I'm profiling a Canon 5D3 with both the Adobe DNG Profile Editor and the Xrite ColorChecker software. It's been about 3 years since I last profiled a camera, so I'm re-doing the learning curve. My question now is how and why the DNG Profile editor depends on a "base profile?" Specifically, why does the DNG PE Chart Wizard generate different results depending on what base profile is used.
I see in the documentation that "all color adjustments made in the DNG Profile Editor are defined relative to a base profile." I understand that logic when making a custom profile via manual tweaks. You have to have a starting point. But I don't understand that logic when using the Chart Wizard. I expected the Chart Wizard to arrive at the same pre-defined target point regardless of the starting point. It does not seem to do that.
I discovered the difference by using an apparently bad workflow. I shot my colorchecker chart, converted the CR2 to DNG and brought it into Photoshop via ACR to inspect. That stored "Adobe Standard" as the base profile in the DNG.
Then I fed this DNG to the DNG PE Chart Wizard and generated a profile. I opened the image in ACR and applied "My Profile", which became the base profile in the DNG file. I thought I did something wrong, so I ran the same DNG through the Chart Wizard again and generated "My Second Profile." That version looked very strange, so I did it again and made "My Third Profile."
Now I have three profiles. My First Profile was made from Adobe Standard base. My Second Profile was made from My First Profile base. My Third Profile was made from My Second Profile base. Each iteration becomes more strange (bad), so this is clearly not the proper workflow. But what is? What base profile should be selected for Chart Wizard and why does it matter?
Being curious, I did the same exercise using the Xrite ColorChecker software. That software generates the same result, regardless of what base profile is stored in the DNG files. I'm not sure I like the results, but at least they are consistent.
DNG Profile Editor lets you define color edits (in the first tab) using a set of color control points. These control points in turn define a color lookup table used to perform the color correction when processing a (raw) image.
When you use a Base Profile, the resulting color table in the final profile is a combination of the base profile's color table, plus the color table defined by any edits that you've added in the first tab (using the Chart Wizard counts as adding edits to that first tab).
The reason you can get different and less smooth results if you apply the Chart Wizard iteratively is because you are applying lookup table after lookup table. The current color table-building method used by DNG PE has some limitations regarding smoothness of color profiles if two color control points are placed too closely (this can happen with the Chart Wizard, or if you specify two points manually that are close to each other). These problems can become more noticeable if you apply the DNG PE iteratively.