PHOTOSHOP And The LIF²T © Method

If you're using a monochrome (black & white) webcam or other monochrome ccd imager, this
tutorial is for you. It is also useful for processing the luminance channel in RGB color images.

The LIF²T Method (Lasso, Invert, Feather, Filter, and Tone) is my organized approach to the post
processing of grayscale webcam images in Photoshop.

For the rest of the tutorial I'll be using my image of M64 the Blackeye Galaxy and a few other deep sky
objects because they lend themselves well to demonstrating the processing techniques we'll be using.
Look at M51 at the end of this tutorial where the labels on each image indicate the tools used.

The steps outlined here are not by any means the last word in image processing but merely represent
the level I have reached in my own learning curve. I hope my sharing them will move a fellow
amateur astronomer somewhat closer to the 'perfect' image.

A very useful way to follow this tutorial is to right click on the image of M64 below and select 'save
picture as', then open it in Photoshop. That way you can use the techniques as they are discussed.

Make sure Photoshop is set to RGB Mode
(Mode/RGB Color) before proceeding.

LASSO   INVERT   FEATHER

At the outset I want to discuss the three most
important tools in Photoshop for deep space
image processing: Lasso, Invert and Feather. I
use these three in almost every aspect of image
processing including stretching, toning and
filtering. Image post processing of deep sky
objects can present some unique challenges.
For example, most galaxies have fairly detailed
inner cores while at the same time they can
have very wispy almost ephemeral spiral arms.
Nebula can have similar characteristics where
you have to process detailed inner cores and
wispy outer cores or bloated stars that are
embedded in the nebulosity itself. If you
attempt to process these images as a whole you will gain detail in one portion of an image while
sacrificing another. That's where the Lasso tool comes to the rescue which is usually found in the
Photoshop tool box and looks ,as the name implies, like a lasso with a knot on the end. Using the lasso
tool just draw a circle anywhere on an image or draw several circles by holding down the shift key as
you draw each one. Make sure you close the end of the circle completely (first image of M64 below).

Now go to Levels (Image/Adjust/Levels) and make a sharp move using one of the sliders. You will see
that the tone within the circle changes significantly while the rest of the image remains the same (middle
image). Now click on cancel, leave the circle where it is and move your mouse pointer up to 'Select' and
click on Inverse. Go back to Levels and move one of the sliders sharply to the left or right. Now the
image area outside the circle changes and the area within the circle remains protected (bottom image).
Now we have a technique where we can protect a galaxy core while we work on getting some definition
to those wispy spiral arms or protect the arms while working on the core.

But if you were to just use these two tools alone, you would soon find out that for some reason the two
or more separate areas you processed independently of one another just don't look natural. Their edges
are too sharp and they don't blend well together. That's where the Feather tool becomes one of the
handiest tools on Adobe's invention list. This tool is located in the Lasso tools dialog box where the
brush sizes are also located. Click on Lasso options and you will see the Feather box where you can set
the size in pixels. I usually work in pixel sizes from 5 to 50. Experiment with this setting and you will see
that the different Lasso'd areas now blend very well together with no more sharp edges. You must draw
a new lasso for each change in feather size to take affect. Once you are done making your adjustments
to a protected area just click on the image and the end result will appear. Keep in mind that a side effect
of processing different areas of an image is that the tones of these parts may not match and will require
additional adjustments usually involving the use of levels or curves.

Once you have set your feather size in pixels and drawn your lasso you may want to view the actual size
area that will be affected prior to making any changes. To do so just click on the Quick Mask button
located at the bottom of the tool bar. It's one of two buttons that look like the sun or a Japanese flag and
is the one located on the right. The lasso'd area will be in red. As you change the feather size and then
redraw your lasso from Standard Mode (the Japanese flag button on the left), then switch back to Quick
Mask mode (the Japanese flag button on the right), the red area will change. Try it. Here's an image with
the feather set to 10.

Tip: Hmmm .... I wonder what
would happen if we set feather to
50 and then drew a lasso around
the entire M64 galaxy and clicked
on inverse? Then we played
around with the Levels sliders or
Curves or maybe Selective Color.
I'll bet the entire background
would change without anything
happening to the galaxy at all! Read on.

When you have a complicated shape
like M1, The Crab Nebula (see image
below), with all of its surrounding
filaments, you may want to try a
slightly different technique to protect
it from processing or to process it alone. Click on the Quick Mask button, then select the Eraser tool and
choose the smallest or second smallest brush you can find and begin to draw over the filaments. Once
finished you can then draw as intricate an outline as you want all the way around the portion of the nebula
near the inner tips of the filaments. You may want to use the Zoom tool to enlarge the image before
drawing. You'll see that the lines will all be in red. When you're done with that, pick larger size brushes until
you have completely filled in the outline. The second image below shows a partial fill in as well as the line
outlining the nebula.

