How to combine individual R,G,B channels into 16bit output?

Nobody has claimed this yet.

What are you trying to achieve?

Selectively extracting single R,G and B channels from three different 16bit input tiff files. Then combining them to a new 16bit output tiff. With srgb output color space (8bit) everything works as expected. As I switch to rgb16 colourspace for output I get a pure black image.

Have you searched for similar questions?

Yes but nothing yet seems to point me on what I'm doing wrong.

Are you able to provide a minimal, standalone code sample that demonstrates this question?

```javascript
Promise.all([
sharp('input1.tif')
.extractChannel('red')
.toColourspace('b-w')
.toBuffer(),
sharp('input2.tif')
.extractChannel('green')
.toColourspace('b-w')
.toBuffer(),
sharp('input3.tif')
.extractChannel('blue')
.toColourspace('b-w')
.toBuffer()
])
.then(images => {
sharp(images[0])
.joinChannel([
images[1],
images[2]
])
//.toColorspace('srgb')
.toColorspace('rgb16')
.tiff({
compression: 'none'
})
.toFile('output.tif');
});
```

Output file:

Are you able to provide a sample image that helps explain the question?

Too large of files.

Start by running the provided JavaScript sample and compare the TIFF output when using srgb versus rgb16. Check the sharp and libvips colourspace behavior involved in extractChannel, joinChannel, and 16-bit TIFF output; done means the three channels are combined into a non-black rgb16 TIFF.

Written by the indexing model from the issue text.