After trudging through all those scary numbers, we now know that ISO 200 is twice as fast as ISO 100, that 1/60 second is half the time of 1/30 second, and that f/4 is twice as fast as f/5.6. If I did my job well, we even learned that without anyone’s brain dripping out of their ears and onto their keyboards.
Note: the word “fast” in photography generally means “captures more light” when it’s talking about ISO or aperture. When talking about shutter speed, though, “faster” means just the opposite– 1/60 is faster than 1/30, but 1/30 lets in twice as much light. It’s confusing.
What might or might not be obvious now is that we can change two different things and keep the exact same exposure. For example, each of these settings will produce the exact same exposure:
| ISO 100 | f/4 | 1/60 sec | baseline |
| ISO 100 | f/2.8 | 1/120 sec | faster (wider, more light) aperture, faster (less light) shutter speed |
| ISO 200 | f/4 | 1/120 sec | faster ISO, faster (less light) shutter speed |
| ISO 200 | f/5.6 | 1/60 sec | faster ISO, faster (wider, more light) aperture |
| ISO 400 | f/5.6 | 1/120 sec | ISO four times as fast, shutter speed twice as fast (less light), aperture half as fast (narrower, less light) |
The first line is our baseline measurement. On the second one, we opened up the aperture wider to let more light in. In order to keep the exposure constant, we need to capture less of the light, so we keep the shutter open for half as long.
On the third and fourth lines, we increase the ISO, which records more light To balance it out, we either keep the shutter open for less time, or we make the aperture smaller– either of those will let less light in.
The fifth line is tricky! We’ve quadrupled the ISO, which means we’ve increased it by two stops. In order to compensate for that, we made the aperture smaller by one stop and we also made the shutter speed faster by one stop.
The fancy technical term for this is reciprocity– it really just means that if you change one setting, you can balance it out by changing another one, and get the same result.
So how would you use this? Here’s an example. Let’s say you’re taking a picture of a group of people, some of them standing behind the others. You put the camera in aperture priority mode and pick f/4 and ISO 100. When you try to take the shot, you find out that the best shutter speed is 1/30, and that’s too slow for you to hold the camera steady– you need at least 1/50 sec. What do you do?
Well, you can try using f/2.8 and 1/60. That will get you the same exposure, but at a faster shutter speed. But wait… now you’re at f/2.8, and when you focus on the front row of people the back row is out of focus, or vice versa. You really need f/4 to get everyone in focus.
Finally, you set the ISO to 200, which lets you use an aperture of f/4 with a shutter speed of 1/60. Voila! You get your shot.
The way exposure settings play together is a little bit like having a squishy ball in your hand. When you squeeze one part to make it smaller, another part gets bigger. Squish two parts, and the third one gets a lot bigger. Squish squish squish.
Easy, huh?
Stop Shooting Auto! 
If you’re looking for somewhere to go, What about white balancing?
Sir or Madam,
I am using a “4×5 Press Camera” with an ISO of 400. If I were to to take a photograph using the “Sunny f/16 Rule”, what would I set my shutter at?
If I desired a good amount of “depth of field” against a water backdrop, what would I use then?
My college instructors cannot seem to explain this simple enough for me to understand.
Thanks.
Dear Sir or Madam,
Can you continue to explain “reciprocal settings” some more with more charts?
On the other hand, if I have studied my exposure chart correctly, “f/16” is used for a sunny day, so, how is it that I can use, say, a a different setting like f/8 on a sunny day, and still get a good picture on a sunny day? Does the shutter speed go up or down to compensate?
For I thought that a setting like “f/8” was for darker, cloudier days?
I really find these concepts difficult to follow. Please break it down to me like I’m 12 years old (without being condescending).
Thanks.
Brian, I’ve never used a 4×5 camera, so I can only make some educated guesses.
The sunny f/16 rule says that on a bright summer day, if you set your aperture to f/16, your shutter speed should be 1/ISO. So if you’re using ISO 400, at f/16 you would use 1/400.
As for reciprocal settings, let me see if I can explain by example. Let’s take your example above, where f/16 and 1/400 would create a correctly-exposed photo. What if you want to use f/8 instead of f/16? Well, f/8 is a larger opening than f/16. In fact, it’s two stops wider, so it lets in four times as much light.
If f/8 lets in four times as much light as f/16, then you need to compensate by keeping the shutter open for a shorter period of time. In fact, you need to keep the shutter open 1/4 as long as you would at f/16. So at f/8, you would use 1/1600 for the shutter speed.