Once the nebula mask is fully filled in click on the standard mode button to the left and you'll see a nice
outline of the Crab Nebula. Now when you attempt to make a change in the image, only the background
will change. Select inverse and only the nebula will change. That's right, just the opposite of what
happens when you draw just a simple lasso. If you do not see the outlined area when you go from Quick
Mask back to Standard Mode, just do this: while in Quick Mask mode double click on the Quick Mask
button and click on 'Selected Areas' then click ok. Then delete your image, reopen it and the functions
should work as described above once you have redrawn and filled in the Crab Nebula and switched
back to Standard Mode.

And here is the final result, a clearer image showing more defined filaments.

Tip: What would happen if we clicked the
Quick Mask button, set the brush size to the
second largest size, outlined just the filaments
alone and nothing else, went back to
standard mode, clicked on inverse and
adjusted the brightness by using lets say the
curves tool? Take an image you have or right
click on my image of M1, save it and try it!

TONING

This portion of the tutorial includes a
complete step by step demonstration of how
to process a deep space image using
Photoshop and at the very end PixInsight.

Please keep in mind that the following
discussion involves the manipulation of
grayscale images but I use many of these same techniques for color images as well.

Lets move deeper into Photoshop where all of the 'heavy LIF²Ting' (sorry, couldn't resist) of image
manipulation is done. I use Photoshop 3 for image processing and while other higher versions of
Photoshop have the same tools they may be in different locations.

As we go through the tutorial and make use of the Levels and Curves functions, you may notice that your
histograms in Levels and your curve adjustments in Curves don't match up with my instructions. That's ok
because the way you use the tools will never completely match the way I use them. Just try to come close
to matching the images shown. Always pay more attention to learning how the tools are actually used rather
than the specific adjustments I instruct you to make.

After opening the final Registax image, I always start out a Photoshop session by going to Levels
(Image/Adjust/Levels).

Here's an image of M64 which was stacked in Registax3 that you can work on while we are going
through the tutorial (just right click on it and 'save picture as') and load the image into Photoshop. Keep
in mind as we go through this portion of the tutorial that we are working in JPEG or .jpg format which
contains less information that the normal .bmp format I normally work in. So we won't be getting a final
result in the image we normally would. But it will be useful enough to show what this technique can
accomplish.

When you first open the Levels window you see a histogram chart, the filled in black portion of which
represents all of the information contained in the image. Our task is to keep all of the information we
want and to throw out what we don't want. It's actually a lot simpler to do so than you might think
because all we are essentially doing is setting new black and white points in the image. Take a look at
image just below. That's the histogram chart of the above M64 image before any changes have been
made. There are three slider triangles, the one on the left is shaded black, the middle is shaded gray and
the far right is shaded white. They represent all of the tones in the image from black to gray to white and
everything in between.

Once you have loaded the M64 image
into Photoshop, click on the Lasso
tool, set your Feather to 10 and
encircle the galaxy core. Then click on
Inverse and then on the Quick Mask
button. You should see the galaxy core
shaded in red. Remember, any area
shaded in red is the protected area and
only the area outside it will be affected
by any adjustments to the image. If the
core is not shaded in red, switch to
standard mode and go back and click
on Inverse again.

Now we are ready to make our adjustments. Look at figure number 1 of the figures labeled 1-4 below.
This is the histogram of the non protected area outside the galaxy core before any adjustments have
been made. Open the Levels window and you should see close to the same histogram. I say close
because you probably encircled just a little bit different area of the core than I did. First drag the black
slider triangle on the left towards the right just up to the edge of the beginning of the histogram (see
figure 2). Drag the white slider on the right to the left until the middle gray slider reaches the unbroken
part of the graph (as in figure 2). Looking at the image, you should see that the spiral arms have
brightened quite a bit and that we have some noise on the outside portions that we will have to get rid
of. Click on the preview box if you want to see the before and after images. Click ok. The important
point of our adjustments using Levels is that we haven't thrown away any of the original information in
our image that we started out with. So all of your hard work at the telescope getting this image in the
first place isn't wasted.

