M42 CS3 layer mask question

[Astroscot2]

Hello, I may be missing the obvious but I seem to have got stuck trying to combing a short and long exposure image using Layer Masks.

I understand the technique by Jerry Lodriguss however when I get to the point where I need to view the mask along side the image using VIEW - NEW VIEW to alter it I dont have the option on CS3.

I had a quick look on the net and see that someone mentions using WINDOW - ARRANGE - NEW WINDOW but that does not allow me to see the mask? Anyone else tried Jerrys technique in CS3 and can point me in the right direction?

Thanks

Mark

[samtheeagle]

I had the same issue Mark, I couldn't find how to create the preview window, but tbh just switching back and forth between the mask and the layer worked ok. But a real time preview wouldn't hurt if someone can show us how

[Dave Smith]

I've just had my first go at this http://stargazerslounge.com/imaging-deep-sky/124864-m42-running-man.html

Here are the instructions that I followed which I obtained from a link on here, but unfortunately cannot remember the source. (If anyone recognises it, I would like the reference)

Objective; to combine images of different duration in order to cover a high dynamic range (HDR), a problem always encountered in M42 and often in galaxies. In Photoshop 7 it was easy, or at least familiar. Things have changed in Ps CS3.

-Shoot 3 exposure durations. I used 10 secs, 60 secs and 5 mins. I think maybe 12 or 15 secs might have been better. The Tak is about f5 so adjust accordingly.

-Open 2 images which we'll call the Long and the Short.

-Select, Copy and Paste the short onto the long. It is best to have co-registered them first but you can do it now; make the top layer only 50% opaque and push it around till it ligns up. Then go back to 100%.

- In Layers click on Layer Mask icon, the little rectangle with a circle in it.

-NOW GO TO CHANNELS. This is what's changed!

-Alt click on the white mask rectangle in the layer mask channel and have only that channel visible (using the eyeball symbol. De-eyeball the other channels.)

-Ctrl V to paste the short onto the white mask screen. It shows in grayscale.

-Go to Wndow>Arrange>New window for Short. In this window you will see what your work in progress looks like but you will work on the gray mask image, not the new window. However, you will be looking at the new window while mutilating the mask.

- In Filters put a huge Gaussian Blur on the mask image. About 30?

- In Curves grab the graph and haul it around like crazy while looking at the result in the new window. You will soon see what changes have what effects. When you get it right the Short comes through the mask in the right places to fill in the burned out sections of the Long image.

- In Colour balance or Curves you can match the colours of one or other image as selected to get a seamless blend. Keep looking at the window showing the work in progress.

-When happy, Flatten Image and repeat the process for your third data set.

Dave

[martin_h]

Was this it?

Compositing 2 Different Exposures via Layer Masks

[Astroscot2]

Thanks Dave, I recon thats what im looking for, will give it a whirl tonight.

Out of interest has anyone tried HDR in PS as an option, does this tool work for astro shots?

Thanks

Mark

[Dave Smith]

Was this it?

Compositing 2 Different Exposures via Layer Masks

No, I don't think so Martin. My quote above is a simple copy and paste from the original. Thanks anyway.

Dave

[Dave Smith]

The above reference was from Olly Penrice. Thanks Olly.

Dave