Color images come out black and white

[ttrinko]

I've just started using pixinsight and it seems that for most subjects the final LRGB image looks black and white.  I assume I'm doing something wrong.

I have 4 300s exposures in each of the 4 channels-- L R V B-- and I create 4 integrated images one for each band. SNR in all looks good.

I then combine them which produces a highly green tinted image.  I do DBE and then color calibration and I'm left with an image that looks colorless.

Any thoughts?

Thanks!

[dpaul]

I'm a beginner here but presumably you are stretching them first before LRGB combining - that I believe is what you should be doing - works for me!

Hope this helps (if I'm right)

David

[RickS]

Have you tried a simple RGB combine without the L?  If the L is much stronger than the colour data then it will wash out the colour.  You could also try a big saturation boost with CurvesTransformation (drag up the pink Sat curve.)  That will show if there's colour there but too unsaturated to see easily.  If you can't figure it out then upload sample files (perhaps a smaller crop) to Dropbox or similar and I'd be happy to take a look.

David: you can use LRGBCombine with linear or non-linear data.  Just don't try to combine linear and non-linear data at the same time.

[dpaul]

Hi Rick,

That's interesting - any preference for doing the stretching before or after LRGB combining?

Thanks

David

[RickS]

That's interesting - any preference for doing the stretching before or after LRGB combining?

Hi David, my personal preference is to process Lum and Colour separately and combine near the end, so I always do that final combine with stretched data.  It's also perfectly feasible to combine while linear and I'm sure there are folks that prefer that too.  I don't think either approach is the one true path

Cheers,
Rick.

[dpaul]

Hi Rick,

I've been stretching each one before combining too. This seems the logical thing to do because each colour may not have the same optimum level of stretch.

Thanks

David

[RickS]

I've been stretching each one before combining too. This seems the logical thing to do because each colour may not have the same optimum level of stretch.

Hi David,

I don't stretch the colour channels individually.  I combine them when linear and then use some method of colour calibration to match the channels (mostly PhotometricColorCalibration these days.)  It's only the Lum and the combined RGB that I process separately and combine later.

Cheers,
Rick.

[ttrinko]

Thanks! I've got it working now. I think I was having problems because I wasn't delinerizing the images before LRGB combining

[dpaul]

Thanks Rick,

I guess the advantage of stretching the colours 'after combining' means you can colour calibrate the combined result linearly - correct?

David

[RickS]

Thanks! I've got it working now. I think I was having problems because I wasn't delinerizing the images before LRGB combining

Glad to hear you sorted it out.

[quote author=dpaul link=topic=12087.msg74127#msg74127 date=1517138772
I guess the advantage of stretching the colours 'after combining' means you can colour calibrate the combined result linearly - correct?
[/quote]

Yes David, if you're going to do accurate colour calibration then it needs to be done while the data is linear.

[dpaul]

Thanks Rick

I just started a separate topic but can be answered here!

Once I've done the colour calibration on the combined RGB ''linear'' file, how do I best then combine it with the luminance file.
I did the colour calibration as suggested (looks ok), I then stretched it and tried to combine with a stretched Luminance file but in LRGB combination process, it only ''sees'' the Luminance file. 

Help!

Thanks

David

[RickS]

Answered in the other thread...