At 828x528, it would definitely be light on detail. Acceptable is a value judgement. A couple of examples from the early days—my first camera was the classic Nikon Coolpix 990, which Time Magazine named "Machine of the Year". It was only 3.34MP, and CF cards were small capacity and very expensive.
Over dinner, I was running out of card space and reduced my resolution to 1024×768, and happened to get a lovely portrait of a friend. I printed it 8×10 and it remains on the family living-room wall to this date. Her father was a noted expert on parrots, and a full resolution (2048 x 1536) shot of a macaw's head caught his fancy. He borrowed the file and had a 24×36 print made from it against my advice. A few years later, I was in his city and visited him. The print looked remarkably good from anywhere in the room. At reading distance sharp detail in the feathers was lacking compared to say a D800, but still it was an amazingly acceptable image. Resolution was less than 60 PPI!
People seem to think that there is an absolute threshold below which a picture somehow falls apart. It simply does not exist. Clearly an image at 240 PPI will be more detailed than one at 120 PPI, but it may take a direct comparison to notice. A portrait will certainly be a lot more forgiving than a forest landscape. More resolution than 240 PPI may not gain you anything, but it won't hurt anything either. I now shoot at 12 and 16MP, so when I print, I use the whole image, or what is left after cropping, and scale it to the paper size.
Scanning for a print, I would go for 240 or higher simply because it will give me all the detail I can see and it is no bother to do so. If someone came with a 90 PPI file and asked me to print it, I would do so, after saying that it will be somewhat thin on detail.
Viewing distance is key. As I mentioned, at reading distance I could see a slight advantage to 240 PPI over 180. At arm's length the difference vanished. With large prints, the resolution of the eye falls off more rapidly than detail when viewed at a proper distance. If a print looks good at reading distance, when greatly enlarged, it may look even better. For decades, Kodak mounted an 18'×60' photo mural high above the concourse of New York's Grand Central Station. Close up, it had dye clouds the size of tennis balls, but from the floor, the murals looked crisp and of very high quality. In the beginning, they used large format custom-built cameras, but the last ones were done with 35mm cameras!
Since MTF curves and DxO Marks are incomprehensible to most people, selling cameras by megapixels has been the chosen way. A 16MP camera is not automatically twice as good as an 8MP camera. Sensor quality, AA filter, lens quality, lens aperture, shooting off tripod in perfect light—or not, subject and camera movement, skill in processing and printmaking, all are every bit as important. Above all, a decent print of compelling content will trump a perfect—but boring—print every time.
