Ricoh GR vs. Nikon Coolpix A Review
Aberrations and Flare
All three cameras exhibit a small amount of barrel distortion; this distortion will most likely not be noticeable in everyday photographs. The Coolpix A is worse than the other two, requiring a +1.5 correction in Photoshop. Both Ricoh cameras only needed an adjustment of approximately +1.0.
The Coolpix A has a fair amount of vignetting at all apertures. At F2.8, unlike the distortion, the vignetting can be easy to spot in everyday photos. The GR has some vignetting at all apertures, but it is nowhere near as severe, as it is tough to spot at F4 and above. Those who look carefully will notice that there is very slight darkening of the corners. The amount of darkening is noticeably more pronounced on the Coolpix A, suggesting that its lens doesn't do as good of a job of fully covering the APS-C image circle.
The GRD IV shows negligible vignetting throughout its aperture range.
Flare and Ghosting
All three cameras are remarkably resistant to lens flare and ghosting, though the Coolpix A seems to be best in this respect, with the GR being better than the GRD IV. Generally speaking, unless you are pointing the GR or Coolpix A at the sun, it is very difficult to induce flare. The flare is also worse in the corners than in the center.
We were able to capture an example of very noticeable flare in the center of the frame with the GRD IV.
Coolpix A - Flare Example (Corner, 100% crop)
GR - Flare Example (Corner, 100% crop)
GRD IV - Flare Example (Center, 60% crop)
The higher degree of distortion and vignetting that the Coolpix A exhibits also means that it is more prone to chromatic aberrations (purple fringing). In practice, you will only ever see fringing in the corners, and it isn't severe enough to have a significant impact on your photos.
The GR also only shows come fringing in the corners, but to a much lesser extent. We were not able to observe any significant fringing with the GRD IV.