Now go to Select and click on
Inverse so we can adjust just the
galaxy core alone. Open Levels and
you should see something similar to
figure 3. This is the histogram of the
galaxy core alone (which also
includes the slider adjustments that
we are going to talk about next).
Move the left slider (black) to the
right until it is just touching the edge
of the histogram. Move the right slider
(white) to the left a small amount until
it reaches the beginning of the first
small spike in the graph. If you don't
see a spike, just move it in about the same amount. There is nothing magic about this second slider move.
I just decided to do it because I liked the affect on the image. Nothing more. I threw out just a small amount
of information for what I perceive to be the greater good for the image as a whole. You'll learn this through
practice and experimentation. The galaxy core should now be quite a bit darker than its surroundings.

Next, click ok to close the Levels window and then click anywhere on the image to make the Lasso
disappear. Save your image.

When you save an image you should give it a name that includes the tool you just applied to it. In this case
something like m64levels-core-spiral.jpg to signify that the core and spiral arms were adjusted using
Levels. It's very important to do this at each major adjustment point because, if you are unhappy with the
final result, you can start over again at any point in the process.

Your M64 image should be similar to the one on the left below. Your image from within Photoshop will
probably appear lighter which is ok (saving in the .jpg format can sometimes cause the image to be
darker).

Our next task is to clean up the
image area outside the galaxy by
throwing out some information in the
histogram. This is a third method and
probably the fastest (the other two being
setting a new black point and selective
color) for clearing up background
clutter. Click on the Lasso tool and set
Feather to 30; then draw a lasso around
the entire galaxy to include both the core
and spiral arms. I went out about 1/4
inch extra around the galaxy spirals to make sure I didn't wipe out any potential information there. Select
Inverse, click on the Quick Mask button and check on how much of the galaxy area your protecting. Click
on the Standard Mode button. Now click on Levels to open the Levels histogram window. Referring to figure
4 above, were looking at the histogram which represents all of the noise outside the galaxy that we want to
get rid of (except, of course, for the stars). So let's wipe it out. Move the left slider to the right until it reaches
the bottom right side of the graph. Notice in the image how the graininess disappears as you make this move.
There is a small amount of information in the graph that trails out to the right of this that we don't want to get
rid of because that is where the stars are located. To see what I mean take the far right slider and move it to
the left. As you do so, and the middle slider reaches the right side of this information, the stars should start to
brighten. As you proceed further to the left they will brighten considerably. Don't go too far to the left or you'll
begin to approach some information in the spirals that will distort their tone. When your satisfied with the stars
brightness level, click ok and then click anywhere on the image to remove the Lasso. Save your image. Now
your image should look similar to the one on the right above. The background looks much better.

It's now time to even up the tone difference between the core and the spirals and the best place to do that is
using the Curves function (Image/Adjust/Curves). This is the stage where Curves become more useful
because you are able to make more subtle tone adjustments than you can with Levels. First click on the
Lasso tool, set feather to 20 and draw a Lasso around the galaxy core. Now open the Curves window. We
want to lighten the tone of the core but not too much because it's naturally darker than the surrounding spirals.

A very uniform and simple adjustment method for Curves that is useful for any kind of deep space image
involves the placing of 3 dots on the diagonal line from where you will make all adjustments. You can always
try other techniques later (one of which I explain below) but for now this is an excellent method. Referring to
the figure below, place three dots in the A, B, C positions indicated in figure 1 below by just clicking on each
spot. Keep in mind while making these curve adjustments they don't have to be exact and you may want to
alter my instructions to suit your own taste.

Now holding down the ALT key click
anywhere on the curves graph. You
should see smaller squares as in figure
2 on the right (if not just follow along
with the larger squares). Referring to
figure 1 below, beginning at the A
position, click and hold down while
moving diagonally up until you reach
just a little beyond the top left corner
of the small square. Leave position C
where it is. At position B move the dot straight up about halfway up the square. Click ok. Now the core
matches a little closer with the spiral arms.

Go to Select now and click Inverse so
we can protect the core and work on
the spiral arms. Launch Curves again,
hold down the ALT key and click to
get back our large squares and set
your three points again at positions A,
B, C. Press the ALT key and click to
go back to small squares. Referring to


figure 2 on the right, drag position A to the top left corner of the small square.
Drag position C to the bottom right of the square. Drag position B directly up to the top right corner of the
small square. Click ok. Save your image. Below left is the result of the curves adjustments. You should still
see the lasso around the core. If not, lasso the core again.

