Tracking: Camera Data info for iPhone / iPad devices


(Mal Duffin) #1

I’ll keep the collected data at the top of the post and update as required. For tracking, BOTH Focal Length and Sensor Width are the main two factors required. I don’t have all these devices, so confirmation from board members who do and who have tested tracking will help validate the info here.

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Model : Sensor Width (Landscape/Portrait) : Actual Focal Length : Focal Length (35mm equivalent) : ( Field Of View )

iPhone 3G/3GS : 3.39mm / 4.54 mm : 3.85mm : ??? : ( 37mm )
iPhone 4 : 3.39mm / 4.54 mm : 3.85mm : 29mm: ( 37mm )
iPhone 4S : 3.39mm / 4.54 mm : 4.28mm : 35mm : ( 43.2mm )

iPad 1/2 = iPhone 3G/3GS?
iPad 3 = iPhone 4?

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To Test: When your point tracking looks good, you don’t have to re-do this part. Solving is where this camera info becomes important - it is required to convert the tracked points to 3D space. Different lenses make things look closer / further, so having a wrong focal length will really show when you try to match up eg a 3D plane with a tracked point in the corner of a room, and the source video. Correct numbers for both are key for getting this to work as accurately as possible before tweaking other settings.

Source Info ( info differs based on what sites you visit )…

The actual focal length on the original iPhone (2G), iPhone 3G/3GS, and iPhone 4 (rear-facing main camera) is 3.85mm.
The field of view (35mm SLR camera lens equivalent) for each model is listed here:
Original iPhone (2G): 37mm
iPhone 3G: 37mm
iPhone 3GS: 37mm
iPhone 4 (rear-facing main camera): 30mm

If the sensor is 3.39 mm tall (referenced to landscape mode), then half that is 1.695 mm. Focal length for the iPhone 4 is listed as 3.85 mm. atan(1.695/3.85) is 23.75 degrees from center to top, or 47.5 degrees top to bottom.
For the longer dimension 4.52/2 = 2.26 mm, atan(2.26/3.85) = 30.41 center to side, or 60.8 degrees left to right (again referencing with respect to landscape orientation).
So 60.8 degrees horizontal by 47.5 degrees vertical.
ADDED much later:
The focal length for the newer iPhone 4S back camera is listed as 4.28 mm, but with the same sensor dimensions as the older iPhone 4. So:
2atan(2.26/4.28) = 55.7 degrees, by 2atan(1.695/4.28) = 43.2 degrees
or roughly a 4 to 5 degree smaller field-of-view compared with the iPhone 4.

Seems there is a little mistake in previous calculations OV8830-G04A sensor has dimensions 4592x3450 um
Then correct angles are:
2atan(4.592/(24.28))180/pi = 56.423
2
atan(3.450/(2*4.28))*180/pi = 43.903
It becomes very crucial in sensitive applications.

Focal Length (35mm equivalent):
iPhone 4 29 mm
iPhone 4S 35 mm

Original Post-----------------------------------------------------------------

Hey there,

If any artists out there have been trying out the new Tracking and Solving feature of Blender, and using iOS devices for capturing the video, what settings have you been using for the Camera Data?

More specifically, what focal length and sensor width values are you using? If we can get this data for a number of popular handheld devices ( iOS / Android eg Samsung S2 ), we can see about getting the presets included with a future version of Blender.


(Richard Marklew) #2

Have you tried the forum search, this has been asked before. Sensor size is straightforward from looking at teardowns from sites like ifixit and a simple google search of part numbers.


(Richard Marklew) #3

You seem to be quick at replying to my previous posts, but I’m not sure if you’re being sarcasticly unhelpful or just annoyingly obtuse and perblind.
It means you would get the same answer as in that thread and I didn’t feel like repeating myself. The sensor size seems to be that given. If the size is that, then that’s the figure you should use in the tracking camera settings. If it’s 5mm, you don’t use 10mm, you use 5mm.
If you want data, you should get real data, not data that ‘seemed to work’ in a users tracking. If it’s not correct it may be ok to get away with in one tracking but not in someone elses.


