Perhaps you have heard the term "exposure triangle" in which the three components of exposure are shutter, aperture, and ISO. In photography, there is much discussion about these components of exposure. But so often I see the discussion of one take place independently of the others. We will discuss in depth shutter speed and how it affects motion in our image, or aperture and how it affects depth of field, or ISO and digital noise. What I don't often see is discussion as to how the three interelate, a "reciprocal" relationship. As a result, we can end up doing a lot of "hunting" around for settings in manual mode turning dials this way or that and not understanding why we can't get proper exposure. I believe that understanding reciprocity is a key element in photography, and particularly toward mastering manual mode.
Correct exposure is acheived when shutter, aperture, and ISO are in balance with each other. Reciprocity simply means that if one of the three components of exposure is changed, then one or both of the other components must be equally adjusted to maintain correct exposure. Let's say for example that a landscape scene meters correct exposure at 1/200s, f/4, and ISO 400. If as a photographer we decide an aperture setting of f/4 does not suit our goal for this image, and we change it two stops to f/8, then either the shutter or ISO must also be changed equivalently by two stops; the shutter to 1/50s or ISO to 1600. Or, you could split the two stops between both the shutter and ISO resulting in a shutter speed of 1/100 and ISO of 800.
(As a quick refresher, a "stop" in photography is the halving or doubling of light. ISO stops are the easiest; 100, 200, 400, 800, 1600, etc. Shutter speed is also rather intuitive for the most part with full stop values being along the lines of 1/30s, 1/60s, 1/125s, 1/250s, 1/500s, etc. Aperture is the odd one of the bunch with full stop values being f/1.2, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, etc. On most cameras, exposure settings can be changed in 1/3 stop increments. This is handy to know when using dials on camera as you can turn the dial three 'clicks' and know that you have changed the setting by one stop.)
Now on most cameras, the ISO can be set to Auto or to a specific value. The shutter priority and aperture priority modes of the camera allow us to input specific values for the shutter or aperture respectively, and the camera then balances out the other two components automatically on our behalf to acheive correct exposure. If however, you have independently set the ISO to a specific value, then the camera can only automatically change the aperture when in shutter-priority mode, or the shutter when in aperture-priority mode. In Program mode, the camera selects both the shutter and aperture settings. But regardless, in these three modes the camera is performing the reciprocity, or the "balancing" of the three exposure components on your behalf via automatic setting of either one or two of the three exposure components.
Now that you understand reciprocity, let's revisit Manual mode. When in Manual mode, I personally find it easiest to simply step through each of the three settings in order of priority to me based on the scene and my goal for the image. If at some point I reach an unsatisfactory setting then I may have to go back to the beginning and reevaluate the priority of my settings. So let's use a landscape scene again as an example. We prioritize aperture as most important because we want deep depth of field. So we dial f/8 into the camera. We'd like a high quality image so we set ISO at 100. Now we're left with shutter and when we use the meter indicator (see your camera's manual for metering display specific to your model) we show correct exposure at 1/15s. Well now let's assume we have neither a tripod nor a lens with image stablization so 1/15s is going to be too slow as we're liable to have a blurred image from camera shake. But we know from experience that we should be able to get a crisp hand-held shot at 1/60s, so we raise shutter speed by two stops (1/15->1/30->1/60). Now we must address either the aperture or ISO (or both), so we revist the priority of depth of field over the potential of image noise. Deciding that a deep depth of field is paramount to our landscape image, we choose to raise ISO by the reciprocal two stops (100->200->400). At ISO 400 the noise should be minimal and we are now ready to take our exposure!
How about one more example a bit more complex. It's slightly dusky, and we're taking a photo of a friend on a street. Here we decide shutter is most important because we want a nice sharp image of our friend. So we dial in a shutter speed of 1/125s, and already have ISO at 100 from early in the day when it was brighter. Using the camera's metering indicator it seems we cannot dial in an aperture to get a proper exposure because its 'bottoming out' at f/3.5 while the meter still shows underexposure. So we set the aperture at f/4 and now revisit priority of the other two components. We'd really like to stay at 1/125s for shutter, so lets raise ISO and see what happens. We crank up the ISO and at ISO 1600 the camera's metering finally says we have proper exposure. Ok, so we'll have a bit of noise, but it's a dusky street shot and a little bit of noise probably fits the scene. So we could take the shot. But let's say you really, really, want lower ISO. Well, we can't do much with aperture being a 1/3 stop from our lens limit, but we can revisit the shutter setting knowing that if we lower our ISO by a stop (1600->800) we will have to also slow the shutter speed by a stop (1/125s->1/60s) to maintain the balance of the exposure triangle. Reciprocity. We think about going a stop further (ISO 800->400 & shutter 1/60s->1/30s) but we decide 1/30s is 'iffy' handheld so we compromise at the 1/60s and ISO 800 asking our friend to hold nice and still. Viola!
