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3d view focal lenght and camera focal lenght don't match (2.73 rc1)
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Description

The 35 mm default focal lenght of the 3d view doesn't match the 35 mm camera default focal lenght.

In the 3d view the perspective correction is about doubled respect to the camera.

For example, I usually use a 50 mm camera because it reflects the human eye perspective. To match the 50 mm camera perspective in the 3d view I have to set the lens parameter to 100 mm. That is twice the camera value.

It would be correct to fix the 3d view so that it matches the camera when setting focal lenght values.

Event Timeline

Bastien Montagne (mont29) lowered the priority of this task from 90 to 30.Dec 27 2014, 5:32 PM

Quickly checked, could not reproduce that at all, to me a camera view at 50mm and a perspective view at 50mm are matching perfectly. Please add data demonstrating your point (screen captures, .blend file…).

I'm very sorry it's my fault I wasn't aligning the camera properly to do comparisons. If I align with ctrl+alt+0 it works fine.

Indeed it is a long time now that I use 100-50 to match and I never felt that it was wrong. Again sorry that I wasted your time I'll use more caution next time before posting.

Bastien Montagne (mont29) changed the task status from Unknown Status to Invalid.Dec 27 2014, 7:55 PM
Bastien Montagne (mont29) claimed this task.

Ok, thanks, we can close this one now. :)

sorry, it seems I was too fast in blaming myself ..

I just managed to work out the case when 50mm camera and 100mm view matches. I included two pictures and the blend file to show this.

Just open the blend file (loading the user interface in the options) and use num pad 0 to switch between camera and 3d view. You'll see that 3d view and camera view match perfectly, even if the 3d view is 100mm and the camera is 50mm.

The reason behind this is that if we use ctrl+alt+0 to match the camera to the view it works just fine, but the camera frame is dimensioned about 1/4 of the 3d view. If we zoom the 3d view to have a full frame of the camera, the perspective doesn't match anymore, and we have to switch the 3d view to 100mm to have a perspective match.

This is why I use 50-100 so I can match the camera with a full framed 3d view. This is useful when using ctrl+alt+0 because I can use the full screen as if it was the camera. While if I use 50-50, ctrl+alt+0 frames about 1/4 of the screen instead of framing the whole screen.

So if we use 50-50 then camera and view match but the camera is framed 1/4 of the view, and if we zoom the view then the perspective doesn't match anymore.

If we use 50-100 then the camera matches the full framed 3d view. No need to zoom "back".

So, if we want ctrl+alt+0 to frame the full 3d view, then the correct setting is 50-100. This is why I say that 50-50 doesn't match.

If we use 50-50 then ctrl+alt+0 frames 1/4 of the view only instead of framing the whole view.

Sorry that I'm jumping in/out with this topic, it was a little tricky to find out ..

I do not understand the issue, this is a matter of zooming, you can zoom out in camera view until it matches exactly your non-camera view… I really see no bug here.

Thank you very much indeed for your reply Bastien, I'll try to explain better and I hope to be clear this time.

Zooming and focal lenght are related each other and in fact they are the same thing. Indeed when you zoom you change the focal lenght. This is basic photography and optical knowledge.

Now if you set the 3d view to 50mm and the camera to 50mm, then use ctrl+alt+0 to match the camera with the 3dview, you will see that the camera doesn't frame the full 3d view, but it frames only the center part of it, about 1/4 of the total area. This is indeed because the the 3d view focal lenght (zoom) doesn't match the camera focal lenght (zoom). So you need to zoom in to match the whole 3d view with the camera frame.

Now if you set the 3d view to 100mm and the camera to 50mm, then use ctrl+alt+0 to match the camera with the 3dview, you will see a perfect match. The whole 3d view is framed, no need to zoom in. This means that to match the 50mm camera you need a 100mm 3d view. This also means that the 3d view focal lenght and camera focal lenght don't match, as I used as the post title.

This may not seem a big issue to anyone that is not a director or photographer. But having a 3d view that matches the camera greatly helps to better position the camera (when using ctrl+alt+0 for example) and to better have a sense of proportions and perspective right inside the 3d view, without having to use a separate camera view for this.

Adding Campbell as CC here to get second advice, but I do not see any bug here, 'zooming' in 3dview (scrolling) does not change focal length, and it does not affect the same factors even depending on view types.

In camera view, scrolling affect a property dedicated to this view only, view_camera_zoom, which by default (startup scene) is set to 20.0. If you set it to zero (two scroll steps backward), you get perfect match between camera and non-camera perspective views.

(In non-camera perspective views, scrolling just changes the position of the 'virtual' camera along the view axis, view_location parameter).

Well, as a matter of fact the point of view (position) and focal length (zoom) are the two factors related to framing (view area).

If it is as you say and everything works fine, then it is not clear why ctrl+alt+0 frames 1/4 of the view. It should be "align camera to the view". That is, what is seen (framed) by the view should be seen (framed) by the camera. And this doesn't happen.

To make this happen you have to set the view to twice the focal length of the camera. If this is not a bug it is certainly something being somewhat weird and unexpected. I hope we can agree on this.

Again thank you very much for you kind reply and your patience. Of course my purpose is to help when I see something odd. But at times I feel to be a PITA and I always fear to waste the very precious (indeed) developers time with something silly. Hope this is not the case.

bye :)