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mister3d
12-31-2009, 08:21 PM
Hi guys. I have a question about barrel distortion in lenses. I noticed that in modern movies it's much less present that in those of 15-20 years ago. So is it the advancement in lenses, which became more rectilinear or in digital correction?

jtvergarav
01-02-2010, 04:34 PM
Hey man.

I don't know the answer, but if it helps in something... you have probably seen the DD BTS's.

in some you see a lens correction after all the elements were added, is that what you mean?

if so, I guess it still happens since they are pretty up to date

mister3d
01-02-2010, 08:17 PM
Hey man.

I don't know the answer, but if it helps in something... you have probably seen the DD BTS's.

in some you see a lens correction after all the elements were added, is that what you mean?

if so, I guess it still happens since they are pretty up to date

Hi. What is DD BTS's? And thanks for attention.

Ikonos
01-02-2010, 11:33 PM
DD BTS...

I guess it means:

Digital Domain's Behind The Scenes




On your subject: Question is interesting but I ask myself if it's pertinent. I remember very short focal length on Shining, yet I remember the straight lines as... well straights, no curvature.
Might be very dependent of the quality of the lens ?

mister3d
01-03-2010, 03:49 AM
DD BTS...

I guess it means:

Digital Domain's Behind The Scenes




On your subject: Question is interesting but I ask myself if it's pertinent. I remember very short focal length on Shining, yet I remember the straight lines as... well straights, no curvature.
Might be very dependent of the quality of the lens ?
Hmm... I have no idea, since I have no real shooting experience. What makes sense is that digital correction is much more common today, and considering that the distortion is persisnent, it's not that hard to correct.

beaker
01-03-2010, 05:13 AM
Hi guys. I have a question about barrel distortion in lenses. I noticed that in modern movies it's much less present that in those of 15-20 years ago. So is it the advancement in lenses, which became more rectilinear or in digital correction?probably the lenses. Panavision doesn't sell their lenses(rental only) and is always updating them.

Rarely do we do digital correction for the lens distortion. It unnecessarily softens the plate.

mister3d
01-03-2010, 05:28 AM
probably the lenses. Panavision doesn't sell their lenses(rental only) and is always updating them.

Rarely do we do digital correction for the lens distortion. It unnecessarily softens the plate.
Is panavision something like a serious standard in lenses? And for what reason they don't sell them? I thought that such a transform won't affect the sharpness too much, because you're just moving pixels from one place into another.

Ikonos
01-03-2010, 04:37 PM
Is panavision something like a serious standard in lenses? And for what reason they don't sell them? I thought that such a transform won't affect the sharpness too much, because you're just moving pixels from one place into another.

They don't sell them because this is the way the industry works. Lens are very expenseive and studios don't have neither the money nor the need to possess all the lenses. For each shooting the production (the direcotor of photography I guess) choose wich cameras/lens they are going to use and rent them for the time of the shooting. This way Panavision can keep his mounts, upgrade them, keep the inner parts secret....

I guess it's this way.


Second thing: You are wrong about each pixel moving. In fact, almost all the pixels will individually move... for X amount of pixels PLUS a fraction of pixel ( 54,3 pixels for exemple) this leads to filtering, ergo: Smoothing the image.

mister3d
01-03-2010, 10:42 PM
Second thing: You are wrong about each pixel moving. In fact, almost all the pixels will individually move... for X amount of pixels PLUS a fraction of pixel ( 54,3 pixels for exemple) this leads to filtering, ergo: Smoothing the image.
Yep, you are right. If we allocate the pixel between 2, it will inevitably blur. Thanks for the explanation.

earlyworm
01-06-2010, 02:13 PM
Panavision operates primarily as a rental company - who just happen to make their own cameras and lenses. They also supply other makes of cameras, lenses and accessories for sale and rental. But their own brand of gear is rental only.

You'll still see lens distortion in modern films, perhaps the reason it seems less obvious is that less films are shot using anamorphic lenses these days, which tend to have quite a bit more lens distortion in them - there are various reasons why filmmakers choose spherical lenses over anamorphic ones, but one reason in particular is that it's a bit trickier to do VFX using anamorphic plates as you've got to contend with quite a bit of lens distortion on the plate.

Here's an example of an anamorphic frame from Punch Drunk Love...

http://www.earlyworm.co.nz/3D/images/pdl2distort.jpg

In order to matchmove this shot we'd need to remove the lens distortion from the plate...

http://www.earlyworm.co.nz/3D/images/pdl2undistort.jpg

I've done a rather haphazard undistort using Photoshop, typically each lens used on the film is measured for distortion by shooting a checkered grid. Once the CG is lit and rendered, the inverse of this undistort is applied to the CG image in the composite so it matches the filmed plate. The only time the undistorted plate is ever used is when you need to matchmove or model off the plate.

Ikonos
01-06-2010, 04:41 PM
Thanks Will, this is helping :)

Cleavon
01-12-2010, 12:49 PM
In photography, a rectilinear lens is a photographic lens that yields images where straight features, such as the walls of buildings, appear with straight lines, as opposed to being curved.

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