Digital Camera Image Resolution                Back to Notes on Photography
by Makoto Honda                September 20, 2005

General

The tables below show height/width dot count and the sensor resolution (based on the sensor size) for various sensor mega pixels (MP). Combined with the lens resolution, we calculate the final image resolution (system resolution) captured on the digital sensor. Multiplying this by the area (sensor size) yields the total dot counts in the captured image. This is an ultimate measure of how sharp the picture can be. The tables show the digital camera's mega pixel number in the range of 1 MP (mega pixels) to 64000 MP (64 giga pixels). The lens resolutions in the range of 200 to 600 lp/mm (line pairs per millimeter) are used. The tables have been prepared for 8 different camera formats: 

(1)  1/2.7 inch format      (area size = 4.0 x 5.3 mm)
(2)  1/1.8 inch format      (area size = 5.3 x 7.2 mm)
(3)  Four-Thirds format    (area size = 13.5 x 18.0 mm)
(4)  APS-C format          (area size = 16 x 24 mm)
(5)  Full 35mm format     (area size = 24 x 36 mm)
(6)  5 x 7 cm format       (area size = 50 x 70 mm)
(7)  4 x 5 inch format      (area size = 100 x 125 mm)
(8)  8 x 10 inch format    (area size = 200 x 250 mm)

These tables help me answer various questions, including:

a)  Has the current digital SLR cameras reached the film-based 35mm SLR cameras in terms of resolution?
b)  How does current APS-C (so-called DX-format) DSLR cameras compare with full 35mm format DSLR cameras?
c)  At which MP resolution must Nikon move to the 35mm full-frame format?
d)  Can a DSLR reach a film-based 5x7 camera?
e)  Can a digital 5x7 camera reach or surpass a 4x5 camera?
f)   Is it meaningful to continue increasing the MP number for so-called point-and-shoot compact cameras beyond, say, 10 MP?

How to read the table: The first three columns of the table show the sensor's mega pixels, pixels along width and height, and the sensor resolution (lp/mm) based on the sensor size. The remaining columns show the image resolution (system resolution) in lp/mm and the corresponding total dot count for various lens resolutions (from 100 lp/mm to 600 lp/mm).

Some point-and-shoot cameras today offer 8 MP (mega pixels), and the mega pixel war has no sign of letup. Some of these compact cameras have a tiny sensor size of about 5 x 7mm. This is one fifth (linearly) of the full-35mm format. That is, the full 35mm format has 25 times larger area. That means if we pack these photocells over the entire 35mm format size, the total mega pixel count would be 175 MP. We still have many issues to overcome for small er sensors, not least of which is a noise problem, especially at higher ISO settings. But these problems will be solved eventually. So, a 35mm format camera with 200 MP is not unrealistic, even today. And, maybe 1000 MP tomorrow. This is my justification for providing the table covering 64 giga pixels.