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Author Topic: Confused About iPhone XS Max Focal Lenghts  (Read 1003 times)

Slobodan Blagojevic

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Confused About iPhone XS Max Focal Lenghts
« on: May 17, 2019, 03:09:05 pm »

It has two lenses, 4.25mm and 6mm.

The wide angle has apparently an equivalent focal length of 26mm (in full-frame terms). Then when you want to use the other lens, the screen offers a "2x" icon to press. Most, if not all, reviewers put that lens equivalent at, naturally, 26mm x 2 = 52mm.

And yet, 6mm divided by 4.25mm equals 1.4x factor, which would put the other lens in the 37mm category, not 52mm.

What gives!?
« Last Edit: May 18, 2019, 03:55:58 pm by Slobodan Blagojevic »
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Bart_van_der_Wolf

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Re: Confused About iPhone XS Max Focal Lenghts
« Reply #1 on: May 17, 2019, 06:43:53 pm »

What gives!?

When you try taking a perpendicular picture of e.g. a ruler, and you select 2x, what happens? Does your field of view see half of the length?

Cheers,
Bart
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Slobodan Blagojevic

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Re: Confused About iPhone XS Max Focal Lenghts
« Reply #2 on: May 18, 2019, 01:12:55 pm »

When you try taking a perpendicular picture of e.g. a ruler, and you select 2x, what happens? Does your field of view see half of the length?

It does, based on my not-so-scientific measurement.

However, it does not explain the mystery of why the tele lens is not listed as 8.5mm if the wide is 4.25mm. Does that mean that, to reach 2x, a combination of optical and digital enlargement is taking place?

Manoli

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Re: Confused About iPhone XS Max Focal Lenghts
« Reply #3 on: May 18, 2019, 01:38:23 pm »

It has two lenses, 4.25mm and 6mm.

Does it ?

The only spec I've seen is that of the front lens being an f/1.8, the telephoto an f/2.x

The '7' was a major upgrade w/ a new lens and sensor.
The 'Xs' is essentially the same lens(es) but the sensor has been increased to a 1/2.5" w/ increased pixel size 1.4nm, net result being that the old 28mm is now somewhat wider , ditto for the second lens.

None of the app developers can access the telephoto part of the cam subsystem. Apple has kept that secret. Net result being that you can only RAW capture using the wide angle. Telephoto capture in RAW is strictly 'verboten'.

If it is indeed a 2x zoom, it wouldn't be unreasonable to guess that Apple have some hidden hocus pokery and the zoom section isn't purely optical.
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Bart_van_der_Wolf

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Re: Confused About iPhone XS Max Focal Lenghts
« Reply #4 on: May 18, 2019, 01:47:55 pm »

It does, based on my not-so-scientific measurement.

However, it does not explain the mystery of why the tele lens is not listed as 8.5mm if the wide is 4.25mm. Does that mean that, to reach 2x, a combination of optical and digital enlargement is taking place?

That was exactly what I was trying to get at. If the focal lengths indeed are 4.25 mm and 6 mm then there is an additional 1.4167x digital zoom involved to reach the 2x linear scaling factor. But there is surprisingly little info about the focal lengths. Maybe it's recorded in the EXIF metadata?

Cheers,
Bart
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Slobodan Blagojevic

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Re: Confused About iPhone XS Max Focal Lenghts
« Reply #5 on: May 18, 2019, 02:32:10 pm »

...Maybe it's recorded in the EXIF metadata?

This is what LR displays:

Slobodan Blagojevic

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Re: Confused About iPhone XS Max Focal Lenghts
« Reply #6 on: May 18, 2019, 02:36:41 pm »

... Net result being that you can only RAW capture using the wide angle. Telephoto capture in RAW is strictly 'verboten'...

My LR Mobile delivers DNG raws with the tele lens.

Bart_van_der_Wolf

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Re: Confused About iPhone XS Max Focal Lenghts
« Reply #7 on: May 18, 2019, 02:58:56 pm »

This is what LR displays:

Well, 4.25 mm and 6 mm it apparently is.
The rest must then be 'digital zoom', despite it being advertised as optical zoom.

Cheers,
Bart
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32BT

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Re: Confused About iPhone XS Max Focal Lenghts
« Reply #8 on: May 18, 2019, 03:21:32 pm »

Unless behind the 6mm lens there is still the old smaller sensor...
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Slobodan Blagojevic

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Re: Confused About iPhone XS Max Focal Lenghts
« Reply #9 on: May 18, 2019, 03:42:11 pm »

Unless behind the 6mm lens there is still the old smaller sensor...

Ha! Clever.

Would they really use two sensors?

Manoli

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Re: Confused About iPhone XS Max Focal Lenghts
« Reply #10 on: May 18, 2019, 07:36:04 pm »

My LR Mobile delivers DNG raws with the tele lens.

I doubt it.

Lr can delivers DNG, but they're not necessarily RAW - possibly linear DNGs from gamma encoded JPEGs or TIFFs. They are not "RAW files" in that they've already undergone a demosaicing process but they are indeed DNG files in a linear gamma ...(Schewe)

Proof: try zooming in any of the true RAW capture apps - you can't. You'll get a message "zoom not supported in RAW capture". Try zooming in Lr Mobile, camera set to RAW capture and no such limitation exists. There's your answer.

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Slobodan Blagojevic

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Re: Confused About iPhone XS Max Focal Lenghts
« Reply #11 on: May 19, 2019, 01:27:08 am »

I doubt it.

