Normally, black enhancement is a linear adjustment which proportionately darkens all areas of the picture causing an unwelcome reduction in midrange brightness. In digital printing with fixed linear curves and ICC profile, you need to do the tedious job again to put more ink for black enhancement, with taking 3 to 4 hours. Even through the repeated tedious job of re-linearization and re-profiling, it does not gives you the satisfactory effect in the output. The result may be too dark or your media may not be able to keep oversaturated ink. How to enhance the dark shadow area to block the light without changing whole colors? This is one of main difficulties in daily signage printing work.

First of all, you're recommended to build linearization curve at maximum level until ink flows (oversaturated). That means, you're advised to use maximum amount of ink until your media can absorbe it. The amount of ink can be adjusted at lower level later by color correction, but it is hard to increase the ink level over the pre-fixed linear curves. By using the curves as wide as possible, you have more room to adjust ink saturation for backlit application too.

1. Simply you can increase the ink level of 'Linearization curve'. In this way, ink amount will be increased linearly over the whole range of the curve and your midtone of output can be too dark.

2. First of all, you need to increase 'K' ink limit to be higher, with maintaining the mid-tone colors as it is. For this, TOPAZ Rip provides 'Increase DMAX' option, where you can put any color more saturated in dark zone uner precise control. For example, when you put '25% more K ink for higher than 70% of K level', your linearization curve for K will be changed as the below piucture. You'll see only dark zone ink level can be increased without effect on midtone.

So, now you're using maximum phisical ink saturation in dark area only, for your special backlit applications. In this way, you can enhance your other colors like C, M, Y in dark zone separately.

3. After putting maximum of phisical K ink on dark zone, if you need further enhancement of black color for really dark background of backlit, there's 'Black Enhancement' tool. TOPAZ Rip provides 'Black Enhancement' which allows you to put more CMY ink on all area where K is placed. For example, if you'd like to put 30% of each CMYK ink to K, C=10, M=40, Y=0, K=80 will be changed to C=40, M=70, Y=30, K=80.
In this way, you can get darker black than 100% K. Also you can change the gray-balance tones by setting different portion of C, M and Y to K.