PNG to DEM-TIFF height file max out black white

Thank you for all your responses.

As far as I am aware, greyscale height maps are usually 16 bit ones.

If you need height maps with full 16bpc greyscale ranges, you will have to look elsewhere, and avoid Photoshop. Unless you don't mind outputting 16bpc PNG images that are choked.

Photoshop's "16bit per channel" mode is not true 16 bit per channel, and will cut off full 16bpc image range to a value range starting at 0 and ending at (2^15) +1. It's basically a programming trick to simplify calculating with the values: 0-32767 + 1 = 32768 values is simpler to calculate with (simple one-shift divisions) rather than 0-32767. Basically what PS works with are 1 to 1 values on the end points and doubling up in the middle.

So, while Photoshop's "16bit" mode requires 16bit to represent this (2^15)+1 , and it only uses that to handle the +1 value to simplify and speed up internal calculations. But in effect if you feed Photoshop a full 0-65535 value range height map greyscale image or a high/full range 32bit image for down-sampling to 16bit, Photoshop will reduce that to a 32768 range one instead of the expected 0-65535 range.

A conversion basically that reduces it to a 15bit value range. Without telling you.

In short, it is impossible to output a full range 0-65535 value range 16bit height map from Photoshop. Of course, the question is whether this matters in practice: the original data actually may not be using the full 16bit value range or not.

Still, PS potentially throws away a huge amount of your 16bit data IF your source data does map beyond 32768 values.

https://forums.adobe.com/people/Vanilla+Vanilla  wrote How to max out black white in Photoshop? So, maxing out the grey colors extending them to a maximum black level and white level.

Can you translate that into understandable English or are you trying to describe what threshold does?