[kh1234567890]

I just looked at the page for the iPhone 6s, and while they brag about 12 megapixels and 4K video and even mention the lens being f/2.2, at no place do they mention the sensor size or lens focal length.

4.15mm f/2.2 - 29mm FF equivalent

[tibbitts]

You wouldn't want an accessory that makes your lens a stop faster AND a wider FOV? Ok, whatever. I would.

I just don't see a big demand for a wider FOV for Pentax-mount FF lenses on APS bodies, so my comment was more along the lines of why would a manufacturer produce the device for Pentax, regardless of usefulness.

[Nicolas06]

That's commonly called a normal lens.

https://en.wikipedia.org/wiki/Normal_lens

+1 !

What more funy if we go futher on this topic is that our eyes have a focal length of arroud 15-22mm depending on how you mesure. The 22mm is associated to a typicall 40-60 field of view where 1 eye can still see signifcant details. That equivalent to a 28mm in APSC or 43mm on FF or 22mm on m4/3 or 15mm on a 1" sensor. The 2 last sensor size, respectively m4/3 and 1" are so going to give result the more like our own eyes. By that standard, using a 50mm on a 35mm body is not that satisfying and APSC with a 35mm while not ideal is already better ! That of course an approximation because we have 2 eyes... We have a panoramic view of arround 180 field of view... That's why picture are often shoot in landscape mode and screens are also in landscape mode... But unfortunately the lense that provide such angle of view on a camera do have different perspective rendering and so do not feel natural... You can't have the same as what our eyes see... Either you get the full panoramic view with heavy distorsion... Either you get the perspective rendering and magnification but loose most of the field of view!

The next funy topic would be the appertures... People love theses day the large apperture like f/1.4... That something ours eyes don't have neither. The best we can do is f/2.8 and that for light gathering, not creative deph of field that obviously is counter productive: the goal is to have everything in focus when you try to see something ! Not the reverse. Anyway with a 15-22mm lense, this is not going to be the kind of bokeh theses 85mm f/1.4 fanatics love to use !

Some people are nostalgic of the 35mm format that they used not because it is better but basically because it was the least expensive and smallest format available back in time with "so-so" quality. Would they had higher quality standard, they would have used significantly larger format with quite different focal length range... After all the camera producting the best pictures are still using quite large film and are not even digital.

But today, there kind of snobery to think that 35mm format is the graal and that everything should gravitate arround it... Even through it is now used only by a minority of people.