Dear Nik, thank you for response. I will be happy if a selective adjustment and a grain tool will be added to RAW Power.
Concerning real film grain. Real film granulation appears non-equally. The grains are most visible in the midtone areas, much lesser visible in the highlight and dark areas, and almost disapoears in the most dark areas of Zone 0 (according to Ansel Adams 10-zone system). Most of the grain emulation tools was created by young persons, who do not remember the “pre-digital era” thus never seen how real grain looks. DxO, Capture One, and Snapseed developers created correct grain tools like in a real film frame, while the others merely superimposed a grain pattern equally on both the highlights, midtones and darks that is incorrect and looks poor to everyone who once developed scanned film frames over decades.
As you understand from the above, to achieve the correct grain look a grain pattern is applied using a hill-like opacity curve, which has about the one-third height at the highlight end of the histogram and almost falls down at the dark end of the histogram. Also, in this case the granulation looks voluminous, not flat. This is the answer of a DXO woman sent to me ten years ago when I corresponded with the DXO personnel on this subject. Scroll down the article on this theme for detail: there on bottom of the discussion are many other illustrative pictures and links to many other articles on this theme. But all of those points to the aforementioned bell-like curve showing the film granulation lesser at the highlight end and even much lesser at the dark end of the histogram.
It is simpler to show ratrher than explain by words. So, below are screenshots, a 100% magnification, made from my film frames. Two types of film are presented here — Kodak Tri-X and Rollei IR-400 — because they manifest the most beautiful and sharp film granulation. These are 6 x 7 film frames scanned with an Imacon/Hasselblad drum scanner in 2014 at a 4,800 dpi resolution. When printing such super-MegaPixel scans on a 75 x 100 cm paper, they show a very nice granulated texture. Otherwise, say, if printing a digital image in such a large format without a film grain superimposed, it looks soapy that is absolutely rejected by collectors and art fans in general.
P.S. A little bit of offtop. As a matter of fact that there is also a problem with the magnification of digital images, because for printing a 75 x 100 cm needs a 120-130 MPx image. Here is also a problem with iOS software. A Windows/MacOS workflow uses Benvista PhotoZoom Pro (costs 160 Pounds) with its a patented magnification algorithm of which has no other alternative for 600X+ magnification. There is only one iOS program application, Big Photo, which uses a similar algorithm. But it gives only a PNG-8 output in the moment. I already contected the developer on this subject; he obligated to add PNG-24 and TIFF 8 and16-bit output to the forthcoming release.
So, below are a few of 100% magnification screenshots from my scanned film frames. You can easily see how the real film granulation has a maximum in the midtone areas, is a bit lesser in the highlight areas, and is much lesser in the very dark areas (on the black tree branches). Snapseed follows this way, so producing the film granulation in the right way, but only using a very large grain. Darkroom for iOS — does not; it applies the granulation equally throughout the image.
I hope this will be useful to you. — Dmitri