I recently read on Wikipedia (can also be found on other sources) that the first photographs/cameras needed exposure times of several images, sometimes up to hours.

e.g. The caption for this image:

It is a view of a busy street, but because the exposure lasted for several minutes the moving traffic left no trace

I couldn't find any explanation for these long exposures. Thanks in advance!

  • 2
    \$\begingroup\$ Low sensitivity of the plate... Around 0.001 ISO for a daguerreotype. \$\endgroup\$
    – xenoid
    Commented Apr 26, 2020 at 8:27

1 Answer 1


This is due to the low sensitivity of the plate... Around 0.001 ISO for a daguerreotype.

Photography chemistry made some progress in two centuries. This said, in the film era, 100ISO (100ASA, actually) was a fast film (about the fastest color film you could get), and the regular color film of the 60/70s was 25ISO/ASA.

  • \$\begingroup\$ This said, in most of the film era, B&W film was used for most still photography, which was available in much higher speeds (and more conducive to being "pushed" even higher) much earlier than for color film. Color film was mostly for high budget movies well into the 1960s, when the number photo enthusiasts shooting color reversal slide film for their personal photos started to grow. Color photos generally weren't accepted within "high art" photography until the '70s and '80s. Most news photos were still shot on B&W into the late '80s or early '90s. \$\endgroup\$
    – Michael C
    Commented Apr 27, 2020 at 13:55
  • \$\begingroup\$ By the early to mid 1970s, 200 ASA color negative film was very common and almost universally used in "instamatic" cameras in the 110 and 126 (cartridge) formats. I'd agree that 25 ASA and 50 ASA were the most widespread color reversal (slide) films used by amateur/enthusiast 135 format shooters. But that was a very small part of the overall consumer market, and pros were still mostly shooting in B&W and often pushing Tri-X, introduced in the 120 format in 1940 and offered in 135 in 1954, and similar films well past the nominally rated 400 ASA. \$\endgroup\$
    – Michael C
    Commented Apr 27, 2020 at 14:10

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