Cineversity

Hi,
I’m messing around a bit with the iPhone 6S Plus (because it’s always in my pocket.)  I gathered these specs:
Aperture size
F2.2  
Focal length (35mm equivalent)
29 mm
Camera sensor size
1/3” 

But I admit, I’m not entirely sure what to put where in the C4D settings.  The 29mm is a 35mm equivalent, so i’m thinking it’s wrong to just enter 29mm.  Where C4D does it’s own calculation, it seems that entering 44.69 in sensor size gets close to 29mm equivalent (as far as C4D is concerned) but I seem to be getting odd results. 

Any advice appreciated…and I know iPhone should not be my first choice for bigger projects

Thanks so much!
Biagio

Hi Biagio,

An 35 mm equivalent means that a lens with a 29mm focal length will result in the same field of view as the iPhone is doing it, based on your data

If one does the math, this is a horizontal filed of view of ~63.6º and a vertical field of view of ~45º. Those would be my main values.

As for the 1/3”—well—old traditions: if they sell well, they never die
The measurement typically given in inch are based on the tube which had covered in the old days the camera “sensor”. Sony for example loves to measure it this way, as you well know for the EX-1, three 1/2” sensors work inside, but they are only 6.6 x 8.8 mm in size. Which would result in a diagonal of 11mm and not a 1/2” or 12.7mm

So the idea how that circle is drawn around the sensor is kind of fuzzy.

The pixel size is typically given as ~µm = 1.22 for the 6s+ (?), which might give us a rough idea about it. The max res is (?) 4032x3024, but the video is take from and which resolution? UHD or HD… or?

With this comes the difficult part, what area of the sensor is/was used for video? Which format and what “crop” of the sensor will be shown.

The smaller the sensor, the less precise is the center point of the optical axis to the sensor center.

How much stabilization was applied and zoomed in to avoid cropping again and is there rolling shutter already partially corrected?

Is there any lens correction done or is there distortion left?

I have not found any answers to that, well, I only researched it sine I read your question, but make tests, and if you have, run it through other tracking apps, e.g., SynthEyes, to gain some more data.

Keep in mind that lenses have no crop factor, sensors have (if at all). A lens projects its image independent from the sensor it projects to. In this way all data will influence the result.

====

Set the data one time “unknown but constant” and one time Focal 29 and sensor 36, calculate both and compare.
If you take a video, take a full still shot (same POS/POI) as well and compare the size to your video. This gives you an idea how much sensor size is really involved for your video image. A simple tangents-math will give you the “real” focal length used, again, real means here what field of view the focal length in conjunction with the sensor size has produced (I’m not a big fan of the term crop factor, it is not really correct and lead to false data.

My best wishes

As always, Dr. Sassi, thank you for your thorough and helpful reply.  You’re amazing
I’m using an app called FilmicPro to shoot UHD (?)  It’s shooting 3840 x 2160. I have done no lens correction and shot with image stabilization off.  I also picked a shot without (visible) rolling shutter. So I tried to keep the camera from “doing anything” to the video, and then I didn’t do anything to the video, either.

I will run the tests you mentioned and report back when I learn more.  Again, thanks for your kind and quick reply!

All the best,
Biagio

You’re welcome, Biagio!

It was a pleasure to do.

Based on your data in the last post, try a 30.455mm focal length with a 36mm sensor size. Since I have said my text about cropping stuff, I feel free to do it
Also, as you calibrate the scene in terms of length, this scale in the data should work… fingers crossed.

Have a great evening.