Does changing film ISO on a Lomography Spinner 360 change the effective f-stop the right way around?
Asked 7/3/2012
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A review says the Spinner 360 has two aperture settings, marked sunny and cloudy, roughly equivalent to f/16 and f/8 when using ISO 400 film. It then claims that using ISO 200 film gives you "f/11 and f/5.6," while ISO 800 film gives you "f/22 and f/11." That seems backwards to me. Since slower film needs more light, I would expect ISO 200 to correspond to wider apertures, and faster ISO 800 to correspond to smaller apertures if shutter speed stays the same. Is the review wrong, or am I misunderstanding how ISO/aperture exposure equivalence works on this camera?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
14y ago
2 Answers
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You can't change the aperture by changing the ISO. There's an equivalence for exposure, but the wording of the review is confusing.
Your understanding of how the equivalence works is exactly right.
The review may be trying to say what forsvairr notes in a comment — that (assuming constant shutter speed) to maintain the same exposure given by f/16 @ ISO 400 with ISO 800 film, you'd need to go down a stop to f/22. But since you can't with this camera, that really makes no sense.
Or they could be trying to say that using faster film gives an exposure change like opening the aperture but getting the numbers wrong. (Not to mention mashing the idea of stop equivalence into "aperture is exposure".)
I'd just ignore any parts of this review that include math. :)
Originally by user1943. Source · Licensed CC BY-SA 4.0
user1943
14y ago
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You’re right: the review’s equivalence is backwards or very poorly worded.
Changing film ISO does not physically change the aperture. The Spinner still only has its two actual aperture settings. What changes is the exposure equivalence: if shutter speed stays the same, slower film needs more light and faster film needs less.
So relative to ISO 400:
- ISO 200 needs 1 stop more light, which is equivalent to opening the aperture 1 stop: f/16 → f/11, f/8 → f/5.6
- ISO 800 needs 1 stop less light, which is equivalent to closing the aperture 1 stop: f/16 → f/22, f/8 → f/11
So your understanding is correct. The most sensible reading is that the reviewer was trying to describe exposure compensation by changing film speed, but got the direction mixed up. In short: changing ISO changes exposure sensitivity, not the camera’s actual f-stop.
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