Problem: you're a full city block away and you need a photograph that can be enlarged to the extent that you can positively identify the person on the balcony.
Solution: a high-quality 180mm lens, a strong tripod, and Bluefire Police™ film, developed in Bluefire HR™ developer.
The print above on the left is an approximately 4x6 inch enlargement of a full 35mm frame. 4x6 is the standard "snapshot" enlargement size. The photograph was taken from the distance of approximately a city block (about 90 meters or just under 300 feet) from the man on the balcony. The lens was a Nikkor f2.8 180mm telephoto, a standard high-quality surveillance lens, at f8, which is close to its optimum aperture.
Most 35mm negatives begin to show grain, which degrades detail, when enlarged to 8x10 or 11x14 inches, or about 10x to 12x enlargement. The detail above right is enlarged to approximately 35x. It is grainless.
The detail below is an enlargement of 67x. Even at this extreme enlargement, grain does not degrade image detail. The full frame enlarged to 67x would make a print about 95" (almost 8 feet, 2.4m) wide. The enlargement was made with a condenser enlarger, which accentuates grain. Loss of image detail is entirely due to the resolution limits of the lenses that made the photograph.
Here's a question: how many bolts are used to hold one of those balcony rails to the building wall?
It is possible to enlarge the 35mm negative above to such an extreme degree that you can actually answer that question. The image below is of a flange holding the rail to the wall, next to where the man is standing. The head of a single bolt can be seen, clearly enough for our purpose.
You are looking at something that is ordinarily impossible to photograph, a detail approximately 3/4" in diameter (18mm), photographed from a distance of around 300 feet (90m).
At this extraordinarily narrow angle of resolution, the camera's 180mm lens is obviously beyond the limit of its power of resolving detail, and the image is still not being degraded by grain. The degree of enlargement? About 250x.
For complete exposure and processing information, click here (requires Adobe Acrobat reader).
To buy this film, go to the Bluefire catalog page.