rpavich Loc: West Virginia

What are stops.

good question.

A stop is just a unit of measure in photography. It's the doubling or halving of the amount of light let in when taking a photo.

It's that simple.

Here is a link to understanding what a stop is in more depth.

http://www.photographymad.com/pages/view/what-is-a-stop-of-exposure-in-photography

jerryc41 Loc: Catskill Mts of NY

Yes, you can, but the fewer filters the better. Sometimes, you don't have a choice. Another consideration is vignetting. The more things you have in front of your lens, and the wider your lens, the greater the chance of vignetting.

mborn Loc: Massachusetts

1 stop is a doubling or halving of the amount of light let in when taking a photo. you can adjust this with Aperture, shutter speed, or ISO

repleo Loc: Boston

I understand 'stops' for ND filters. Where it gets confusing is when, for instance, they describe a 10 stop ND as a 1000X or as a 3.0.

Longshadow Loc: Audubon, PA, United States

I wonder if the "stop" association originally came from the lens- when adjusting the aperture, there are clicks at each position, where the ring "stops" turning when it hits a detent. So you rotate the aperture ring three clicks, or stops. Did the original lenses only have "full" stops? Do we now have half-stops clicks on the lens? Now I have to go look at the dictionary or Wikipedia.......

tcthome Loc: NJ

Lee has articles & videos on there filters at there web site. Explains the metering & stops process. I just watched them yesterday. They should help.

Good luck.

GKR

Thank you.

DavidPine Loc: Fredericksburg, TX

Stops are a unit of measure used in photography to measure relationships of exposure between ISO, Shutter Speed and Aperture. It seems complicated but it makes sense in the photography world. Study the "Sunny 16 Rule" for a sunny day and if you will write down and compare how you can relate the stops to virtually make the same image with the different exposure stops you may be able to see the relationships. This may seem a little simple but it will help turn on some lights.

BlackRipleyDog

Hey guys, Sounds like it is trolling time again on the UHH.

jerryc41 Loc: Catskill Mts of NY

Here are lots of links about ND filters. Like other aspects of photography, naming and terminology could be better. An ND4 is two stops, and an ND8 is three stops.

ND chart -
http://www.alexwisephotography.net/blog/wp-content/uploads/2009/07/BKS_ND_Chart.pdf

http://www.alexwisephotography.net/blog/2009/07/23/neutral-density-reference-chart/
http://digital-photography-school.com/beginners-guide-buying-filters/
http://digital-photography-school.com/step-by-step-guide-to-long-exposure-photography/
http://www.the-digital-picture.com/Reviews/10-Stop-Neutral-Density-Filter.aspx
http://www.cambridgeincolour.com/tutorials/neutral-density-filters.htm
http://www.alexwisephotography.net/blog/2009/07/23/neutral-density-reference-chart/
https://www.youtube.com/watch?v=ZpNtAXbaNr0
https://www.ephotozine.com/article/how-an-nd-filter-can-remove-crowds-from-busy-shots--27054

phlash46 Loc: Westchester County, New York

You need some education! Get Bryan Peterson's book "Understanding Exposure" on Amazon.

a6k Loc: Detroit & Sanibel

At the risk of over simplifying but in order to be helpful,

Light level changes are perceived by the camera and by our eyes as a "linear" change but in reality it's an "exponential change" when measured in units such as "lumens" or "foot-candles". A "stop" is a change from one level to the next by either 2x or 1/2, depending on which direction. It seems a constant change but it's not.

In lens openings, we divide the diameter of the opening into the focal length so a 25mm opening on a 50mm lens is F2.0 As it happens, the area of the opening that is 1/2 of F2 is F2.8 then 3.5 the 5.6 and so on. It's just the conventional set of measurements that manufacturers use and photographers expect. But a 1 stop change doesn't have to from or to those numbers.

A little math: area of a circle is pi x radius squared. So area of a 25 mm circle is pi x 12.5 x 12.5 = 490.8. So the diameter of F2.8 on a 50mm lens is 17.86 and the radius is 8.93 which makes the area 250.4. That is approximately half, you see?

Now for shutter speeds, it's the amount of time the shutter is open. That's why you will see 1/30, 1/60 and so on. for reasons of convenience, they usually go from 60 to 125 instead of 120 then it's as expected: 125, 250, 500 and so on. Of course, electronic camera can do all the in-between's too, both for lens openings (aperture) and shutter speeds.

ISO (previously ASA) is the number representing the sensitivity of the sensor (or film). It often goes in stops, too, but, again, modern cameras can use partial stops. Anyhow, the same half-or-twice relationship holds. An ISO of 100 vs an ISO of 200 will need a 1 stop change in the light in order to produce the same exposure. That's why ISO is shown on light meters.

To paraphrase Gertrude Stein, a stop is a stop is a stop. We call that "reciprocity". In other words, if you increase the lens opening (lower number) by one stop you can shorten the time the shutter is open by one stop. And so on. Stops are the same "size" as Exposure Value (EV) numbers. One EV is one stop. But EV is a real measurement while a stop is relative; it measures change.

In the world of both film and even digital sensors, you will eventually hit "reciprocity failure" where due to physics and chemistry, the 1-up, 1-down rule will begin to fail. In the normal range, though, it works.

Please note that the amount of light in a change of 1 stop or the amount of light in a change of 1 EV is not equal across the range. That's because of the linear vs exponential nature of our perception of light. You can ignore this and your pictures will be the same but it's fun to know.

Now go read up on it and don't trust on-floor sales folks who may or may not have a clue. Also, you may want to review some recent posts by selmslie: http://www.uglyhedgehog.com/user-profile?usernum=16389
If I have made any mistakes here you can count on him to catch me.

repleo Loc: Boston

Many newer cameras don't distinguish between 'full' stops and 1/2 or 1/3 stops anymore - they just show them as a continuous stream of numbers. This makes it difficult to appreciate the relative simplicity of the reciprocity relationship of the exposure triangle. If I didn't have traditional 'full' stops ingrained in my memory from my youth I would never be able to grasp the relationship. Unfortunately my brain is no longer young and the development of previously unaffordable F stops and unachievable ISOs adds to the confusion.

BebuLamar

What do you mean? Most new cameras show in 1/3 stop

Haydon

Some strobes are metered in 1/10 stop increments and I find it problematic to a represented number when I'm use to 1/3 stops in camera.