M42 Orion nebulosan - Mikael Skafar

[Galleri]

Ny bild i galleriet
Objekt: M42 Orion nebulosan
Exponering: 15x4 60min
Fotograf: Mikael Skafar
Kommentar: Den obligatoriska Orion nebulosan som bör bli bättre för vart år? Förra året blev det ingen bild för min del på denna. Vädret var om möjligt ännu sämre det året. Nu fick vi två fina kvälla i december i varje fall. Tyvärr strulade jag till det så jag fick inte mer än en timmes exponering. Kul att få med the running man också. Min första bild på denna. Lite självkritik då, innan någon annan sågar den Följningen skulle kunna vara bättre. Har fortfarande inte finjusterat denna. Man vill ju fota, inte hålla på och justera hela tiden Så lite diamant stjärnor blev det allt.


Klicka for att se stor version av bilden

[GAIS]

Kul att se att du levererar igen!
Tips: Ta ett gäng 10s + 30s + 60s åxå.
Du lägger snabbt samman dom i PS via "masks", då får du en bild där inga områden blir brända och generellt ett klart mer spännande resultat (se hur man gör sist i inlägget).
Att göra en kopia med hård DDP samt tighten star edges maximalt i t.ex NEB och sedan lägga den i en layer med 20% opacity mot orginalet är oxå ett bra tips.
Följning tycker jag verkar vara OK - men kan säkert tweakas...

Se nedan hur man lägger ihop flera olika exponeringtider i PS:
- Kör du PS2 eller senare använd "HDR" (File > Automate > Merge to HDR) - då fixas allt tämligen automatiskt.

- Lägre PS versioner:
Some deep-sky objects, such as M42 and M31, exhibit such a large brightness range that it is impossible to record detail in the bright core as well as the faint outlying parts in a single exposure. Long exposures are needed for the faint portions, and short exposures are needed for the bright parts. We can overcome this problem by combining two exposures of different lengths into a single picture that captures the entire dynamic range of the object. This is done with a mask that blocks parts of one image while allowing the corresponding parts of the other image to come through.

The best way to create a mask to composite two different exposures together is by using a blurred black and white copy of one of the original images itself.
Creating a mask with this method offers the most accuracy and control because the mask is exact - it is made from the image itself, and it can be adjusted with brightness and contrast moves in levels or curves.
In this example, the long exposure will become the base image and the shorter exposure will become the layers on top of it. Each layer will have a mask.
The secret to getting the blend perfect is that the mask will be made from the overexposed portion of the longer exposure, and the changes in the composite will be visible as we adjust the mask.
Here we will use 4 different exposures, one 600 seconds, one 150 seconds, one 30 seconds and one 8 seconds. Each exposure is roughly two stops different than the next one. All were shot with a Canon 20Da at ISO 400.


Layer mask keyboard shortcuts


Alt-click on the layer mask thumbnail icon in the layers palette displays the layer mask.
Shift-click on the layer mask thumbnail icon in the layers palette turns the layer mask on and off.

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Procedure
Open the images in Photoshop.
Copy and paste the exposures as layers.
Create a layer mask for each layer.
Paste the previous exposure into the mask.
Blur the masks.
Adjust the brightness and contrast of the mask.
Tweak the color of the layers.
Flatten the image to combine the layers and save the file.


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1. Open the Images in Photoshop
All of the images should be calibrated and their background neutralized. They should be should be aligned and registered.
600 Sec 150 Sec 30 Sec 8 Sec

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2. Copy and Paste the Exposures as Layers
Open the Layers Palette using the menu command WINDOW > SHOW LAYERS.

The layer's palette will allow us to composite multiple images together in various different ways with the masks.

Copy and paste the shorter exposures on top of the longer one in order of exposure.


Photoshop's Layers Palette
Click on the 150 second exposure image.

SELECT > ALL

EDIT > COPY

Click on the 600 second exposure image to make it active.

EDIT > PASTE

Repeat this procedure for the 30 second exposure and the 8 second exposure.

The 600 second exposure will be the background image. The 150 second exposure will be layer 1. The 30 second exposure will be layer 2. The 8 second exposure will be layer 3.

Photoshop will then paste the short exposure on top of the long exposure, but the bottom image (the long exposure) will not be visible. It is still there though, as evidenced by the thumbnail image in the Layers Palette background layer. It is just hidden by the image in the layer on top.

Clicking on the icon of the eye for a layer in the layers palette will toggle the display of that particular layer on and off. When the eye for a layer is off, that layer is hidden and the layer under it will be visible.


