Colour adjustment/enhancing

Discussion in 'Graphics Programs and Photo Gallery' started by PlasticSpanner, May 26, 2005.

  1. PlasticSpanner

    PlasticSpanner TPF Noob!

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    Can anyone give me some pointers to get me started? I got some good star photos a couple of weeks ago but a couple were spoiled by car headlight pollution. This particular one I want to keep as it has 2 shooting stars in it and a rather nice star cluster near the bottom left of center.

    Is it possible & how, to level out the "background colour to just get a very dark blue/black but keeping the detail of the stars and how can I enhance the star cluster to make it more noticeable?

    Many TIA :thumbup:

    [​IMG]
     
  2. Meysha

    Meysha still being picky Vicky

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    This is tough!!
    I've played with it a bit in PS and got a few options for you to try. To get rid of the pollution change it into a black and white picture wither either the channel mixer (click the monochrome box at the bottom) or I tried it with Image->Adjustments->Match Colour and increased a bit of the luminosity and reduced the colour intensity.
    What you'll want to end up with is the stuff you want to keep white and the stuff you want to dissapear blackish.

    Then create a layer beneath that with the sky colour you want. Then change your now B&W stars' layer blending mode. Try a bunch of different ones like Pin Light, Linear Light and Hard Light.
    I found that Pin Light worked the best for me - but you lost the star trails, but it did bring the stars out a little more.

    Also, you've got a glitch in this scan on the left hand side the scanner stuffed up and blurred a big long line.
     
  3. Meysha

    Meysha still being picky Vicky

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    Forgot to post a pic of what I got. It's not very good but at least it's got rid of that yukky orange glow.
    Photo1

    Oh , if you then make a duplicate of your star layer and change it's blending mode to Colour Dodge you'll bring out more of the background stars (or that could just be pollution I can't tell.
    Photo2

    Edit: Took photos down, due to pure shame :lol: and a much better version done by pursuer.
     
  4. Cuervo79

    Cuervo79 Guest

    I personally would not do the color dodge, but play with the color burn option so the light part in the center starts to have the same tone as the edge, then just flatten image and play with the curves.....
     
  5. Nikon Fan

    Nikon Fan TPF Noob!

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    I would suggest trying to duplicate the layer and then choosing a blend mode of multiply or overlay. You could probably also add a solid color either dark blue or black and choose different blend modes until you come up with something you like. You could also adjusts curves and levels as well...that should give you a start, but not really sure how well it will work :)
     
  6. pursuer

    pursuer TPF Noob!

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    This is a common problem in astrophotography and is easily solved.

    Duplicate the image in PS, apply a dust and scratches filter to the the copy just strong enougth to remove all the stars. You will be left with just the background color, subtract this from the origional.

    [​IMG]

    Adjust levels and apply Usharp mask to taste :)
    [​IMG]

    Whoops, I almost forgot, its been awhile since I have done this. Another method which often gives better results is to invert the copy then appy it to the origional using color burn, after applying the dust and scratches filter of course.

    [​IMG]

    This method preserves more of the stars color, red to blue depending on the tempature of the star.
     
  7. Meysha

    Meysha still being picky Vicky

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    Ok say bye bye to my attempts.
    That's the difference between the astrophotography god that is pursuer and me - someone who can't even see the stars in my current city.
     
  8. pursuer

    pursuer TPF Noob!

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    Oh and I would be interested in hearing the exposure details for this, film, digital, apature, ISO, Exposure time, equipment used?

    Edit: don't feel bad Meysha, there are a lot of funky tricks used in astro photograpy. :hug::
     
  9. PlasticSpanner

    PlasticSpanner TPF Noob!

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    Thanks Pursuer Thats amazing! I was trying Meysha's suggestion & was going to ask how I can preserve the star colours too!

    Many thanks to everyone with their suggestions! :thumbup: I've copied them to a text file for future rescues! Meysha, why did you take your attempts down? You should see some of mine! :lmao:

    I don't really like using PS to alter a photo but prefer to get it right on film the 1st time if possible!

    The Photo was taken with a Praktica BMS, ASA200 colour film, 18 second exposure. 28mm lens on F1.8. A better one was with the same settings but for 12 seconds but it didn't capture the 2 shooting stars (and another at 15 seconds had a plane through it!) :x ! The extra 6 seconds caught more stars in the Milky Way but over exposed the constellation stars and Achird just below!

    The Constellation is Cassiopeia (The 5 brightest stars just below centre looking a bit like a stretched out W) and the bottom of the frame is just above the Andromeda Galaxy. Next time I'll put Cassiopeia at the top of the frame & get Andromeda too!

    Any suggestions on un-trailing star trails? I have a couple of good ones that have gone on for just a bit too long & stretched the stars! :confused:
     
  10. pursuer

    pursuer TPF Noob!

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    No problem, im glad I could help.


    You can't over expose stars, they are just points of light :scratch: With the aid of tracking mounts exposures often run ten minutes or more, the deeper the better :) Are the overexposed stars in this image or did you crop them out?

    It is possible to some degree with specialized astrophoto software that includes a deconvolution function, but if you want my advice I wouldn't bother. Just keep the exposures short enougth that the stars are still pin point.

    Normally I would agree with you 100%, but astrophotography is an exception to the rule. Post processing, often heavy post processing is the required norm.

    For example because you are just using a tripod that doesn't account for the earths rotation you can only take short 10 sec exposures.

    What I would do I your case is take 15-20 10 sec exposures of the same area. Then I would use software such as registar to make sure all the images were perfectly aligned. Once the images were aligned I would stack or combine them in photoshop and do the standard level adjustments. Lots of processing involved but the end result would overcome the short exposure times and produce a killer image.
     
  11. PlasticSpanner

    PlasticSpanner TPF Noob!

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    By Over exposed I mean they have lost their colour and just turned white! :(

    I have a reflecting telescope but a friend has a bigger scope with a motor drive that I can piggyback on! :D He also has AstroArt software but I've never used it & it takes him ages to finally sit down & use it! :lol:

    This exposure isn't too bad for trailing as it's quite close to the pole star polaris (North). With a 50mm lens at F 2.4 I can get 20 seconds without trailing but further away I am down to about 10-12 seconds.

    I have a film in for processing today with moon shots on so I'll have to see how they come out! My last attempts were too bright & blurry! :lol:
    My attempts at Jupiter and moons with a 200mm F4 lens turned out blurry too (a bit like the image when star testing a scope) This might be in the lens so I'm going to try a prime focus off my friends telescope.
     
  12. PlasticSpanner

    PlasticSpanner TPF Noob!

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    Is Registar any easier to use than AstroArt?
     

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photos taken from praktica bms