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By Matt Spinelli, 10/18/2005 (updated 4/19/2006, see box below)
In part one of this user guide we evaluated the
user interface. Now we will look into the photo editing aspect of s7raw. All
photo editing adjustments are made within the third panel of the editor and
contain the following tabs: Adjust1, Adjust2, Detail, Curve, Lens, and Color.
In this section of the tutorial we will focus on each individual tab, one at a
time.
Making Adjustments - Rotate, White Balance & Sensitization
The first tab, Adjust1, has three primary functions. The first function
is rotate. This simple control will either rotate the image to the left
or right by 90 degrees. The second function is white balance. The white
balance of the raw image can be adjusted in three ways. The first way is by
selecting a preset white balance from the first 11 options in the drop down
box. The below screen shot displays the options available:
Please note that the custom1 and custom2 options do not
appear different from each other, nor are they editable. This most likely will
be addressed in a future version of s7raw, or perhaps I have not figured out
their use. In any case, most of the other options are self explanatory. The
most useful white balance option is spot. Spot allows us to select a
portion of the image that we know to be a neutral gray point. In other words,
we should click on an area that should be void of color. For example, if an
image has a red, or some other color tone, in an area that we know should be
white, black, or gray, clicking on this area will correctly change the white
balance. This is one of the most accurate ways to adjust the white balance of
the raw image.
The twelfth option available is the second way to adjust white balance. When
color temperature is selected it enables the slider below the drop down
box to be adjusted. The higher the number is, the warmer the colors; the lower
the number, the cooler the colors. Unfortunately, the current version's white
balance by color temperature is not accurate. This is acknowledged on s7raw's
website.
The third way to adjust white balance is to fine tune the RGB channels
ourselves. This can be adjusted in addition to the above mentioned methods.
Moving the sliders to the right does not add brightness to a channel. Checking
the histogram verifies this. What happens is that when a channel is adjusted to
a higher value (slider moved to the right), it expands the channel to cover a
wider range, not merely shifting the histogram as in a simple brightness
adjustment. The opposite is also true when the slider is moved to the left
(lower value), as it collapses the channel into a smaller range. Interestingly,
this has a similar effect to that of the next function, Sensitization, but done
on an individual color channel.
Sensitization, also know as exposure compensation, is similar to
white balance in that it will expand (slider moved right) or collapse (slider
moved left) the colors and brightness levels of the raw image as a whole. It is
best used in conjunction with the white balance options. Lastly, the
vivid and green check boxes will toggle on and off vivid color
processing and green color enhancement. Basically these two options adjust the
colors as described.
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UPDATE 4/19/06: It was brought to my attention that some checkboxes have three states
(checked with a white background, checked with a gray background, and not checked). Well after
hearing back from the s7raw's development team, apparently a gray checked vivid color or green
enhancement checkbox indicates that the effect is applied at 50% instead of in full (white background).
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Adjust1 Tab Tutorial
To summarize the photo editing adjustments that can be made on this tab lets
walk through a short tutorial for adjusting white balance and sensitization. To
start with we will use the same image that was used in the Raw Photo Editing with s7raw article. This image works
really well in demonstrating the power of raw editing with s7raw because it was
purposely shot underexposed in incandescent (normal indoor) lighting. This
causes the image to appear dark with a very warm cast. Remember, there are two
ways (not including color temperature) to adjust the images white balance and
we will walk through each method. The raw image also has severe vignetting at
the corners. All of this makes it a great example off showing of the power of
raw photo editing. However, vignetting won't be addressed until we go over the
lens tab.
The original RAW image can also be downloaded so that those who would like to
walk through these tutorials can practice in addition to reading. This raw
image will be used as an example in the majority of this user guide. You can
download the raw image by clicking on it below. Note: the file size is
5.9 Mb and is in the zip format.
Example #1 - Using the Presets
Step 1: Determine which preset it best to use. In this example, the
background of the image should be white, or a shade of white such as grey.
Selecting incandescent does not properly adjust this image as there still is a
yellow cast to the background even though that was the lighting in which the
photo was shot. Auto does slightly better but the background still isn't white
or grey. Using spot and clicking on the open background changes the white
balance correctly. Notice that the background is grey and the RGB channels are
lined up similarly.
Step 2: Look at the histogram. After the white balance has been
adjusted we can easily see that the image is still dark and that the histogram
doesn't have any information in the brightest levels. To compensate we adjust
the sensitization by +0.7.
Example #2 - Fine Tuning
Step1: Leave the preset to as shot and make sure the check box next to
fine tune is checked. Adjust each channel until all three colors line up with
each other, or until the areas of the image that are suppose to be white or
grey become as such.
Step 2: Look at the histogram. Depending on how we adjusted the
white balance we may need to adjust the exposure compensation. Since fine
tuning each channel has a similar effect to what the sensitization function
applies, we have a choice to make. We can either boost the fine tuning values
or we can boost the exposure compensation to achieve the same result. Again,
the goal is to have the histogram expand across all available brightness
levels. In this case we will adjust by using exposure compensation by moving
the sensitization to +0.8.
As we have seen, the Adjust1 tab primarily edits a raw image's white
balance and this can be done in multiple ways. The above two examples show that
near identical results can be achieved from various methods of editing. Next we
will talk about the Adjust2 tab.
Continue to part 2b - making adjustments with
the Adjust2 tab
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