I am noticing that with some blown sky situations if I use a parametric mask on the magenta area and then use the channel mixer to drop the red value to that of the green value, some level of the blue sky can often be recovered.
David On 13-06-07 08:22 AM, Rob Z. Smith wrote: > OK, let me substitute 'not quite white' instead of grey. > > Imagine what is probably the most frequent use case of blown out areas in > clouds. Rather than losing all detail my thoughts are that it might be best > to do something like map (255,255,255) to white but say (255,254,243) to some > averaged value such as (254,254,254). That would avoid colour casts but > still avoid throwing away such highlight detail as remains in the unblown > channels. I think it would look better than a large expanse of pure white. > > But retaining colour information would be better provided it doesn't cause > colour casts. Raw Therapee have put a lot of work into this but even there > you still you get colour casts, sometimes. Whenever we invent data with some > interpolation algorithm there is always going to be the odd example that > throws it. > > I haven't worked on a blown colour casted highlight reconstruction recently, > but it strikes me that we can perhaps deal with such colour casts more easily > in dt than any of the other raw converters. Let's say our reconstruction > causes a typical magenta colour cast in the reconstructed areas around > totally blown highlights - I suspect we could just use our parametric masks > to run a magenta subtracting colour change just on the brightest pixels and > if necessary add a drawn mask as well. > > -----Original Message----- > From: Chris Siebenmann [mailto:c...@cs.toronto.edu] > Sent: 07 June 2013 15:13 > To: Rob Z. Smith > Cc: darktable-users; c...@cs.toronto.edu > Subject: Re: [Darktable-users] Best way to recover highlights that are blown > in processing? > > | On 13-06-06 10:14 AM, Chris Siebenmann wrote: > | > I would be happy to see a highlights reconstruction option for 'if > | > any channel is clipped, set the pixel to white'. I might even turn > | > it on all the time. > [...] > | > | It might be nicer if such an option set the pixel to grey rather than > | white using the values of the remaining unblown channels to take a > | best guess at how near to full white that grey should be. > > My thinking on this is that white splotches on pictures look less ugly than > grey splotches. To some extent we are trained (especially now) to expect very > bright areas in pictures to be white; I'm not sure that very bright areas > looking grey instead will look at all pleasent. I wouldn't be surprised if > they came out looking rather wrong. > > - cks > > The content of this email is private and confidential, and unless otherwise > stated only the intended recipient may use the content of this email for its > intended purpose. If you are not the intended recipient, you may not retain, > copy, forward or disclose the information herein, and we ask you to notify > the sender or contact our Customer Services department on 0844 633 1000 or at > cssupp...@nhbc.co.uk The copyright and all other intellectual property rights > subsisting in or to the contents of this email belong to NHBC or are used > with the permission of the owner and all such rights are reserved. Recipients > are asked to note that opinions, conclusions and other information in the > contents of this email that do not relate to the official business of NHBC > are neither given nor endorsed by NHBC. 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