Merging RGB in Photoshop

[resonator77]

can anyone advice how to merge RGB channels in Photoshop? It is CS4 extended version. I believe it must be the same method in older versions of PS.

Many thanks in advance.

[NickH]

Create a new RGB image, and copy each of the channels in as layers...(open the channels view (in layers view)

[steppenwolf]

You must first align your three filter channels to allow for any changes in image orientation due to the filter changing, especially if using a manual filter wheel. Open the three mono image TIF files (Red, Green and Blue) and convert them to Greyscale by selecting Image - Mode - Greyscale for each image. Open the Channels palette by selecting Window - Channels. Click on the Channels palette menu and select 'Merge Channels'. Select 'RGB' from the drop down list box, set 'Channels' to '3' and click on 'OK'. Using the list box, specify which file applies to each of the three colours and click on OK. Your RGB colour image will immediately appear.

[resonator77]

Steppenwholf,

crystal clear guide, thank you . Can it be done leaving the image .bmp after Registax? assuming there isnt any image shift in celestial object (saturn leaves 2 minutes to take all RGB channel), should the RGB channels still be aligned?

Nick thank you for quick reply, how can I create new RGB image?

[NickH]

Select your current image, CTRL+A then select CTRL+N to create a new one... with the same size and set mode to RGB

[steppenwolf]

Can it be done leaving the image .bmp after Registax?

Yes, it can, I always assume TIF files are in use because I prefer to work in 16bit depth rather than the 8bit depth of .BMP files

assuming there isnt any image shift in celestial object (saturn leaves 2 minutes to take all RGB channel), should the RGB channels still be aligned?

I am not a planetary imager so cannot be confirm for certain the amount of rotation but if the total imaging time was 2 minutes I would not expect a problem with alignment, to be honest.

[NickH]

2 mins on Saturn will be fine ...unless you're imaging at F64 (only Selsey applicants need consider this :-)...and there is a defined spot feature on the surface.. and even then, you'd probably get away with it

[resonator77]

I would not dare F64

[davy999]

I know this is an old post but I am trying to create LRGB images in CS5, and I convert the Lumi image to RGB, then the instructions in Every Photon Counts" says merge RGB, this is grayed out in CS,

help.....!!!!

[martin_h]

Merge the RGB as above, process - levels & curves etc

Open the Lum as a seperate image - process.....

Convert to RGB, with the Lum image active select all, copy

Open the RGB image and paste the Lum over it as a new layer - if you set the blend mode to difference you can shift the image about to align it, when done change the blend mode to luminance.

Finish processing then flatten the layers to make 1 image

[martin_h]

The above can be found here - with pictures! http://stargazerslounge.com/imaging-tips-tricks-techniques/57834-lrgb-imaging-primer.html

[ollypenrice]

Yet another way;

Co-register the L to the RGB so they are perfectly aligned.

Convert the RGB to Lab colour in Image Mode.

Split channels in the RGB image.

Then just Combine channels and when prompted replace the Lab 'Lightness' image with your Lum image.

Olly

[davy999]

Hi guys

Thanks for the input but I am obviously doing something totally wrong.

I have stacked each colour in Maxim, saved into 4 fits files, I have aligned these in maxim (but not stacked) so that all 4 images can be easily aligned in PS and saved again.

I then open all four files in photoshop, I select the luminansce image and convert to RGB. When I look at channels I see RGB / R / G / B channels, this seems to be what the instructions suggest but when I go to the options in channels the merge is greyed out and despite everywhere saying I can then assign one of the colour images to each colour channel I have no option for this.

Am I being a complete idiot and overlooking something fundemental? be honest.. I can take it ! )

edited - once all four files are basically processed I need to create a new RGB image? and that is the point where I get to assign each image to a channel in RGB? <getting very confuddled>

[steppenwolf]

I have just re-tried the procedure detailed in my book to make sure I'm not going nuts and it works just fine!

I think the problem is that you probably have a background layer to one or more of your images. Try flattening each of the four images

[davy999]

Hi Steve

I tried with PS and gimp, both wouldnt work, will try again when I get home, will check for background layers, but I am fairly sure there isn't any.

What version of PS are you using?

Obviously my brain didnt want to work last night, will try again later.

Thanks for your help

Dave

[SteveP]

Dave

There are several ways to do this in PS as you've probably now realised. I usually do the RGB combine in Maxim or wherever, import the combined image and the L image into PS and combine the two images there by pasting one layer onto the other. Have a Google for Don Waid's site where he describes this technique more fully.

Alternatively, if you have a spare $14, have a look here for Annie's Actions. They're very good value

Morris Astronomy: Annie's Astro Actions Version 2.0 Released!

Steve

[martin_h]

I think I see your problem, dont convert the LUM to RGB until you have combined the seperate RGB files.

Just load the seperate R,G,B files, and, with any one active click the channels tab and use the dropdown menu - merge channels - RGB colour.

When they are merged you should have 1 file open (RGB). Load the LUM file change mode to RGB colour. Select all - copy. Make the RGB file active and paste the copied lum over.

[steppenwolf]

What version of PS are you using?

I am using CS3

You don't have to separately convert the Luminance channel to RGB at any time during the process, you can paste it as a greyscale on top of the RGB data as a new layer and it will automatically match the mode of the background layer (in this case RGB)

[martin_h]

I am using CS3

You don't have to separately convert the Luminance channel to RGB at any time during the process, you can paste it as a greyscale on top of the RGB data as a new layer and it will automatically match the mode of the background layer (in this case RGB)

Well you learn something new every day! I didn't know that.

[SlipperySquid]

May seem a daft question, but why don't you just combine them in Maxim?

Also does anyone have a problem with CS4 and fits files(using windows 7 32bit)? I've used fits liberator and that just doesn't work for me? I just convert my combined images etc to tiff's and import them to cs4 a bit of a pain really.

Sorry for the hijack but it still seems sort of on topic!

Matt.

[steppenwolf]

May seem a daft question, but why don't you just combine them in Maxim?

No reason why not if you have Maxim, Maxim will do the job nicely as well.

[davy999]

ok ok ok

Mr Thick has fixed it

I didnt realise that i hadnt flattened the blue image

Once this was done it worked immediately, I have stuck the lum. layer over the top, high pass filter, unsharp mask and make stars smaller and now have an LRGB image I am fairly happy with. Will upload to DSO image folder.

Thanks for your help chaps. hope this helps anyone else daft enough not to know what they are doing.