I previously posted a test of the G9 at full zoom. Here I post the results of my test using the G9 at its widest angle of 7.4mm (which is supposed to be equivalent to 35mm).
These photos were taken handheld, using the JPEGs. (I thought I was shooting RAW, but after I reviewed the shots, to my horror, I discovered they were actually JPEGs.) Because the G9 applies heavy sharpening to the JPEGs, there was no need for me to do any additional sharpening.
First, the full photo, from the F2.8 shot:
And a comparison of 100% crops:
| F Stop | Center | Upper right corner |
| F2.8 |  |
 |
| F4.0 |  |
 |
| F5.6 |  |
 |
| F8.0 |  |
 |
In the center crops, I can barely tell the difference from F2.8 to F5.6, although F4.0 seems slightly better than either F2.8 or F5.6. At F8.0, resolution is clearly lower due to diffraction.
In the upper right corner crops, things look a lot worse. Ugly purple fringing is present. Wide angle seems to be the lens’ weak spot. The best crop is the one taken at F5.6, which shows the most detail and the least purple fringing. The F8.0 crop is worse than the F5.6 crop due to diffraction—in fact, the F8.0 crop has less resolution than even the F2.8 crop.
CONCLUSION: for maximum resolution from center to corner, stop down to F5.6, but do not stop down past F5.6 (or possibly F6.3 at the telephoto end) or you will lose resolution because of diffraction.
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