Stops in Shutter speed and Aperture.
Hi.Just two quick questions....

How much is a stop in shutter speed? is 1/30 one stop from 1/60? How about in aperture?Do we have a formula for each of them?.


Comments (13)

AlphaAlex wrote:.

Hi.Just two quick questions....

How much is a stop in shutter speed? is 1/30 one stop from 1/60?.


Howabout in aperture?Do we have a formula for each of them?.


A stop is a doubling or halving of the amount of light.Take a look at this page:


Comment #1

In this link there is a chart about 3/4 of the way down the page. It shows stops in Speed, aperture, ISO and corresponding ev..


AlphaAlex wrote:.

Hi.Just two quick questions....

How much is a stop in shutter speed? is 1/30 one stop from 1/60? Howabout in aperture?Do we have a formula for each of them?.


Comment #2

Or if you want a table:.


Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window.

'Photography is not a level playing field, don't compare cameras that way'.



Comment #3


A stop in aperture halves or doubles the light getting through the lens depending on which way the numbers go. Lower numbers double and higher numbers halve..

An equivalent in shutter speed doubles or halves the length of time the thing is open. So double one and halve the other and you get the same exposure..

Example: start at f/2 and go to f/28 and you halve the light but go to f/14 and you double it. Ditto f/8 to f/11 halves the light and so on..

I don't have to explain about and seconds do I?.

Regards, David..

Comment #4

Old and incomplete and outdated info....

First of all, yes, your example is a difference of one stop..

In the old days, the numbers I saw in some of the charts linked to so far were the only common f stops and shutter speeds, but with the rise of electronics, there are lots of new numbers..

Many cameras have one third of a stop differences between numbrs, and some have one have stop differences..

So you can go from f4 to f4.5 to f5 to f5.6 to f6.3 to f7,1 to f8 on the scale inside a camera, and you have progressed one stop from f4 to f5.6, and another stop from f5.6 o f8, in one third of a stop chunks..

But if you go from f4.5 to f 6.3, you've slso moved a stop, cutting the light comin g into the camera in half..

Shutter speeds used tom, most commonly, go from 1 second to 1/2 to 1/4 to 1/8 to 1/15 to 1/30 to 1/60 to 1/125 to 1/250 to 1/500 to 1/1000 but these are often in one third increments now, too./.

For instance, 1/125 to 1/160 to 1/200 to 1/250 is one stop,in one third of a stop changes..

Many of the charts don't show these modern, more precise, indicators..


Comment #5

Yes, there is a formuls. It is very simple. Every time you open up one stop in f/numbers you are letting in twice as much light if you go the other way you are letting in 1/2 as much light. The same is true with shutter speeds faster is 1/2 as much slower is twice as much. This is the "inverse square law of light". This is the teacher talking.

But five is thirtytwo times six is 64 times. So you have to be accurate in the exposure. Check in google for "inverse square law of light"...

Comment #6


The question was about "a stop" and "one stop" and so I replied about them..

I can easily confuse the issue by talking about half or third stops but this is the Beginners' Forum and we don't want to get too complicated by explaining how camera went in different steps until about 1946 or so..

But I can still reel off the old stops of f/35 f/45 f/63 f/9 f/125 and f/18; mainly because I have old cameras with them on the lenses and exposure meters like it as well and I use them still. And then there's the shutter speeds to match and oddities like dials with 1/20s 1/30s 1/40s 1/50s 1nd 1/60s....

In fact these were just part of a sequence including the so called modern ones of f/28 f/4 f/56 and so on. So in in thirds it runs f/28 f/32 f/35 f/4 f45 f/5 f/56 f/63 and so on..

All that really happened was that the stops ran from a different third and, of course, the f/35 set were called "European" and the new ones "international" so nothing really changed but the marketing made the old ones seem ancient..

Would you like me to explain the older American system that had f/8 and then f/16, where f/8 was really f/11? I've that on an elderly MF camera that's purely a display item these days as the bellows have gone to the dark room in the sky..

BTW, what is modern is that we stop physically in thirds; until a while ago they ran in ones but had the half stops with a "click" position. But with electronics the old thirds can be used for both shutter and apertures. Fun isn't it?.

Regards, David.

PS There's a nice picture of a Leica IIIa for sale on ebay here;item=360026792107&_trksid=p3984.cTODAY.m238.lVI with the stops and shutter speeds just visible if you look. F/125 shows clearly in one of the pictures and here a elderly Elmar lens with the old markings;item=360026792107&_trksid=p3984.cTODAY.m238.lVIbut you have to look at all the pictures...

Comment #7

Thanks for your reply!.

