2.40:1 Center extraction

[Kim Frank]

I grabbed this framing chart in an articel about THE GIRL WITH THE DRAGON TATTOO (I can't remember wich one exactly)

I really like the idea of being able to pan and scan in post.

My question is: With this frame extraction, what is the crop factor I need to calculate?
In other words: What focal length do I need to use to get for example an 35mm equivalent in the final cropped frame?

And why exactly did they use 3600 x 1500 - is this a 4K final? I thought 4K resoloution is around 4000 horizontal pixels?

I'm really bad in maths, so I would really appreciate your help

Regards
KIM

EDIT: Found out how to calculate it. Read post 5 if you're interested.

 

[Kim Frank]

I'll try a little BUMP on my question, because I would like to use this technic for a shoot next week and am trying to find out if the Arri Allura 18-80 fits my needs on the short end.

 

[Björn Benckert]

It's because they shot part of the movie on red one / 4k and Finsher wanted to master in 2:41 but he also wanted to record a larger "look around area" to be able to "rerack" the shots in post. Then as I heard they moved on to epic and recored parts of the fim in FF5k but only used 3600x1500 so then he got even more lookaround to choose from. I guess he figured that almost 4000 pixels was good enough, and if it's shot correctly, then yes 3600 pixels is quite enough. And as I heard they pulled out and used the full 5K horisontal width for some shots as well.

 

[Kim Frank]

Thanks Björn...

Main thing I'm wondering about is how to calculate the magnifying aspect for the focal length using a crop factor like this.

Also I'm wondering how they get the Resolution they are starting with: 4352x2176 2:1.
All I can find about Red resolution are these Numbers:
RED One "4K" modes are as follows:

4.5K = 4480x1920 | 2.33:1
4K 16:9 = 4096x2304 | 16:9
4KHD = 3840x2160 | 16:9 (this is commonly known as quad-HD or 4xHD 1080p)
4K2:1 = 4096x2048 | 2:1

Or is there the possibility to shoot 4.5K 2:1 with RED MX?
Where can I find the different shooting aspect ratios with the resolution output. Nothing like this in the manual.

 

[Kim Frank]

All right. After extensive searching on the board I found the answers I was looking for. In case someone needs to know this at some point, here is how to calculate the Crop Factor for any given Centercrop:

1. To calculate the crop factor you need to know the recordable area size of the sensor (or negativ). For example: Super-35 is 24mm wide and FF35 is 36mm wide. To determine the crop Factor from FF35 to Super-35 you simply need to devide these numbers to get the crop for matching the horizontal view. So: 36/24=1,5.
Now you can either multiply or devide your focal length with this crop factor to get the equivalent. For Example: To get the Field of View of a 35mm on FF35 on Super-35 you'd need a 23mm (35/1,5=23,33). The Field of View of a 50mm on Super-35 would match with a 75mm on FF35 (50*1,5=75)

All right. That I knew. My question was, how to calculate the crop factor for the centercrop of the image they used in 'Dragon Tattoo' wich was 3600x1000 for the RedOneMX and 4122x2048 for the EPIC. Here's how to:

2. So you nee to know the area size of the sensor being used to determine the Crop Factor. To do hat you simply need to multiply the recorded resolution by the size of photosites (sensor pixels). All RED cameras at the moment share the same sensor so the size of the phtosites is 5.4 microns or 0.0054mm.
The maximum resolution of the RedOneMX at 4.5K is 4480 in width what equals 24,19mm of the sensor is used (4480*0,0054=24,19). The MX at 4K 2:1 is 4096 = 22,1mm (4096*0,0054=22,1). EPIC at 5k is 5120 = 27,64mm.
Same for any centercrop you perform in postproduction as in 'Dragon Tattoo' where the centercrop of 3600 in width equals 19,44mm of the sensor was used (3600*0,0054=19,44).

3. To calculate the Crop factor you again simply need to devide by the recorded (or cropped) area size of the Sensor or negative. So the crop factor of the 'Dragon Tattoo' Centercrop (19,44mm) in relation to the width of te RedOneMX at 4.5K (24,19mm) is 1,24 (24,19/19,44=1,24). The Numbers from Super-35 to this centercrop are nearly the same (24mm/19,44=1,23).
For example: you would need to use about a 40mm with the centercrop to get the field of view of a 50mm on Super-35 or MX at 4.5K (50/1,23=40,65). In relation to a 50mm on FF35 you'd need a 27mm when using the 'dragon Tattoo' Centercrop.
Okay one last time, how did I get these numbers: To find out the crop factor devide the width of FF35 (36mm) by the width of the sensor area used with the Centercrop (19,44mm). So: 36/19,44=1,85 crop factor. Now to find out what focal length equals the field of view of a 50mm on FF35 when you want to use the centercrop in post simply devide the focal length by the crop factor: 50/1,85=27,02.

Maybe that helps someone else aswell. By the way the centercrop they used with EPIC in 'Dragon Tattoo' (4122x2048) equals a sensor size used of 22,25mm in width (4122*0,0054=22,25). In relation to Super-35 that only makes a Crop factor of 1,07 (24/22,25=1,07).

 

[PatrickFaith]

Awesome compositing with GWTDT. In the blu-ray edition of "THE GIRL WITH THE DRAGON TATTOO" they go over the reframing (I'm perty sure I saw that in the extra's area). Another real good talk at http://jonnyelwyn.co.uk/workflow-fo...sual-effects-the-girl-with-the-dragon-tattoo/ (is totally worth the time to watch that entire clip ... is titled part2 on the page with the wrong image ... but is a great walk thru of nuke 4k process).

In nuke when you crop/center their is sampling options ... they didn't show the actual pop up of the selection in nuke for that, I'd like to know the algorithm they used, since it looks so nice(i.e. I"m assuming it was one of the cubic options).