Jump to content


Photo

Red Epic W 8k Helium crop factor for anamorphic


  • Please log in to reply
5 replies to this topic

#1 Alex Birrell

Alex Birrell
  • Basic Members
  • PipPip
  • 55 posts
  • Student
  • London, UK

Posted 08 December 2017 - 06:05 PM

Hello!

 

Can anyone tell me definitively the crop factor when using 2x anamorphic lenses on the Red Epic W 8k Helium in 8k 6:5 mode?

 

I've seen lots of answers for similar questions on this forum but mostly for the 6k Red Epic prior to the new sensor or talking about the VV Red Weapon 8k so I'm getting a bit confused!

 

Thanks!


  • 0

#2 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 20306 posts
  • Cinematographer
  • Los Angeles

Posted 09 December 2017 - 10:47 AM

8K 6:5 mode is 18.92mm x 15.77mm. 4-perf 35mm anamorphic projection aperture is 21mm x 17.5mm.

 

I assume when you say "crop factor" you mean in comparison to 4-perf 35mm anamorphic.  17.5mm divided by 15.77mm gives you a 1.11X crop factor if you compare vertical view.  Same goes for 21mm divided by 18.92mm.


  • 0

#3 Daniel Klockenkemper

Daniel Klockenkemper
  • Basic Members
  • PipPip
  • 57 posts
  • Cinematographer
  • Los Angeles, CA

Posted 09 December 2017 - 12:53 PM

RED has a fairly useful tool on their website that will provide the dimensions of any of their sensors, at any resolution window:  http://www.red.com/tools/crop-factor  For what it's worth, the 8K Helium and 6K Dragon sensors have almost the same dimensions, so if you've shot 2x anamorphic 6:5 with a Dragon then 2x anamorphic 6:5 on Helium should give you almost exactly the same perspective.
 
That said, crop factor confuses so many people, and it gets misused in all kinds of ways.  I find it much more straightforward to determine the normal focal length for the format you're shooting. 
 
Based on the dimensions David's provided, by doubling the horizontal dimensions we get virtual capture areas of 42mm x 17.5mm for 35mm 4-perf scope, which has a diagonal measurement of 45.5mm; and 37.84mm x 15.77mm for RED Helium 8K 6:5, with a diagonal of 41mm.  The crop factor between the two works out exactly the same as David's calculation, 1.11x, but I wouldn't get hung up on the numbers - I'd think of a 40mm as a typical normal perspective, and from there decide if my normal lens for that movie would be wider or longer than that based on my approach to the story. 

  • 0

#4 Adrian Sierkowski

Adrian Sierkowski
  • Sustaining Members
  • 7496 posts
  • Cinematographer
  • Los Angeles, Ca

Posted 09 December 2017 - 02:02 PM

A 40mm ANAMORPHIC would be a pretty WIDE lens . . . at least in one of it's dimensions ;)
 


  • 0

#5 Daniel Klockenkemper

Daniel Klockenkemper
  • Basic Members
  • PipPip
  • 57 posts
  • Cinematographer
  • Los Angeles, CA

Posted 09 December 2017 - 03:02 PM

Well, the whole idea is that it's less wide on a RED than it is on 4-perf film.  ;)
 
If you want the numbers, out of PocketAC: 
  • For 35mm scope, projected, the "normal" value of 45.5mm gives a 49.5 degree field of view.
  • You'd usually round up to a 50mm, for a 45.5 degree field of view - slightly tighter.
  • A 40mm would give you an FoV of 55.3 degrees.
     
  • For RED Helium 8K 6:5 2x, a 40mm lens gives you a 50.6 degree FoV - about 1 degree wider than the theoretical "normal" of 35 scope.
  • To match a 50mm lens on 35 scope, you'd need a 45mm lens on the RED (which doesn't exist in many lens sets).
  • That 50mm lens on the RED gives a 41.5 degree FoV - tighter. 
  • To match the 40mm on 35 scope, the RED would need a 36.1mm lens.  Rounding down to a 35mm lens, you'd get a 56.8 degree FoV.
This is in a perfect world of theory, where anamorphic lenses wider than 50mm don't start to get noticeable distortion in some cases.  
 
In any case, shooting with a typical set of 2x anamorphic lenses on a RED means getting an FoV that's either slightly tighter or more wide than what you'd get with 4-perf 35mm film.
 
And I did say not to get hung up on the numbers.  :)

  • 0

#6 Alex Birrell

Alex Birrell
  • Basic Members
  • PipPip
  • 55 posts
  • Student
  • London, UK

Posted 09 December 2017 - 05:43 PM

That's great, thanks for the answers!


  • 0


Broadcast Solutions Inc

FJS International, LLC

Willys Widgets

Ritter Battery

Abel Cine

CineLab

Visual Products

CineTape

The Slider

Aerial Filmworks

rebotnix Technologies

Gamma Ray Digital Inc

Media Blackout - Custom Cables and AKS

Metropolis Post

Glidecam

Paralinx LLC

Wooden Camera

Technodolly

Tai Audio

Rig Wheels Passport

New Pro Video - New and Used Equipment

Tai Audio

Media Blackout - Custom Cables and AKS

Rig Wheels Passport

Gamma Ray Digital Inc

Willys Widgets

Wooden Camera

Paralinx LLC

CineLab

rebotnix Technologies

Abel Cine

FJS International, LLC

CineTape

Technodolly

The Slider

Aerial Filmworks

Broadcast Solutions Inc

Ritter Battery

New Pro Video - New and Used Equipment

Visual Products

Metropolis Post

Glidecam