Shutter speed and aperture

Hi everyone.

 

Im a first time DSLR user, just recently bought a canon rebel t6i, and Im trying to understand how the ISO, Aperture, and shutter speed play together. I think I might have it figure out but I wanted to ask.

 

Is the key of which setting to use dependant upon the situation?

 

It seems that each has several functions but they all relate to light as well. So I was having a hard time distinguishing between when to use the settings. So in short, Aperture for portrait using shutter speed and iso to control light?

 

Shutter speed when photographing something fast moving for motion or freeze effect and use aperture for lighting?

As you have probably already determined, aperture, shutter speed, and ISO all work together to provide a properly exposed image. Aperture would be most important when you want to control the depth of field (DOF). If you want a shallow DOF (as often you do with your example of portraiture), you would use a large aperture (smaller number like f/2.8). A landscape would usually require a smaller aperture (like f/11) to get as much of the scene as possible in acceptable focus. When aperture is the priority, the shutter speed is allowed to fall where it may. However, if the resultant shutter speed is too slow, you would need to resort to using a tripod or to raising the ISO. Shutter speed would be a priority where you want to stop action, for example. The aperture, in this case, would be secondary, and ISO would be used to keep the shutter speed up to where you want it. As you said, all of these things depend upon the situation and what you wish to accomplish with an image. Edited March 31, 2018 by alan_olander

Many books have been written about the relationships between shutter speed, aperture, ISO, light, and subject matter, and about the way they affect the look of photographs. There is plenty of information on this site, if you click on the "Learn" tab at the top of the home page, then "How To" and "Techniques".

 

For example:

 

Basic Photo Tips: Aperture, Shutter Speed, and ISO

 

Missing Pages: Depth of Field

 

Basic Photo Tips: Depth of Field

Hi, I would suggest to think of it like this: (forget the ISO speed for now) the shutter speed and aperture (f-stop setting) work together like a see-saw on the children's playground. When one side goes up, the other needs to come down. You are trying to get a "correct" amount of light to the sensor, and this is a combination of the size of the opening (the aperture) and how long the light is allowed to come through (the shutter speed duration).

 

Once you have a correct combination, the other correct combinations are like the see-saw. If you make the aperture larger, then the shutter time needs to be shorter. And vice versa. The common "currency" for this is in equivalent f-stops, where each full f-stop change the exposure by a factor of either one-half or two, depending on which direction you are going. Here's an example: say that you have determined that a correct exposed is 1/125 second (shutter speed) at f/8 (aperture). But you decide that you want a faster shutter speed, say 1/250 second. On your see-saw, you have pushed down the amount of light coming through the shutter by one half, equivalent to one f-stop reduction. So the other side, the lens aperture, has to increase by one f-stop, with a larger opening - in this case to f/5.6 (I know this because I have the sequence memorized).

 

This see-saw effect works through all combinations - just count the f-stop equivalents up on one side and down on the other. Or, just change one item and let your exposure meter set the other.

 

Now, for the ISO speed: think of this as similar to the volume control on a radio. If the sound is too soft, turn the volume up. With the digital camera, if the amount of light is too low, turn the ISO speed up. Each time you double the ISO speed, this is equivalent to one f-stop more light. With the see-saw example, you can think of the ISO setting as raising or lowering the entire see-saw in order to keep a correct exposure.

 

So the whole idea is to use these three things to keep a "correct" exposure. You can use any method that works - do it manually, or let your meter do it in whatever mode you prefer, even auto-ISO if you like.

 

The basic rules for selection are: shutter speed controls "motion blur," and the lens aperture controls how much of the scene, distance-wise, is in focus. If you want only a narrow zone to be in focus, you want a physically large lens aperture (this means a small number, like f/2 or f/2.8), and the focus will be fairly critical. I'm sure John's links will cover in good detail.

 

Best of luck.

Shutter speed when photographing something fast moving for motion or freeze effect and use aperture for lighting?

Maybe yes, but within limitations. You 'll develop a feeling for needed DOF someday (an occasional glimpse at tables or online calculators is helpful!). if your AF is more likely to nail an approaching subject at f5.6 than at f1.4, crank up the ISO (if you can).

Shutter = Time of exposure

Affects sharpness due to movement of camera, subject, or both during that time.

Aperture = Amount of light admitted through lens for exposure.

Affects depth of field (area near to far that will be in focus at the same time)

ISO = Sensitivity to light reflected from or emitted by subject.

All three can be adjusted for various desired creative effect depending on circumstances.

