Vray Camera Compositing: Red Epic

[EricKlein]

Hello everyone!

I have a question that constantly haunts me onset of green screen shoots. It seems I'm never able to get a great camera match from 3dsmax to the real-world.

I'm determined to change this on an upcoming shoot.

We will be shooting on the Red Epic, and I'd like to understand the lensing I should request to match the attached cam settings: basically a vray cam w/ a film gate of 35mm and a focal of 24mm?

I think I need to match the film gate of the camera first, right? And then I can determine the focal length and they should match?

thoughts?

Eric.

[EricKlein]

got a few views...any ideas?

[chriserskine]

film gate size depends what res you are shooting with since its crops the sensor. here's a website that should help

http://arenafilm.hu/alsog/dofcharts/...ns=redzoom1850

[EricKlein]

fantastic, I really appreciate your reply.

If you could indulge my ignorance just a bit more:


It looks like the epic at full frame is at 5120x2700. As my final output will be 1920x1080, is it possible to use this chart to get the right info?

I do want to shoot full frame to get the extra data so it's easier to key, so my past approach would be to look for a scalable multiple, such as 2048x1080, and assume that would loose a bit of frame left and right onset, but my footage will match my render.

So: If I set my vray film gate as shown (35mm), render at 2048x1080, shoot the epic at full frame (5120x2700), and use the Red 18mm-50mm zoom lens, match my digital camera location in the real world...I should be able to match my footage?

another potential issue: If we mix real-time onset, we need to make sure the aspect matches the monitor as well, right?


http://www.red.com/products/epic

thanks again,

Eric.

[chriserskine]

I found this over at the nuke forums. which has some more details
http://forums.thefoundry.co.uk/phpBB...d5dfb82fe07c20

but it looks like epic has a slightly smaller film gate.

as for looking at the both on set, i can't really help you but I assume you would be correct.

quoteing a couple of the comments from the nuke fourm -----
"The Red can capture footage in a variety of ways, 4K 16:9, 2K 16:9 etc, and they all crop the sensor in different ways.�To find out what sensor size you should use, just multiply the pixels of your image by 0.0054 (the size of the pixels on the sensor in mm).

For example, if the camera captured footage in 4K 16:9 (4096x2304) you could calculate the sensor size like this:


4096*0.0054 = 22.11mm
2304*0.0054 = 12.44 mm


/Simon


2011/10/10 Misho Ristov <misha@fx3x.com (misha@fx3x.com)>
[quote] Red One 0.96 in
Red Epic 1.0885 in

-
Misho "

[EricKlein]

Interesting. So if I was to follow this, I could keep my renders at 1920x1080, which simplifies a lot. One more question then: I assume by this idea I would adjust the film gate on my vray camera to 22.11mm, and move my camera to match my desired shot?(make it look like it did w/ a wider gate)

[EricKlein]

ps...the mention in that thread of camera presets makes me drool...we need that for vray!

e.

[chriserskine]

yeah that should work if you shoot in 4k 16:9, and just set your zoom to the same as the real lens.

I would try and do a test shoot if you can. to make sure it all looks right.

[EricKlein]

Thanks for looking into it with me. It's always a bit of fudging onset, but I want to learn to get it right (as possible)!

[EricKlein]

One update:

Red Epic 4kHD is actually 4800x2700, so the film gate should be 25.92mm

Eric


quote:
...with red because it crops the sensor for different recording sizes the backplate will change depending what size you are recording (i have an epic myself)

the pixel size is 5.4 microns( 0.0054mm)

to figure out the backplate multiply this by the recoding size
largest recording area on the epic is 5120x2700 or 27.65mm x 14.58mm

the largest 16x9 recording size is 4800x2700
or 25.92mm x14.58mm

so the sensor is not 30mm...even if it is it does not record to a 30mm wide area of pixels...to put in a proper backplate with red you have to realize it will change with all format sizes...

just remember times pixels by 0.0054
the ratio is the same for red one, epic-x epic-m and red 1mx...the all have the 5.4 micron spacing

http://www.ssontech.com/phpBB2/viewt...b0669be6356561

[Jens_3deutig]

hi eric,

we done a job using red epic footage aswell and shooted with 100mm macro master prime from arri but this doesn´t matter.tracking was done using 27.7x14.6mm as filmback (shooted @5k 25 fps, 5120x2700 px) and all is working very well.

after that we had a maxcamera inside max with 27,7mm for aperture width (render dialog) and nearly 100mm as lens in the cam settings, if u put theese values into a vray cam or using a maxscript that converts max cams 2 vray cams all should match.

hope it could help,

cheers,
jens