Would setting it to 13.1MP allow for a greater ... PPI in my final picture?
In terms of PPI, no. In fact, your effective PPI in the final picture is reduced. When you choose smaller image sizes in camera, when the picture is taken, the full sensor is still used. However, when the camera's processor goes to write the image to a JPEG file, the image is first downsampled. This has the effect of being able to discern fewer fine details in the reduced picture.
Nikon's D3200 specifications page gives us the following (I added the sensor conversion to inches):
- Image sensor: 23.2 x 15.4 mm CMOS sensor (0.913 x 0.606 in)
- Image size (pixels) [L]: 6,016 x 4,000 (24,064,000 pixels)
- Image size (pixels) [M]: 4,512 x 3,000 (13,536,000 pixels)
- Image size (pixels) [S]: 3,008 x 2,000 (6,016,000 pixels)
Thus, depending on whether L, M, or S is chosen in the camera settings, the D3200 will perform as either a 24 MP camera, 13.5 MP camera, or 6 MP camera. In all 3 cases, the entire CMOS sensor area is used to take the image. In other words, regardless of L/M/S setting, it is still a crop-sensor (1.5 crop factor) camera.
- For the Large setting, no downsampling is performed. Thus the effective PPI of the sensor image is: 4,000 pixels / 0.606 inches = 6,601 PPI.
- For the Medium setting, a 4:3 downsampling is performed. Thus the effective PPI of the sensor image is: 3,000 pixels / 0.606 inches = 4,950 PPI.
- For the Small setting, a 2:1 downsampling is performed. Thus the effective PPI of the sensor image is: 2,000 pixels / 0.606 inches = 3,300 PPI.
Returning to your question, but addressing "Sensor Pixel Area" (I read that as effective pixel (sensel) size),
Would setting it to 13.1MP allow for a greater Sensor Pixel Area ... in my final picture?
Yes. At the following image sizes, your effective sensel size is approximately:
- Large setting: 14.8 µm²
- Medium setting: 26.4 µm²
- Small setting: 59.3 µm²