Photography is faster than scanning, but I found I will capture excellent detail with a flatbed scanner. The scanner is set up to focus precisely at the platen where your document is, and the lighting is mostly very even and consistent. With a digital camera, you will have to have an even lighting set up and the lens axis should be aligned perpendicular to the document stage to avoid distortion. If you shoot at the maximum resolution with no compression, you may achieve a good digital record of your documents. But I find a flatbed scanner to be more than effective at this and less expensive than and digital camera copy setup. I find that even with positive focus, there's an inherent bit of softness that may obscure fine detail, like extremely small type, very light type of very fine lines as in an engraving. What the digital camera is very good at is documenting items than aren't flat. Or are too large for a flatbed scanner, like artwork, old photographs larger than 8x10", coins, medallions, or other metallic objects that need more directional lighting.
If a resolution of 0 is desired, no alpha will be used, allowing for a more precise Scan quality. To change the dpi setting, click on the image/paper tab in the scan settings window. You will now see “Diameter in DPI”, it sets the maximum scale of the dpi settings. If the setting is too low, the image will appear blurry, while if the setting is too high, the scan quality will suffer. How will this impact me? I have not tested. However, it has not looked like an issue yet. But that's all I've noticed, so I'm not going to go any farther. I think the only other effect would be that there would be a slight blurriness to the scan. Of course, this could easily be overcome by reducing the scale factor. How to get it? You can just copy the image/paper (or “PDF”) file. It should be saved as a .pdf or .psd.