Neither aperture nor shutter speed stand alone. In the same situation, if one changes then the other one has to stay constant. You said, “I thought that a setting like f/8 was for darker, cloudier days.” Well, it’s a good starting point for darker days. If f/16 and 1/400 is the right setting on a sunny day, then f/8 and 1/400 might be the right setting on a cloudy day. However, f/4 and 1/800 would get you the same exposure, as would f/16 and 1/100.
In summary, start by keeping one of the three things constant. In these examples, ISO is constant. If the aperture goes down by one stop, the shutter speed needs to go up by one stop. If the aperture goes up by one stop, then the shutter speed needs to go down by one stop.
Does that help?
Hi,
Thanks so much for creating these tutorials! I’ve been reading so much jargon I’d started to lose the motivation to try – everything was so confusing and I was tired of just getting lucky every so often and not understanding how I had actually created a shot.
I’m due to start a part-time photography course tomorrow and was freaking out (as I joined the more advanced class by accident – don’t ask!)but after reading through your tutorials I feel more confident about walking in.
I don’t even have a clue how I ended up finding your site but it’s been an absolute godsend, definitely ‘favourited’! You’ve made SLR photography really accessible- so thank you loads :-D
Jojo (Glasgow!)
Yay! Good luck with the class.
I was flipping through your photo stream and noticed that you have a lot of vignetting in your recent photos. Is that a deliberate effect, or is it an artifact of the lens that you’re using?
Hi,
The class went really well – it turned out to not be the scary advanced class I’d thought it was, lots of people with similar ability, in fact a great mix so I’m looking forward to next week!
Ha, the old vignetting..I’m afraid its nothing more than me getting vignette-happy after learning it from a tutorial. I actually think I’ve overdone it in a few photos but it’s part of the learning curve I guess!
Jo :-)
Hey!
I just wanted to shout out and say thanks (even though I’m about 2,5 years late haha), your guide has been very useful for me as an amateur. I’ve really learned a lot, and I’m sure this is gonna come in very handy when I’m going for better pictures this year around while skiing in Sweden. THANKS!
Lots of snow is going to cause your camera to want to underexpose your subjects. There are several ways to compensate for that (manual mode, exposure compensation, spot metering), so play around with a few test shots early on and pick what works best for you.
wow….I needed to find you today..xxxxxxxxxxxxxxx Thank you so much. Finally can take a decent photo without the blow outs!!!
thanks so much for your tutorial – its the best I have read. way back when I loved photography and knew a lot of this stuff, but in the 20 years since I got busy doing other things. I bought a digital slr ages ago and hadn’t really ever learnt how to use it and couldn’t be sure I remembered the basics correctly. Now I feel confident to get practicing and even joined a comp to motivate me http://www.photomarathon.com.au/. it should be fun!
Great tutorial, much better than the book whose name I shall not mention. I kind of got the general idea. So I basically tweak the aperture, ISO and shutter speed to get proper exposure. Now can I assume when my camera’s meter is on 0 I have the correct exposure? If so, that makes it easy, as I adjust the various parameters, the meters moves between -2 and 2, so when I am at zero take pic? Is that a good rule of thumb or is there more to it?
That’s a very good rule of thumb, yes, and most of the time that will get you a very good exposure.
However, there *is* more to it than that. Your meter is basically trying to make the whole image average out to 18% gray– a good overall average for most scenes. However, the meter can’t read your mind, and it can’t tell when a scene isn’t a normal one.
Imagine, for a minute, that you’re taking a picture of a snowy landscape with a single tree in it. This is not a picture that should end up at an average of 18% gray. Rather, this scene should be white with slightly darker shadows, and one dark tree somewhere in the image. If you rely on your meter for this, then you’ll get a picture that’s way too dark.
Similarly, imagine you’re taking a picture of a spinning light at night. If you rely on the meter for this, the camera will massively overexpose the image and everything will be blah.
Scenes like this are the exception, though, and not the rule. In most situations, when the meter reads zero you’ll be pretty close to the right exposure. It’s worth understanding how to recognize those situations, so that when you encounter them you’ll be able to adjust accordingly.
Oh, here are some great examples. Go to this page:
http://www.rockslidephoto.com/gallery/saga-visions-of-the-iceland/
and look at the image Grass and Volcanic Alluvium. If Joe had just blindly relied on the meter, that image would be a washed-out gray with a splotch of bright green. Scroll down the page to Dettifoss Mist II, and you’ll see the opposite situation– an image that’s meant to be bright all over.