It is suggested to use the shutter speed of 1/focal length in order to get a blur-free image. Lets say I am using a focal length of 200mm, and if I turn on my image stabilization, let's assume it lets me use a shutter speed that is 3 stops slower, what shutter speed will that be? Will it be 1/25 ? .

Thank you..


Comment #8

1 stop is 100% more or 50% less light, same is true of aperature or shutter. So f8 at 125 is the same exposure as f16 at a 60th. This allows us to chose from a range of correct exposures and bias to lens or shutter characteristics...depth of field (lens) or frozen or blurred motion (shutter). Study focus vs depth of field, and shutter pan, drag, etc. to understand why you might chose different combinations of shutter an aperature...

Comment #9

That's wrong - out of date - unclear, etc., too..

One of the dangers of using film-based informtion in a digital world..

It was a rule based on lenses and focal lengths on 35mm film cameras..

With cameras that use larger film, the shutter speeds can be longer, and with cameras that use smaler film, or sensors, the shutter speeds should be shorter..

For a Canon 5D, not a bad rule. For a Nikon D70s, the shutter speeds will be too long, leading to blur..

And, for any situation, the steadyiness of the photographer matters..


Comment #10

AlphaAlex wrote:.

Thanks for your reply!.

It is suggested to use the shutter speed of 1/focal length in orderto get a blur-free image..

That was a rough rule of thumb from the use of 35mm film cameras..

Using a digital camera which may have a sensor size smaller than a 24x36mm frame, the rule needs to use the 35mm "equivalent" focal length. For many DSLR cameras, that means multiply the lens focal length by the "crop factor" of around 1.5 or 1.6. The result is the shutter speed will be higher in order to reduce shake.But it is still only an approximation.Regards,Peter..

Comment #11

Having the f stops in your brain really does help in composing, lighting adjustments, and in reading about photography. What I will be giving you is f stops at one stop increments, but on your camera, you probably have 1/3rd increments to choose from. This also helps in your exposure compensation scale you can use in your camera, the large lines are one stop and the small lines 1/3rd stop..

So first memorize this, be able to say it quickly in either direction:.

1 - 2 - 4 - 8 - 16 - 32 - 64.

Now memorize this, also able to go in both directions:.

1.4 - 2.8 - 5.6 - 11 - 22 - 44.

Now finally memorize this:.

1 - 1.4 - 2 - 2.8 - 4 - 5.6 - 8 - 11 - 16 - 22 - 32 - 44 - 64.

So if I tell you stop your lens "down" one stop and you are at f 8 you will set instead? (Stopping "down" means to make your aperature smaller).

If you are at f16 and I tell you to open up your lens two stops, you will set your camera at?.

How much faster is a 50 f1.2 Canon lens over a 50mm f1.8 lens, in terms of stops?.

I find I have to re-memorize the chart about once a year, or basically remind myself of it, but after a while, you don't think about it, you just know it..

Others have given you good info on shutter speeds and of course ISO doubles or halves as well (one stop faster or slower).Rationally I have no hope, irrationally I believe in miracles.Joni Mitchell..

Comment #12


When you've memorised that, ie:-.

1 - 1.4 - 2 - 2.8 - 4 - 5.6 - 8 - 11 - 16 - 22 - 32 - 44 - 64.

Sit down with a piece of paper and square each number and you'll find they run like this (starting with 1) roughly:-.

1 - 2 - 4 - 8 - 16 - 32 - 64 and so on..

So they double because we're talking about areas of glass and areas of film but simplify things by using the dia of th aperture and the focal length which are, of course, proportional..

I said" roughly" because the figures engraved on the lenses in the old days had to be rounded a little to make them small enough to fit. So they engrave 56 on the lens barrel rather than 5656854 etc..

As for the rule of the reciprical of the focal length in mm being the speed used, it's an old rule and was always an approximation. In the old days my camera would have primes of 35 mm, 50 mm, 85 or 90mm, 135mm and 180mm etc. But look at the shutter speeds and for 85 or 90 mm I'd have to use 1/125th second and the next highest shutter speed was 1/250th so the 135 and 180's would be fired at that and so on. All in all it was a rough and ready rule. (Things went downhill when zoom were becoming popular, affordable and good enough to use for serious stuff, imo.).

BTW, my take on IS is that it's there to try and make up for the fact that modern cameras have no OVF and are waved about in the air in a sort of mock Nazi salute. Most camera shake is caused by using little screens instead of proper view-finders. And people generally hold the things (I mean wave the things about) with just one hand. Go back to film and you'd have a heavier, "T" shaped camera that was held up to the face with two hands. So handheld second shots were easy with a bit of practice..

Regards, David..

Comment #13

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This question was taken from a support group/message board and re-posted here so others can learn from it.


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