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17 Hrs with Bell, Book and Candle...

ollypenrice

By ollypenrice
in Imaging - Deep Sky

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blackparticle

blackparticle

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It's the green aspect of RGB that seems a bit pointless to me. From what I can tell, there is nothing in the sky that is naturally "green" and it's only there to produce yellow and cyan in our images in combination with the red and blue channel.

So wouldn't it make sense to go after the yellow to begin with?

Another advantage of a pantone-esque approach would be that you then have the possibility of more than 3 layers with which to balance the colour. I also suspect that the resulting image would have a better FWHM due to its narrower band during capture and it would also make for a much more vibrant ink print.. but that's a whole different thing altogether. :)

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fatwoul

fatwoul

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Have you ever tried CMYK imaging? CMYK is more like a traditional ink printing process.

You're a real fan of CMYK, aren't you, bp? I can see why, though, after the improvements you made to my M42. Give it a try, Olly, I'm an instant convert! I'm sure it isn't ideal for every subject, in fact my hunch is that it might work better on emission than reflection, but I'm going to go and mess around with it now.

Another vote from me for POW, Olly, for sure. Partly because the image itself is, of course, spectacularly creepy (I'm not even sure why, but the comments about Halloween and spookiness sum it up). I think it's because of the two little impish fellas dancing around the bonfire. Excuse the butchering of your image, Olly, but I think these two little characters just became my favourite nebulous entities:

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blackparticle

blackparticle

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You're a real fan of CMYK, aren't you, bp?

heh. Only because I have done print work and know how it works. Add into that the fact that when you print images they are done in CMYK anyway unless you have access to a very expensive photo-optical RGB printer. The transfer from RGB to CMYK in photoshop always leaves photos looking a little weird though as the gamut is more limited than RGB... CMYK has no "pure" red for example.

Imaging in CMYK is a whole new ballgame though as you would require BCYMRK to cover the complete spectrum. You could probably replace C with H-beta or OIII though and Red with Ha or SII.

For most of us this is probably overkill but Olly's pictures are more than worthy of being turned into art prints using proper printing plates. While RGB prints are good (and certainly good enough for screen), nothing compares to the colour definition of a full range CMYK + additional Pantone print. To get the best out of this process you'd have to capture the data accordingly though.

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fatwoul

fatwoul

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heh. Only because I have done print work and know how it works. Add into that the fact that when you print images they are done in CMYK anyway unless you have access to a very expensive photo-optical RGB printer. The transfer from RGB to CMYK in photoshop always leaves photos looking a little weird though as the gamut is more limited than RGB... CMYK has no "pure" red for example.

Yeah a little...lifeless is the word I fall onto when talking to students about converting images between RGB and CMYK. We have a a photo-optical printer in our room; a Fuji Frontier 570, that I use to print my better images. It does a nice job (started jamming now, though!), and is set up for sRGB. But if I wanted to start using our Epson printers, then I'd definitely want to investigate CMYK further.

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Shibby

Shibby

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Wow, that's just stunning (in a spooky way:evil7:) If you struggled with noise, it's certainly not apparent in your final result!

Excuse the butchering of your image, Olly, but I think these two little characters just became my favourite nebulous entities:

My eye was those little fellas too!

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ollypenrice

ollypenrice

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Thanks all and, Werner, yes I agree that there was too much red. New edition below with some additional cleaning. This print palette discussion is great and something I'd like to know more about. Any web links or books out there on getting good prints?

Noise; I'm a bit of a donkey on this and feel that the best solution is to shoot more data. However, 18 hours of extra RGB is maybe a bit too much even here and I don't see less having much effect. I don't have much experience with noise reduction filters so I'm pretty clumsy with them.

Sorry but the original was also flipped.

For Werner;

VdB141-Ghost-Nebula-16-Hrs-X2.jpg

Olly

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ollypenrice

ollypenrice

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Try this site for starters Olly. It's the first one that popped up on a search. I'll have more detailed look for you later to see if there is something more astro-specific.

Photoshop CMYK Tips

Do you have a set of coloured filters like the Meade 4000 ones?

Meade® Series 4000 Photo-Visual Color Filters

Thanks very much for the link and, no, I only use LRGB/Ha/O111 as of the present...

