I tried a few of those scanner apps on my iphone 6+ and wasn't really impressed at all with the quality of the OCR. I was certainly not impressed with the price! I'd guess that the engine allowed within a phone app is not even close to the full featured software on a desktop. I seriously doubt it's due to the quality of the picture. The peeps over at
https://www.diybookscanner.org/forum/ use cheap cameras on their scanner units all the time with great results. They also have free software specifically designed to OCR book scans from those cheap cameras. Perhaps that will help??