We introduce the Dual-aperture (DA) system which is a novel camera based on depth from defocus (DFD). However, conventional method for DA system has an object color dependency problem, which comes from color transition region between objects or textures in an object. This problem is very important because it results in errors in depth map. For this reason, we propose a 2-step process to obtain the improved depth map compared to the conventional method. First is new interpolation method to align the edge in different color channel using IR channel information. Second is the process to adaptively select suitable color channel for the depth extraction. In addition, experimental results indicate that we can obtain the improved depth map only with a small amount of additional computing time, or about 1% of the computing time for the conventional method.