Shutter speed when photographing something fast moving for motion or freeze effect and use aperture for lighting?

 

It just occurs to me that when you said "aperture for lighting," you may have been referring to the use of electronic flash.

 

The things that I've said are based on the assumption of continuous light. Electronic flash brings in a complication. Essentially the flash is faster than a typical shutter, such that changes in the shutter speed barely affect the flash exposure. So changing the aperture (or ISO speed) is normally the main way to affect flash exposure (the other way is to change flash power or distance).

 

However, there ARE some special cameras that can "flash sync" at very high speeds, that CAN cut off some of the flash exposure. Likewise, there are some special flash units that can make the flash last long enough that the shutter speed can have an effect.

 

Anyway, the use of electronic flash brings some trickiness into these rules. The easiest way to deal with an electronic flash on a DSLR is to use one that your camera can control. You set the camera, and then the camera controls the brightness of the flash (read the camera manual for specifics). But if you have any specific uses or questions, go ahead and toss them out here.

Jill - If you haven't already secured a copy of the owner's manual for your camera, which will explain many of the functions you inquired about, in simple easy to understand terms, you can easily do so at www.butkus.org. I'd also encourage you to go to your local library and get a book on photography for beginners, which should again address your questions in straightforward, easy to learn fashion. Then come back here with more focussed questions. There is a learning curve so keep at it until you begin to feel comfortable...we've all been there.

I like to call the relationship between shutter speed, ISO, and aperture the "exposure triangle". As noted, there are tomes and volumes written on the interrelationship between these factors. The most important thing to remember is that a correct exposure is a variable combination of these factors. For a given exposure, changing one component will require changing one or both of the others. While simple in concept, it can be very complex in execution. After all else is said, the best thing for a learner to to do is to note a recommended exposure, set the camera on manual, and then experiment with one setting at a time to experience how that change impacts the image. 50 years after taking my first photo I am still experimenting and learning how to use the exposure triangle to make creative and meaningful images.

Aperture would be most important when you want to control the depth of field (DOF). If you want a shallow DOF (as often you do with your example of portraiture), you would use a large aperture (smaller number like f/2.8). A landscape would usually require a smaller aperture (like f/11) to get as much of the scene as possible in acceptable focus. When aperture is the priority, the shutter speed is allowed to fall where it may. However, if the resultant shutter speed is too slow, you would need to resort to using a tripod or to raising the ISO. Shutter speed would be a priority where you want to stop action, for example.

 

Funny enough, the way I work I often use an AE mode that's a bit counter-intuitive for what I'm trying to achieve.

 

If I'm handholding in ambient light, I'll often use the largest aperture available so as to get the highest shutter speed possible(with digital I'll then go to an ISO that gives me what I want). Once again, the same situation, if DOF is important I'll often use shutter priority, set the slowest shutter speed I think I can handhold, and let the camera pick the smallest aperture possible.

 

When I'm working in manual mode(I have a lot of cameras where that's the only option) I often work with that mindset also.

 

In general, though, I tend to work with an aperture priority mindset-whether as a discreet auto exposure mode or in that mindset. There's an in-between maximizing shutter speed and maximizing DOF, and that's maximizing lens sharpness. I take many photos where I'm close to infinity, so DOF isn't so important. Maximizing SHARPNESS is, though, and for many lenses that's somewhere around f/5.6 or f/8.

 

BTW, my D800 has humbled me with regard to DOF. Most charts/scales work out to somewhere around acceptable sharpness in an 8x10 print. At 100% magnification from a high resolution camera, almost nothing will be in perfect focus.

This is this is one of those concepts that is difficult to grasp when you first pick up photography, but is actually very simple if explained properly, and if you practice. For a nicely exposed photo ( I.e not too dark or too light) your camera wants the correct amount of light for the given scene you are photographing. If you put your camera in auto mode, and point it at anything, the exposures it has chosen will be shown in the viewfinder as a combination of two variables, shutter speed and aperture. This will be the values that the camera thinks are best, based on its own electronic brain. You can choose to chnage these values if you wish.

