I am using machine learning techniques for computer vision.

However, I am unsure of where to address my questions about computer vision. Sometimes the questions are about manipulating the image and sometimes they are about the machine learning algorithm I am using. Mainly I want to know where to ask questions about the intersection fields of computer vision and machine learning.

Questions about the machine learning algorithms (as long as they're actually about the algorithms and not about specific implementations) are clearly on topic here. In this case the fact that the data is coming from vision will probably be relevant, but may not be central to the question.

Questions about what image manipulations make sense to perform are probably more on topic and more likely to get a good response at Signal Processing (about "the art and science of signal, image and video processing"), which has an active image-processing tag.

Questions about specific implementations of any of the above may be on topic at either of those sites, but also look at Stack Overflow, Computational Science, and maybe Code Review, depending on what the problem is.

There used to be this Stack Exchange proposal: Image Processing and Computer Vision. But it got closed:

[image-processing] is the #1 tag on our Signal Processing site. After 11 months in development, the Community Team has reviewed this proposal and concluded that we should not try to split this subject off into another site. – Robert Cartaino♦ Apr 6 at 15:53

In addition to the other options listed here, I would think computer vision falls within the purview of artificial intelligence. There is now an AI SE site, and I notice that it has a computer-vision tag.

Sites which have a computer vision tag might be interesting. The number of quesions asked there is an indicator for how relevant this might be. However, you should also consider that some sites (like StackOverflow) are much bigger than others (like datascience, which might be a good fit for you).