Does that help?
Yes that does help and i am glad to know a large percentage of the time I can use the camera’s meter to take correctly exposed photos. However, your examples have me asking myself what do I do in those situations. Specifically your snow example, my wife and I are going to Alaska in a few weeks and given your above example I am not sure what to do… I guess my next question what to do in those cases, how do I get proper exposure without a ton of photography experience?
So what if it’s a ‘weird’ lighting situation?
If the scene is a dark one, you want to shoot it so that your camera thinks that you’re underexposing (think -2 rather than 0). If the scene is a bright one, you want to shoot it so that your camera thinks that the shot is overexposed (e.g. +2 rather than 0).
Now, the hard question… how much should you underexpose or overexpose? I recommend taking a couple of test shots and looking at the results, so that you can see about what the right ballpark is. It might be 1, 2, or even 3 stops away from what the meter says, depending on the situation. There’s no one right answer.
If there’s a comparably-lit scene in a different direction, try metering from that and using that setting. If the lighting is the same, the exposure should be the same for both scenes.
You can also bracket your shots. Shoot the one that you think is right, but also take images at one stop below and one stop above your guess. If your guess is close, then one of the three shots should be right.
You can practice this before you go to Alaska. Go outside and put a few sheets of white paper on the ground, then put a small object on top of the paper. Practice exposing so that you have the right exposure for the object and the paper is bright white. Try different techniques and see what works for you.
EV compensation and stops are different right? Stops only refer to adjusting aperture, ISO, and shutter? Or can +1 on EV be considered 1 stop. I guess I am looking for a scientific answer on exposure, if this then do this, but photography is an art and a lot of what I read ends up being well it depends… I guess if I have the basics down, then what to do, when, only will come with experience…
Stops are essentially the unit of measurement for total exposure. Exposure compensation (EV compensation) is a way of telling the camera to do something other than what its meter says. The unit of measurement is stops.
Let’s say that you have your camera in aperture priority mode, the aperture set at f/8, and you’re shooting at ISO 100. Remember, in aperture priority mode you choose the ISO and aperture, and the camera picks the best shutter speed. You take a test shot. The camera chooses 1/500 sec for the shutter speed. You look at the test image, and it’s too dark, so you decide you want one more stop of exposure. What do you do?
You could put the camera into manual mode, ISO 100, f/8, and choose a shutter speed of 1/250. “Hey, camera! I’m the boss here and you do what I say.” By slowing down the shutter speed to half of what it was, you’ve increased the overall exposure by one stop. Voila! A perfectly exposed image. Yay!
Ah, but there’s something else that you could have done. You could have left the camera in aperture priority mode, and set the exposure compensation to +1. In essence, you’re telling the camera, “Make your best guess about what to do, then overexpose the image by one stop.” The camera would now do exactly what you chose to do– ISO 100, f/8, 1/250 sec.
Exposure compensation is a cool tool, but be careful to turn it off when you’re done. I’ve left it on accidentally and then wondered why all of my images were too (dark/light).
You do such a good job of explaining this stuff, I did the white paper example and yeah with +2 the paper looked white and not grey! I think I have a good foundation thanks to your site. One other thing, I usually look at the histogram after I take a pic, I assume that is a good way of making sure you took a good pic? As long as nothing is out to the far left/right your good? Cause the middle of those histograms vary wildly in the photos I take.
Yes, what you say about the histogram is usually true. I have a couple of articles on histograms on the site.
Most of the time you want a more-or-less center-weighted histogram, but sometimes you don’t. I bet that the white-paper example had a weird-looking histogram.
If you haven’t looked at the histogram for that image yet, don’t do so yet. First, think about what you think the histogram should look like for that image. Draw yourself a little sketch of what you expect to see, and only then should you look at the histogram. I bet you’ll have a pretty good guess.
Awesome website. I know almost all of these basics, but I am still reading it to make sure I didn’t miss something in my learning and I am completely enjoying it!!
I just wanted to point out one correction in the table. The last line comment says shutter speed four times as much, but it is really shutter speed two times as much and aperture half as much
Thanks much!
Thanks! I just fixed it, I think. I added some verbiage while I was in there, because the whole faster/slower thing is confusing.
What a refreshing approach to a subject that can seem like it was invented by stuffy old men in tweed jackets and tobacco pipes in a leather-filled room somewhere.