Ricoh GR vs. Nikon Coolpix A Review
Both the Coolpix A and the Ricoh GR employ contrast detect autofocus systems. Contrast detect autofocus directly analyzes the live view image and reports an AF lock at the focus setting that maximizes the overall contrast within the selected AF area. As this approach requires trial-and-error, it is generally slower than the phase detect AF systems found in DSLRs.
We found the overall autofocus performance of the two cameras to be rather disappointing. While autofocus speed is fine in bright outdoor conditions, in low light and in macro mode the cameras were so slow that we often preferred to focus manually.
The GR focuses slightly faster than the Nikon in good light. In low light, however, the opposite holds true. While the GR misses focus completely at times while indoors, the Nikon feels more decisive, and it can reliably lock focus even without its AF assist light as long as there is a reasonable amount of contrast in the AF area. The Nikon's wide AF area isn't quite as large as that of the GR, though, so you will often times have to move it around to lock focus in low light.
Although their AF speed is not stellar, both the GR and the Coolpix A focus very quietly. The GRD IV, while faster thanks to its hybrid AF system, has a rather noisy focus motor.
What's the bottom line? Don't expect the GR and Coolpix A to work well for photographing fast-moving subjects, and don't be surprised when you switch to manual focus mode out of frustration with the AF.
Other Focusing Modes
While the Coolpix A only has 3 focusing modes (AF, macro, and MF), the GR and GRD IV also include fixed infinity focus and "snap focus", a setting that fixes the focus setting to a preset distance. Snap focus also engages when the camera doesn't have time to AF.