How does iPhone 15 Pro Max achieve the three "normal" focal lengths?

[Slobodan Blagojevic]

Namely, 24, 28, 35 mm?

The "normal" one used to be 24 mm in previous models. Now, they offer a choice of "normal" lenses, with a possibility to choose onde of the three as a default "normal" lens.

So, the question is, how do they achieve those focal lengths? Optically? Or just a digital zoom adjustments? If the latter, than I assume the designations of 28 and 35 mm are there simply as a convenience for photographers accustomed to the traditional focal lengths?

[fdisilvestro]

Or just a digital zoom adjustments? If the latter, than I assume the designations of 28 and 35 mm are there simply as a convenience for photographers accustomed to the traditional focal lengths?

Yes, exactly like that.

[francois]

It's just a convenience thing.

You may already have read this review from the Halide app guys, here. It's for the 15 Pro Max but the 24, 35 and 50 mm settings are the same across both iPhones. The reviewer says that he loves it but also "...there's more freedom in shooting at 24mm and cropping afterwards...".

[armand]

I'm not entirely certain it's only cropping. You can shoot the same subject and see what's the size of each photo, if the size is getting smaller than it's cropping, if the size remains the same than it's doing something else in the background

[fdisilvestro]

Any file out of the camera app in the iphone is a processed file. Apple Pro Raw are linear raw demosaiced, processed.

Additionally, the only way to get a 24MP file out of the 12/48 MP Quad sensor is throung post processing.

[Slobodan Blagojevic]

Here are screenshots of file infos for all three "normal" focal lengths. The file dimensions remain the same, so, if only cropping, then there must be some upresing involved?

[francois]

I'm not entirely certain it's only cropping. You can shoot the same subject and see what's the size of each photo, if the size is getting smaller than it's cropping, if the size remains the same than it's doing something else in the background

I've read somewhere (maybe on the Halide guys's blog) that the 24 MP images are done computationally. So it's not exactly  (or only) cropping.

[armand]

I was trying to give my answer to that but the forum is angry with the post

[fdisilvestro]

If you do the math, cropping the image from a 24mm equivalent lens from 48MP to 24MP, gives the field of view of a 35 mm lens, so you could say that 24mm & 28mm are downsized to 24MP, and 35mm are just the maximum crop without resizing.

[armand]

The iPhone sensor has 48MP which are downresed to 24MP if you don't use the raw max, so the 28mm and maybe the 35mm are downresed from the remainder 48MP, so the total resolution stays the same but you lose some dynamic range maybe. Overall I don't think you gain much by shooting at 24mm and cropping after if you are already set to crop.