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3. Create a Layer Mask for Each Layer
Click on Layer 1 in the layers palette to make it active. The background of layer 1 in the layers palette will turn dark blue to indicate that that is the layer that is active.


Create a mask The Layer Mask


Click the Mask Icon in the Layers Palette to add a layer mask to Layer 1. It is the little circle in the square at the bottom of the Layer's Palette.

Now you will see a white box appear in the top layer in the layer palette. This is where you will paste the mask. The mask is linked to the layer as indicated by the chain link icon between the thumbnail icon of the image in the layer, and the blank white thumbnail icon of the mask.

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4. Paste the Previous Exposure into the Mask
Click on the background layer in the layer's palette to make it active.

SELECT > ALL and EDIT > COPY. This copies the 600 second exposure to the clipboard.

Make the mask active in the Layers Palette - hold down the ALT key and click on blank white mask box in Layer 1. The image display window will now turn white to indicate that it is the mask.

Paste the 600 second exposure into the mask for layer 1. Edit > Paste.

The 600 second exposure will be pasted in as a black and white mask. This is done automatically, since this mask is technically an alpha channel which is a black and white channel only.


Layers Palette with Masks
Repeat this procedure with each layer, using the exposure for the previous layer as the mask for the layer on top of it.

In other words:

The 600 second exposure is used as the mask for layer 1.
The 150 second exposure is used as the mask for layer 2.
The 30 second exposure is used as the mask for layer 3.

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5. Blur the Masks
Click on a mask in the layers palette to make it active.

Apply a Gaussian Blur - FILTER > BLUR > GAUSSIAN BLUR. You may have to experiment here with the size of the radius of the blur as this will depend on the resolution of the image that you are working on. Low resolution images will require a smaller pixel radius and high resolution images will need a larger radius. For a 1 megabyte image, try a blur of 2-3 pixels. For a 10 megabyte image, try a blur of 10 pixels.

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6. Adjust the Brightness and Contrast of the Mask
Click on the mask icon in the layers palette to make the mask active.

Open the Levels dialog box IMAGE > ADJUST > Levels

Drag the black point at the bottom left to the right until most of the sky background is black.

Repeat this process for each layer mask.


Layer 1 Image Contribution Layer 1 Mask


If you make only layer 1 visible by clicking its eye icon on, and the eye icons of all the other layers off, you will be able to see the contribution of the image in layer 1 to the final image. This is the portion of the image that is pasted down into the background image. The final image will be make up of parts of different brightness from each layer.

The checkerboard pattern is Photoshop's method of indicating transparency, the portion of the image that will contribute nothing to the final image. The transparent portions will be filled in by the image on the background underneath this layer. Click the eye icon for the background layer to make it visible again. Now you can see how the composite is progressing.

The curve for the mask for each layer can be adjusted in many different ways to achieve the exact result you are looking for. Work on one layer at a time with the layers on top of it turned off. Experiment by changing the black and white points and adding a point in the midtones and adjusting it. Watch the results in the image.

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7. Tweak the Color of the Layers
After you have worked your way up the stack, and adjusted the brightness and contrast of the masks, the layers should blend seamlessly into the background below it. The color however may not match exactly.

Click on the icon of the color image on each layer, and adjust the color with Curves to make it match the color of the overall image. Since the mask is present, the corrections you make will only be applied to the core area of the composite.

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8. Flatten the Image to Combine the Layers and Save the File
Save this image with both the layers and the masks as a file with the Photoshop file format (.psd). Then you can experiment with it again at a later date without having to go through all of the pervious steps.

When all of the areas have been adjusted so that they blend together perfectly, combine the layers permanently by selecting Layer > Flatten Image.

The image should now have a full range of detail from the bright core of the Trapezium to the outer loop.

[Bengt]

Hej Micke!

Det är inte många bilder det blivit i december här nere under årens lopp. Tror knappt jag tagit en enda bra bild i just december . Molnen och diset brukar läga sordi på denna månaden i Skåne.

Trist att du fortfarande inte fått till din drift 100% rätt. Orunda stjärnor stör oss gamla rävar och( kanske mest oss själva )

Du får vara nöjd ändå med att fått skördat några pixlar innan säsongen börjar igen i slutet av april


Bengt

[Robert]

Kul att du fångade den. Själv har jag latat mig en del. Inte blivit så mycket tid med en liten pojke som inte vill sova förä'n vid midnatt

Förutom följning som inte riktigt verkar vara av normal Skafar klass så verkar du inte haft helt perfekt fokus? Kanske det som gjort stjärnorna lite större än du borde fått tycker jag. Annars en trevlig bild. Kanske lite för brun bakgrund mellan M42 och M43