 

Let’s say the camera chooses 1/500th of a second at f4. This would give the correct exposure, and is the length of time the shutter is open and the size of the hole that lets the light in. You could equally get the same correct exposure if you halved the size of the hole, but you would need to double the length of time the shutter was open to get the same ‘amount’ of light. So you could use f 5.6 and 1/250th of a second instead ( note halving the size of the hole doesn’t take you from f4 to f8). Alternatively, you could double the size of the hole and halve the shutter speed, so 1/1000th of a second at f2.8 would equally be OK. Or 1/2000th at f2, or 125th at f8, 60th at f11, 30th at f16. All these combinations are valid. Which one younchooose as you rightly say depends on how much you want to be in focus ( smaller the aperture, the more depth of focus you will get) and whether or not you are focusing on something that is moving ( shorter shutter speed freezes motion). In the above example, if shooting a landscape for instance you might chooose 1/60th at f11,since you want the depth of focus. If you were shooting your kids running round the garden, maybe 1/500th at f4 since you don’t want the kids all blurred.

 

The ISO can come in to play here too. Let’s say you want to use 1/500th to shoot your kids, but the camera says 250th at f2 is the correct exposure. You can increase your shutter speed to 1/500th, but you would have to open up the aperture to double the size of the hole to get a correct exposure. This takes you to f1.4. However, maybe your Lens doesn’t have a maximum aperture of f1.4, it only goes to f2.? What to do? Well you can double the sensitivity of the sensor ( or film) which means you can still use the 1/500th at f2, and get the correct exposure. Good luck

Maybe yes, but within limitations. You 'll develop a feeling for needed DOF someday (an occasional glimpse at tables or online calculators is helpful!). if your AF is more likely to nail an approaching subject at f5.6 than at f1.4, crank up the ISO (if you can).

 

Hi there, Thanks for replying..

which tables do you mean? and or a calculator?

I have been reading a ton of info online and books, so I feel like I am beginning to understand.

As you have probably already determined, aperture, shutter speed, and ISO all work together to provide a properly exposed image. Aperture would be most important when you want to control the depth of field (DOF). If you want a shallow DOF (as often you do with your example of portraiture), you would use a large aperture (smaller number like f/2.8). A landscape would usually require a smaller aperture (like f/11) to get as much of the scene as possible in acceptable focus. When aperture is the priority, the shutter speed is allowed to fall where it may. However, if the resultant shutter speed is too slow, you would need to resort to using a tripod or to raising the ISO. Shutter speed would be a priority where you want to stop action, for example. The aperture, in this case, would be secondary, and ISO would be used to keep the shutter speed up to where you want it. As you said, all of these things depend upon the situation and what you wish to accomplish with an image.

 

 

Thanks for replying, I appreciate the input.

Jill - If you haven't already secured a copy of the owner's manual for your camera, which will explain many of the functions you inquired about, in simple easy to understand terms, you can easily do so at www.butkus.org. I'd also encourage you to go to your local library and get a book on photography for beginners, which should again address your questions in straightforward, easy to learn fashion. Then come back here with more focussed questions. There is a learning curve so keep at it until you begin to feel comfortable...we've all been there.

Thanks for replying, I appreciate the input.

 

I have printed the manual, but a beginners book is a good suggestion. Thanks. again! : ) You've all helped me a ton.

Welcome to the site!

Depth of Field Table & Online Depth of Field Calculator for example. There seem smart-device apps available too, including entire photography courses. Goal of DOF tables / calculators should be to give a rough idea of what which aperture produces at what focal length. - Things were a tad easier, back when there were no zooms and each lens had a DOF scale engraved. Trying to memorize an entire table is surely going too far, but since you mentioned portraits maybe look up a distance like 1.5m or 4' and figure out which aperture to use with either your environmental portrait or headshot focal length.

Welcome to the site!

 

Thank you. : )

There's an old saying in photography. F/8 and be there.

Im a first time DSLR user, just recently bought a canon rebel t6i, and Im trying to understand how the ISO, Aperture, and shutter speed play together. I think I might have it figure out but I wanted to ask.

 

Is the key of which setting to use dependant upon the situation?

 

Good advice above. Here's my take:

 

You have something in your scene that has a certain brightness. You want that to appear at a specific brightness level in your image.

 

There are four things you can control:

• Aperture
  
• Shutter speed
  
• ISO sensitivity
  
• Exposure compensation
  

Okay, five, if you throw in flash. But I'll come back to that.

 

So...

