Question about camera moving vs. focal length
XoechZ
Posts: 1,102
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
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Comments
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).
I believe Hitchcock made extensive use of the technique.
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)?
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 believe Hitchcock made extensive use of the technique.
Hitchcock did everything first : DISCUSS ;)
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.
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.
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.
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.
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.
Does anyone find changing render dimensions to a landscape format breaks the camera focal length.
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.
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 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
I'm guessing that its somehow a fundamental mistake and won't be fixed before V5.0.
I'm not seeing what you are in DS4.6 at 50mm but my focal distance is not set to 200 something either.
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.
And this with Render dimension set to 1:1 with 5.53mm Focal Length camera (extreme wide angle).
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).
Render dimension set to 1:1 with 50mm Focal Length camera.
edited and removed by user
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.
edited and removed by user
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.
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.