{"id":38270,"date":"2022-11-11T00:00:00","date_gmt":"2022-11-11T00:00:00","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/?post_type=purple_issue&p=38270"},"modified":"2022-11-25T12:41:56","modified_gmt":"2022-11-25T12:41:56","slug":"handling-problem-greens-in-your-astrophotos","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/2022\/11\/11\/handling-problem-greens-in-your-astrophotos\/","title":{"rendered":"Processing: Handling problem greens in your astrophotos"},"content":{"rendered":"\n
PROCESSING<\/span><\/h5>\n\n\n\n

Handling problem greens in your astrophotos<\/span><\/h2>\n\n\n\n

Using a Photoshop plug-in to easily balance colours around deep-sky targets<\/p>\n\n\n\n

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BEFORE<\/h5>\n\n\n\n
\"\"
The original stacked image of the Flame, Horsehead and Orion Nebulae before applying any colour-balancing measures, captured with a William Optics RedCat 51 and Canon 6D, 18x 3\u2019 exposures at ISO 1600, stacked in DeepSkyStacker <\/figcaption><\/figure>\n<\/div>\n\n\n\n
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AFTER<\/h5>\n\n\n\n
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Charlotte\u2019s final image, processed in Photoshop using the HLVG plug-in to remove troublesome green colouration <\/figcaption><\/figure>\n<\/div>\n<\/div>\n\n\n\n

Effective colour management can really boost your astro photos. Without it, deep-sky objects can get lost against a noisy background. This is not to say you should aim for flat, black backgrounds with white stars. That can look unrealistic and unrepresentative of a deep-space environment. <\/p>\n\n\n\n

Colours in space are a tricky thing to replicate. Our cameras pick up details that our eyes simply cannot. However, their sensors \u2013 which vary greatly depending on camera type, model and age \u2013 all pick up colour differently, so the same deep-sky image can look very different from camera to camera. Some produce more colour (or chromatic) noise than others, resulting in a noisy or off-colour image to process. <\/p>\n\n\n\n

One channel that creates chromatic noise problems is green. Typically, unless imaging comets or the Northern Lights, this is one colour that astrophotographers wish to reduce or eradicate. Given that most astronomical objects do not emit visible green light, it is associated with noise, and can subdue nebulous details or discolour stars. Anything green in a deep-sky image is therefore usually an unwanted artefact we want to edit out. <\/p>\n\n\n\n

Hasta La Vista, Green <\/strong><\/h5>\n\n\n\n

Here we will take you through the steps to use Hasta La Vista, Green (HLVG) to deal with this troublesome colour. HLVG is a Photoshop plug-in developed by Rogelio Bernal Andreo that has been around for over a decade. It is compatible with recent versions of Photoshop and it is free. <\/p>\n\n\n\n

Start by downloading the plug-in from www.deepskycolors.com\/archive\/2010\/04\/26\/hasta-La-Vista-Green.html<\/a>. <\/p>\n\n\n\n

Locate the folder on your computer (usually in the \u2018Downloads\u2019 folder). This will be in a compressed format. Right-click the folder and click \u2018Extract All\u2019. To move the uncompressed file into Photoshop, navigate to the Photoshop plug-in folder. This is usually somewhere like C:\\Program Files\\ Adobe\\AdobePhotoshop2022\\ Plug-ins. Drag the HLVG file into this folder. HLVG can now be found in Photoshop by clicking Filter > DeepSkyColours > HLVG. <\/p>\n\n\n\n

We applied HLVG to our stacked, widefield image of the Orion Nebula, captured using an astro-modified Canon DSLR. Cameras that have been modified to allow in extra \u2018red\u2019 infrared light can complicate the colour-balance process because our red channel has a lot more data compared to the green and blue channels. HLVG therefore comes in handy. <\/p>\n\n\n\n

\"\"
Screenshot 1: Before deploying the HLVG plug-in, the colour balance of the stacked image is first adjusted using Photoshop\u2019s Levels. This brings up a histogram of the image <\/figcaption><\/figure><\/div>\n\n\n\n

Before applying HLVG, we balanced the colours using the \u2018Levels\u2019 function, found at Image > Adjustments > Levels (see Screenshot 1<\/strong>). We ensured the histogram was set to \u2018Colours\u2019. In the Levels window, we dragged each of the anchor points in the red, green and blue channels so that they touched the edge of the curves. We checked the histogram each time to make sure the red, green and blue curves were roughly the same size and sitting neatly on top of each other. We repeated this process three times by right-clicking on the Levels layer and selecting \u2018Merge down\u2019 so that it merged into Layer 1. We then repeated the colour balance steps again. After the third time, we started to see noise in the image, so we stopped. <\/p>\n\n\n\n

