Processing colour in unbalanced exposures

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Lawrence
Posts: 73
Joined: Thu Jun 04, 2015 1:30 pm

Processing colour in unbalanced exposures

Post by Lawrence »

I'm puzzled about a quotation in the colour processing module:

"StarTools enables you to keep M42's colour constant throughout, even in its bright core. No fiddling with different exposure times, masked stretching or saturation curves needed. "

In M42 the trapezium stars are bleachd out in any normal exposure length so to maintain them as 'real' one has to take a separate exposure. The above suggestion implies that one exposure fits all. I am still a beginner with ST so I would appreciate a further explanation if possible?

TIA

Lawrence Harris
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Re: Processing colour in unbalanced exposures

Post by admin »

Hi Lawrence,

StarTools will attempt to recover color in pixels that have not been overexposed in any of the channels. The "bleaching out" so often seen is an artefact of processing techniques; it is not inherent to the data. Stretching the data as a whole will cause colors to be stretched/compressed as well. This causes desaturation in the highlights and distortions elsewhere. By separating luminance and color and only stretching luminance, this distortion of coloring can be avoided.

Making a high dynamic range composite is never done to recover coloring, rather it is done to recover detail. Depending on how deep you'd like to go, a single exposure of M42 may indeed be enough.

I hope this makes sense,
Ivo Jager
StarTools creator and astronomy enthusiast
Lawrence
Posts: 73
Joined: Thu Jun 04, 2015 1:30 pm

Re: Processing colour in unbalanced exposures

Post by Lawrence »

admin wrote:Hi Lawrence,

StarTools will attempt to recover color in pixels that have not been overexposed in any of the channels. The "bleaching out" so often seen is an artefact of processing techniques; it is not inherent to the data. Stretching the data as a whole will cause colors to be stretched/compressed as well. This causes desaturation in the highlights and distortions elsewhere. By separating luminance and color and only stretching luminance, this distortion of coloring can be avoided.

Making a high dynamic range composite is never done to recover coloring, rather it is done to recover detail. Depending on how deep you'd like to go, a single exposure of M42 may indeed be enough.

I hope this makes sense,
Yes, it does. Thanks. I'll look back at my data.

Lawrence
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