Olly

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blackparticle

blackparticle

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When it comes to printing, the process is very similar to narrowband. Each "plate" is made up of a monochrome image which is then assigned a specific ink colour. CMYK is the standard colour palette although, like I mentioned, doesn't totally cover the full spectrum although most eyes will never perceive this.

Strangely, the more words you know for different colours, the better your colour perception.. which is why artists have an amazing sense of colour.

The first place to start would be to get hold of a Pantone colour booklet. This lists all the colours available by mixing CMYK and other additional ink colours.. even metallics. (Metallic inks look amazing)

Here's a PDF to get you started.

http://www.hessler.com/PANTONE®%20color%20bridge%20CMYK%20PC%20copy.pdf

For an image such as this one I'd try an orange filter as the starting point. A desaturated orange is going to give you the brown tone in the dust clouds and should be a lot quicker than shooting CMY or having too much overall luminance. That layer would then be mapped to a pantone colour... Something like 4485PC for example.

Next a blue filter could be used to bring out the blue stars.. Maybe 310PC for the ink.

Once those are layered in Photoshop, you can then work out if you need a dedicated luminance layer or if you can make an artificial one when combining the blue and orange layers.

When it comes to print, if done on white paper, 3 plates would be made up. One for black and 2 for the colours. Or.. You could print to black paper and use a reverse luminance white ink as an underprint and overlay the colours onto that. Black paper printing can look really special if done correctly but you have to have that white underprint for it to work.

Btw.. It was Hugh Heffner who made me realise the importance of quality paper, inks and techniques regarding printing. There is an excellent article in one of the books I have on how he demanded the highest quality when starting Playboy. :)

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opticalpath

opticalpath

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Fabulous image Olly - I've never seen anything quite like it!

What a shame you couldn't use the full contrast of your Lum image. Did you try multiple luminance layering using many small incremental steps in Lum layer opacity and colour saturation? If you build it up slowly enough, you can sometimes wring a bit more out of the Lum data.

It's a real stunner though!

Adrian

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opticalpath

opticalpath

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Fabulous image Olly - I've never seen anything quite like it!

What a shame you couldn't use the full contrast of your Lum image. Did you try multiple luminance layering using many small incremental steps in Lum layer opacity and colour saturation? If you build it up slowly enough, you can sometimes wring a bit more out of the Lum data.

It's a real stunner though!

Adrian

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ollypenrice

ollypenrice

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Fabulous image Olly - I've never seen anything quite like it!

What a shame you couldn't use the full contrast of your Lum image. Did you try multiple luminance layering using many small incremental steps in Lum layer opacity and colour saturation? If you build it up slowly enough, you can sometimes wring a bit more out of the Lum data.

It's a real stunner though!

Adrian

Hi Adrian,

I did layer mask different stretches of of the luminance layer to cover the dynamic range. I'm not sure I follow you on your suggestion though. When do you apply the colour? I did stretches of the L and of the RGB till both were at their noise limit and then combined them. But I couldn't apply the L at more than about 75%.

Do you mean make an LRGB combination (or several) at shorter stretches?

Curiously the RGB layer was almost featureless in terms of colour contrast. I did boost it in Lab colour mode by putting contrast curves into the a and b channel as I often do. (Good tip from MartinB there!)

Olly

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opticalpath

opticalpath

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Hi Olly.

The technique I was referring to is the one described by Robert Gendler - specifically to address the difficulty you described: combining a high contrast Lum image that overwhelms a much lower contrast/ saturation RGB image.

Untitled Document

The idea is to do an initial LRGB composite but reduce the Lum layer opacity to 50% or less. Flatten the image, increase colour saturation a bit and apply a slight blur. What you have now is a stronger and better contrast colour image that can be used as an improved RGB layer in a new LRGB construction. Because the RGB layer is a bit stronger this time, you can combine the Lum at somewhat higher opacity - say 70%.

You can repeat the process several times to build up contrast in the RGB layer and combine it with more and more of the Lum. I've found it useful with very difficult images to do it in multiple small steps, building up RGB intensity and Lum opacity gradually from a low level.

Adrian

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