Er . . . Howzat?

[Astrosurf]

I've tried using curves and other facilities in Photoshop to try to get the Orion nebula as close to natural as possible. Any tips?

Alexxx

[jgs001]

It's looking good so far Alex, but I think there's a bit more there to come out... You could try moving the central point on that levels adjustment towards the main peak in the Histogram... but... watch out... the histogram also looks like you've clipped into it a bit at the bottom end, and that can lose you some of the fainter stuff... you want to try and avoid having the main peak hit the left hand edge.

[roundycat]

this might help Astrophotography

Dennis

[Astrosurf]

Thanks guys. That Astrophotography link looks good.

John, how do I prevent the left-hand edge of the histogram being clipped? I used the RGB/K setting in DSS first, then brightness/contrast in PS, the Colour Balance in PS and readjusting in both!

If I move the central point towards the histogram a bit, the whole image brightens. Do I then use brightness/contrast in PS again?

[jgs001]

Sadly, there is no quick answer Alex...

I stopped using the DSS adjustment tools, there's not really enough fine control, and even the DSS author says they are not designed for proper editing. In PS, you have to have the histogram display open so you can see what's happening, that way when you make an adjustment in curves etc, you can see, with the preview turned on, what the histogram looks like. I also really, only use the curves tool to adjust the image.

[roundycat]

I won't comment on DSS and its abilities but never use the Brightness/Contrast tool in PS, that one really is for amateurs. Use Curves for almost everything.

Dennis

[Astrosurf]

Thanks guys. I'm afraid I am an amatuer and can't get the twitchy histogram to do the same! It's just too sensitive for my clumsy hands. I'll just keep trying.

JGS001, when you say you can adjust the curves and see the histogram at the same time in preview, how do you set that up? I can't open both at the same time!

[jgs001]

I think if you click View, Histogram it'll show up... it should, I think, appear where you have the preview and Info boxes..

You can also use the info box to help ... select the eyedropper tool... hold down shift and click on a point in the sky background... ideally somewhere you have no stars or neb... then repeat with a bright star... this should show the RGB values of both points in the info box. Aim to have the background at about 30/30/30 ish..., you'll see if the star hits 255/255/255 (blown)... that last may not be an issue... but if it's a red star that goes to that, you'll lose the colour info.

[Astrosurf]

Thanks John. I can't get the values you suggest, but I'll keep trying!

[jgs001]

When you bring up the curves tool, if you click on your background point in the image you'll see it marked on the curve itself, I think it's probably alt click to put the point on the curve, then you can adjust it. The values in info will adjust to show the effect of the curve, so you can adjust to the values you want ish

[roundycat]

its Ctrl Click!

Dennis

[jgs001]

Thanks Dennis, been to long since o used windows for this.

[Astrosurf]

Interesting! Howzis? I feel I should darken the background a bit. Can't seem to avoid the overdose of red without the colour balance tool though.

[MG1]

If you adjust just the red channel you should be able to reduce the tint.

You could either do this using the levels (view the histograms seperately by clicking the little down arrow on the histogram tab...if that's not visible the select Window>Histogram) or curves which is a little more subtle and flexible IMHO.

You can select just one channel by using the pull down tab in the curves or levels tool....

To darken all channels create a new curves adjustment level

Layer>new adjustment level>curves

then select the very bottom of the curve and shift it to the right....you should see the histogram shift to the left. I take it until the bulk of the histogram buldge is up to the left. Have a play, but try to avoid clipping the blacks.

If you just click at the bottom of the curve then use the arrow keys you can adjust it one bit at a time.

Hope that helps

Michael

[kookoo_gr]

you could try to use the auto color, levels,contrast and curves and see what happens. in my dslr images they always turn out green. by using these options the image comes out normal and then i play with levels and curves to adjust the image to my liking

[roundycat]

Any chance you can post a slightly cropped (to keep the size down) and very low compression (high quality) jpeg of this picture?

Dennis

[Astrosurf]

Thanks guys! You're being great.

I'll have to read up on the Layer>new adjustment level>curves tool! It's strange that some options aren't available for TIFFs.

I'll find the time one day to read the *&)&*^&!!! manual so I don't keep pestering you all!

I've attached a cropped jpeg at 1.93MB. I hope that's not too big!

