Black and White adjustment layer mystery

[Mr_rossduncan]

I'm struggling to work out why a B&W adjustment layer in Photoshop will not have any effect after sending over an image from LightRoom.

If I apply a B&W adjustment to an image in LR then send it over to Ps it remains a DNG 16bit RGB image, however if I then add, to that image in Photoshop, a new adjustment B&W layer it will have no effect.

If I send that image over from Lr without any B&W adjustment first, then add a new adjustment layer in Ps, it works just fine.

It's quite frustrating, I often will work on an image in LightRoom first, including changing it to B&W, before adding final tweaks in PS, I'd love to know why an image converted to B&W in Lightroom will then be unable to have final adjustments applied to it in PS.

[D Fosse]

I don't get this.

If the image is B/W coming out of Lightroom, why would an additional B/W adjustment in PS do anything?

What am I missing?

[Mr_rossduncan]

Hi,
You're not missing anything; I was just trying to figure out what was going on.
I quite often will make some adjustments in LR then continue to do some more work in PS.
Often much later on, months or even years later I'll reopen an old file that's come through from LR.
Sometimes for instance, I might feel in hindsight that the image needs some more contrast, or a tweak to the curves, lots of different things really.
My query was what's going on with the B&W adjustment layer, why doesn't it have any effect.
I think I've worked it out now with an explanation from another user.
Cheers

[D Fosse]

You may be confused by the fact that it says "dng" in the Photoshop tab. But it's no longer the same file! When you send it from Lightroom, it's rendered into an RGB gamma-encoded new file, completely separate and different from the original raw file. All the adjustments are now baked into the pixel data of the new file.

An open file doesn't have a file format at all. It just says dng to indicate where it comes from. File formats are storage containers.

It's also possible that you are confusing this with opening as smart object. A smart object is a complex file that contains an embedded copy of the original file. In this case that would be a copy of the original raw file. This copy can be reopened and readjusted by the Camera Raw plugin. But then you have to specifically "open as smart object".

[Mr_rossduncan]

Hi,
Thanks for the explanation, it goes a long way to explaining what's going on.
Particularly the bit about an open file doesn't have a format at all, I didn't ever realize that.
Cheers
Ross