Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

oldannie

Generating color from RGB's

Recommended Posts

Please can someone tell me what I'm missing!  Am trying to generate a colour image from some RGB's imaged with my mono Atik 460, stacked and aligned in DSS.  In his book , Dark Art or Magic Bullet Steve Richards describes a straightforward process: open all three stacked subs in photoshop, activate the red channel and via the Channels sub menu select 'merge channels'.  The rest is easy I guess but whatever I do 'merge channels' remains stoically greyed out! I've imported all three as 16 bit tifs, greyscale, all the same size etc.  It must be something so obvious I've missed and it's driving me mad!

 

Cheers

Annie

Share this post


Link to post
Share on other sites

I think the step you've missed out is that you need to convert the red channel to RGB mode. (Image - Mode - RGB.) What this does is make your one channel (greyscale) red image a three channel image. All three channels are identical so its appearance won't change but the steps which follow replace the red channel's clone G and B channels with real G and B channels.

Olly

Share this post


Link to post
Share on other sites

Thanks Olly but have already tried that and it doesn't work. There's a more complex method described by Scott Ireland where you have to do that but not in Steve Richards version.  Have also seen  Sara Wager's utube of the simple method which is exactly the same as Steve's.  I just don't understand why the merge channel remains greyed out it's got to be something really obvious .

 

Annie

 

Share this post


Link to post
Share on other sites

*Edited* please ignore, didn’t read the opening post properly and thought you might have been working  with 32 bit DSS autosave images.

Edited by Oddsocks
Did not read opening post properly.

Share this post


Link to post
Share on other sites

When you say 'activate the red channel' - what are you doing to do that?

The method I used to use to create an RGB from the three colour filter grayscale stacks is:

Open the three grayscale images in PhotoShop
One of the three images is the image displayed, it doesn't matter which one
Click on the Channels palette
Click on the lines icon on the right hand side of the Channel palette
This brings up the sub menu where you find the menu item Merge Channels...
Select that menu item
Set Mode to RGB Colour & Channels to 3
Click OK
Assign the right grayscale images to the right channels
Click OK
Hey presto a new document is created that is RGB colour

I hope that makes sense and works for you!
 

Share this post


Link to post
Share on other sites

No problem 'Oddsocks'

 

Gav - that's exactly what I've been trying to do but  after I've opened one of the images, gone to channels and clicked on the lines icon on the right hand side the option 'merge channels' is greyed out and no matter what I do it remains greyed out.  I just can't see why?  It seems such a straightforward process.  I seem to remember using this method some time ago and it worked.  Not now and haven't changed anything. Still PS CC and windows 10.  It's driving me mad!!

Share this post


Link to post
Share on other sites

Ah, yes, frustrating... can you share the three tiff files and I will open them up on my machine and have a go?

Share this post


Link to post
Share on other sites

Are you opening all three images up, so you have all three open in photoshop simultaneously and then clicking the channels things on one of them?

Share this post


Link to post
Share on other sites

I think amidst the many things I've tried I have had all three opened simultaneously but I'll have another go at that before I take you up on your offer to try and open the files on your machine though I guess there will be a problem sending tif files - the last time I used dropbox I couldn't send as we have a very low broadband speed.  If we're lucky we get 3mps.  If we moved to fibre am told it should increase to 4mps!!

Share this post


Link to post
Share on other sites

What I do is import all three tif files into photoshop and then activate one of the tif files before selecting channels and then open the  submenu (the three little lines on the right) which shows a number of options , including 'merge channels'.  Merge channels is always greyed out (amongst other options).  Have tried  floating all three  tif files just to make sure and todate nothing works.  I would expect merge channels to be greyed out if I had only imported  one file  or if there was something amiss with the files.  

Share this post


Link to post
Share on other sites

Mmm, curious... and all three are grayscale images?

The only other thing that I can offer is a TeamViewer session into your machine to have a look to see if I can work out what is going on...

Share this post


Link to post
Share on other sites

All three are grayscale.  It must be something so obvious it's not obvious!! Am going to take my laptop and files over to a contact (newly discovered) who says he has had success using this straightforward method.  If we can't work it out watch this space.  If we do sort out the problem I'll post the outcome.

