Epic at 4K and older lenses

[Andre Brandao]

Hello dear friends!

If it's not too much trouble, I am in need of your expertise!

I am on pre-production of a feature project with the Epic here in Brazil and I'll be using older lenses, a set of Zeiss Super Speeds MKII and a Cooke 20-100 T3.1 Zoom. These older lenses do not cover 5K, most obviously, but at 4K (which is a little smaller than 4-perf Super 35mm), and croping at 1:2.4 (the film's release aperture) I get no problems of seeing the image circle beyond what the lenses were designed for; that means no vignetting and no dramatic loss of resolving power at the edges, etc. My friends at the rental house where I am getting the camera from told me that at 4K I would get exactly the same image than at 5K, meaning same dynamic range, etc, without seeing what I most certainly would not use. And the added benefit of smaller data rates is not to be ignored.

Also, at post we are going through an entirely 2K pipeline (R3D > 2K DPX grading > 2K DCP), so coming from 4K is a rock solid starting point.

My question is: Is there is something I have failed to notice? Or perhaps am I misinformed in some matter? Also, has anyone had any good/bad experiences shooting in a similar way?

Thanks in advance!

PS: If this has been discussed in another thread, please post it's address as a reply, for I was unable to find anything.

 

[Timur Civan]

works great. I had a Cooke 18-100. 4k looks great.

 

[Björn Benckert]

There is a lot of films shot in 4k so nothing wrong with that. But a bigger sensor and more source pixels means that you will get a higher quality source image shooting at 5K. It gives less noise, better resolution and wider FOV on the same focal length. To me, if finishing at 2k the image esthetics are what differs the most you will see it if you flip between 4k and 5k even on the little touch screen monitor. 5K looks simply like a bigger format camera.

So as you aspect ratio is 1:2.4 it might be so that the lenses you will use will hold up for 5K wide as 2.4:1 is you delivery format then the image circle might cover, if the final delivery was 16:9 then you probably have problems with black corners.

If I was the one to choose I would make sure to have a screen guide on the monitor that was set to 1:2.4. Then start at 5k, if the lens at hand does not cover your guide then I would slide down to 4k. As mixing between resolutions will not cause any problems. So maxing out on the resolution on a per shot / lens basis is what I would do.

 

[Nick Morrison]

Consider also that the wider lenses are more likely to vignette at 5k than the longer ones. I have a hunch that the 50mm and 85mm Super Speeds are probably fine at 5K. But as Bjorn suggests, you should do a thorough test.

 

[Andre Brandao]

Thank you all for the prompt response!

I have tested the Zeiss Super Speeds, and even though I don't get any vignetting at 5k even with the 18mm, at the edges all the "ageing" of the glass is very noticeable, with a quite steep decline in resolution getting worse toward the edges. With the Cooke 20-100 3.1 zoom I got completely black corners at the wider end, even when using 5K WS (2.4), which turns it into something of a 35-100, if I don't go wide enough to see the edges. Also, as I stop them down, they improve quite a bit, and from about 2.8 1/2 or 4 and on, they look much sharper.

That's a good way to go about it Bjorn, since changing resolution is so simple with the Epic, and I don't believe It would create problems in post. I'll keep that in mind.

I have recorded tests to compare 4k and 5k, but was unable to go through with them on post, due to the holidays. Anyway, I'll let you guys know what became of them once I get back to work, and maybe post some images, if anyone is interested.

Thanks!

 

[PatrickFaith]

So as you aspect ratio is 1:2.4 it might be so that the lenses you will use will hold up for 5K wide as 2.4:1 is you delivery format then the image circle might cover, if the final delivery was 16:9 then you probably have problems with black corners.

I'm with Bjorn, I have a lens that at normal 5k it vignette's a bit, but at 5KWS mode on the epic it doesn't vignette at all. RED picked the 5k 2.4 crop so most lenses will work, also like all above stated, you need to test.

If your working with NUKE and if there are problems only every now and then(like a horizon shot), make sure you do a pure "grey board" shot, that way you can remove the vignette in post(just takes 4 nodes if your in linear: loadfile(greycard)->blur->subract(reverse - middlegreyvalue)->add(greycard_normalized+footage) [actually only takes 2 nodes if you do this in a prestep]).

 

[Phil Moreton]

Hi Andre,

Any update on those cooke 20-100mm images. Would love to hear your final conclusion and summary with the lens at 5k and 4k.

 

[Jeremy 0sbern]

If you're doing widescreen at 5K with a nice set of Zeiss Superspeeds, it'll be fine for a feature. The Cooke would vignette, though.