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Histogram alignment


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HI, when aligning the RGB channels in either DSS or PS, where on the line do you line them up? I don't mean putting the 3 together, I mean in DSS what point on the curve or in PS where in relation to the left or right of the line?  Thanks guys,

Steve

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Hi Steve. I'm not an expert, but I have a very basic DSS tutorial on my blog page at the link in my signature that might help. I would link to it, but I'm using my phone and a bit limited! 

Mark

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As a rule of thumb I'd say the top left of the histo peaks should be aligned.

levels%20aligning-M.jpg

Personally I wouldn't do it in DSS but in Photoshop or a an equivalent programme because, at each stretching iteration, you'll probably have to realign them anyway.

Olly

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Thanks guys but it's not really what I mean. In DSS,  you can move any of the R,G or B channels anywhere along the curve. Similarly in PS by adjusting the black point marker in levels you move the corresponding channel to the left or right. I can move all 3 independently so is there a spot where they should be moved to e.g to the extreme left or in the middle? Looking at Olly's screen grabs the peaks all begin right at the left side so is that where I should be aiming to move my channels to?

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As Olly says, DSS isn't the best for this, but in my tutorial the aligned channels can be locked and moved together so that the bottom curve of the S-Curve pases through as much of the combined channels as possible. It's not perfect but will help you see what might be in your stack....for me this is usually 1/3 to 1\2 of the way from the left.

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We may be talking about two different things. In terms of colour balance I think that a good starting point is to have the top left of each histo peak aligned. I would check this between each iteration of the stretch, whether in Curves or in Levels. (You can stretch in either. Levels is easier, Curves allows you to be more sophisticated.)

Then there is the business of how far back to clip the black point. Not foo far is the answer!

Black%20clipping.-L.jpg

Olly

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With DSS you almost always HAVE to do something so I do exactly what @wxsatuser does as I find that this gives an image with a dark but not clipped background and plenty of headroom. worth making tiny tweaks (very hard to do the controls are crap!) as if you can get a colour-balanced background balancing the final result in PS is much easier.

Confession - I often increase saturation by 20% in DSS as well, it really seems to help ease final processing.

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4 minutes ago, Stub Mandrel said:

With DSS you almost always HAVE to do something so I do exactly what @wxsatuser does as I find that this gives an image with a dark but not clipped background and plenty of headroom. worth making tiny tweaks (very hard to do the controls are crap!) as if you can get a colour-balanced background balancing the final result in PS is much easier.

Confession - I often increase saturation by 20% in DSS as well, it really seems to help ease final processing.

The problem with global saturation boosts is that you boost unwanted colour gradients as well. Best to be selective and do anything like that in layers so you keep the modification only where you want to keep it.

Olly

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The R, G & B sliders in DSS can be a bit 'wayward' at times! Fine control of them can be done by first clicking on the wee triangular slider (to align and activate the mouse pointer on the right colour) then tickling it along with taps on the up/down arrow keys. Works wonders if you have a sticky mouse :)

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18 minutes ago, SilverAstro said:

The R, G & B sliders in DSS can be a bit 'wayward' at times! Fine control of them can be done by first clicking on the wee triangular slider (to align and activate the mouse pointer on the right colour) then tickling it along with taps on the up/down arrow keys. Works wonders if you have a sticky mouse :)

Dang! I tried L & R arrows to no avail!

 

1 hour ago, ollypenrice said:

The problem with global saturation boosts is that you boost unwanted colour gradients as well. Best to be selective and do anything like that in layers so you keep the modification only where you want to keep it.

Olly

 

I'll bear that in mind.

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