Step-by-step guide to making your own images
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| Using the Photoshop FITS
Liberator plug-in. |
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| Assembling and renaming layers. |
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| Changing mode from greyscale to RGB. |
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| Creating a level adjustment layer. |
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| Adjusting the levels with the levels
window. |
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| Creating a curve adjustment layer. |
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| Adjusting curves. |
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| Creating a Hue/Saturation adjustment
layer. |
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| Giving a layer a hue. |
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| The hue values given in the table corresponds
to the primary colours of the RGB system (courtesy: adobe.com) |
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| Making the layers transparent by setting
the layer mode to screen. |
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| The result so far, all layers are visible
to give a colour image. |
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| Fine tuning creates a more aesthetically
pleasing image. |
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| Cropping the edges also gives a good
impression. |
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| Are you satisfied now? |
Step 1: Download
- Download a set of FITS-files from the Example
data set page into the directory folder you want to work
in.
Note: If your dataset contains more or less than three exposures
you have to adjust the values of the hue mentioned below. If it
contains two layers a third "psedogreen" layer can be
created (in Photoshop CS, and 7.0) by adding the two existing
layers - the blue and the red layer - to a new layer and divide
this by two. in detail this is done by: "Image - > Calculations".
Choose the blue layer as "Source 1 Layer", "channel
Grey", the red layer as "Source 2 Layer", "channel
Grey". "Blending Add". "Opacity 100%". "Scale 2".
Step 2: 'Liberating' the FITS format images
Below is a simple step-by-step example using a specific FITS file from the examples on the FITS Liberator web page:
- Open the images one by one in FITS Liberator.
- Set the White and Black level sliders in the histogram to give a nice contrast without too much black and too saturated areas.
- Click Auto Scaling.
- Try different Stretch functions to enhance fainter parts of the image.
- Click OK.
- Repeat for the other images in the same dataset.
Now you have 'liberated' the data from the FITS format, the rest
is hard work in Photoshop.
Step 3: Assemble the different exposures into different layers
of the same image
You should now assemble the three images into one file. If the
layer window does not automatically open, you can activate it
through window -> layers (or by pressing F7).
- One way of doing this is: select all in one image (short cut:
Ctrl+a) - then "copy" (Ctrl+c).
Choose another image. Paste (Ctrl+v) the first image into the
next image. This will create another layer in the first image,
so you now have two images together in each their layer.
- Rename the layers as you paste them as there are usually little
visual difference between exposures (just double click on the
name). Give them logic names like "656nmos-green".
- Repeat with the third image, so you get all three images together
in the same window, just in each their layer.
- The layers should be in chromatic order, the first layer will
be blue, so put the file corresponding to the lowest wavelength
in the first layer, the middle wavelength in the second layer
and the highest wavelength in the last layer that will become
red (the layers are counted from the bottom of the screen and
up).
- Note that users of Photoshop Elements have
to convert the layers to 8 bits/channel first with:
Image -> Mode -> Convert to 8 bits/channel
If you have accidentally gotten the layers in the wrong order,
you can drag them up and down as appropriate.
Save time and trouble
The action you can download from our download
page takes care of step 3 through 7. So if you play the action,
you can then go ahead to step 8. This will save you a lot of work.
- So unless you are really interested in Photoshop detail, we
recommend you play the action and then proceed
to step 8.
On the download page there is a short description on how to
load and play the action.
Step 4: Change mode to RGB
The grey scale images should now be converted to RGB images.
- Do this by choosing image -> mode and then choose RGB as
shown in the illustration.
Step 5: Making a level adjustment layer
Now it is time to add some adjustment layers that allows you
to change the intensities and colour of the layers. Having these
as individual layers makes it easy to go back and re-adjust some
settings later on.
- Choose a layer by clicking on it.
- Then add an adjustment layer by choosing Layer -> New Adjustment
Layer -> Levels, as is shown in the illustration.
- Remember to check the box "Use Previous Layer to Create
Clipping Mask" (or "Group with previous layer”
in Elements 2.0). If you forgot, delete the layer and make it
again.
- When the Levels dialogue box appears, you can slide the markers
appropriately or wait and do this later.
Step 6: Making curves and hue adjustment layers
- Add another adjustment layer, this time choose Curves (not
available in Elements 2.0).
- Also check the box "Use Previous Layer to Create Clipping
Mask" (or "Group with previous layer” in Elements
2.0).
Curves do the same as the stretch function earlier, but here
it is possible to manipulate the stretch function by dragging
the curve. Curves should be used with care. The main strength
of this tool is its ability to emphasize either the light of the
dark part of an image.
- Add a third adjustment layer, Hue/Saturation.
- Here you must also check the box "Use Previous Layer
to Create Clipping Mask".
According to the layer you are making the adjustment layer for,
choose the following values:
| Colour |
Blue |
Green |
Red |
| Hue |
240 |
120 |
0 |
| Saturation |
100 |
100 |
100 |
| Lightness |
-50 |
-50 |
-50 |
These values corresponds to the primary colours of the RGB system
in Photoshop.
It is important to check the box "colorize" when the
curves dialogue window pops up.
- Repeat step 5 and 6 for the other two original layers, so
you end up with three correction layers for each of the original
layers.
Step 7: Making the layers transparent to see all the colours
- For each of the original layers (the exposures
themselves), the mode should be set to "screen", as
it is done in the illustration.
- For each of the linked adjustment layers,
the mode should be set to "normal", as it is done
in the illustration. This is where you can spend a lot of time
later selecting the best mask to suite the final image detail
and blend. Changing between “Normal” and “Overlay”
or “pin light” etc for example can have a dramatic
effect. Also the sliders on the output can be moved to find
the best detail, but for the start you may want to just use
the "auto" setting.
This will make the layer transparent, and it is the equivalent
of having the three different layers behaving as slides instead
of as paper images.
Step 8: Making the image look good
- If you used the action, or if you did not touch the sliders
during the manual operation, you should now go into each of
the different correction layers and balance the colours. You
do this by double clicking on each of the nine correction layer.
Generally it is advised to get as large a dynamic range as possible
in the image, but much of this work is all a question of taste.
Now you should have a nice, well balanced colour image on your
screen and it is time for some real fun! (now is a good time to
save your image if you have not done this so far!).
- Try for instance to remove some of the corrections by clicking
on the "eye" to the left of the level. Put it back
by clicking again. You can also redo the corrections by clicking
on the appropriate correction level.
When you decide you cannot use more time on this fine tuning,
you might have an image that looks somewhat like this figure.
Step 9: Cropping
The image will definitely look better if you crop it.
- Pick the cropping tool in the toolbox in the left side of
the screen. Mark the area you want to keep, and choose "crop"
in the image menu (or double click inside the selection)
- You can compare your result with the draft image to the right
(made by a professional).
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