• Aperture controls the rate at which a lens lets in light. Think of filling a pool of water: if you use a bigger pipe that lets water through faster, it'll fill up quicker; with a narrower pipe, water flows through slower and the pool takes longer to fill. All else being equal, a wider aperture increases the brightness of your image and a narrower aperture decreases the brightness. Wider apertures reduce depth of field (less of your subject will be in focus, but this also makes the subject stand out from the background). Lenses aren't perfect, and many optical aberrations get better at smaller apertures. On the other hand, if you reduce the aperture too much, diffraction will start to soften the image. f/8 is a reasonable compromise starting point if you're not going for a different creative effect (and don't need more light). Pet peeve: aperture is expressed as a fraction, so remember that "f/8" is smaller than "f/2" because 1/8 is smaller than 1/2. If you try to remember it as "bigger aperture = smaller number" (looking only at the denominator of the fraction) you'll get confused.
  
• Shutter speed controls the amount of time light is contributing to the image. With the pool of water, the longer you run the hose, the more water ends up in the pool. A fast shutter speed freezes motion (because the subject doesn't have time to move during the exposure) and hides camera shake. A slow shutter gives you some motion blur, which can make the scene look more dynamic. Because you can get the same amount of light to the scene with a fast (smaller) shutter speed and a wide aperture as you can with a slow (longer) shutter speed, a lens with a wide maximum aperture is known as a "fast" lens and a lens with a narrow maximum aperture is known as a "slow" lens (both terms are relative compared to what else is available at the same focal length - f/5.6 is "slow" for a 50mm lens but "fast" for an 800mm lens, for example). All else being equal, the longer the shutter speed, the brighter the image (because more light is getting in).
  
• ISO sensitivity (which used to be determined by your film and on a dSLR is a setting you can change for each image) changes how the image looks for a given amount of light; think of it like changing the size of the pool you're filling with water. It's effectively an amplifier on the signal you're getting from the light. The problem is that the more you turn up the sensitivity, the more noise you get instead of image data - it's like turning up the volume on an old radio, you'll get hiss as well as louder music. All else being equal, increasing the ISO makes the image brighter, and decreasing it makes the image darker. If you increase the ISO sensitivity, you can have a narrow aperture (to give you a deep depth of field and avoid optical aberrations) and a fast shutter speed (to avoid blur) so as much as possible is "sharp" - but you'll get noise in the image. Decrease the ISO and something else has to compensate. Note that with a lot of modern sensors, it can be useful to underexpose because you can get nearly as much information out of an image by adjusting it after the fact as you can by changing ISO, and if you underexpose you don't blow your highlights.
  
• Exposure compensation determines how bright you want the image to be compared with how bright the camera's meter is configured to make it look. I consider it to be a fourth parameter because you can control any three of these and let the camera control the fourth. If you control aperture, shutter and ISO, you have control over how bright the image is. If you control aperture and ISO, you can get the camera to change its shutter speed by adjusting exposure compensation. In most cameras, you can control aperture and shutter speed, and exposure compensation can then adjust ISO for you.
  
• How do you avoid noise, keep the image bright, use a small aperture and a fast shutter speed? Add more light to the scene. Which you can do with a flash. The flash is very brief, so shutter speed is mostly irrelevant (so long as you pick one long enough that the whole sensor is exposed during the flash), but aperture matters - even for a very fast flash, the aperture determines how much light gets through. In most situations, a flash only partly contributes to the lighting of the scene.
  

So to your camera modes:

• Aperture priority. You set the aperture (and probably the ISO) and the camera sets the shutter speed. (Some cameras let you set a "minimum shutter speed" as well, after which the camera starts bumping the ISO up - this is a good way to ensure you don't get camera shake.) This is useful for landscape photos (where you might want a deep depth of field but not care about how long the exposure takes because you're on a tripod and nothing's moving), for portraits in good light (if you specifically want to blur the background), etc. Do this if you want to control the depth of field artistically.
  
• Shutter priority. You set the shutter speed (and probably the ISO) and the camera sets the aperture. (If the camera bumps into the lens's maximum aperture, it might have the option to start increasing ISO.) Use this if you don't care too much about the exact aperture, but want either to force motion blur or to freeze motion.
  
• Program mode. The camera picks an aperture and a shutter speed that works for the exposure. You can then use "program shift" to change them while keeping the exposure the same - as you increase the aperture the exposure time decreases and vice-versa. This isn't a bad choice for the "hand the camera to someone else" situation, but it's also useful if you want to balance aperture and shutter speed but might run into the acceptable limits of either, or if you don't especially care about either (say a relatively static subject at a distance where depth of field is irrelevant).
  
