Re: It there a way to determine photo resolution

Some people use the term "resolution" to describe the total number of pixels in a camera's active area. One can calculate this "resolution" simply as the product of the active area's width and height in pixels. For example, a camera with a chip measuring 1000 pixels wide by 1500 pixels high would have a "resolution" of 1,500,000, or 1.5 megapixels.

The traditional meaning of the word "resolution", however, is "the angular size of the smallest detail which can be discerned in a picture." That is, if one took a photograph of a football game from high in the stands, one could certainly distinguish each player, but not, probably, the shoelaces on each player's cleats. The smallest detail visible might be, say, the decal on each player's helmet. As seen from high in the stands, the decal might subtend an angle of one tenth of one degree: that would make the "resolution" of the picture one tenth of a degree. Note that the same camera could see smaller items if moved down to the sidelines: a photojournalist there might be able to take pictures which show the shoelaces on cleats very clearly. The resolution would still be one tenth of a degree, but now, since the camera is closer to the player, that angle would cover a smaller physical item.