In summary, the knowledge of reciprocity is empowering, very much so in Manual mode, but also in the priority modes when ISO is not set to Auto because you may choose to start tweaking the ISO more often by a stop or two while in priority modes if you know you're but a stop or two away from the shutter or aperture you'd really like. Also, if you find yourself "hunting" for settings in Manual mode, an option might be to get the correct exposure dialed in no matter the settings you wind up with. Then once the correct exposure is metered, you can now evaluate the priority of the settings knowing as you raise or lower one, that you must also raise or lower one or both of the others equivalently. For me, once I grasped the law of reciprocity in exposure, I felt very empowered and Manual mode took on a whole new ease.
I hope this is useful information, all the best, and happy shooting!!!
Much if not all of this has been, and is being, covered the new Camera Settings Challenges by @camerasavvy.
Depending on your camera, the whole issue of getting proper ISO, shutter and aperture for a "standard" metering, your last complex situation, is "A" priority, ISO-Auto with Auto-Slowest-Shutter-Desired. Not only will it handle all the computations automatically, raising ISO as the last resort, but it can automatically adjust the "slowest-desired-shutter" depending on the focal length of the lens, assuming hand held. Especially in "A" mode, these settings (Nikon call them ISO Sensitivity Settings, Canon ISO Speed Settings) can be set once and seldom touched again. If you don't like the camera's AUTO shutter choice, like it's too fast because you have VR/IS lenses, you can further adjust the camera's algorithm for that once and be done.
Exposure compensation and/or spot/center metering, in conjunction with all this, handle desired deviations from the metered matrix/evaluative values in a totally predictable and desirable fashion.
Yes, you basically should understand the machinations going on the background, but once you understand the principles, delegate that computational drudge work to the camera and its technology, while you concentrate on the stuff that the camera technology can't do. Basically composition, framing, and shooting technique. Even Focus and Auto Focus fits here since the camera usually needs a lot of help from you. After all, you paid for that expensive camera with all that technology. Understand it and use it, reserving the executive command decisions for yourself while the camera deals with the minutiae of exposure.
If shooting action, sports, Motion Stop/Motion Blur, then you may wish to turn it off and try "S" or "M" (S&M, did I really write that?) and specifically set ISO to a fixed value. But for your everyday everything else, please don't advise people to make shooting and exposure such a chore.
Thank you! I found this most helpful as I am just starting to get a handle on the exposure triangle. You did a super job of explaining and I really appreciate that you took the time to reach out to us newbies and share that.
@frankhymus Wow. Well I did expect you to chime in because when it comes to any "know-how" topic you almost never fail to. What I didn't expect was your rude response. Your closing statement, "But for your everyday everything else, please don't advise people to make shooting and exposure such a chore" I found very rude. I don't think at any point in my post I advised that anyone use any particular mode whatsoever. And who do we think we are to dictate what people do or don't need to know regardless if they have interest? What I did take the time to write, both for my own pleasure, and for those that may be possibly be interested, is the law of reciprocity as it relates to the exposure triangle. This theory is completely independent of camera modes. Being familiar with it though can bring benefit in any mode. I don't know about you, but I'm always in Manual mode in my head regardless of what mode the camera is in. I'm always checking the settings it came up with and what my other reciprocal options might be if one of the three components is borderline to my liking.
Frank, there's nothing that pushes my button more than hearing someone say, "Oh, forget about that XYZ stuff, you don't really need to know it", and that's what your response said. It said Joe, "You really shouldn't have bothered to post all that. It's all well and good but there's really no purpose because no one really needs to know it. Here, I will tell them how the camera can do it for them and that's all they need to know. Now go away and let us Camerasavvy people handle the dissemination of any information." Well Frank, that's how I read your response anyway. It's not the only time you've done it to me when I've posted, and you've also done it to others. I don't appreciate it.
