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I'm not experienced in photography and would like to get some knowledge about the terminology.

My question is: What defines an objective? Or: When would you define something as an objective?

I mean, would you still call it an objective even when there are no lenses in it? I know this example might not make sense. Just imagine an "objective" has several apertures and/or filters.

I hope this makes sense somehow.

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  • \$\begingroup\$ I'm sorry I can't open the Link due to 400 Bad Request. Did you mean this \$\endgroup\$
    – MoeJo
    Apr 18, 2019 at 13:57

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By definition, an objective lens is a lens which converges light to produce what's called a "real image" — a projection that can be observed on a screen, or (as in the case of camera) recorded on film or a sensor.

Binoculars and microscopes have objective lenses which converge the light and then also eyepiece lenses which diverge it again.

A stack of glass or apertures which does not produce such an image is not an objective lens. In fact, without a curved surface, you don't really have a lens at all, let alone an objective lens (and the term "objective" in this context is really just short for "objective lens").

In conversational English in the context of photography, we generally call the thing that screws to the front of a camera body a "lens", not an "objective". We even do that when the "lens" in question contains mirrors — we say "a mirror lens". Or, even though it's not technically a lens at all, we say "pinhole lens".

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    \$\begingroup\$ To my knowledge as a native speaker, "Objektiv" (noun) is only used to mean '(photographic) lens' - the English noun 'objective' would roughly translate as "Ziel" ('goal'). The adjective "objektiv" is the same as the adjective 'objective' in English. \$\endgroup\$
    – flolilo
    Apr 18, 2019 at 14:18
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    \$\begingroup\$ Note that some objectives are made with mirrors, and may or may not have lenses. Although, most of the time "objective" and "lens" may be synonyms. \$\endgroup\$
    – vsis
    Apr 18, 2019 at 14:24
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    \$\begingroup\$ @vsis That's a good point, although because language is messy and frustrating, we deal with that by saying "mirror lens" or "pinhole lens". Technically not correct, but that's never stopped English. :) \$\endgroup\$
    – mattdm
    Apr 18, 2019 at 14:29
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    \$\begingroup\$ There is also a (disappearing) usage, at least in American English, among the photographic community where "the objective" of a complex lens system with multiple elements/groups is a reference to the front/first element or group where light enters the lens. For example, : "A 300mm f/4 lens must have an objective at least 75mm in diameter." This usage was probably more true of prime lenses, where the front element was the converging lens and most everything behind it were for corrective purposes. That's not as much the case with many modern internal zoom or internal focus lenses. \$\endgroup\$
    – Michael C
    Apr 18, 2019 at 17:06
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    \$\begingroup\$ I've seen a few older photography textbooks that use it that way with regard to photographic lenses. It may be a case of the physics community and the photographic community having different meanings for the same word(s). Like, for example, "focal plane." \$\endgroup\$
    – Michael C
    Apr 18, 2019 at 17:15

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