Orpington Astronomical Society

Astronomy => Technical => Topic started by: JohnP on Jan 24, 2009, 09:52:33

Title: Another Photoshop Question..
Post by: JohnP on Jan 24, 2009, 09:52:33
I have one more question...

When I sometimes edit a B&W 16bit image in Pshop I notice that the grey colours are sometimes 'green' - is this a screen calibration thing or is it something to do with the way PShop is set up. How bad it is depends on how dark/ bright the image is?

Any ideas?

Thks,  John
Title: Re: Another Photoshop Question..
Post by: RobertM on Jan 24, 2009, 10:44:50
If Image->Mode shows Greyscale then it should be monochrome and not show any colours.
Title: Re: Another Photoshop Question..
Post by: Mac on Jan 24, 2009, 12:04:46
QuoteI notice that the grey colours are sometimes 'green'

anychance of doing a screen dump just so i can see,
it might be the way your monitor is posibly set up,

as robert said, if your in monochrome, then there shouldn't be any colours.

Open a colour image
create an adjustment layer which is a solid colour.
Select black and click ok, you should have a completly black screen.
then on the dropdown menu where it says normal, select colour.

This will give you a B&W image from the colour.
See if you still get the green artifects.
If so its probably your monitor calibration,
If not, then i'm puzzled.

p.s. the advantage of doing a B&W this way, is that you can highlight the colour image greens for example, and bring those out.
leaving the other colours as they are,
where in a B&W image, the greens are the same shade of grey as other colours.
so its much harder to pick out the individual colours
Title: Re: Another Photoshop Question..
Post by: JohnP on Jan 24, 2009, 15:43:39
Mac - Here is a screen dump...

The green is very subtle & difficult to see - If you zoom in on horsehead you can see it (just...) - I'm thinking it may well be the screen calibration as last night it seemed a lot more prominent (not as much natural light..) What do you think?

John

(http://homepage.ntlworld.com/john.punnett/graphics/oas/green.jpg)

Title: Re: Another Photoshop Question..
Post by: Mac on Jan 24, 2009, 17:58:57
I've had a quick look at the screen dump in my photoshop and its competly grey, no colour information at all.

So its possibly looking like your screen calibration,

One other way to quickly check,
Click on the eye dropper tool
and select the green colour
then double click on the colour picker so that you have the colour picker visible,
and then use the eyedropper to check the colours,

every colour around the horse head was coming out at a shade of grey, there were no aditional colour values,
all the RGB values were equal, as you would expect.

run adobe gamma, to calibrate your monitor, it should help.

Mac.
Title: Re: Another Photoshop Question..
Post by: Mike on Jan 25, 2009, 12:16:23
It is totally grey to me too.
Title: Re: Another Photoshop Question..
Post by: JohnP on Jan 25, 2009, 14:38:54
Thks Mac - Since posting it I have checked it on my laptop & it looks grey on that as well so I figure it must be monitor calibration. I will download & run Adobe Gamma & see what results I get. Thks for all your help on this.

John
Title: Re: Another Photoshop Question..
Post by: Ian on Jan 25, 2009, 16:15:27
you might already have it. PS installs it at the same time. It'll be in the control panel iirc