How far would you blow up a shot of 5K epic footage....

[Eric Rainey]

How far would you blow up a shot of 5K footage so that you couldn't tell the difference at HD resolution(1920x1080)?

I am editing a job(not shooting it) and was asked how far can we blow up a shot. The person will be shot on green screen "head to toe". The director wants to be able to blow into the shot from "chest to head". So the question is how much would you blow up the shot and not worry that the image is getting soft.

2nd question- Last time we did a shoot like this we were going to rotate the camera 90degrees and the DP said he didn't want to do that because of the curve of the lens.."the head and feet would be more distorted." Me not being comfortable on the set and with lenses and distortion would think this might happen in a wide angle lens but not in a telephoto lens..? If this is true, what lens would there be no distortion with the head and feet?

Thanks
Eric

 

[Noah Yuan-Vogel]

That is a bit surprising to me as well. I would tend to expect that the same subject shot from the same distance with one lens horizontally and another lens with 1.9x longer focal length shot vertically (as would be needed in to fill the vertical frame in a 1.9:1 aspect ratio image with the same subject height) would not generally be more distorted since although a greater portion of the lens's coverage is used, less distortion would be likely in a longer focal length. Of course it depends on the lenses and their distortion properties relative to one another though, but for most modern lenses I would not expect it to be an issue.

As for blowing up 5k, I imagine pixel peepers might start seeing differences in high frequency detail starting beyond a 3k crop scaled to 1080p which is a 1.66x blow up from 5k. Definitely wouldn't go past 200% or a 2.5k crop.

 

[Gavin Greenwalt]

If you can convince them to shoot portrait oriented then you should be able to shoot 3k C.U. from a 5k vertical wide.

If I had to guess I would say here is why they think it's "Distorted". If you shoot a 100mm and want to frame in landscape you'll need to move back a good 50+ feet. But if you want to frame for portrait w/ a 100mm you'll be able to move in much closer. So people being the generally oblivious people that they are will just move the camera up close enough for the 100mm to fully frame the person. Your perspective will be then from like 25 feet instead of 50. What you need to tell them to do is frame up like normal with their preferred 'perspective' and then find a lens long enough to fill them in portrait from *that same location*. That will give you the same perspective on the person as shooting it in landscape.

You can then shoot a grid chart with the lens when the client is gone and undistort any barrel distortion in post without losing much resolution or sharpness.

P.S. that all being said, one of the nice things about epic is that you get a nice uncompressed 5k chromakey. That would be my largest concern with this arangement. Just rent a scarlet for the day and use it as a B-Cam for the Closeups.

 

[Eric Rainey]

Thanks guys!!!
I did my own really QUICK test with my EPIC. I used a $70 plastic lens and shot both landscape and portrait. I could blow up the landscape 240% and the director was ok with it....so success!

I would attach some stills but I don't have a url to use. Is there a different way to upload photos on reduser or am I not seeing the right button?

Thanks again!!!!

 

[Gavin Greenwalt]

I just use Photobucket.com