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Question

Gaussian blur banding question

Forum|Forum|6 years ago
November 17, 2019
1 reply
4694 views

Hello,

I have an issue when applying gaussian blur on my photos.

I'm working in 16 bits, that means when I export photos from lightroom to photoshop my export parameters are all in 16 bits under lightroom.

I checked that my image => mode is in 16 bits aswell under photoshop. I'm working in Prophoto RGB colour mode.

My screen is a BenQ SW2700 calibrated with a spyder pro 5. That means a 12 bit compatibility screen.

The problem is when I apply a Gaussian blur on Photoshop, even a small one (let's say 30 px) banding appears on my picture.

Is there something I didnt set up correctly ?

PS :

- My photoshop version is 21.0.0 and Lightroom is 8.4.1

- I'm working on W10

- My GC is a Geforce 1060 6Gb

This topic has been closed for replies.

davescm

Community Expert

Unless you have set up 30 bit display in Photoshop >Preferences >Performance >GPU Advanced and have a display chain that supports 30 bits all the way through i.e. GPU card and driver (open GL), monitor and use of the correct ports then you will be using 8 bits /channel for display. If any link in that chain is not capapble then you will only have 8 bits/channel.

Note : Lightroom uses dithering to hide banding even on 8 bit displays so do not assume that because you see no banding in Lightroom you are using more than 8 bits for display

Dave

W

WraithBandAuthor

Participant

Many thanks Dave for your explanations.

I think ports isnt a problem nor my monitor but maybe the GC.

Under NVIDIA control panel I can't change to 10bpc (it's greyed out to 8 bpc).

I 'll try to find out why.

Anyway I'm just surprised that a simple gaussian blur (even a small one) triggers so much banding !! I wanted to try adding a small orton effect to one of my photo and it's a total mess (banding). I'm just wondering if there isn't another issue on my Photoshop settup. That means one cannot apply a gaussian blur in 8 bit without banding...

D Fosse

Community Expert

If it's not in the data, can you explain to me why when I post the result on whatsapp with my mobile, the banding is still here ?

I suppose mobile phones are 10 bit compliant ?

That's an 8 bit jpeg (or png).

The whole point here is that banding happens in 8 bit color depth, not 16. At 8 bit depth, like in your display pipeline, you only have 256 discrete steps per channel. With a narrow gradient, banding cannot be avoided.

In addition, jpeg compression is very aggressive and very destructive, and introduces its own banding.

Oh, BTW, why would phone screens be 10-bit capable, when only the most expensive desktop monitors are?

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