This short Tutorial will show how I configure the Epson TWAIN
module to obtain optimum results. The screen grabs are all based on
using TWAIN module (Version
5.51) with the Epson Perfection 1200
Photo Scanner, but many of the settings should be compatible
with later versions. The objective is to get the scanner driver to a
state were no automatic controls could influence the scan.
An Adobe Acrobat version of this Tutorial can be downloaded by
clicking the PDF Icon
Typically, it is best to set the scanner driver to scan at 100%
with a resolution of 300ppi. Higher resolutions are not required.
Also, ensure that you have the driver set to scan 24bit colour and NOT
36bit (high-bit colour mode on Epson 1600 series scanners). The
following screen grab gives you an idea of how the scanner window
should look. If it doesn't show these controls simply click the
"Advanced" button.
Twain Driver Controls
First we must configure the driver (1), simply press the
"Configuration" button and the following dialog box should
appear.
It is ESSENTIAL that the three options circled in red are
all disabled (unchecked). If ANY of these options is ON
you will be allowing the scanner driver to automatically determine
the range of the target and the results are likely to be poor.
The next step (2) is to configure the scanner "Image
Controls", namely "Highlight", "Shadow",
"Exposure", "Threshold" and "Gamma".
The following screen grab shows the various settings for Epson Twain
4.x. For hose working with Epson Twain 5 set the Highlight value to
250 as this will prevent the software automatically adjusting the
exposure scale. Don't even
think about using the "Eyedropper" tools or you
will alter the balance.
We want all those items circled in YELLOW to be pre-set to
the values shown above, ONLY the GAMMA control
(circled RED) will be varied. The default gamma value is 100.
NOTE: 100 is NOT equal to gamma 1. If it were equal
to a gamma of 1 you would not be reading this tutorial! My own
comparison with a wide range of scanners suggests the value of 100
is MUCH closer to gamma 1.8.
Now we want to ensure that "Tone Correction" (3)
is set correctly. I have found that the default values are probably
the best, so my recommendation is leave this dialog set for "Linear".
The remaining two Twain driver controls circled in "Yellow"
should NOT be touched.
Since we have the scanner module configured, all we need do now
is make a pre-scan of the target print. We are trying to get an
image that is neither light nor dark. As explained above, ONLY
the gamma value needs to be adjusted and you should see the preview
scan updating as you move the gamma slider to the left or right.
Adjusting the Gamma Slider
I suggest that you make the first scan at a gamma of 100. When
the image opens in Photoshop choose "Levels" and
check the spread of the data. Ideally, the data should spread from Shadow
to Highlight as shown below. Do NOT be tempted to edit the
target image in Photoshop to make the data spread look like the
screen grab, ALWAYS rescan the target with a revised gamma
value.
Photoshop Levels - Ideal
Spread of Data
If the scan results in a data "spread" similar
(identical peaks and troughs isn't necessary or even likely) to that
shown above, then it is likely that a good profile can be created.
Simply move on to the next stage of making the custom printer
profile. However, if the scan looks like the following screen grab
it is almost certain that the scanner gamma was NOT set to
the ideal value and so you should rescan using a different gamma
value.
Scanner Gamma was set
higher than required
The above screen grab shows the result of scanning with gamma
value set to high. Typically, the scan will be light and lack
contrast. I have found that depending on the paper/ink/printer
combination; gamma values in the range 80 to 120 are
best (Epson Twain 5.x users should find these values
correlate to 0.8 and 1.2).
I hope this short tutorial helps resolve the problems Epson
scanner users are having when trying to make custom printer
profiles. Certainly, I have found that using the approach described
above allows me to create very good profiles using either ColorVision
Profiler RGB or Monaco EZcolor. It also works for Praxisoft
WiziWYG as an alternative to the configuration I previously
suggested (that method still works perfectly okay). However, WiziWYG
seems to favour gamma values slightly higher (100 plus) than
Profiler RGB or EZcolor, but the spread of data shown in Photoshop
Levels is still the KEY indicator as to whether a successful
profile can be obtained.