[MG1]

The options are dependant upon the bit depth. (number of colour values per pixel)

Generally if you import a FITS file or Tiff from DSS (I believe) it will be a 32bit file.

You will be able to make level adjustments, but not curves.

For that you need to convert it to a 16bit file by selecting 16bit colour from the Image>Mode menu.

I tend to stretch levels in 32bit then do the majority of my editing in 16bit and then save 8bit jpegs for the web.

Looking good by the way....very good!

michael

[roundycat]

thanks for posting the jpeg again. I thought it might be worth trying to get some more out of the image, mine is shown below. Without wishing to overload you with excuses remember that you cannot usually get much from a jpeg. The colour is compressed and the 8x8 pixel jpeg artefacts really prevent any sharpening from working.

I just stretched this one gently using Curves and re-set the background colour bias the same way. A small amount of High Pass filtering was used to accentuate the gas shock fronts. A star layer was used to mask off any effect of HP filter on the stars. A filter as harsh as High Pass will kill your stars completely.

Other people have their favourite methods and if they work for them, fine. For my money regardless of your expertise in Photoshop I would concentrate on Curves and remember it can do virtually anything you want with the colour in a picture if you have some data depth there. Stretching your picture took just a couple of minutes, no colour balance, no brightness/contrast and no adjustment layers.

Most of the tools under Image - Adjustments are like using sledge hammers compared to Curves. Levels is even worse than that. Levels allows you to adjust black and white points, neither of which are much use and one central point (gamma). Curves allows you up to sixteen adjustments in each channel.

Dennis

[Earl]

I hope you dont mind but I had a play, there is quiet a bit there, I think im laking in the skillz to get it out though

[Astrosurf]

I hope you dont mind but I had a play, there is quiet a bit there, I think im laking in the skillz to get it out though

Thanks for trying. There's more green in there so I know more where to get to. You're also getting the same strange layered 'distortions' that I was getting. It seems to be more in the RAW images than the TIFFS. I wonder what causes them?

[Astrosurf]

thanks for posting the jpeg again. I thought it might be worth trying to get some more out of the image, mine is shown below. Without wishing to overload you with excuses remember that you cannot usually get much from a jpeg. The colour is compressed and the 8x8 pixel jpeg artefacts really prevent any sharpening from working.

I just stretched this one gently using Curves and re-set the background colour bias the same way. A small amount of High Pass filtering was used to accentuate the gas shock fronts. A star layer was used to mask off any effect of HP filter on the stars. A filter as harsh as High Pass will kill your stars completely.

Other people have their favourite methods and if they work for them, fine. For my money regardless of your expertise in Photoshop I would concentrate on Curves and remember it can do virtually anything you want with the colour in a picture if you have some data depth there. Stretching your picture took just a couple of minutes, no colour balance, no brightness/contrast and no adjustment layers.

Most of the tools under Image - Adjustments are like using sledge hammers compared to Curves. Levels is even worse than that. Levels allows you to adjust black and white points, neither of which are much use and one central point (gamma). Curves allows you up to sixteen adjustments in each channel.

Dennis

Wow! OMG wow! Thank you!!! I'm not sure what your techniques mean, but I'll work through your explanations and hope for the best! I have some dictaphone recordings from the first imaging day which I recall went into the teqniques you're describing (and which I've forgotten!), so they might help. I'm using TIFFs so I hope I can get a good load of detail.

It would be good to have simply an imaging processing day for every imager to have a go at their pics en masse!

Thanks for all your help guys. I really appreciate that. Let's put this one to rest now before I explode with detail and excitement, and you get tired!

Thank you!

XXX

[ollypenrice]

Fine bit of work from the Dennis! Fine bit of image capture from the Astrosurf!

It is all in there. The real killer is operating at a distance. If we could all sit around the table and fight for control of the keyboard it would be so easy. The image is going to sing.

Olly

[Zakalwe]

I hope you don't mind, but I had a play too, as I am trying to get a grip with this processing malarky.

Stretched in curves. Neat Image to remove some noise. Duplicate layer and then high pass filter. more tweaking in Curves.

I should have done something with the stars as I think the High pass has over cooked them.

This link has some really good tutorials and tricks

[Zakalwe]

And a slighter better one