DVX100a Exact Lens Information

M

Michael_Blackbourn

Active member
Hi. I'm a Visual Effects artist, and I'm looking into doing some shots with DVX footage. What I'm looking for is exact mesurements of the camera guts and possibly how that translated into film numbers.

Mesurement in inches of the camera's aperture width and height: (ie: not 1/3" ccd)
Focal distace convertion for the focus "numbers" in the DVX
35mm motion picture film equivilants for the lens, and wether this would be full ap, or academy.
The multiplier for the above calculation (for motion picture, not still).

Thank you very much.

Michael Blackbourn
 
I take a shot at this. Some of this is probably wrong, though.

1)The actual number of pixels on an NTSC DVX CCD is 770x492 for each chip.
Of course, you can only access 720x480 of them.
2)The stock lens has a focal length of 4.5mm to 45mm.
3)The "crop factor" from a (rounded off, obviously) 24mm x 36mm negative would be 7.2 in the
4:3 aspect.. Of course a still negative is 2:3, so the factor is relevant only for horizontal field of view.
4) A FullAp or S35 frame is (rounded off, obviously) about 22mmx18mm, I believe... So the
"crop factor" would be around, what.. 3?
5) Who uses an academy frame non-anamorphically, anyways?
6) Compression artifacts kill you. You might consider the reel-stream.com modification for an
uncompressed output from the DVX100.. or another camera altogether.

DVXuser Rich_Lee has plenty of experience as visual artist and the camera...
maybe he could chip in some kind words...
 
Ok then. What would the (non rounded) numbers be for both the height and width of the capture area be? around 7mm by 6mm? That dosent sound right, and is heavily rounded....
I'm hoping someone else who's had to match 3D cameras to the DVX will drop a reply in here.

Thanks.

Michael
 
It sounds like your application would be considered pretty "specialised" and hence outside the
realm of everyday knowledge for most members of this primarily 2 dimensional group...

You might try contacting the following:

Developer of the 3D-DVX100 system
www.21stcentury3d.com

Developer of the Uncompressed DVX100 modification
www.reel-streem.com

Cinematography Video-Only Forum
www.cinematography.com

I do have some exact dimensions for film and 2/3" diagonal video frame sizes, but I think
inferring anything from those numbers would be less than the pinpoint accuracy you require.

Would be happy to report findings if I can find the book....

Brian Wells
 
Michael_Blackbourn said:
What would the (non rounded) numbers be for both the height and width of the capture area be? around 7mm by 6mm? That dosent sound right, and is heavily rounded....
Click to expand...

As a person who is interested in motion graphics and animating but with zero practical
experience in the field, what is the point of knowing the aperture dimensions with film?
With video? Would you mind really explaining this well? I don't get the chance to ask
questions around here very often...

Thanks,
Brian Wells
 
If you want to match the angle of view AND depth of field in a 3D program you need to know the film back size, aperture stop, and lens (or angle of view). It also helps for doing 3D tracking of footage if you can feed the software as much as you know about the plate your working from.

Mike
 
Most 3D tracking programs today will automatically calculate FOV or Stock lens doesn't it? but of course the more real world parameters you enter the better and more accurate i suppose. With regards to depth of field, different 3D programs have different ways of calculating depth of field and most of the time it wouldn't even match the actual footage. you still have to adjust and refine the virtual camera parameters to simulate the real world camera. even then, you still have to adjust a number of parameters in post to blend the CG seamlessly with the background plate. What 3D program do you use and what kind of effect are you trying to achieve? Maybe you'll only need certain things that are important to pull off an effect.
 
Seems like knowing the Exposure Index for a capture medium would be more valuable in
calculating DOF and field of view since EI ultimately determines how you expose. My .02

FWIW, there is no constant EI on video according to everything I've read on the subject...
Which is all subjective.....
 
Yes most tracking software does auto guess the lens and film back info. However, my experience has show that giving it as much real info about the footage leads to a much more useable track, the main benefit is that it will give you a tracked scene in the proper scale. And with Lightwave (one of the 3D programs I use). It uses real world jittered camera for rendering which will actually do proper DOF. But I need to feed it the right film back size, aperture, and lens.

Mike
 
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