Understanding 'stops' in photography is considered basic, but, if you were like me you really didn't worry much about it until you realized you had absolutely no clue what it meant + was solely relying on the 'little ticker in my camera' to get 'close to the middle ticker'. Clearly I was a professional. Whatevs. It's cool, I made it work but the more knowledgable I became about my camera the more I realized I needed to master the whole 'understanding stops in exposure' thing--especially if I wanted to pick up film. It seems like a complicated concept, but it's truly not although it IS important to understand stops and how they work, not just that "my photos look best when these two tickers line up in camera". WTH is a 'stop' (hammer time!) anyway? Exposure is the measure of light captured within an image, and is effected by three different factors: iso, aperture, and shutter speed. A stop is the term of measurement used to compare the three. (Don't worry--it will make sense shortly). Since there are three different factors that effect exposure there are three different types of stops for each: stops in aperture, stops in iso, and stops in shutter speed. It's typically measured (like a fraction) in full (1), one half (1/2), and one third (1/3) stops. For now, we will just focus on full stops. I'm not that great with math.
1. ISO: [1 full stop doubles (or halves) the sensitivity to light]
Full ISO stops: 100, 200, 400, 600, 800, 1600, 3200, 6400.
Example: Going from 100 to 200 iso is one full stop and since you are going up in iso you are increasing the sensitivity to light by double. Going from 100 to 400 iso is increasing by two full stops and so fourth. Going backwards from 400 to 100 iso is decreasing two full stops and halving the amount of light sensitivity.
*note: if your camera allows you to use an iso in between 100 and 200, then the camera functions are set-up to allow for one half and/or 1/3 stops, not just full stops, so take that into consideration (or just change it while you learn unless you like the flexibility! Personally it confused the shit outta me).
2. Aperture: [1 full stop doubles (or halves) the size of the aperture opening, thus doubling or halving the amount of light the lens lets in].
Full Aperture Stops: 1.4, 2.0, 2.8, 4.0, 5.6, 8, 11, 16
Example: Going from 1.4 to 2.0 is one full stop making the size of the aperture smaller so it is halving the amount of light let it. Going from 1.4 to 2.8 is two full stops and still making the aperture opening smaller thus decreasing the amount of light let in. Going from 4.0 to 2.8 is one full stop and increasing the amount of light let in by double because the aperture is physically getting wider!
*note: again, your camera (or lens!) may allow for one third stops for accuracy ( 1.4, 1.6, 1.8, 2.0). See what yours is set to and remember your math fractions so that you don't get yourself confused! These stops I find the most helpful to memorize as aperture effects a lot of different things about exposure.
3. Shutter speed: [1 stop doubles (or halves) the amount of light, thus doubling or halving the amount of light + movement the lens let in]
Full shutter speed stops: 1/125, 1/250, 1/500, 1/1000, 1/2000, 1/4000
Example: from 1/125 to 1/250 is one full stop and halving the amount of light let in (because the shutter is going faster!). From 1/500 to 1/2000 is two full stops, also decreasing the amount of light let in. From 1/4000 to 1/2000 is one full stop and doubling the amount of light let in (because the shutter is now slower--allowing for more light).
*note: if you have an in-camera meter (a graph with lines and a little ticker below that moves when you scroll the set dial on your camera--see example below), you are changing the shutter speed when you move the dial and can see your exposure (correct exposure, under or over) via that little graph measured in stops.
Still with me? Fabulous. Thank you. Continue on for a visual I worked real hard on. Errrr. Real diligently. Get your mind outta there.
Howwwwwww in the world is this helpful, you ask?
Well, if you're a digital shooter, it helps to know how to change your different settings to get the amount of light (or lack there of) that you need for a proper exposure. Also, you know that little ticker mentioned before that you see in-camera? Yeah. That thing (diagram pictured above). That's your in-camera meter and it is what helps tie in the whole 'stops' with 'the ticker' thing. Your in-camera meter is the equivalent of an old school hand held light meter (what most film shooters hang around their necks) and it helps you determine the lighting of a scene and how to best expose for it using your shutter speed. It will also tell you by the lines moving around if your settings are ready for a proper exposure, overexposure, or wayyyy underexposed, and by how many stops (the ticker lined up in the middle denotes your camera considers that proper exposure, then to the left or right is over or underexposure measured via stops. The directions vary based on camera brand (nikon or canon) but you can tell with the plus sign meaning overexposed and the minus sign meaning underexposed). With that information, YOU can then decide if you'd rather get another full stop (increasing your light by double!) via a slower shutter speed, or changing your aperture or iso. The meter simply gives you information about your current settings and how you may need to change them via stops (that you've now memorized) to best suit you. Because remember, your camera is just a piece of equipment--you use it to make a style and exposure that best dictates your style.
If you're a film shooter, a lot of films look best if overexposed 1 to 2 stops. Some even 3! THIS helps you figure out what a STOP is so you can properly overexpose to get the dreamy look you desire. Example: you have fuji 400h film. You've heard it looks best if overexposed at least two stops (it does). So, how do you go about doing that? Well, your film's iso is already 400, so two stops overexposed (think: 'more light!') would be 100 iso (remember the chart!). So you load your 400 iso film but set your hand held light meter to think you're using 100 iso film, that way you will get a shutter speed reading for what would be 100 iso--in turn overexposing the film in your camera by two full stops via iso. But say that you can't shoot at the given shutter speed for 100 iso--it's just too slow for the lighting you're in. Maybe you can make your aperture wider (lowering the number), possibly getting an extra stop there via aperture instead.
I think of it as 3 places to get more stops in light and if I can't get my light all from one place I can 'mix and match' to get an extra stop here, or a stop there.
SEE! Knowing STOPS and being all 'techy' makes a DIFFERENCE!
Whew. There's a lot to it, and you kinda have to be comfortable with the basics of camera functions to wrap your head around it, but once you memorize the numbers and THINK about it when shooting, it starts to TOTALLY make sense and you aren't just arbitrarily setting readings anymore.
+ if this made NO sense to you--feel free to let me know. Or just google. :)
Reading the meter info source: Digital-Photography-School.com. The rest of the info from my brain. (so if there's an error correct me. haha)