Check your balance <\/strong><\/h5>\n\n\n\n

We could see that despite balancing the colours as much as possible, our image had a distinctly green tinge to it which suppressed both the Horsehead and the Orion Nebulae. Now was the time to use HLVG. We clicked Filter > DeepSkyColours > HLVG. This brought up the plug-in menu (see Screenshot 2<\/strong>). Because there was still a significant amount of green, we selected \u2018Strong\u2019 before clicking \u2018OK\u2019 (\u2018Medium\u2019 and \u2018Weak\u2019 options are available if you don\u2019t want to remove all the green). The green removal command was applied to our image and we could see it created a more realistic background (see Screenshot 3<\/strong>). <\/p>\n\n\n\n

\"\"
Screenshot 2: Having adjusted the red, green and blue channels, a distinctly green tinge still remains. Clicking Filter > DeepSkyColours > HLVG > Strong effectively removes it <\/figcaption><\/figure><\/div>\n\n\n\n
\"\"\/
Screenshot 3: The far more natural-looking nebulae once the green tinge has been eradicated by HLVG. Further processing then produces the final image (see above) <\/figcaption><\/figure><\/div>\n\n\n\n

With the green now dealt with, to finish processing we made a series of final adjustments to the image\u2019s brightness and contrast (Image > Adjustments > Brightness\/Contrast), vibrance (Adjustments > Vibrance & Saturation) and selective colour (Adjustments > Selective colour). To further reduce noise, we also applied Photoshop\u2019s median filter (Filter > Noise > Median) and noise reduction functions (Noise > Reduce Noise). The result, a final, naturally coloured image is shown above. <\/p>\n\n\n\n

<\/div>
\n
3 QUICK TIPS <\/h5>\n\n\n\n

1. <\/strong>Consider using HLVG\u2019s \u2018Strong\u2019 setting for deep-sky nebula and \u2018Medium\u2019 or \u2018Weak\u2019 for comets or planetary nebulae. <\/p>\n\n\n\n

2. <\/strong>Use hide all\/reveal all masks to apply HLVG to the background or object only. <\/p>\n\n\n\n

3. <\/strong>To maximise HLVG\u2019s impact, try applying it after every colour balance in \u2018Levels\u2019, after merging down the layer. <\/p>\n<\/div><\/section>\n\n\n\n

\"\"<\/figure><\/div>\n\n\n\n

Charlotte Daniels is an amateur astronomer, astrophotographer and journalist<\/p>\n\n\n\n

<\/p>\n\n\n\n

<\/div>\n\n\n\n

ALL PHOTOS: CHARLOTTE DANIELS<\/p>\n","protected":false},"excerpt":{"rendered":"

Using a Photoshop plug-in to easily balance colours around deep-sky targets <\/p>\n","protected":false},"author":24,"featured_media":38264,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ub_ctt_via":"","purple_page_number":"78","purple_custom_meta_purple_page_number":"78","purple_seq_number":"1","purple_custom_meta_purple_seq_number":"1","purple_source_article":"article_78-1.xml","purple_custom_meta_purple_source_article":"article_78-1.xml","purple_source_issue":"December-2022","purple_custom_meta_purple_source_issue":"December-2022","purple_external_id":"December-2022-78-1","purple_custom_meta_purple_external_id":"December-2022-78-1","purple_issue_code":"|0000086559||","purple_custom_meta_purple_issue_code":"|0000086559||","purple_android_product":"com.im.skyatnight.211","purple_custom_meta_purple_android_product":"com.im.skyatnight.211","purple_ios_product":"com.im.skyatnight.211","purple_custom_meta_purple_ios_product":"com.im.skyatnight.211","purple_web_product":"","purple_custom_meta_purple_web_product":"","purple_publication_id":"075fab74-0a21-4201-866a-899d6c41c40c","purple_migrated":"","kt_blocks_editor_width":""},"categories":[34],"tags":[14],"featured_image_src":"https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/11\/7654a2af-6d5b-450f-83df-41281c09ee65.jpg","author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"acf":{"readingTimeMinutes":"5","apple_news_title":""},"uagb_featured_image_src":{"full":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/11\/7654a2af-6d5b-450f-83df-41281c09ee65.jpg",1216,857,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/11\/7654a2af-6d5b-450f-83df-41281c09ee65-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/11\/7654a2af-6d5b-450f-83df-41281c09ee65-300x211.jpg",300,211,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/11\/7654a2af-6d5b-450f-83df-41281c09ee65-768x541.jpg",768,541,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/11\/7654a2af-6d5b-450f-83df-41281c09ee65-1024x722.jpg",800,564,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/11\/7654a2af-6d5b-450f-83df-41281c09ee65.jpg",1216,857,false],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/11\/7654a2af-6d5b-450f-83df-41281c09ee65.jpg",1216,857,false]},"uagb_author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"uagb_comment_info":0,"uagb_excerpt":"Using a Photoshop plug-in to easily balance colours around deep-sky targets","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/38270"}],"collection":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/users\/24"}],"replies":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/comments?post=38270"}],"version-history":[{"count":8,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/38270\/revisions"}],"predecessor-version":[{"id":39389,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/38270\/revisions\/39389"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media\/38264"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media?parent=38270"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/categories?post=38270"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/tags?post=38270"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}