Michael S. Briggs
12-Oct-2003, 15:15
The resolution of photo paper is rarely discussed because it almost always exceeds the needed resolution. Photo paper is much slower than film, so it should be easy to make it with resolution at least comparable to film -- but the film is typically enlarged, and paper typically isn't, so film (and lens, etc.) will typically be the limiting factor in resolution, almost never the paper.
The book "Photographic Sensitivity" by Tadaaki Tani has a graph from 1970 (Fig. 1.7) showing the typical properties of Sensitivity and Resolving Power for various photosensitive materials. B/W papers are shown as having resolving powers ranging from 80 to well over 100 line pairs per mm (lp/mm). The next figure places two not-identified color papers at resolutions of more than 100 line pairs per mm. These resolutions are all far beyond the resolving power of the human visual system, so unless one wants to magnify the print, the resolving power shouldn't be an issue.
Ctein in "Post Exposure" reports that the discontinued Ekaflex prints only resolved 20 lp/mm and that some people could notice the difference. He also states that the typical paper for color-negatives can record about 65 lp/mm, while B&W papers can reach 125 lp/mm.
The only modern (non-alternative process) material that I know of in which the print resolution is perhaps discernable is Polaroid prints. Careful examination (e.g., peering at them with my near-sighted eyes) will show them to be slightly softer in sharpness than conventional prints. This fits in with data provided by Polaroid, e.g., the pdf datasheet for Type 52 B+W film has an MTF graph which shows the modulation response falling to 50% by 4 spatial cycles per mm.
The Polaroid figure shows how far most print materials exceed the required resolution. When I look at a Polaroid print I don't notice poor resolution. Perhaps if one had a comparison print of the same subject made with conventional film and paper one might easily notice the difference.
The book "Photographic Sensitivity" by Tadaaki Tani has a graph from 1970 (Fig. 1.7) showing the typical properties of Sensitivity and Resolving Power for various photosensitive materials. B/W papers are shown as having resolving powers ranging from 80 to well over 100 line pairs per mm (lp/mm). The next figure places two not-identified color papers at resolutions of more than 100 line pairs per mm. These resolutions are all far beyond the resolving power of the human visual system, so unless one wants to magnify the print, the resolving power shouldn't be an issue.
Ctein in "Post Exposure" reports that the discontinued Ekaflex prints only resolved 20 lp/mm and that some people could notice the difference. He also states that the typical paper for color-negatives can record about 65 lp/mm, while B&W papers can reach 125 lp/mm.
The only modern (non-alternative process) material that I know of in which the print resolution is perhaps discernable is Polaroid prints. Careful examination (e.g., peering at them with my near-sighted eyes) will show them to be slightly softer in sharpness than conventional prints. This fits in with data provided by Polaroid, e.g., the pdf datasheet for Type 52 B+W film has an MTF graph which shows the modulation response falling to 50% by 4 spatial cycles per mm.
The Polaroid figure shows how far most print materials exceed the required resolution. When I look at a Polaroid print I don't notice poor resolution. Perhaps if one had a comparison print of the same subject made with conventional film and paper one might easily notice the difference.