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Focal length multipliers & sensor size?

Ed Watkins

Ed Watkins

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Hey all,
I'm just working on an iPhone app for an Angular Field of View Calculator, Dimensional Field of View Calculator, and Lens Equivalence Calculator so I was wondering:

Does anyone know the actual focal length multipliers values for the RED with different lenses, I looked in the F.A.Q and forum and couldn't find the answer.

Is there a FLM when using standard 35mm film lenses on the RED (i assume not)?
And what are the FLM's for 16mm lenses, s16mm, B4 and Nikon lenses on the RED?

Also does anyone have the sensor/film sizes for the RED, s35mm, 35mm (standard), s16mm, and 16mm (standard) in mm?

Any help would be massively appreciated.

thanks,

Ed.
 
Ed Watkins said:
Hey all,
I'm just working on an iPhone app for an Angular Field of View Calculator, Dimensional Field of View Calculator, and Lens Equivalence Calculator so I was wondering:

Does anyone know the actual focal length multipliers values for the RED with different lenses, I looked in the F.A.Q and forum and couldn't find the answer.

Is there a FLM when using standard 35mm film lenses on the RED (i assume not)?
And what are the FLM's for 16mm lenses, s16mm, B4 and Nikon lenses on the RED?

Also does anyone have the sensor/film sizes for the RED, s35mm, 35mm (standard), s16mm, and 16mm (standard) in mm?

Any help would be massively appreciated.

thanks,

Ed.
Click to expand...

DON'T multiply focal lengths - it's leads down a path filled with confusion and half truths.

DO think in terms of horizontal and vertical angles of view. It's relevant to what you are trying to do. It would be great to have a program like P-Cam for the iphone.

I apologize if this sounds preachy, but it's been covered many times on this list.

You're certain to find what you are looking for in terms of sensor size used, in various formats, with the briefest of searches.

Matt Uhry
www.mattuhry.com
 
Matt Uhry said:
DON'T multiply focal lengths - it's leads down a path filled with confusion and half truths.

DO think in terms of horizontal and vertical angles of view. It's relevant to what you are trying to do. It would be great to have a program like P-Cam for the iphone.

I apologize if this sounds preachy, but it's been covered many times on this list.

You're certain to find what you are looking for in terms of sensor size used, in various formats, with the briefest of searches.

Matt Uhry
www.mattuhry.com
Click to expand...

Hi Matt,
Thanks for the feedback,
I understand peoples objections to using LMF, but I'd like to give the option anyway as it is a matter of choice whether to use them or not.

I'm no trying to make a P-cam replacement, I have neither the coding skill, nor inclination to tackle such a project. I merely want to create a small light weight app that has a few useful features on it that DP's/AC's regularly use with the RED.
Namely: DoF calc, storage space calc, max frame settings calc, angle of view calc, and lens equivalence calc.
 
In relationship to 35mm film format and doing my math for horizontal coverage with the RED sensor in 4K as basis:

RED 4K: 22.12 x 12.44mm, 1.0x
RED 3K: 16.59 x 9.33mm, 1.33x
RED 2K: 11.06 x 6.22mm, 2.0x
100mm in 4K is 100mm, in 3K like 133mm and in 2K like 200mm.


In relationship to 35mm still photography:
35mm still: 36 x 24mm, 1.0x
RED 4K: 22.12 x 12.44mm, 1.63x
RED 3K: 16.59 x 9.33mm, 2.17x
RED 2K: 11.06 x 6.22mm, 3.25x
100mm in 4K is like 163mm, in 3K like 217mm and in 2K like 325mm.

If you want to do direct calculations, you can use 5.4u for the pixel size.

I hope this helps and doesn't cause confusion.
 
The only time you really may need to do some calculations is when ordering your lenses, if you are not familiar with the field of view of certain focal lengths when used on a 35mm movie camera, but otherwise, it's important that you mentally stop doing these conversions in your head and just get used to what a certain focal length sees when used on the set.

So when you put the 18mm lens on the camera, for example, you are already familiar with what the view would be. You're not going to spend four weeks on a feature, several times a day, mentally converting the focal lengths of each lens you have to what the 35mm still camera equivalent would be, for example.

The other time the conversion may be necessary is when switching between 3K and 4K modes and you need exact matches in sizes, though generally you don't need to be that precise. For one thing, unless you use a zoom lens, your prime lens sets don't come in perfect matches to all your calculations when converting. So it ends up being done by eyeball anyway.

Anyway, I'm still not sure why so many people are obsessed with these conversion factors...
 
I also happen to agree with both of you. I have personally never needed to do these calculations, however someone requested it as a feature so I thought I'd throw it in.

The only time I thought that the calculator would come in handy when needing to match 2K, 3K, 4K shots

Thanks for all the help though!
 
David Mullen ASC said:
The only time you really may need to do some calculations is when ordering your lenses
Click to expand...



if i shoot 4k in 18mm Zeiss master prime and then later while i'm shooting i change to 2k resolution, the focal length will be equal to 32mm Zeiss master prime, so to speak?


so "theoretically" i could buy 18mm,40mm,100mm Zeiss master prime lens and could achieve the same visual quality as a full set of lens would in film camera?


Edit: my final delivery would be to broadcast 1080i/p or SD.
 
sky1walker said:
if i shoot 4k in 18mm Zeiss master prime and then later while i'm shooting i change to 2k resolution, the focal length will be equal to 32mm Zeiss master prime, so to speak?


so "theoretically" i could buy 18mm,40mm,100mm Zeiss master prime lens and could achieve the same visual quality as a full set of lens would in film camera?


Edit: my final delivery would be to broadcast 1080i/p or SD.
Click to expand...

The 2k shots will look very noticably different/inferior to the 4k shots, even on 1080 delivery.

If you really want to do something like this, I suspect you will get better results with a 2x converter on the lenses.

If you can only buy three lenses, I would just try and pick 3 that you can live with for general work. And then maybe the 2x converter for the rare situation when it's really needed.
 
sky1walker said:
if i shoot 4k in 18mm Zeiss master prime and then later while i'm shooting i change to 2k resolution, the focal length will be equal to 32mm Zeiss master prime, so to speak?
Click to expand...

Well, again, your terminology demonstrates the basic conceptual problem -- if you shoot 4K on an 18mm lens and then you switch to 2K windowed, the focal length is still 18mm. It's just that it has a narrower field of view.

So it would be more accurate to say that your field of view using an 18mm in 2K windowed mode would be equivalent to a 36mm in 4K mode, than it would be to say that the focal length would be equal to a 36mm. I'm just being pedantic, I know.

But no, you can't really just buy three lenses and then use 2K windowed mode simply to create illusion of having three more inbetween focal lengths, due to the loss of resolution compared to shooting in 4K mode.
 
David Mullen ASC said:
So it would be more accurate to say that your field of view using an 18mm in 2K windowed mode would be equivalent to a 36mm in 4K mode, than it would be to say that the focal length would be equal to a 36mm. I'm
Click to expand...


On editing the footage in FCP, can i use 18mm 2k windowed mode as a 'close up' shots and 18mm 4k footage as a 'mid shoot' ? (for 1080 delivery?)

in a 'normal' shoot, how will it be done?
 
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