In the meantime thanks for your responses Gav - much appreciated.

 

Annie

Share this post


Link to post
Share on other sites

 

4 hours ago, oldannie said:

All three are grayscale.  It must be something so obvious it's not obvious!!

I'm not sure if this will help but I once had three open grayscale images and I noticed that the merge channels was greyed out in PS under the channels menu- the reason was that one of the grey scale images actually consisted of more than one grey scale layer.  Flattening the gray scale image with the multiple layers solved the problem.  

Alan

  • Like 1

Share this post


Link to post
Share on other sites

Thanks Alan and Gav.  It turned out to be a wrong setting in DSS!!  The whole process worked as it should once I had tried changing various settings in  DSS and settled on checking something called 'background calibration' (well called something like that).

Thanks for all your responses - much appreciated.

Watch out for more naive questions from me!

Annie

 

  • Like 1

Share this post


Link to post
Share on other sites

Managed to stack and align  RGB subs in DSS and generate a colour image in photoshop.  This was my first attempt at imaging since moving from DSLR to CCD, using a Takahashi 106ed, Atik 460ex, mono with Baader filters in the Atik EFW filter wheel.  Target was the Crescent nebula and I took R 9x600sec , G 6x600sec and B 9x600sec, stacked with darks, flats & bias frames.  Have started to process in photoshop, though not very experienced at processing.  Have not got very far when I noticed an odd patch of colour along the bottom of the Crescent, mainly centre right.  I maybe should have posted this in the imaging forum though perhaps the problem lies with my mediocre attempt at processing!

Not sure what the parameters are for attaching images so hope this works!  It's 521kb JPEG .Cresc_RGB_JPEG_web.jpg.be003f178faca61814becc15b989ccd0.jpg

Annie

  • Like 1

Share this post


Link to post
Share on other sites

Looks like an issue in your green channel. This target does have a strong green outer shell from OIII emission but what we see here certainly isn't that. What does the green channel look like on its own?

Maybe you have a problem with your green flats? If so you could try the flats from a different filter. This usually works fine.

Alternatively (or as well) you could download Rogelio Bernal Andreo's Hasta La Vista Green available free-or-donation from his Deep Sky Colors website. This is very like Pixinsight's SCNR green routine. It is very rare that I don't use SCNR green on an RGB image because, for some reason, green is the problem channel. That apart you have a lovely result with the background and stars (the hard parts) looking great.

Olly

Share this post


Link to post
Share on other sites

I'll go back and look at all three channels as I recall this issue crops up on two channels but can't remember which two - I suspect it's the blue and green.  I have been thinking of downloading Hasta La Vista Green so will do that.   Am also intending to add some luminance data probably Ha - something else to get my head round - but would like to sort this issue out first.

Thanks Olly and for the comment  'lovely result'.  

Annie

Share this post


Link to post
Share on other sites

What I always do is open all 3 stacked images, press ctrl a then ctrl c to select all and copy it. Then I click file and open a new clip board. Change from greyscale to rgb then paste the RGB images into the corosponding channels. Slight crop to get rid of any dodgy edges then process as normal. 

  • Like 1

Share this post


Link to post
Share on other sites

Thanks for that 'Sub Dwarf'.  I seem to have cracked the process of generating a color image from RGB but still have no idea about the 'swatch' of color which  appears  on the blue and green stack  and hence on the merged RGB.  Have taken a new lot of flats (though don't think flats are the cause)  and am going to re-stack and perhaps try one less green sub and one less blue sub to give me R 600sec x 9, G 600 sec x 5 and B 600 sec x 8 though again not sure this will have much effect.  Also yet again check my settings in DSS and then will have tried everything I can think of.  This was my first image using a CCD camera and am a bit worried that the color swatch is going to appear on subsequent images if I don't discover the cause now.  Imaged using: Takahashi 106 ed, Atik  mono 460 ex and stand alone guider, Lacerta MGEN.

Share this post


Link to post
Share on other sites

I think so Carol but will make sure I do when I start from the beginning again!

 

Annie

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.