Author Topic: Focal length/lens issue?  (Read 7228 times)

yak

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Focal length/lens issue?
« on: February 13, 2012, 10:57:30 pm »
February 13, 2012, 10:57:30 pm
Traditionally computer programs try to mimic camera lenses in terms of real world lens, such as 14mm 28mm, 54mm, etc. etc. SketchUp does a very good job mimicking camera lenses I don't see that same effort using Lumion.

The overall focal length,even its lowest setting, is extremely unnatural, except for those looking for very, very dramatic effects. I don't see any interior AVI's produced with Lumion showing, anything other than unnaturally elongated elements in the perspective. 

Also why is the focal length slider, missing from the photo taking feature screen one should have a choice of the type of lens to use. in both picture taking and animation.

the 3 attached pics are all screen captures that clearly show the amount of distortion. the last pic is a SketchUp pic.

Re: Focal length/lens issue?
« Reply #1 on: February 14, 2012, 11:39:26 am »
February 14, 2012, 11:39:26 am
Hi Yak, there's a long discussion about focal length in the following thread:
http://lumion3d.com/forum/index.php?topic=2872.0

By the way, you don't seem to have any Lumion license keys attached to your email address?

If you have a license you can post requests for new features in the Wish List section (which is only available for paying customers).

yak

    Reputation: 0
Re: Focal length/lens issue?
« Reply #2 on: February 15, 2012, 07:04:24 pm »
February 15, 2012, 07:04:24 pm
I don't know what answers I'm supposed to be able to gain from that thread ? When I'm standing in my hallway looking at several pictures on the wall that have a Square profile, none of them look as elongated as those produced by Lumion. Which makes an interior presentation in Lumion an unacceptable, option for a client presentation, I'm currently working on.  :(

p.s. I don't own a copy of Lumion. the Firm I work for does! And they do allow me to use their computer, on the weekend for some personal experimentation. 

Re: Focal length/lens issue?
« Reply #3 on: February 15, 2012, 07:12:23 pm »
February 15, 2012, 07:12:23 pm
I don't know what answers I'm supposed to be able to gain from that thread ?

If I understood you correctly, you're saying that you don't like the default focal length in Lumion, but I don't understand why you don't modify it in Lumion? In the thread above, Remko explains that he compared the focal length in Lumion with real-world lenses and it proved accurate. So if you double-click on the focal length slider and type in x degrees, it would correspond to a similar real-world lense in 16:9 format.

p.s. I don't own a copy of Lumion. the Firm I work for does! And they do allow me to use their computer, on the weekend for some personal experimentation.

What I meant was that you requested some options for stock lenses. Requests like these tend to drown in the General Questions section. If you were allowed to use the company account to log into the forum, you would be able to post this request in the Wish List section. Otherwise the developers (Remko/Ferry/Arthur) might not notice your suggestion.

Alternatively, with your permission, I can move this thread to the Wish List section, but you won't be able to read any replies after that, until you log in with an email account with a Lumion license.

Gaieus

    Reputation: 44
Re: Focal length/lens issue?
« Reply #4 on: February 15, 2012, 07:23:33 pm »
February 15, 2012, 07:23:33 pm
Vak, in SketchUp (as far as I can see, the bottom image is SU), press Z for the Zoom tool and then with the Shift key held, scroll your mouse wheel. You can achieve the exact same "wird" focal lengths like the default Lumion.

As well as in SU, in Lumion, you can also set this (maybe not this easily). In fact, if you go extreme, you can even achieve an (almost) parallel projection.

I do not like too wide angle lenses myself either (although on the other hand, I cannot even understand architects' obsession with shift lens effects and two point perspective unless it comes from some outdated, paper based depiction they cannot help) but sometimes in interiors, you need to cheat a bit and crank it up otherwise you can only see a bit of the room (at least on a still image).

Re: Focal length/lens issue?
« Reply #5 on: February 16, 2012, 12:43:27 am »
February 16, 2012, 12:43:27 am
Traditionally computer programs try to mimic camera lenses in terms of real world lens, such as 14mm 28mm, 54mm, etc. etc. SketchUp does a very good job mimicking camera lenses I don't see that same effort using Lumion.

The overall focal length,even its lowest setting, is extremely unnatural, except for those looking for very, very dramatic effects. I don't see any interior AVI's produced with Lumion showing, anything other than unnaturally elongated elements in the perspective.  

Also why is the focal length slider, missing from the photo taking feature screen one should have a choice of the type of lens to use. in both picture taking and animation.

the 3 attached pics are all screen captures that clearly show the amount of distortion. the last pic is a SketchUp pic.



The projection is pretty much similar in all programs and it's all the same math. The focal length setting was specifically tweaked to replicate it's analog counterpart. By default the editor cam uses a wide angle lens to prevent tunnel vision but you can easily change it to any focal length you want. For a 50mm lens you set the focal length to around 41mm becauso of the expanded fov of the 16:9 aspect ratio. At this setting the depth perception should be the same as the human eye.

The only thing we can do is to enlarge the film size to rediculous sizes to prevent tunnel vision and still have a small fov. We chose 35mm film and i think that's good enough. Cameras with huge film is EXTREMELY rare. I think kubrick was famous for using a special NASA camera for barry lyndon which allowed him to mimick the perspective of paintings of that time (and film scenes with insanely low light levels! Some scenes were only lit by a few candles!)
Stanley Kubrick's Barry Lyndon [Scene 4] (The video's owner prevents external embedding)

For for low perspective shots you would normally need a zoom lens and film from a distance but with big film you can place the camera closer to the subject. Mathematically it should be possible to pull the camera back and reduce the fov so the near clip plane maintains the same size and only the far clip plane gets reduced in size. Visually this means that objects near the camera maintain their size while far objects get bigger so the overal perspective is reduced. If you want such a shot now you can zoom in and increase the near clip distance to remove any unwanted objects from the foreground. This does not really work for moving cameras because the pivot point of the camera is so far back it's difficult to make the camera make sharp turns.

A slider which would allow you to blend between a orthogonal and perspective camera should offer a real solution.


yak

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Re: Focal length/lens issue?
« Reply #6 on: March 02, 2012, 09:08:04 pm »
March 02, 2012, 09:08:04 pm
I don't know if there are any tennis fans here. But there are 2 types of video cameras used to capture a typical tennis match on TV. Both type of video cameras are normally placed behind the players to capture the entire court and play in one field of view. The typical video camera makes the tennis court look unusually long. This typical camera is almost never used for capture video from major matches. What is used instead is a Camera with a foreshortening lens that squeezes the courts length and at the same time brings the tennis player on the other side of the net closer, making viewing much more desirable. Perhaps a foreshortening lens approach would help with interior perspectives, in Lumion.

cbcarch

    Reputation: 4
Re: Focal length/lens issue?
« Reply #7 on: March 02, 2012, 09:49:31 pm »
March 02, 2012, 09:49:31 pm
I have been around the world on this several times.
Attached is a PDF which explains the camera in Revit.

I found it very interesting and helpful.

cheers