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Support for unlicensed users => Post here if you can't find your License Key => Topic started by: stucki on August 20, 2013, 05:46:53 pm

Title: camera settings human eye
Post by: stucki on August 20, 2013, 05:46:53 pm
Hi guys,

i got a problem with my latest video and the client telling me the perspective doesnt match the human eye.

Can you please tell me the right settings for the lumion camera to simulate a human eye.
Is handheld camera the only place where i should set the camera, or does the camera setting in moviemode override this setting ?

Please be quick about this  ;) i have to render the movie again this evening ....
thanks in advance
stucki
Title: Re: camera settings human eye
Post by: stucki on August 20, 2013, 07:19:47 pm
i found in the forums something about 41 mm.
Lumion camera by default in moviemode has 15mm.

if i switch to 41 mm it doesnt look more real to me.

which xx mm is the right setting for the human eye ?

Title: Re: camera settings human eye
Post by: Jared G. on August 20, 2013, 08:41:09 pm
Quote
Reference: Light, Color and Vision, Hunt et al., Chapman and Hall, Ltd, London, 1968, page 49 for "standard European adult":

Object focal length of the eye = 16.7 mm
Image focal length of the eye = 22.3 mm

The object focal length is for rays coming OUT OF THE EYE. But for an image on the retina, the image focal length is what one wants. E.g. see: http://galileo.phys.virginia.edu/classes/531.cas8m.fall04/l11.pdf. (http://galileo.phys.virginia.edu/classes/531.cas8m.fall04/l11.pdf.)

So this explains the commonly cited ~17mm focal length, but the correct value is ~22 mm focal length

Also, you should note that even at this focal length, the image will not look the same as eyesight. The reason being your eyesight is a composite of 2 lenses, where as the camera is a single lens. You should tell your client that the video recreates a camera, not human eyes.
Title: Re: camera settings human eye
Post by: stucki on August 20, 2013, 09:52:03 pm
Also, you should note that even at this focal length, the image will not look the same as eyesight. The reason being your eyesight is a composite of 2 lenses, where as the camera is a single lens. You should tell your client that the video recreates a camera, not human eyes.

thanks very much !
really apriciated !
Title: Re: camera settings human eye
Post by: stucki on August 22, 2013, 03:34:24 pm
maybe lumion should by default have this value for cameras.
or is 22 not the right value ?
Title: Re: camera settings human eye
Post by: byzantium1200 on August 22, 2013, 04:46:25 pm
Also we have the inside of a sphere for a detector and heavy postprocessing which makes the resulting image nearly distortion free whereever we look at (unless you wear eye-glasses).
Title: Re: camera settings human eye
Post by: TJS on August 22, 2013, 08:14:54 pm
Also we have the inside of a sphere for a detector and heavy postprocessing
Some of us anyway...:D

Thanks for info. I'll try using 22.3mm to see if my rendered seem more natural.
Title: Re: camera settings human eye
Post by: peterm on August 23, 2013, 02:45:11 am
Here's a couple of links to replies by Remko on the camera in Lumion.

I haven't done the maths for a 35mm.

HTH.

1.  reference of camera zoom-settings (http://lumion3d.com/forum/general-discussion/reference-of-camera-zoom-settings/msg18505/#msg18505)

2.  Focal length/lens issue? (http://lumion3d.com/forum/general-discussion/focal-lengthlens-issue/msg21043/#msg21043)
Title: Re: camera settings human eye
Post by: Jared G. on August 23, 2013, 05:21:31 am
I reshot the first video I made with Lumion with 41mm just quickly... I like how it looks! I think I will implement this in the future.

41mm: 50mm (41mm Lumion Lens) (http://www.youtube.com/watch?v=u8iUTzwFBtk#)

original (15mm) Residential Pool House with Lumion (http://www.youtube.com/watch?v=avtRIj5yBj8#ws)
Title: Re: camera settings human eye
Post by: stucki on August 23, 2013, 10:22:33 am
so if i am right i should use 41 mm for real proportions, or is it 50 mm.
i need an definite answer from the developers, please.
I really hate it when my customers tells me the proportions are wrong, and i cant for sure if hes right or wrong.

And please dont take another 3 days for an answer. this project really is in a hurry.

thanks
stucki
Title: H.U.M.A.N.E.Y.E.
Post by: BABE™ on August 23, 2013, 10:58:41 am
Hi stucki .........

the BT  animation program ,uses 45 as there default camera setting, and
 most photographers use higher for Beauty shots.....The Higher the more FLAT
but you cant just change the focal length and expect the same scene to look similar
you would have to realign the camera.
Title: Re: camera settings human eye
Post by: peterm on August 23, 2013, 12:19:58 pm
If you look at the graphics provided by BABE it seems that all the images are the right proportions (as they are in Lumion).  It is all a matter of what scope the desired field of view is (landscape through to sports etc) as to which focal length should be chosen.  Notice architectural landscape indicates an 18mm so in Lumion the default 15.

