What is the definition of the large aperture lens mentioned on the mobile phone? For example, how many apertures does the large aperture of iphoneF2.4 and HTC ONE S F2.0 correspond to SLR?

I'd be happy to answer your questions.

As for the aperture, generally speaking,

The formula is, aperture F= lens focal length D/ entrance aperture diameter φ. Accurately speaking, this formula is limited to direct light, in other words, professional astronomical telescopes can refer to it. The general photographic lens uses more lenses to correct the phase difference and loses more light. So it can't reach this level. Therefore, the accurate aperture of the photographic lens is t value, T=F value/square root of light transmittance.

So although the aperture value of the photographic lens is the same, the actual aperture size will not be the same. But the lens marked with T value must be the same.

This is the standard of aperture. The aperture definition of a photographic lens is the same. Aperture is just a numerical value, which does not represent the amount of light entering the lens.

Let's talk about SLR aperture and mobile phone. The photosensitive element of mobile phone is very small. And the SLR is very big. The actual physical focal length of a mobile phone divided by the aperture is the aperture. This data may be larger than some lenses of SLR. This is normal.

As for the aperture of the mobile phone, it corresponds to the aperture of the camera. It also corresponds.

Besides, the aperture of your mobile phone is larger than that of SLR. You must have noticed that the maximum aperture of the zoom lens is only 2.8, and the head can be easily focused at 1.8. This is related to lens structure, lens coating and glass material.

First of all, you should understand several aberrations of the lens, such as dispersion, coma, spherical aberration and so on. Because the zoom lens needs to correct the phase difference of several focal segments or more, it is necessary to use more or higher refractive index glasses and aspherical mirrors. But these problems are that the more lenses, the more aberrations. Therefore, subjectively, the aperture must be small to minimize stray light scattering in the lens.

As for the back-illuminated type. It's good to have it, but it's no big deal not to have it. You need not worry too much. At least at present, cameras with large negatives have natural advantages over cameras with small bottoms in terms of latitude.