Darkening an image

[AstroLuke]

Hi there everyone,

Ive just been out taking some images. After running them trhough deepsky stacker i put the final image into photoshop. I start using curves, a couple of times in a row since the image is very dark. The image starts getting brighter and i use some levels. After doing levels -> curves, 2 times the image is kinda bright and i want to use levels. But i cant since i will loose data if i use levels more.

So my questien is. When i get to a point where i cannot use levels anymore but my image is still to bright, what do i do? I can see loads of details when using curves but i cant darken the image :S

Hope you understand my complicated problem

/Lukas

[Marcus daniel]

Well, lets start at the basics, I could help you if you told me what camera you were using, then i could help there mate

[AstroLuke]

Im using an olympus e-420

[Dave Moulton]

Hi Lukas,

This can be a problem it would be good to see an image to just see how bad the problem is.

In curves if you hover the mouse over the outside of the target within the image a ghost square is shown on hte curves line use this as an anchor point and click on the the line in this area. Place the mouse half way between this point and the bottom of the line an pull down slighly to darken the background.

Gradients can be a problem and there is a superb plug in for photoshop to get rid of those and even the sky background its called Gradient Xterminator by Russel Cronan and is well worth investing in

Dave

[ollypenrice]

There is a clear explanation of levels and curves on Rob's website, here.

Middlehill Observatory, Dorset UK. The Astrophotography of Rob Hodgkinson.

The key thing in levels is not to clip data. Keep some flat data line left of the start of the main peak.

Maybe you have a lot of light pollution in the image? This might be the excessive brightness you are talking about. I'd post an image in the Image Processing Help and Advice section.

Olly

ollypenrice's Photos

[AstroLuke]

problem | Flickr - Photo Sharing!

Heres a picture. I could use curves another time on this image a last time and still see new detail popping up, but i wouldnt be able to adjust the levels afterwords without loosing data.

There is very little light pollution in the image

[Dave Moulton]

Lukas just sent you a pm

Dave

[AstroLuke]

No i dont think you have. I atleast havent recieved any.

/Lukas

[ollypenrice]

The feathering of the histogram shows that you have stretched the image past the noise limit. You simply can't take the image quite as far as you have done and need more data, perhaps in longer subs, I suspect.

Olly

[Dave Moulton]

No i dont think you have. I atleast havent recieved any.

/Lukas

My fault aa permission tab was unchecked . Apologies you should have it now

Dave