PS curves tutorial

[Peter Ward]

Hopefully this will be of some help to novice astro-photographers. While there are other ways to approach the problem experimentation is the key, and you can always hit the "undo" key if you don't like the result

http://www.atscope.com.au/BRO/tutorials/dsrlcurves.html

Peter

[leon]

Could be handy Peter thanks for the link.

Leon

[dugnsuz]

Thanks for that Peter.
Doug

ps...while browsing your site I came across this...
http://www.atscope.com.au/BRO/wholeshebang.mov
Fantastic stuff, hope you don't mind me sharing it here on your behalf?

[turbo_pascale]

Peter,

Thanks for the tutorial. Short but sweet.
I thought you were a Mac nut? Since when are you on a PC????

re: Quicktime VR movie
It's a great image. If you could only stop the trees from moving it would be perfect!! I have to say, I've just been moving around, zooming in and out for 5 minutes. It's wonderful.

Turbo

[Peter Ward]

Turbo,

Glad you like the VR

I use Mac's *and* PC's ;) However the VR was done on a Mac

[turbo_pascale]

Was the VR done with a DSLR or a CCD? I recall you used a fisheye lens for this. Do you recall the details?

Turbo

[Peter Ward]

I grabbed the VR data about a year ago, with a great bunch of people at Mudgee, using a Canon 5D, Sigma 8mm fisheye on a G-11...which only just coped :).....camera noise reduction was on....and I recall I was shooting RAW frames.

It would be interesting to re-shoot with a CCD in RGB + Ha (on the to do list)

I rather like High Res VR images... but am only a novice.... as there some simply mind blowing examples out there:

http://www.panoramas.dk/fullscreen6/f52-sydney.html

http://www.panoramas.dk/moon/apollo-17-2.html

Plus many many others....

[sheeny]

Thanks, Peter. Very succinct!

Al.

[Hagar]

Thanks Peter, Should be interesting to experiment with.

[Alchemy]

A nice straightforward tutorial, thats the sort of stuff that can help people.
Good post.

[Tamtarn]

Had a go at altering our image of Tarantula which we posted on 22-11-07. Used your curves tutorial Peter. Haven't altered the images in any other way other than the curves. What do you think ??

1st image our original the other three variations of adding colour curves.

37164

371653716637167

Barb

[dugnsuz]

I know I'm wrong because thems in the know have told me so, but I think the "blue" version straight from the DSLR has the most natural look/feel.
The wispy nebulosity on the edges of the spider look better to me!
I am a rookie but I'm just going with the gut!
( Just had a curry for tea though!!!!)
Cheers
Doug:thumbsup:

[Peter Ward]

Praise Jehovah! :) (just joking)

We could talk about gamma correction...but in so far as colour goes..yep! definitely at the right end of the spectrum again. Well done!

[h0ughy]

Gee I can feel the love in the air.......thanks Peter for the turotial link and the advice

[netwolf]

I must be doing something wrong because my whole background turns red when i do this. What am i missing.

Regards
Fahim

[turbo_pascale]

Fahim,

Two possibilities (coming from a complete novice, please take it with a grain of salt).

1) maybe you need more subs - not enough differentiation from the background noise.

2) If that's not the case, then perhaps it needs more stretching. I've been reading "The Zone System" by Wodaski, and the curves correction as Peter describes is step 1 of an iterative process of resetting the black level, then stretching again, etc etc.
eg. In photoshop, CONTROL-L, set the black level just below the first peak. Might only be 1 or 2 from the left (of 256).
Do the curves thing (CONTROL-M) as per Peter's example (Wodaski calls this the "standard curve"). THEN.... go back to levels and see if you have moved the histogram. You probably now have room at the left of the curve again, so reset the black level, then off to the curves screen again. Repeat until it doesn't get any better. Judicious use of the undo feature recommended.

Please excuse me too, if this is basic, but I've not seen a post here describing this process in any more detail. If there is someone more versed in the process or can explain it better, I'd be keen to hear it expressed differently too.

Turbo

[netwolf]

Turbo,

Ah I see, i think its both 1 and 2. I will give it a go.

Regards
Fahim

[Peter Ward]

Fahim,

No problem. You can anchor the bottom of the red curve by clicking on it there, then and adjust the curve higher up. The levels tool can also be used.

You can also tweak the lower end of both the green and blue curves so the sky remains blue/grey black.

[netwolf]

Yes i have seen that while mucking around with it that you can indeed set your black and white levels in the Curves by clipping it to the bottom or top.