question:
    Number 1 is logical to me - perspective and depth is always a good thing in digital images. But when do you need number 2? Is there a reason why I should flatten an image (besides shorten a nose in a portrait)?

    Perspective and depth is neither a good or bad thing, it's just part of the visual toolbox.

    As I touched upon, a flatter perspective is more flattering for figure work or portraits. Try rendering a head shot at 120mm and at 50mm. Compare the two and you'll see the difference. Lighting plays a huge part in this too. For a character portrait you want strong direct light to pick up the features but in a glamour shot you generally want to soften the lighting as much as you can.


    examples:

    character: http://www.renderosity.com/mod/gallery/index.php?image_id=2243315&user_id=654859&np;&np;
    glamour: http://www.renderosity.com/mod/gallery/index.php?image_id=2180247&user_id=654859&np;&np;
    action: http://www.renderosity.com/mod/gallery/index.php?image_id=2370577&user_id=654859&np;&np;
    emotion: http://www.renderosity.com/mod/gallery/index.php?image_id=2153813&user_id=654859&np;&np;
    Learning the visual language can have a bigger impact on your renders than learning the software.

  • JimmyC_2009JimmyC_2009 Posts: 8,891
    edited December 1969

    RoguePilot said:
    Szark said:
    Using a Higher (longer) lens will narrow the field of view which help when focusing on a particular figure without as lot of the background visable.

    I think you mean depth of field.

    Is that a camera dependent setting in Studio? I thought it was a seperate setting.

    Actually field of view is also a valid point too. Sorry.

    To see DOF in DAZ Studio, you have to switch it on, but the same rules (almost) apply to DS as in the real world with a proper camera.

    To reduce DOF

    Use a longer focal length lense (ie: 250 mm instead of 50mm)
    Reduce the camera to subject distance
    Use a larger aperture (ie: f1.8 instead of f16)

    To increase DOF, do the opposite

    Use a shorter focal length lense
    Increase the Camera to Subject distance
    Use a smaller aperture.

  • SzarkSzark Posts: 10,634
    edited December 1969

    RoguePilot Nope I wasn't meaning DOF at all but more Field of View really. Using a larger lens like 100MM is effectly using a tele lens and therefore the field of view will be narrower that a 35mm lens.

  • wancowwancow Posts: 2,708
    edited December 1969

    I'm not sure this has been mentioned, but we saw this a lot in Battlestar Galactica (the new one), where they'd have a wide shot, then zoom in, and I'm almost certain that was going from say 35 mm to like 200 mm rather than using camera movement. Another neat effect is when you "pull"

    In Poltergeist there's a shot where Jobeth Williams is running down a hallway, and the hallway seems to extend. That's done by having a long focal length and pulling it down to a very short focal length. Objects appear flatter with a longer focal length, and they look rounder with shorter lengths.

  • Rayman29Rayman29 Posts: 0
    edited December 1969

    Does anyone find changing render dimensions to a landscape format breaks the camera focal length.

    9x1_50mm_camera_veiw.JPG
    1850 x 903 - 89K
    9x1_50mm_perspective_veiw.JPG
    1851 x 905 - 178K
  • srieschsriesch Posts: 4,241
    edited December 1969

    Another quick test to see the effect change: try putting a figure in the middle of the scene and a cube along the very edge of your scene (to simulate an interior wall corner, a building, a support post, etc. render. Make a huge change the focal length, then move the camera in/out to compensate, render again. You can cause/remove distortion to the angle of the (supposedly) perfectly vertical line of the cube by doing this.

  • Rayman29Rayman29 Posts: 0
    edited December 1969

    Increasing the focal length is a workaround for the error true. It makes the camera settings a little meaningless though.

    I reported it as a bug, but the response was basically 'No its not'.

  • JaderailJaderail Posts: 0
    edited December 1969

    Rayman29 said:
    Increasing the focal length is a workaround for the error true. It makes the camera settings a little meaningless though.

    I reported it as a bug, but the response was basically 'No its not'.

    Well considering you can do the same thing with a real camera, fisheye and others as well I think the render camera does a good job of mimicking the real settings.
  • Rayman29Rayman29 Posts: 0
    edited June 2014

    Well that would be the case with say 15mm to 28mm focal length but not with 50mm and above.

    The problem is a landscape format is reducing the camera's effective focal length, when it should just crop the frame as it does in a portrait format.

    Render dimension setting should not effect the camera or Perspective View

    Post edited by Rayman29 on
  • Rayman29Rayman29 Posts: 0
    edited June 2014

    I'm guessing that its somehow a fundamental mistake and won't be fixed before V5.0.

    Post edited by Rayman29 on
  • JaderailJaderail Posts: 0
    edited December 1969

    I'm not seeing what you are in DS4.6 at 50mm but my focal distance is not set to 200 something either.

  • Rayman29Rayman29 Posts: 0
    edited June 2014

    This is what I get with Render Dimension set to 10:1 with 50mm Focal Length camera.

    Note that the 10:1 render dimension setting has effectively reduced camera focal length to 5.53mm.

    50mm_from_3m_10x1.JPG
    1842 x 904 - 207K
    Post edited by Rayman29 on
  • Rayman29Rayman29 Posts: 0
    edited December 1969

    And this with Render dimension set to 1:1 with 5.53mm Focal Length camera (extreme wide angle).

    5.53mm_from_3m_1x1_.JPG
    1842 x 906 - 209K
  • Rayman29Rayman29 Posts: 0
    edited June 2014

    Jaderail said:
    I'm not seeing what you are in DS4.6 at 50mm but my focal distance is not set to 200 something either.

    Focal distance is not part of the problem. In the scene above, the camera focal distance is set to 300 (focused on corner of small blue cube).
    Post edited by Rayman29 on
  • Rayman29Rayman29 Posts: 0
    edited December 1969

    Render dimension set to 1:1 with 50mm Focal Length camera.

    50mm_from_3m_1x1_.JPG
    1841 x 904 - 163K
  • linvanchenelinvanchene Posts: 1,355
    edited February 2015

    edited and removed by user

    Post edited by linvanchene on
  • Rayman29Rayman29 Posts: 0
    edited June 2014

    linvanchene, at last a photographer. The bug seems to effect all focal lengths. The 10:1 render dimension was an extreme example, with render dimension set to 2:1, 50mm focal length is effectively reduced to 31.59mm.

    1x1_31.59mm_.JPG
    1506 x 907 - 187K
    2x1_50mm.JPG
    1512 x 903 - 187K
    Post edited by Rayman29 on
  • linvanchenelinvanchene Posts: 1,355
    edited February 2015

    edited and removed by user

    Post edited by linvanchene on
  • Rayman29Rayman29 Posts: 0
    edited December 1969

    linvanchene said:

    The question is: Was this bug introduced in one of the last updates or did we all just not notice for a very long time?

    Looking back I thought that it might have first appeared with the 4.6 release. But I'm now thinking it was the 4.5 release.

  • Rayman29Rayman29 Posts: 0
    edited June 2014

    Here's a list of render dimensions with the approximative focal length correction.

    2:1 multiply focal length by 1.579
    3:1...........................................2.370
    4:1.......................................... 3.172
    5:1.......................................... 3.971
    6:1.......................................... 4.770
    7:1.......................................... 5.561
    8:1...........................................6.329
    9:1.......................................... 7.142
    10:1........................................ 7.936

    Most of the error is removed at any reasonable focal length (8mm to 800mm). As linvanchene pointed out though, for composite work focal length needs to be precisely matched.

    Edit:- The above only works between focal lengths of 40 to 50mm.

    Post edited by Rayman29 on
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