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3dsmax Camera Match w/ Tilt-Shift Lens - Possible?
show user profile  nm8r
I've done a lot of 3ds max camera matching with photos shot with regular lenses and usually do the perspective correction in Photoshop after the fact. Has anyone tried 3ds max camera matching with a photo taken with a tilt-shift lens though? Is it doable? A client will be supplying us with photographs but I'd like to shoot the site myself if I can't do a match on the (tilt-shift) photos they've supplied. Of course, I'm partial to shooting the site myself so the camera equipment is paid off with it.
read 7392 times
2/11/2009 8:48:44 PM (last edit: 2/11/2009 8:48:44 PM)
show user profile  Dub.
not really.

You could write a MR lens shader if you were keen



read 7384 times
2/11/2009 8:51:26 PM (last edit: 2/11/2009 8:51:26 PM)
show user profile  Bolteon
tilt shift as in lens shift? ie forced depth of field on a giant distance of a shot shot?

-Marko Mandaric



read 7382 times
2/11/2009 8:52:59 PM (last edit: 2/11/2009 8:52:59 PM)
show user profile  nm8r
Tilt-Shift lens - like this one for example http://www.usa.canon.com/consumer/controller?act=ModelInfoAct&fcategoryid=156&modelid=7322

read 7376 times
2/11/2009 9:14:10 PM (last edit: 2/11/2009 9:14:10 PM)
show user profile  Error404
I assume you are talking about the shift here. Tilt and shift are two different things.

I believe you can put a "skew" modifier on a regular camera, and that should let you simulate the rise/fall and left/right shift of a shift lens or view camera.

If this is for architeture (to keep building lines vertical while shooting from ground level), you'll most likely leave the camera with no upwards rotation, and then use the scew modifier to match the vertical shift of the lens.

www.DanielBuck.net - www.DNSFail.com

read 7368 times
2/11/2009 10:13:45 PM (last edit: 2/11/2009 10:15:12 PM)
show user profile  Dub.
hrmmm

I was thinking about the DOF as well.

The skew would work fine. And you could probably remap a zdepth with a grad to handle DOF in post.


read 7363 times
2/11/2009 10:18:25 PM (last edit: 2/11/2009 10:18:25 PM)
show user profile  Error404
I think he's talking about converging lines, since he mentioned "perspective correction"

however, the bluring from the effects of tilting the lens is simple, a gradient across the screen for a z-depth is all lyou need. That's all that tilting the lens does, projects the image onto the film at an angle. Well, the effects will be a little different than a gradient z-depth, but it'll be good enough.

www.DanielBuck.net - www.DNSFail.com

read 7360 times
2/11/2009 10:33:02 PM (last edit: 2/11/2009 10:34:21 PM)
show user profile  Bobbyboy
OMG, I never knew you could put a modifier on a lens, never even though about it, that's awesome!
you learn something new every day :)


http://img.photobucket.com/albums/v322/bob9909/xmassig.jpg


read 7356 times
2/11/2009 10:47:49 PM (last edit: 2/11/2009 10:47:49 PM)
show user profile  Garp
"If this is for architeture (to keep building lines vertical while shooting from ground level), you'll most likely leave the camera with no upwards rotation, and then use the scew modifier to match the vertical shift of the lens."

Isn't that what the camera correction modifier is made for? (unless I'm completely misunderstanding what you're all talking about)




read 7344 times
2/11/2009 11:36:38 PM (last edit: 2/11/2009 11:36:38 PM)
show user profile  nm8r
Let me try to explain again:
I usually photograph the site of a building, bring the photo as a viewport background in 3dsmax and use the CamPoint helper to define points in the photo. I then use Utilities - Camera Match so that the new building I've modeled will directly match the background photo and montage properly.
That is - when I render, the new building (in 3ds max) matches and overlaps the old building in the photo background. This is very easily done when there has been no previous perspective correction done on the original photograph. Now my question is whether anyone has tried this procedure with a photograph taken with the tilt-shift lens because it seems like the Camera Match utility may not work in this situation.

Aw, Heck - Maybe I'll just tell my client that I'll reshoot the site and building with a regular lens instead of using the photo shot by their previous photographer who used a Tilt-Shift Lens.

Error: It's actually the tilt(forward or backward movement in a view camera) and not shift that would have the effect of correcting the 3-point perspective (converging verticals much like Camera Correction Modifier would in 3dsmax.

read 7338 times
2/11/2009 11:41:10 PM (last edit: 2/11/2009 11:51:51 PM)
show user profile  Error404
nm8r: you are incorrect. tilt/swing does not affect 'perspective' as you call it. Shifting the lens and/or back of the camera is what enables you to correct for converging lines. Trust me, I shoot with a view camera alot :-)

http://en.wikipedia.org/wiki/View_camera

Read the section under "Rise and Fall" rise/fall is the common term for vertical shift (rise is shifting the lens up, fall is shift down). You level the camera parallel to the building and raise the lens to shoot the building instead rotating the camera upwards, so that the building remains perfectly vertical, no converging. lateral shift is usually just called shift left or shift right, which is what you would use if you are shooting a building at an angle, but want the building face to be flat.

Tilting us used mainly to correct focusing to angle the plane of focus around. Swing is the same as tilt, but on a vertical axis instead of a horizontal axis.