The guide indicates eye sight seems to be 50mm, which would translate as Remko and Jared have mentioned to 41mm.

As Jared mentions in his earlier reply:
Also, you should note that even at this focal length, the image will not look the same as eyesight. The reason being your eyesight is a composite of 2 lenses, where as the camera is a single lens. You should tell your client that the video recreates a camera, not human eyes.

Attached is a PDF for Revit users, if of any use(from one of those other link topics).  Lumion proportions are of  course 16:9.

I have sent a request to one of the developers also for a reply (if possible).
Title: Re: camera settings human eye
Post by: stucki on August 23, 2013, 12:47:21 pm
thanks for your detailed answers !
helps a lot !!
Title: Re: camera settings human eye
Post by: Jared G. on August 23, 2013, 03:13:02 pm
so if i am right i should use 41 mm for real proportions, or is it 50 mm.
i need an definite answer from the developers, please.

to quote Remko:

"The 50mm (41mm in Lumion because of the 16:9 aspect) was chosen because of the perspective distortion. At 50mm objects seem as big as they are. If you zoom out everything looks bigger and a small room suddenly looks spaceous. The same happens when you zoom in. Things look a lot closer together you can also notice this if you move. A wide angle looks like you are moving really fast and a small angle looks like you are moving slow. That's where the 50mm comes from. It's the right zoom to estimate object sizes, angles and proportions."

You guys should sticky that thread. It was incredibly helpful!
Title: Re: camera settings human eye
Post by: Remko on August 23, 2013, 04:03:56 pm
We created Lumion so the focal length corresponds with 35mm full frame. This makes it easier to look up the desired focal lengths.

A focal length which comes close to the human eye is about 50mm.

This is just a common value and I'm not sure this is an exact scientific value. Well actually I'm pretty sure it's not. It's probably what people commonly accept as a good value.

For a more scientific approach there are many things involved. For example: what aspect of the human eye are you trying to match with the camera lens?

For each there are multiple ways to approach this issue. If you want the same field of view you have to take into account that the effective field of view is bigger for two eyes for example.

There are many other ways you can look at this and my opinion is that probably the best way to approach this is to use common wisdom. Use a 50mm focal length and when you need a bit more field of view you could go to 43mm to get a wider area.

As I remember the 50mm in Lumion is comparable to a 16:9 cutout of a full frame 35mm image. When you use a 41mm focal length you effectively have a vertical FOV which is similar to the horizontal FOV at 50mm.

You can look at it like this: Normally in a 35mm camera the lens projects on a square area. In this square area you get a field of view of about 39.6 degrees. The top and bottom are then cut off to get the 16:9 Aspect ration. This means that the horizontal FOV is still 39.6 degrees.

If you look at the chart on this page:

http://en.wikipedia.org/wiki/Angle_of_view#Common_lens_angles_of_view (http://en.wikipedia.org/wiki/Angle_of_view#Common_lens_angles_of_view)

you can see that at 50mm the horizonal FOV is 39.6 degrees. This is the same as in Lumion! The vertical FOV is a bit different but that's because the chart uses a 3:2 aspect ratio and Lumion uses 16:9. Don't get confused by the aspect ratio. Simply concentrate on the horzontal FOV. This FOV is exactly the same as a full frame 35mm camera.

At the same chart is says:
"For comparison, the human eye has an angle of view of about 160° by 75°."

This would translate to a focal length between 2 and 12. This would give you the same FOV as the human eye but would also introduce a huge amount of perspective distortion. Therefore it's better to stick to 50mm. The reason this is possible is because the eye is different than a a camera. The camera projects on a flat plane while the back of the eye is curved. This combined with the fact that you have two eyes results in a perspective distortion of about 50mm lens with the field of view of a 12mm lens.


Title: Re: camera settings human eye
Post by: stucki on August 23, 2013, 04:14:12 pm
thanks again for even more detailed answer !!
Title: Re: camera settings human eye
Post by: Remko on August 23, 2013, 04:18:45 pm
The default in Lumion was chosen so it's comfortable to work with. If you set it to 50mm you'll go crazy because you can't comfortably look around.
Title: Re: camera settings human eye
Post by: Remko on August 23, 2013, 04:28:43 pm
I think you should choose the right setting depending on the situation. Psychology is a huge factor. A certain focal length in a room looks completely different to the same focal length outdoors.

To prove this point try thinking about the moon: The moon always has a size of 0.52 Arc. This means that with the human field of view the moon only is 1/320 of the entire view. On a Full HD monitor this would make the moon as big as only 6 pixels!!!!

On a 50mm lens the moon would be only 1% of the image or 19 pixels! We all have had the impression that the moon is sometimes bigger than other times. We certainly have the feeling it's a lot bigger than 1% of the view. The reason for this is vision psychology. So, here you see that the right focal length depends a lot on the image and the way people interpret the image.

Did you know by the way that the size of the moon in Lumion is bigger than the real moon? The reason is that when we use the real moon size it would look weird and people would think we picked the wrong size :D