What does it mean when something is four times slower?

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What does it mean when something is four times slower?

Postby Codger » Wed Dec 17, 2014 2:32 am

I don't know how to interpret the way some reviewers express differences using the concept of "less" or "slower." I've been interested in Sigma's 120-300mm f2.8 lens (for Nikon) for some time. Just now I read your review that says, when discussing the virtue of lenses with stabilization, " these can let you handhold shots with shutter speeds three to four times slower" when hand-holding :?: . If I'm shooting at 1/1000 and something is four times FASTER, is that now 1/4000th? Or, based on stops, 1/8000? So what does it mean when expressing SLOWER by four times? Did the review mean 1/4th as fast? Four stops slower? I can't get my brain around this description based on how I understand words and their meanings? I'd appreciate clarification. Thanks.
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Re: What does it mean when something is four times slower?

Postby Maestro » Thu Dec 18, 2014 3:38 am

Can you link to the review? I'm unable to find it. And it could be easier to determine the meaning of the remark with the context in which it was made. That said...

In regards to shutter speed, "slower" usually means just that. i.e. slower/longer. (As opposed to lenses, where slower often means darker/smaller aperture/lets in less light.)

Also, Image Stabilization is generally employed so that the photographer can use longer shutter speeds without camera shake causing the captured image to be blurry (when the camera is being hand-held, as opposed to mounted on a tripod, because barring an earthquake, a tripod should be relatively steady.) i.e. the longer the shutter is open, the more likely it is that the camera/photographer will move slightly while the shutter is open. IS tries to compensate for these small movements.

Also, in regards to photography, the common unit of measurement is a "stop" which is based on powers of two. So the meaning is sometimes:

twice = 1 stop, multiply/divide by 2
three times = 2 stops, multiply/divide by 4
four times = 3 stops, multiply/divide by 8

So to use your example, a shutter speed three to four times slower than 1/1000 would be between 1/250 and 1/125.

But it's also possible that the writer could be using "times" synonymously with "stops" (which would make the meaning = 1/125 to 1/60). The context might make it clearer.

Mark
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Re: What does it mean when something is four times slower?

Postby Codger » Thu Dec 18, 2014 7:17 am

Mark, I've got the link to the review (below) and you can find the line in the fourth paragraph. I think my concern with the statement is, I always associate saying "times" something as being a multiplying function, that is, increasing something to make a value larger. In the review, that is clearly the opposite of what is intended. I've read similar statements in other forums and have been equally puzzled why that wording was chosen. Why not say, a third- or a fourth- as much? Or, 33% or 25% of something? Division isn't an alien concept is it? And, since most photographers understand how stops work -- whether in shutter speeds or aperture numbers -- why not express it as "lets the photographer manage the situation safely even three or four stops slower" instead? To me, "times" is an arithmetic function that makes something MORE than it was.

http://www.cameralabs.com/lenses/Sigma/ ... ikon.shtml
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Re: What does it mean when something is four times slower?

Postby Maestro » Fri Dec 19, 2014 2:28 am

Codger wrote:http://www.cameralabs.com/lenses/Sigma/Sigma_telephoto_zooms/Sigma_telephoto_zooms_Nikon/Sigma_telephoto_zoom_lenses_Nikon.shtml

Thanks. Got it. I was looking for a review specifically/exclusively of Sigma's 120-300mm lens.

I always associate saying "times" something as being a multiplying function, that is, increasing something to make a value larger. In the review, that is clearly the opposite of what is intended.

Um, the values do get larger. 1/250 is 4 times larger than 1/1000.

why not express it as "lets the photographer manage the situation safely even three or four stops slower" instead?

My guess is that this gets back to the page not being a review of just one lens. So it uses more general terms because saying 3 stops specifically may not be true for every lens listed.

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