Lr can delivers DNG, but they're not necessarily RAW - possibly linear DNGs from gamma encoded JPEGs or TIFFs. They are not "RAW files" in that they've already undergone a demosaicing process but they are indeed DNG files in a linear gamma ...(Schewe)

Proof: try zooming in any of the true RAW capture apps - you can't. You'll get a message "zoom not supported in RAW capture". Try zooming in Lr Mobile, camera set to RAW capture and no such limitation exists. There's your answer.

I am not sure I follow. What does it mean one can not zoom in a “true” raw app!? Just because some apps can not and LR can is a proof that those are not true raw files in LR!?

Well, I am not as sophisticated as Jeff Schewe, so i usually distinguish jpeg from raw if I can adjust white balance. If jpeg, the only options are As Shot, Auto, and Custom. Raw files offer the full range of wb options.

Manoli

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Re: Confused About iPhone XS Max Focal Lenghts
« Reply #12 on: May 19, 2019, 02:39:16 am »

Slobodan,
Your original question was

It has two lenses, 4.25mm and 6mm.
6mm divided by 4.25mm equals 1.4x factor ... What gives!?

The straight answer is, a 12Mp secondary 2x tele-camera with 1/3.4″ sensor (1.0µm pixels) f/2.4, 52mm equivalent focal length.  But, the API to RAW is only available to developers for the wide lens, not the telephoto.
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Slobodan Blagojevic

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Re: Confused About iPhone XS Max Focal Lenghts
« Reply #13 on: May 19, 2019, 02:45:33 am »

... But, the API to RAW is only available to developers for the wide lens, not the telephoto.

Again, what does it mean? LR can use the tele in the raw mode.

FranciscoDisilvestro

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Re: Confused About iPhone XS Max Focal Lenghts
« Reply #14 on: May 19, 2019, 05:28:15 pm »

1. The iphone dual lens have two different sensors. the 2X image is the result of the larger focal lenght and reduced sensor size. If this was not the case you would have to phisically move the lenses when taking pictures (or moving the sensor internally, which does not happen)

2. The iphone does captures real raw (undemosaiced) images (in DNG format) from both the wide and tele lens (at least using LR). You can easily confirm this with an application such as RawDigger, where undemosaiced files show the property "Photometric Interpretation" as "Color filter array" instead of "Linear Raw"

3. You can zoom the image in the phone while in DNG (at least in LR) and all what it does is to set a crop marquee, which you can then edit in LR (so zooming in the phone is really a waste of time)

So, no magic & no conspiracy

Manoli

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Re: Confused About iPhone XS Max Focal Lenghts
« Reply #15 on: May 19, 2019, 07:56:40 pm »

2. The iphone does captures real raw (undemosaiced) images (in DNG format) from both the wide and tele lens (at least using LR) ... You can zoom the image in the phone while in DNG (at least in LR)

zooming in any of the true RAW capture apps - you can't. You'll get a message "zoom not supported in RAW capture". Try zooming in Lr Mobile, camera set to RAW capture and no such limitation exists. There's your answer.

As a matter of record, Apple w/ the advent of iOS 10.2 (2017) no longer allowed active zoom when in RAW mode (either lens) and no longer allowed developers to set EXIF geolocation in RAW files.. JPEG's and TIFF's however will (still) have the data.

Both these restrictions do NOT apply to Lr Mobile. You can both zoom and see EXIF geolocation data whilst in Lr(dng) RAW. So, at this point, the only definitive explanation we'll get is from Apple and the Lr team.

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Slobodan Blagojevic

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Re: Confused About iPhone XS Max Focal Lenghts
« Reply #16 on: May 19, 2019, 08:58:18 pm »

Thanks all, it makes sense now.

FranciscoDisilvestro

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Re: Confused About iPhone XS Max Focal Lenghts
« Reply #17 on: May 19, 2019, 09:08:04 pm »

As a matter of record, Apple w/ the advent of iOS 10.2 (2017) no longer allowed active zoom when in RAW mode (either lens) and no longer allowed developers to set EXIF geolocation in RAW files.. JPEG's and TIFF's however will (still) have the data.

Both these restrictions do NOT apply to Lr Mobile. You can both zoom and see EXIF geolocation data whilst in Lr(dng) RAW. So, at this point, the only definitive explanation we'll get is from Apple and the Lr team.

LR is not really zooming the image. It is just applying a crop marquee that only LR will respect, and you can change afterwards in Post. If you open the DNG in any other raw converter, the zoom setting will be discarded.

In regards to geolocation, it does not make any sense to disable the recording of the GPS data in the raw exif, and I'm happy that this does not apply to LR


BJL

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Re: Confused About iPhone XS Max Focal Lengths—smaller sensor too
« Reply #18 on: May 19, 2019, 09:19:23 pm »

Unless behind the 6mm lens there is still the old smaller sensor...
I do not know about "older", but definitely smaller: like every mobile phone "telephoto" camera that I know of, it achieves its narrower field of view with the combination of a longer focal length and a smaller sensor (and smaller photosites in most cases too) than the "normal" (i.e. moderately wide-angle) camera. (And yes, each is a complete camera; an integrated lens and sensor unit.)
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FranciscoDisilvestro

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Re: Confused About iPhone XS Max Focal Lenghts
« Reply #19 on: May 19, 2019, 09:57:28 pm »

Having multiple cameras is what allows for functions such as "Depth Map support", available in LR under Technology previews
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