JerryLS Loc: Davenport.Iowa

Hello all Iam very new to pohtog. It looks like I am in the right place.

cockney greg Loc: London E17

Welcome here Jerry, you'll find some very helpful people here so jump in and make yourself at home.

JerryLS Loc: Davenport.Iowa

Like just said I am new to photog so here goes. After doing tons of searches Could some explain to me why the term" Stop" is used when adjusting the aperture or shutter?

cockney greg Loc: London E17

See if this helps Jerry, it's from the search section at top of this page. Hope it helps.

http://www.uglyhedgehog.com/t-127098-1.html

skiman Loc: Ventura, CA

Welcom, JerryLS,

Here is the best I can come up with

•f number
An f-number is a number in the form f/2.0 which specifies the size of the aperture opening.

f refers to the focal length.

f/2.0 means the diameter of the aperture opening is the focal length divided by 2.0.

f/4.0 means the diameter of the aperture opening is the focal length divided by 4.0.

That's why if the number on the right is bigger, the aperture is smaller.

These both measure effective aperture: that is, in a hypothetical single-element lens, what is the diameter of an equivalent aperture placed right on that lens. In a lens with multiple elements, for engineering reasons, the actual aperture opening may differ in order to match up with this.


•stop

It's originally called a "stop" because an old-style aperture ring "stops" at certain settings - that is, it has markings where the ring stops.

These "stops" are specifically designed such that each "stop" lets either half or double the amount of light in as the stops before and after it.

The common aperture stops are f/1.4, f/2.0, f/2.8, f/4.0, f/5.6, f/8.0 and so on. The space between two consecutive numbers in this sequence is what is also called a "stop".

(Note that some aperture rings had half-stop markings in between these too.)

But wait a minute! You may be wondering why each one of these is the previous one divided by root 2 not 2. Why? Because halving the area of the aperture requires dividing the diameter by root 2. This is because the area of a circle scales with the square of its radius.

So even though each number is not double or half its neighbours, it still lets in double or half the light of its neighbours.

Thus, this is why the stops go up in those numbers. Of course, 1.4 isn't exactly root 2. The numbers are simply rounded to only one digit.

Modern digital cameras don't usually have an aperture ring anymore, and let you set the aperture to any value, or to increment or decrement it by half-stops or third-stops. This is the equivalent to setting an old-style aperture ring to rest in between two whole-stop markers (some rings had detents in half-stops to help this).


Now that you know how f-stops relate to aperture and the amount of light reaching the sensor, you can use the term "stops" as a general term to refer to a doubling or halving of light for any reason.

For example, you may refer to quadrupling the ISO setting as "increasing the ISO by 2 stops".

JerryLS Loc: Davenport.Iowa

Thank you skiman that answer is great and just wanted. I have taken a course at a Jr. college and Learned the basic operation of a DSLR Currently trying to leard Lightroom.Thanks again.

JoAnneK01 Loc: Lahaina, Hawaii

Aloha Jerry and welcome to UHH. You'll find many photographers here who are willing to provide advice.

JoeB Loc: Mohawk Valley, NY

Hello Jerry, welcome to UHH.

ebbote Loc: Hockley, Texas

Welcome to the site Jerry.

HowardPepper Loc: Palm Coast, FL

Greetings Jerry, and welcome to the UHH!

Rich2236 Loc: E. Hampstead, New Hampshire

Hi Jerry, welcome to the hog. See…..ask your questions and get one hellofan answer. Hoping to see some of your pictures. And of course make some friends here. We are all for you.
Rich

PAR4DCR Loc: A Sunny Place

Welcome to UHH Jerry, glad you found us. As you can see, just ask the question and you will get answers. Many knowledgeable and helpful members here. Enjoy the forum and post some of your photos.
Don