(mbresciani) #4

Thanks malCanDo, this is really useful!

I have been looking for values like these for ages. I have done forum searches, Google searches and all I got vague answers each with differing figures, and found no actual examples.

This thread would be a great place to get definitive vaules that have actually been proven to work and link to some real iPhone camera tracking videos examples.

(Richard, why would you try to obfuscate? You have gone to the trouble of writing 2 posts so far. Why not be helpful and post figures that have actually worked in a practical example, with video links if it is so easy to get the data?)


(Mal Duffin) #5

Just saw this link while searching on updates, looks like some of the values work OK for iPad devices!

If others have successfully got tracking working, please post the device name and the values that you used. If we can get a good working set of values, we might be able to get them incorporated into the Blender presets drop down list.


(see360) #6

I can confirm your iphone 3GS setting with
focal length = 37 mm
screen size = 35 mm.

These were the settings I used in the 2.59 “Tomato Branch” before tracking made it into trunk (so if anything changed I haven’t verified it). This video used these settings: http://www.youtube.com/watch?v=cvATIcAPj5k&feature=youtube_gdata_player

Richard, there was a time when these settings were not easy to find and sensor size stats were not consistent at various web sites. I arrived at these settings with trial and error, because clearly the tiny eyephone camera lens does not actually have a focal length of 35 mm, but these values worked best in blender after much experimenting. Maybe it will save the next guy or gal a little time : )


(andrewprice) #7

Just wanted to chime in and say thanks for posting this.
Finding this information online is surprisingly difficult. In fact it was one of the many google searches I did that brought me to this exact page. So thanks malCanDo :slight_smile:


(gpaprmh) #8

According to one of my CalibrateCamera.py tests, the Iphone5 that I tested worked out at 33.257mm ( 35mm equiv…which is sw=36mm btw…) for a full pic (5MP), but in video mode (1080) it calibrates to 38.6 because (like most low end cameras) it does not use the whole sensor width for video. Since there is no way to tell exactly how much of the sensor is actually used, you are much better off just using the 35mm equiv…

will start thread on this script soon…


(3pointEdit) #9

I just found this video on youtube that does exactly this! Oh wait it’s gpaprmh’s… great job. Nice integration.


(PhilFX) #10

hi, everybody. i’ve been recently using Autodesk MatchMover to track an iPad3 hd shot. That software is very accurate regarding lens estimation. Hope this will help.


So the iPad3 seems to be 4.280
and 18.453 as 35MM equivalent.
More details in the screen shot…

PhilFX


(gpaprmh) #11

@ PhilFX: Sorry, but I believe you are mistaken…

your sensor sizes are way off - should be in the 4-5mm width range… not 14.7
I believe the 35mm quiv fl would be approx double what you are showing - in the 37-38mm range… sometimes you can get a good solve with a totally wrong fl and often it can be a multiple of the true fl


(uruburei) #12

help
I have a camera of SONY DSC HX 300, do not know how to put the data in the Movie Clip Editor for “camera data” to add in “camera preset”. Could someone help.
I searched this site, but do not know where to put the data.
http://www.dpreview.com/products/sony/compacts/sony_dschx300/specifications


(gpaprmh) #13

It all depends on what mode you are using…according to the specs, you should start with sw = 36, fl = 26.5 if you are shooting 16:9 with (SteadyShot Standard) at minimum zoom… I believe Sony uses a diagonal focal length and blender needs a horizontal focal length so I suspect it may actually be slightly higher (~28mm)

Focal Length (35mm equivalent) :Still 4:3: 24-1200mm
Movie 4:3: 32.5-1625mm(SteadyShot Standard), 34.5-2300(SteadyShot Active)

Still 16:9: 26-1300mm
Movie 16:9: 26.5-1325mm(SteadyShot Standard), 28-1850mm(SteadyShot Active)


(enilnacs) #14

Guys, just for info if you need exact data, wikipedia has updated VERY exact measures of nearly all devices in a GREAT list.

BUT, Remember that the iOS also stabilizes and don’t use the FULL sensor size… how much ? Here i calculated the result: