#1  
Old 11-05-2011, 06:25 PM
Carl
Registered User

Carl is offline
 
Join Date: Apr 2006
Location: Alans Flat
Posts: 375
RGB and Luminance?

Might sound dumb but I understand where the RGB files and channels come from. But I'm shooting with a DSLR. Where does the Luminance layer or channel come from.
Is it shot with an additional filter then combined in photoshop?

I'm about to get into the buying filters game and any guidance would be appreciated appreciated.

Cheers
Carl
Reply With Quote
  #2  
Old 11-05-2011, 06:38 PM
Octane's Avatar
Octane (Humayun)
IIS Member #671

Octane is offline
 
Join Date: Dec 2005
Location: Canberra
Posts: 11,159
DSLR's are one shot colour devices, meaning that RGB is captured along with whatever luminance data there is mixed in the one system.

H
Reply With Quote
  #3  
Old 11-05-2011, 06:45 PM
Carl
Registered User

Carl is offline
 
Join Date: Apr 2006
Location: Alans Flat
Posts: 375
L-rgb

Thanks Humayan
Would this mean; for example; that if i were to image a nebula with my modded DSLR using a UV/IR filter then used a 12nm H-Alpha filter to gain vital information in that nebula, would i then introduce the H-Alpha image as a channel or as a layer over my original image?

Any suggestions

Cheers Carl
Reply With Quote
  #4  
Old 11-05-2011, 08:13 PM
troypiggo's Avatar
troypiggo (Troy)
Bust Duster

troypiggo is offline
 
Join Date: Nov 2008
Location: Brisbane, Australia
Posts: 4,846
Sounds like you're confusing mono camera techniques and DSLR techniques.

If you use a Ha filter on a DSLR, you're still capturing RGB data, it's just that the majority of that data is in the R channel because that's what the Ha filter is letting through. G and B data will just be noise.

Do you have a colour image and want to use Ha as a luminance layer? If so, just put the RGB image in one layer, the Ha in another. Set the Ha layer blend mode to luminance and the RGB one to colour.
Reply With Quote
  #5  
Old 11-05-2011, 08:27 PM
Octane's Avatar
Octane (Humayun)
IIS Member #671

Octane is offline
 
Join Date: Dec 2005
Location: Canberra
Posts: 11,159
You're welcome, Carl.

+1 what Troy said.

H
Reply With Quote
  #6  
Old 11-05-2011, 08:35 PM
Carl
Registered User

Carl is offline
 
Join Date: Apr 2006
Location: Alans Flat
Posts: 375
Combining images

Hi Troy
Thanks for the reply. So am i over complicating the issue? to be honest I just want to get one of those stunning images that we see on our site.

Is it simply a matter of; for example;Creating a finished 5x 5min stack (H-Alpha) and importing that finished file as a layer in Photoshop above my combined RGB image.Then using the layers palate to set the blending mode.

Or is there something special i have to do to create a luminance layer?

I've been using Photoshop for 10 years now and there are always things that dont sink in first, second or sometimes third time round.

regards
Carl
Reply With Quote
  #7  
Old 11-05-2011, 08:42 PM
Octane's Avatar
Octane (Humayun)
IIS Member #671

Octane is offline
 
Join Date: Dec 2005
Location: Canberra
Posts: 11,159
You've got the right idea, Carl.

If you had a monochrome system, you could even potentially mix some red into the hydrogen alpha to avoid the composition taking on that pale disgusting salmony-pink appearance that hydrogen alpha introduces as a pure luminance layer.

H
Reply With Quote
  #8  
Old 11-05-2011, 08:44 PM
JohnG's Avatar
JohnG (John)
Looking Down From Above

JohnG is offline
 
Join Date: Dec 2005
Location: Cootamundra, NSW
Posts: 1,709
Carl

What version of ImagesPlus are you using, if you are using IP4+ you can make a Luminance image to work on using the Split Luminance command under the Colour Menu.

Cheers

Last edited by JohnG; 11-05-2011 at 09:00 PM.
Reply With Quote
  #9  
Old 11-05-2011, 08:48 PM
Carl
Registered User

Carl is offline
 
Join Date: Apr 2006
Location: Alans Flat
Posts: 375
Filters continued

Hi Humayan
I dont have a monochrome camera, mines a single shot DSLR canon modified.
So the H-Alpha will have a horrible Salmon hue, not good. So how do i get around that or am i better off just sticking with my UV/IR filetr

Regards
Carl
Reply With Quote
  #10  
Old 11-05-2011, 11:00 PM
Hagar (Doug)
Registered User

Hagar is offline
 
Join Date: Oct 2006
Location: Australia
Posts: 4,646
Hi Carl, There is a couple of ways to incorporate Ha into a one shot colour frame. No real easy way to get quick and acceptable results though. Using images plus you should be able to separate the luminance layer from the original image. Ha can be blended into this layer using Photoshop. You should also try to blend the Ha into the red channel after separating the RGB channels in IP. This will help to strengthen the red and prevent the image with only Ha in the luminance channel turning quite pink.
You can also blend a small amount of the Ha into the blue and even the green channels in varying amounts to ensure an even spread of colour throughout your image.

Ha blending is not as easy as just blending it into your luminance layer if you want premium results.
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 08:31 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Testar
Advertisement
Bintel
Advertisement