Luminous Landscape Forum

Equipment & Techniques => iPhone and Mobile Photography => Topic started by: Slobodan Blagojevic on May 17, 2019, 03:09:05 pm

Title: Confused About iPhone XS Max Focal Lenghts
Post by: Slobodan Blagojevic 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!?
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Bart_van_der_Wolf 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
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Slobodan Blagojevic 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?
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Manoli 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.
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Bart_van_der_Wolf 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
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Slobodan Blagojevic on May 18, 2019, 02:32:10 pm
...Maybe it's recorded in the EXIF metadata?

This is what LR displays:
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Slobodan Blagojevic 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.
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Bart_van_der_Wolf 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
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: 32BT on May 18, 2019, 03:21:32 pm
Unless behind the 6mm lens there is still the old smaller sensor...
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Slobodan Blagojevic 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?
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Manoli 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.

Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Slobodan Blagojevic 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.
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Manoli 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.
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Slobodan Blagojevic 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.
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: fdisilvestro 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
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Manoli 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.

Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Slobodan Blagojevic on May 19, 2019, 08:58:18 pm
Thanks all, it makes sense now.
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: fdisilvestro 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


Title: Re: Confused About iPhone XS Max Focal Lengths—smaller sensor too
Post by: BJL 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.)
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: fdisilvestro 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
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Manoli on May 20, 2019, 05:52:31 am
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.

Dear Francisco,

I've no desire to engage in a handbags-at-dawn exchange with you, and I'm "happy that you're happy" but that does little to enlighten us. Apple, I'm told, does not allow access to RAW data for the telephoto lens, only the wide-angle. I've passed on info communicated directly from 2 developers via personal email. I've given you the date Apple effected the restriction, it seems abundantly obvious that that limitation still exists. Your post above just confirms this and repeats what I've posted above.

Some developers have circumvented these limitations ( and I agree that the reason 'why' re the EXIF data is not immediately apparent). Moment adheres to Apple guidelines - try zooming in RAW and you'll get a message 'zoom not supported in RAW capture". (see attached)
Others have bypassed restrictions by using a jpeg as well (?) . Halide call it smart RAW.  What exactly is involved I dunno, for sure it's not pure RAW as we been accustomed to and of necessity the shot has already been demosaiced .

If you have factual info to contradict this please educate me - I'll be grateful.
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Manoli on May 20, 2019, 05:53:04 am
... 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 ...

Moving on, it seems that the Huawei w/ Leica optics smartphone has moved up a gear by employing "field-of-view fusion" zoom, using super-resolution algos (up to 3x), and a 5x zoom with technology referred to as 'folded optics'.  Interesting qualitative comparison w/ the Apple Xs at DxOMark.  https://www.dxomark.com/huawei-p30-pro-camera-review/

Expect to see a a variant of this in the 2019 iPhone expected later this year.
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: fdisilvestro on May 20, 2019, 07:26:04 am
Dear Francisco,

I've no desire to engage in a handbags-at-dawn exchange with you, and I'm "happy that you're happy" but that does little to enlighten us. Apple, I'm told, does not allow access to RAW data for the telephoto lens, only the wide-angle. I've passed on info communicated directly from 2 developers via personal email. I've given you the date Apple effected the restriction, it seems abundantly obvious that that limitation still exists. Your post above just confirms this and repeats what I've posted above.

Some developers have circumvented these limitations ( and I agree that the reason 'why' re the EXIF data is not immediately apparent). Moment adheres to Apple guidelines - try zooming in RAW and you'll get a message 'zoom not supported in RAW capture". (see attached)
Others have bypassed restrictions by using a jpeg as well (?) . Halide call it smart RAW.  What exactly is involved I dunno, for sure it's not pure RAW as we been accustomed to and of necessity the shot has already been demosaiced .

If you have factual info to contradict this please educate me - I'll be grateful.

My proof is the DNG files generated by the LR camera. Here is an example, but just in case these images were taken with a iPhone 7 Plus with iOS 12.2 and LR v. 4.3.0

1.- I took two images with the 6.6mm tele lens (should be called normal), one straight and the second with a 200% zoom and here is how they look in LR

First image - no zoom

(https://www.frankdisilvestro.com.au/img/s/v-10/p3425229345-3.jpg)

Second image: 200% zoom

(https://www.frankdisilvestro.com.au/img/s/v-10/p3425229343-3.jpg)

Note that both images have the same size, and the second shows a smaller "Cropped dimension"

2.- When I go to the develop module and open the crop tool you can see that all LR does when zooming is applying a crop, nothing else, and that's why you don't receive the warning in LR

(https://www.frankdisilvestro.com.au/img/s/v-10/p3425229348-3.jpg)

Now is it an undemosaiced raw or a linear raw?

First evidence: Open the image (the zoomed one, but it would be the same with any) in RawDigger and the EXIF shows "Parametric Interpretation: Color Filter Array". You will not get this message it it were linear raw

(https://www.frankdisilvestro.com.au/img/s/v-10/p3425229349-3.jpg)

Second evidence: Open the image in RawTherapee and go to the demosaicing tab and it shows "Sensor with Bayer Matrix" and you can choose the demosaicing algorithm of your liking. Try to do that with a linear raw

(https://www.frankdisilvestro.com.au/img/s/v-10/p3425229358-3.jpg)

So. Yes, LR Produces a UNDEMOSAICED RAW from the iPhone tele lens and zoom is just a CROP (Metadata), it does not affect the raw image.

I don't know if Adobe has any special agreement with Apple, but this is real, try LR if you don't believe me.
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Aram Hăvărneanu on May 20, 2019, 07:51:32 am
The two cameras used two different sensors with different crop factors.
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Manoli on May 20, 2019, 08:29:08 am
Francesco,

Yes, thank you for that.
No doubt that that's accessing the tele lens.
I've already emailed one developer asking for an update. If I get any feed back I'll post it here.
I'm wondering why the discrepancy between apps - however no point speculating, so I'll wait for the reply.

Thanks again,
Best,
M

One question, how do you select the tele lens on your 7 in Lr - Is there a 2x zoom button on the UI ?
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: fdisilvestro on May 20, 2019, 08:57:20 am

One question, how do you select the tele lens on your 7 in Lr - Is there a 2x zoom button on the UI ?

Hi Manoli, thanks for your comment. in the LR camera there is toggle button that has an icon of a lens and you toggle between T (tele) and W (Wide). You can see how they look in the following image (highlighted with red arrows)

(https://www.frankdisilvestro.com.au/img/s/v-10/p3425378381-4.jpg)
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: Slobodan Blagojevic on May 20, 2019, 01:46:15 pm
... Second image: 200% zoom

Note that both images have the same size, and the second shows a smaller "Cropped dimension"

2.- When I go to the develop module and open the crop tool you can see that all LR does when zooming is applying a crop, nothing else, and that's why you don't receive the warning in LR...

Just to make sure there is no misunderstanding: when you talk about 200% zoom, that is not the same as selecting the tele lens/camera, right?
Title: Re: Confused About iPhone XS Max Focal Lenghts
Post by: fdisilvestro on May 20, 2019, 02:48:45 pm
Just to make sure there is no misunderstanding: when you talk about 200% zoom, that is not the same as selecting the tele lens/camera, right?

Right, I selected the Tele lens and on top of that zoomed into the image. I should have chosen a value different than 200% to avoid the confusion.