With the major curve adjustments
completed, tonal range adjustments
come next. Tonal range adjustments can
actually be used as a stand alone curves
method but I use them to fine tune our
previous curve adjustments. I would
expect that your tonal range
measurements will not be exactly the
same as mine, so the dots on the graph
may be in different locations. Just adjust
the curve until the resulting changes in
the image are fairly close to the images in the tutorial. Activate Inverse now so we can work on the core.
Bring up the Curves window and go over to the image and place the cursor over the upper right tip of the
core just inside the lasso (the cursor is in the shape of an eyedropper). As you click and hold the mouse
button you should see a small square appear on the curve window graph. Note its location and go over to the
curves graph and click once on that spot leaving a dot where you clicked. Now go back to the upper tip of
the core and while holding down the mouse button drag diagonally until just before you reach the bright white
circle of the inner core. Note the location of the small square on the curves graph and go over there and click
on that location which leaves another dot. You've just set the fine adjustment area for the galaxy core. We
weren't interested in changing the bright white inner core and that's why we didn't include it in the tonal range
measurement. Figure 1 below is the tonal range of the core before adjustments. Referring to figure 2, move
the bottom point laterally to the right and the top point diagonally down to the left. Click ok to close the
Curves window. As you can see tonal range adjustments require only very fine movements.

Let's set the tonal range for the spiral
arms next. Activate Inverse, and bring
up the Curves window again. Move
the cursor to the right tip of the core
again and click and hold down the
mouse button, only this time move it
just outside the Lasso line and observe
the position of the small box on the
curves graph and go over and place a
dot at that position. Bring the
eyedropper back to the same position
on the image and move it out
diagonally to the very edge of the spiral
arm. Then mark that small box position
on the graph. Now you've defined the
tonal range for the spiral arms. If you
wanted to refine this a little you could
go around to different positions on the
spirals and come up with an average
tonal range but for our purposes one
measurement is enough. Figure 3 above shows the tonal range before adjustments. Referring to Figure 4
above, grab the bottom dot and move it straight up until it reaches the line above it. I told you these were very
small moves. No need to move the top upper dot, unless you want to. Click ok to close the Curves window.
Save your image. The result of the tonal range adjustments is the image above on the right.

Next let's highlight some of the existing structures in the spiral arms using the Dodge tool which has a function
that can be useful in highlighting difficult to process areas such as galaxy arms and nebula detail. You may
have existing objects in an image that you would like to highlight or tone more which is of course what we
have been doing all along. But if you set the exposure of the dodge tool to a very light setting such as 8 to 10
and select a fuzzy brush size which matches the object, filament or swirl you want to highlight and click on or
run over the object you can achieve a very subtle enhancement to the image as a whole. Be careful with the
use of the dodge tool because if you're too heavy handed you can end up adding information to an image that
was not originally there and that's a big no no in image processing.

We want to highlight some of the faint structure in the spiral arms, so select the Dodge tool from the tool box
which is shaped like a black lollipop with a stick on the end (usually at the bottom of your toolbox). If you
don't see the lollipop symbol in your tool box, but see a hand or a sponge instead, go to the Toning tool
options window and select Dodge tool from the drop down menu. Set the exposure level to 10 and make
sure Highlights is selected. Use the first or second fuzzy brush size depending on the object filament or swirl
you're trying to enhance. Then just run the Dodge tool over what you want to highlight. The result of using the
Dodge tool is the upper image on the right. Save your image. You can see that the result is very subtle and in
fact we don't want any big changes here.

Looking at the progress we've made so far, the stars seem somewhat bloated and not as bright as they were
before. Let's correct that. Select the Zoom tool from the tool box and zoom in on a couple of the stars. Then
select the Lasso tool, set your feather size to 2 pixels, and draw a lasso around a star. Then, while holding
down the SHIFT key, draw lassos around the remaining stars. There are a couple of faint stars embedded in
the spirals that we should also highlight (remember to hold down that SHIFT key or you will lose all your
lassos!). Now select the Zoom tool again and while holding down the ALT key click on the image to zoom
out to normal size. The lassoed stars image is on the left below.

Time to bring up the Levels window
and move the left very bottom slider to
the right until it reads '30'. This should
brighten the stars somewhat. Click ok,
and move to Select/Modify/Expand.
Set Expand By to 2 pixels to ensure
that the lassos fall outside the stars.
Click ok. Next go to the Filter drop
down menu and activate
Filter/Other/Minimum and set the
radius to 1 pixel which should debloat
the stars and probably cause them to fade. To correct the star fade, select the Toning tool (lollipop) and in
the Toning tool (black lollipop) options window make sure Highlights and Dodge tool is selected. Also set the
Exposure to 100% and select the smallest fuzzy brush size in the brushes area. Click twice on each star,
which will maintain their relative magnitudes, and each star should brighten. If you go too far in brightening
them, just hold down the ALT key while you click and they will dim with each click. Zoom out to normal size.
Save your image. Your image should now look something like the one above and to the right.