Yes, I'm am fully aware of all the camera features you mentioned, and I assure you I am well versed in them. I use them all as appropriate to my needs and/or shooting conditions. I most certainly did not buy my 'expensive' camera specifically for those features, and some cameras don't even offer them. Actually, I don't buy 'expensive' cameras, it's a waste of money. I run my photography business with a D610. Hardly an expensive camera when most my colleagues are carrying around D4's or 5D Mark III's.
Honestly, I wrote this post as the result of a discussion this weekend I had with another photographer who was asking me some questions. I thought she might benefit from understanding reciprocity and when I brought up and explained it to her it really clicked on a light bulb for her. Because I thought it might be useful to someone else who may be interested, I took the time to post here. You know, I could have answered that photographers question by just saying, "Raise your ISO, you'll be fine". Or, "just enable this or that feature on your camera, forget about exactly why because you don’t really need to know, you'll be fine". Instead, I took 5 minutes to explain reciprocity because I could tell that was the real answer. Now it doesn't matter what mode that photographer uses, she will understand how the three settings interrelate with each other.
I am also quite aware of the "Camera Settings Challenges". Did I step on its superior toes somehow? I do know that the Camera Settings Challenge did cover each of these settings. I don’t recall reciprocity mentioned, it may have been but I didn’t catch it. But don’t worry, I have much better things to do than to take my time writing a post to have it all but summarily dismissed by a self-claimed resident expert, so I won’t waste my time further. It's a pity you don't advise putting any thought into the "minutiae of exposure". Because exposure is, after all, the essence of photography. Without exposure, composition, framing, and shooting technique are meaningless. In fact I don't think there is a more "executive decision" that a photographer can make than that of exposure. All the best in your savvy efforts.
@dbj thanks for posting this, it is something that I am trying to get my head around and am struggling with, so it is really helpful to me. Thanks for taking the time to share your experience with those of us who need the help.
@dbj Thanks for taking the time to do this write up on reciprocity, it was well written and informative, and I'm sure that many 365ers will find it every useful. Frank ,the resident oracle of photography, has managed to collect a following by regurgitating Ken Rockwell and DPreview and challenging anyone who dares to try to disseminate knowledge other then him. Apparently by selflessly adding to the knowledge base on 365 you have challenged his illegitimate claim to the throne.
@dbj Great detailed explanation of all that goes on in the background that modern cameras so easily accomplish. So much has been forgotten; as a traditional film shooter, I really appreciate the effort you've put into this!
While i understand where @frankhymus is coming from saying that there are automated modes that do all this, I'm dont believe that you were suggesting that you say people should go full manual (as some others do on here). I think youre just trying to enlighten people as to how this works so that they can take their knowledge to the next level. This knowledge is probably not required for alot of people but it certainly cant hurt.
I've been in quite a lot of group shoots with some faily experienced photographers (weekend warriors maybe?) who still dont quite understand this properly and end up doing alot more trial and error with adjusting settings / lighting or even asking others.
Personally I think that this information is critical when it comes down to shooting portraits - and especially when youre mixing artificial and ambient
@dbj Thank you for sharing your knowledge :) Well written and easy to follow. I follow the camerasavvy information as well and the more information shared the better we can understand what exactly we are trying to do.
I just feel that a few people are taking themselves maybe a bit too seriously here and I think attacks on Frank Hymus are quite unjustified. He is most generous and always explains anything to anybody who asks in an easily understandable answer.
Very well explained.. and I think it is important to understand the basics and not be entirely dependent upon the technology built into the camera. Ignore Frank… your stuff was good!
@dbj Thank you for the information it was well written and very useful. For the record, I do want to master shooting in Manual and am trying to learn as much as I can about how to use my DLSR, so thank you.
@dbj excellent information and thank you so very much for posting this. please so keep posting, just as in other subjects, even if something has been covered, someone else will add some new perspective. no need to have this devolve into what 365 should not be about.
