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ThaBizness
sage
Reged: 12/28/05
Posts: 378
Loc: St. Louis, MO
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Some times people will comment on images and say "you clipped the black point". How can you tell the black point is clipped? What things are you seeing that tell you the image is clipped?
Just trying to get a better grasp on post processing.
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St.Louis, MO
Orion 8 Inch F/4.9
Orion 80ED
Celestron AS-GT
Orion Atlas EQ-G
Canon 350XT Unmodded
Meade DSI-C
My Astrophotography
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jgraham
Postmaster
Reged: 12/02/04
Posts: 5370
Loc: Dayton, Ohio
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A couple of things usually stand out when I look at an image that is clipped on the black end; the background looks 'too' black, the contrast looks too high, and the edges of duffuse objects like galaxies and nebula suddenly stop instead of fading into the background sky. Images taken under very dark skies can have backgrounds that approach true black, but even in these cases nebulous objects 'fade to black' instead of looking clipped around the edges.
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-John
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Homebuilt scopes from 4.25-16.5"
Meade LXD75-N6/SN6/SC8, DSX-90, ETX-60BB, ETX-125PE, DS-2130
Orion StarBlast, BinoViewers, Coronado PST
Rebel XT/XTi, DSI Pro (I & II), DSI, LPI, Electronic Eyepiece, Phillips SPC900NC
Tasco 60mm Refractors
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ThaBizness
sage
Reged: 12/28/05
Posts: 378
Loc: St. Louis, MO
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Thats helpful, I always tried to get the background as dark as possible without darking the object itself. It looks like that is the wrong way to go about it.
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St.Louis, MO
Orion 8 Inch F/4.9
Orion 80ED
Celestron AS-GT
Orion Atlas EQ-G
Canon 350XT Unmodded
Meade DSI-C
My Astrophotography
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TheNebulai
Pooh-Bah
Reged: 01/26/07
Posts: 1139
Loc: New Jersey
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I am known to do this with my moon pics. I process the back to be so dark that it makes the moon appear overprocessed.
Sometimes on my early Saturn pics, I processed them so far that the outer rings all the way to the Cassini have disappeared so it can really effect the outcome of the final image.
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Equipment:
Z10, Meade 8" LX90GPS, Galileo 120mm
A bunch of EP's, Filters, and Barlows
10*50 Binocs
Sony Cybershot,Philips SPC900NC,DSI Pro,
DMK21AU04/ Astronomik LRGB
Messier Count: 48
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Andrew Welsh
Carpal Tunnel
Reged: 03/28/06
Posts: 2240
Loc: Rochester, NY
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Quote:
Some times people will comment on images and say "you clipped the black point". How can you tell the black point is clipped? What things are you seeing that tell you the image is clipped?
Just trying to get a better grasp on post processing.
The subjective way to describe this is a "burned out" look, or edges that have too high of a contrast.
People are used to seeing a "black" of RGB values around 15,15,15 (which is technically a really dark grey) in images.
A look at the histogram in your image editing program will show this. Is it piled up hard against the right edge (clipped), or does it curve down and trail off at the right edge (not clipped)?
If it helps, I generally make the black point adjustment one of the final adjustments.
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LX200 8" classic, f/10, Meade eq. wedge, .63x FF/FR
Canon 40D and 5D, unmodified
Canon EF 300/2.8L IS, 400/5.6L, 135/2L, 50/1.8, 85/1.8, 35/2, 24-70/2.8L, and Peleng 8mm fisheye
Orion Apex 102mm (4") Mak-Cass
Pimped out with accessories and bling
My DSLR Astrophotography Webpage and photo bucket with full equipment list
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jayscheuerle
Carpal Tunnel
Reged: 01/16/06
Posts: 2989
Loc: S. Philadelphia, PA
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Nature is gradations. If you have flat areas of black or flat areas of white, you've clipped your image. Once this is done, you can't get the data back, even if you make your whites darker or your blacks lighter. Your histogram will show you this. Ideally, it starts a little in from pure black and ends a little before pure white. You want to bring your black and white sliders right up to where the data starts. If you go past that you're clipping data. - j
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12" Green Goblin (trusser w/Protstar secondary and OWL refigured primary)• 6" f/5 Eero2 ball-scope • 6" f/5 Frankenscope • Garrett Optical 10x50 binos • Edmund 8" yoke-mounted red-tube reflector • Edmund 6" GEQ red-tube reflector (on loan to Dad)
Gone, but with lessons learned:
Skyquest XT8 • NexSTar 8i • Eeroscope 6" f/5 ball(sacrifice was not in vain) • Vixen ED80sf • Edmund red-tube 4.25" f/10 • Edmund Astroscan
Facts are stubborn things.
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