FILTER

Let's see if we can gain more detail in the core area by doing an Unsharp Mask. Select the Lasso tool, set
Feather to 5 and draw a Lasso around the core. Open the Unsharp Mask window (Filter/Sharpen/Unsharp
Mask). Set the amount to 100% and the Radius to 3.0, leave the Threshold at 0. Click ok. Now activate
Inverse to protect the core, open the Unsharp Mask window, and move the Radius down to 1.0. This will
sharpen the stars and bring out a few details in the spiral arms. Click ok and click on the image to remove the
Lasso. Save your image.

You'll probably notice that the core and a small part of the spiral arms have a grainy texture. One way to get
rid of this is to use the Lasso tool to isolate the portions of the image you want to smooth and apply a small
Gaussian Blur (Filter/Blur/Gaussian Blur) to them. If you prefer to use Photoshop for this, just draw a Lasso
around the area you want to smooth, go to Quick Mask and make sure it is NOT in red, go back to
Standard Mode, launch the Gaussian Blur window and adjust the Radial slider until you're satisfied with the
results.

But I've found that a better way is to open PixInsight and use the SGBNR function (see the PixInsight link
elsewhere in this tutorial). What I like about SGBNR is that it applies a Gaussian Blur to the image without
affecting any edge features it finds in the image! It just smoothes image areas where there is little or no detail.
Note: PixInsight requires that you be in 1024x768 mode.

From within PixInsight, go to File/Open and load in your last saved image. Hold down the ALT key and
press the N key to activate preview mode. Then go to the image and drag your mouse over the portion of the
image you want to preview (or over the whole image). Select the tab labeled Preview01 which appears on
the left side of the image. Now look at the menus across the top and select Process/General/SGBNR which
brings up the SGBNR window. Under Low Pass Filter, change the Amount from .80 to .40. Under Edges
Protection, change the Dark Sides Threshold to 0.100 and the Bright Sides Threshold also to 0.100.
Now click Preview01 located at the bottom of the SGBNR window and make sure you check the little box
next to the image name, click ok and you should see the preview image change. See the image below which
shows the preview image after the changes were made.

You can now alternate between the
Preview image and the original by
clicking on the tabs at the side of the
mage. If you're happy with the
changes, click on Apply located at
the bottom of the SGBNR window.
Save your image as a .jpg file by
going to Files/Save As.

Let's go back to Photoshop to make
a minor change in the image. Once
you've loaded the image into
Photoshop, select
Image/Adjust/Selective Color, and at
the drop down menu where it says
'Reds' select Neutrals. Using the
sliders, set Black to +6 and Yellow
to -6. In my opinion, this gives a more pleasing appearance to the image without causing any significant change.

Were done! The final image appears on the left below and the original practice image in on the right.

ADDITIONAL FILTERING AND TONING PROGRAMS

I will just briefly mention some additional filtering and toning programs that are free on the internet. These
programs are significant additions to post processing and should not be ignored. They are also very helpful if
you have an image that does not require a lot of detailed processing and just needs a quick cleanup.

Loreal [here] is a specialized program that gets rid of star halos or 'ears' which usually result from a histogram
stretch or additional processing. It is very easy to use; just point and click and the halos are gone!

NeatImage [here] is a very powerful and useful program. If you merely load an image in and just tell it to use
the default settings for image cleanup without changing a thing you will be surprised at the results. Be sure and
try the advanced mode which gives you complete control over noise reduction levels and sharpening. It even
includes the ability to match your monitor colors with printed output. Not bad for a free program! It's one
restriction is you can only save in .jpg format.

PixInsight LE 1.0 [here] Within PixInsight is Pleides older program SGBNR(Selective Gaussian Blur Noise
Reduction) which does just what the name implies: a gaussian blur with noise reduction. I used this on my
M51 image with a good result. Just using this tool alone can improve some images significantly. It's located at
Process/General/SGBNR. I haven't had a chance to explore the rest of PixInsight's features but it does seem
to be a powerful image processing program that I'm sure I'll be using in the future.

Tip: There is a very helpful tutorial about acquiring images by Tom How entitled, 'How I do deep sky
imaging', where he uses a black and white ToUcam SC3 webcam located [here]

As an alternative to this tutorial, there is a very informative tutorial on image aquiring, stacking with
K3ccdTools and post processing using a black and white SC3a webcam by Jan Timmermans. The link is
here.

CONCLUSION

I hope you find this grayscale image processing tutorial useful. It was certainly an enjoyable project for me
to work on.

I fully welcome any suggestions, comments or criticisms you may have (see 'Email Rick' link on the left). After
all, this is a work in progress which I will be revising and adding to as time goes by.

Clear Skys!

Rick Murray

rmurr@verizon.net