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Depending on your camera, the whole issue of getting proper ISO, shutter and aperture for a "standard" metering, your last complex situation, is "A" priority, ISO-Auto with Auto-Slowest-Shutter-Desired. Not only will it handle all the computations automatically, raising ISO as the last resort, but it can automatically adjust the "slowest-desired-shutter" depending on the focal length of the lens, assuming hand held. Especially in "A" mode, these settings (Nikon call them ISO Sensitivity Settings, Canon ISO Speed Settings) can be set once and seldom touched again. If you don't like the camera's AUTO shutter choice, like it's too fast because you have VR/IS lenses, you can further adjust the camera's algorithm for that once and be done.
Exposure compensation and/or spot/center metering, in conjunction with all this, handle desired deviations from the metered matrix/evaluative values in a totally predictable and desirable fashion.
Yes, you basically should understand the machinations going on the background, but once you understand the principles, delegate that computational drudge work to the camera and its technology, while you concentrate on the stuff that the camera technology can't do. Basically composition, framing, and shooting technique. Even Focus and Auto Focus fits here since the camera usually needs a lot of help from you. After all, you paid for that expensive camera with all that technology. Understand it and use it, reserving the executive command decisions for yourself while the camera deals with the minutiae of exposure.
If shooting action, sports, Motion Stop/Motion Blur, then you may wish to turn it off and try "S" or "M" (S&M, did I really write that?) and specifically set ISO to a fixed value. But for your everyday everything else, please don't advise people to make shooting and exposure such a chore.
Frank, there's nothing that pushes my button more than hearing someone say, "Oh, forget about that XYZ stuff, you don't really need to know it", and that's what your response said. It said Joe, "You really shouldn't have bothered to post all that. It's all well and good but there's really no purpose because no one really needs to know it. Here, I will tell them how the camera can do it for them and that's all they need to know. Now go away and let us Camerasavvy people handle the dissemination of any information." Well Frank, that's how I read your response anyway. It's not the only time you've done it to me when I've posted, and you've also done it to others. I don't appreciate it.
Yes, I'm am fully aware of all the camera features you mentioned, and I assure you I am well versed in them. I use them all as appropriate to my needs and/or shooting conditions. I most certainly did not buy my 'expensive' camera specifically for those features, and some cameras don't even offer them. Actually, I don't buy 'expensive' cameras, it's a waste of money. I run my photography business with a D610. Hardly an expensive camera when most my colleagues are carrying around D4's or 5D Mark III's.
Honestly, I wrote this post as the result of a discussion this weekend I had with another photographer who was asking me some questions. I thought she might benefit from understanding reciprocity and when I brought up and explained it to her it really clicked on a light bulb for her. Because I thought it might be useful to someone else who may be interested, I took the time to post here. You know, I could have answered that photographers question by just saying, "Raise your ISO, you'll be fine". Or, "just enable this or that feature on your camera, forget about exactly why because you don’t really need to know, you'll be fine". Instead, I took 5 minutes to explain reciprocity because I could tell that was the real answer. Now it doesn't matter what mode that photographer uses, she will understand how the three settings interrelate with each other.
I am also quite aware of the "Camera Settings Challenges". Did I step on its superior toes somehow? I do know that the Camera Settings Challenge did cover each of these settings. I don’t recall reciprocity mentioned, it may have been but I didn’t catch it. But don’t worry, I have much better things to do than to take my time writing a post to have it all but summarily dismissed by a self-claimed resident expert, so I won’t waste my time further. It's a pity you don't advise putting any thought into the "minutiae of exposure". Because exposure is, after all, the essence of photography. Without exposure, composition, framing, and shooting technique are meaningless. In fact I don't think there is a more "executive decision" that a photographer can make than that of exposure. All the best in your savvy efforts.
While i understand where @frankhymus is coming from saying that there are automated modes that do all this, I'm dont believe that you were suggesting that you say people should go full manual (as some others do on here). I think youre just trying to enlighten people as to how this works so that they can take their knowledge to the next level. This knowledge is probably not required for alot of people but it certainly cant hurt.
I've been in quite a lot of group shoots with some faily experienced photographers (weekend warriors maybe?) who still dont quite understand this properly and end up doing alot more trial and error with adjusting settings / lighting or even asking others.
Personally I think that this information is critical when it comes down to shooting portraits - and especially when youre mixing artificial and ambient
@digitalrogue @frankhymus @dbj