Well after many attempts at photographing a large portrait of a group of Percheron horses under different light conditions, I still was not satisfied with the results. The client and I wanted a digital backup file of the portrait in the event that the original was ever damaged.
It seemed the best resolution I was able to achieve (with professional equipment at the photographer's studio) was still not sufficient to reproduce a large 23" x 40" portrait with satisfactorily results.
With much discontent, I took out my scanner and began the laborious task of scanning the area in about 26 or so different sections and meticulously pasting it all together. When scanning on a small 11 x 14 scanner, the edges of each scan are blurry due to the edges of the paper not being in contact with the glass. Each scanned area had to be carefully cropped of these blurry areas before being aligned and pasted together to form the final digital patchwork.
The final task was to go over canvas, blown up at original resolution (150 dpi), and inspect for any imperfections, misalignment or blurry areas and correct if noticeable. If the flaw was minor, I would use a special tool from Adobe Photoshop to fix, otherwise, I had to rescan the area and add another patch to the digital canvas.
Finally, once satisfied with the patchwork of scans, I merged the areas together and adjusted the contrast levels and color if necessary.
The resulting digital copy was a whooping 120MB file with the exact same measurement as the original. I made sure to save many copies so that I have backups if necessary.