• Manual mode. You control both the aperture and shutter speed directly. If you set ISO yourself, you have complete control over the exposure; if you use exposure compensation to adjust ISO, you have control over the creative aspects and let the camera deal with noise. Use this if you want to control shutter speed dynamically (as you subject moves more or less, or possibly if you're changing focal length and your camera doesn't have an option to do this for you) and if you also want to control aperture creatively. For example, I might be shooting a bird in manual mode, with a wide aperture and a slow shutter speed so I can use a low ISO for low noise. The bird might take off, so I could spin the shutter speed control to reduce the exposure time and freeze its motion. Then it could join a flock of birds, and I want them all to be in focus, so I could spin the aperture dial to increase the depth of field. Then I could increase the exposure time again to give some blur in the birds' wings.
  

Some cameras (notably Pentax) have extra modes for whether you or the camera is controlling ISO in manual mode. For most other manufacturers, this is a menu option.

 

I hope that's some help and didn't cause too much confusion. :-)

 

There's an old saying in photography. F/8 and be there.

 

Yes. There's also an old saying "this image is sharp". Don't look too closely at anything taken by Cartier-Bresson! (This just proves that sharpness is only secondary to a good photo - which is fortunate for some dimly-lit wedding dancing I was triaging last night - but it's worth pointing out that we're much better at pixel-peeping now that we've got, er, pixels.)

Just to emphasize again, any basic, introductory text (digital or film) will cover the interaction of shutter speed and apertures:

 

e.g.,

 

Davis, Phil

1975 Photography. 2nd ed., Wm C. Brown.

 

Swedlund, Charles

1981 Photography. Harcourt Brace.

True, JDM, but while a lot of texts will tell you what aperture does and what shutter speed does, it's possible that you have to try a little harder to determine which automated exposure mode to be in for any given situation (which I think was the question) - especially if the books predate automated exposure, and certainly dynamic changes of ISO!

 

Books are a good thing, but they do, sadly, cost money and/or time (if you're lucky and have a decent library nearby) to acquire. In this modern day and age, web sites are a lot more useful, if you can find reliable ones. There's a lot of misinformation out there, and Wikipedia will only get you so far (and has a habit of referring to some less-than-reliable web sites even when its own content is solid).

 

That said, I realised I didn't quite answer the question properly:

 

So in short, Aperture for portrait using shutter speed and iso to control light?

 

For portraiture you probably do want direct control over the aperture. Too small an aperture will leave the background distracting and not separate the subject from it (if this is what you want), so for that reason you typically want a fairly large aperture. If you go too large, the eyes may be in focus, but the nose won't be, which can be distracting. So yes, you probably want to set aperture first for creative reasons. In Av mode, the camera will pick a shutter speed for you, and you set the ISO and exposure compensation to change the brightness. In M(anual) mode, you can control ISO and shutter speed yourself, and watch the meter in the viewfinder. In P(rogram) mode, the camera is trying to adjust aperture and shutter speed, so you might be fighting it a bit if you're going for a specific aperture and the lighting (or what the meter is pointing at) changes. You probably still want a reasonable shutter speed (say 1/100s plus or minus a bit) to freeze any head sway in the subject and deal with any camera shake, if you're not on a tripod; the details will depend a bit on what's going on and which lens you're using. Generally you probably want to keep the ISO as low as you can, set your aperture creatively, and let the shutter speed drift to keep the exposure correct, keeping an eye out for it becoming too slow (unless you want subject motion). But start with the aperture, yes.

 

Shutter speed when photographing something fast moving for motion or freeze effect and use aperture for lighting?

 

Generally, that's a good start. If something's in fast motion, you can freeze it either with a flash (not so much for wildlife some distance away, obviously) or by having a fast shutter speed. You'll still want to allow for the aperture being adequate for the subject (so you get it all in focus and the background as out of focus as you want), but you can afford a little bit of leeway in the aperture setting, so letting the camera use it to control the light is not unreasonable. That said, it's relatively rare to need an exact shutter speed, rather than just "fast enough" - I shoot in manual mode a lot, but rarely touch Tv mode (or "S" in Nikon speak) because I usually still want some aperture control.

 

So, TL;DR: yes, but generally you end up wanting to control everything, at least a bit. And the sooner someone invents a dimmer switch for the sun so we can control outdoor exposures properly, the better. :-)

 

I hope that helps!

True, JDM, but while a lot of texts will tell you what aperture does and what shutter speed does, it's possible that you have to try a little harder to determine which automated exposure mode to be in for any given situation (which I think was the question)

 

I still don't read the OP as relating primarily to "automated" modes, but regardless, one cannot master any exposure system without a basic understanding of the relationships of ISO, shutter speed, and aperture.