With shift, the lens is still projecting flat onto the film ("flat", not counting minor curvature of the lens projection). With tilt, it's projecting on an angle, so focus is altered.



as for the camera correction modifier in 3d Max, I've never used it, so I don't know.

www.DanielBuck.net - www.DNSFail.com

read 7325 times
2/11/2009 11:52:03 PM (last edit: 2/12/2009 12:11:12 AM)
show user profile  nm8r
We seem to be arguing semantics.
Rise is an upward movement and fall, a downward movement which would change the placement of the image on the film.
Shift - is a sideways movement, is the same as rise and fall except the movemnet takes place from side to side.
Tilt - a forward and backward movement, can change both the shape and focus of the image on the film. Tilt of the back mostly affects the shape of an object and so helps to control convergence (the apparent angling of parallel lines toward each other in a photograph)
whereas Swing is an angled left or right movement and can change the shape or focus of the image.
Taken from :http://www.amazon.com/Photography-9th-MyPhotographyKit-Barbara-London/dp/0131752014/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1234421124&sr=8-1
Wiki is a pretty good source of info though but the Upton / London book is the textbook used in most photo schools.

Interesting discussion here.
read 7303 times
2/12/2009 12:12:24 AM (last edit: 2/12/2009 12:16:18 AM)
show user profile  Error404
Just to clarify, you are wanting the building to have no converging lines (flat), and entirely in focus, correct?

you will ONLY get the building to be flat (no converging lines) by keeping the back of the film parallel with the side of the building which you are predominantly shooting. :-) (without photoshopping, or angling the paper on your enlarger instead) This means you level the camera (since buildings are level, parallel to the horizon, and go upwards perpendicular to the horizon) and then to compose the building you to shift the lens. Shift up to see more the top of the building if you are shooting from the ground, or shift down if you are shooting from the top of another building. shift left or right to compose the building laterally or to see more of one side of the building. If you rotate the camera or tilt the back, your building will not be flat, and you will get converging lines


If you take a photo of a building with the view camera rotated upwards, which means your film is NOT parallel to the building. Then yes, you will need to tilt the back (film) forwards to keep the back parallel with the building. HOWEVER, now your lens is not projecting flat onto the film because the back has been tilted, and you will get only a thin line in focus running through your building. So now you need to apply the same amount of tilt to the front of the lens as you did the back to get everything in focus again. Now, what you have here, is shift. Both the lens and the film are now parallel again, which means you could have just leveled the camera, and shifted the lens until you are happy with the composition. :-)



Yes, tilting the back of the camera (the film) will distort the image. Tilt back to make the foreground look larger, tilt forward to make the top of the image look larger. But in doing so, you are altering focus. Tilting backwards on the film in a landscape usually works pretty good, because you are adjusting how the lens projects onto the film so that (if the landscape is fairly flat) you'll get more in focus front to back. But a tall tree sticking up will not be in focus at the top of the tree. This is very similar to tilting the lens forward, but with the additional distorted foreground (assuming the camera is level each time, back of the camera perpendicular to the ground).

But for buildings, tilting the back will result in the top of the building/photograph not being on the same focus plane as the bottom of the building (assuming you are tilting back or forwards). If you swing the back of the camera left or right (vertical axis tilting) then the left side of the photo will not be on the same focus plane as the right side.


Here is an article that explains shift with a tilt/shift lens for a 35mm camera (the same concept as a view camera, but more limited) http://photo.net/equipment/canon/tilt-shift

and here is a visual layout of what each movement does on a view camera: http://www.imagedancer.com/view_camera_movements.htm

www.DanielBuck.net - www.DNSFail.com

read 7290 times
2/12/2009 12:39:21 AM (last edit: 2/12/2009 1:04:09 AM)
show user profile  nm8r
Like I said, It boils down to semantics.
Here's what I mean:




read 7264 times
2/12/2009 1:04:29 AM (last edit: 2/12/2009 1:04:29 AM)
show user profile  Error404
A and B are parallel to each other. Which is shift on a tilt/shift lens (and usually considered shift on a view camera). And they are both parallel to the building, which means rise would be much easier.

The only reason to angle the camera up, then apply the same amount of tilt to the front and the back (parallel) is if your camera does not have enough rise/shift on it's own, or does not have any rise/shift.

Any photographer who is going to shoot a tall building with a view camera, is most likely going to give the camera as much front rise as it has, (and rear fall, if their camera has rear fall) and if that is not enough, then he will aim the camera upwards (still with full front rise) until the building is composed correctly, then bring the back of the camera parallel to the building again, and then the lens as well. Which is just giving the camera more rise (shift) than it has built in. That is the most logical way to do it, it takes up the least amount of effort.


Yes, it does appear that we are describing the same effect, but effectively the front lens is shifted upwards from the film, as they are still parallel. The fact that the base of the camera is still tilted, and the front and rear standards both tilted forward (the same amount) just means the camera did not have enough rise on it's own, or the photographer just took the difficult way around. But either way, classically I believe this is still considered 'rise', not tilt, since both standards are still parallel.


And on a tilt/shift lens (which your original question stated) there is no way to tilt the back of the camera independent of the front of the lens (since there is only one tilt), you can tilt the lens without affecting the camera, but not the camera without affecting the lenses tilt. So there is only one solution for front rise, which is shift.

www.DanielBuck.net - www.DNSFail.com

read 7260 times
2/12/2009 1:07:03 AM (last edit: 2/12/2009 1:28:42 AM)
 
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