The correct Exposure - a tutorial - Part 1: Shutter, Aperture and ISO
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I am not advocating using the manual settings of your camera at all times. Instead, I am a big fan of the creative zone settings such as aperture priority Mode, Shutter Priority Mode and Program mode. I use these automatic modes 95% of the time and I rarely resort to Manual Mode. Aperture settings determine the Depth of Field (how much of your scene is in focus). Landscape photographers often strive for a very large Depth of Field while Portraits often require a shallow Depth of Field. Being in control of the aperture, the photographer can direct attention and guide the viewer through the image. Shutter speed controls how motion of the subject or your camera will look like in your pictures. A slow shutter will blur fast moving subjects and a fast shutter will freeze them. The three exposure controls: Shutter Speed, Aperture, ISOIf all this sounds confusing and if you feel overwhelmed, you are in good company. There are too many degrees of freedom and too many choices to make, but you can become a master through practice. Introducing ISO sensitivityThe ISO sensitivity (ISO rating, ISO speed) characterizes the sensor or film sensitivity to light. Formerly called ASA rating, digital cameras continue to use the same system introduced a long time ago. It is common to use the term "stop" in photography. One stop in terms of ISO refers to a doubling of our sensitivity. ISO 200 is twice as sensitive as ISO 100 and is therefore "one stop higher." In film photography, we would have to make a decision on the type of film needed before going out on a shoot. One of the great advantages of digital photography is the capability to change the ISO settings for each frame. Use higher ISO settings with caution. High ISO film is wonderful for low light photography, but they have much more grain then low ISO films. A high ISO setting on your digital camera will also produce more noise in your image. Modern SLR cameras have very low noise and I would not hesitate to use even higher ISO settings to "get the shot." Digital SLR cameras have less noise than point and shoot cameras at the same ISO setting, since their larger sensor means they are more light sensitive (a large window lets in more light than a small one). Shutter SpeedThe shutter is covering the film or sensor and only when the shutter-release is pressed, do we open the shutter for a pre-determined time to let light pass through our lens to the sensor. We also use "stops" to measure shutter speeds. Each stop doubles the time the shutter remains open and thus doubles the light sensitivity of our camera (e.g. 1/160s is twice as long as 1/320s). For handheld shooting, we require at least 1/(focal length) or shorter to avoid camera shake (if no Image Stabilization is used). For a Rebel XSi with 50mm lens, this means 1/80s or longer (the rebel has a focal length multiplier of 1.6, so 50x1.6=80). ApertureThe aperture is the size of your lens opening. It controls how much light we let pass to our sensor. Aperture also determines Depth of Field and is measured in stops (f-stops for aperture). Each stop doubles the amount of light we let pass (f/4 is two stops larger then f/8). Using Shutter Speed, Aperture and ISO controls for Exposure
Now that we understand ISO, Shutter Speed, and Aperture, we need to learn how to combine them to create an exposure. This is the most important thing to understand in photography and the reason I spent so much time creating the diagram. The combination of Shutter Speed, Aperture, and ISO as well as the focal length and focus point fully control how an image looks like. Any given brightness level, requires a certain sensitivity to capture it. In my diagram, I encoded the brightness levels of a scene with colors. A dark scene requires a sensitive camera system (slow shutter speed, wide-open aperture, and/or high ISO). A small f-stop number (e.g. f/2) corresponds to a wide-open aperture that is very bright. Lenses that open up to f/2 or wider are often quite expensive. The message to take away from this diagram is the possibility to trade off. For any given brightness, an increase in shutter speed (e.g. to freeze motion), requires a wider open aperture (less depth of field) or an increase in ISO speed if the aperture cannot be increased anymore. Trading off shutter speed for aperture is one of the basic rules. A small aperture (large Depth of Field) often requires a tripod, as the shutter speed decreases. Landscape photographers often work with tripods even during the day for exactly this reason. Increasing ISO is not an option, due to the added noise. On the other hand, a tripod is not always an option. I did many of my indoor shots of old missions with a higher ISO setting and a short focal length. The short focal length helps me to capture everything in the scene, but it also lets me shoot at slower speeds handheld without camera shake becoming a problem A very bright scene lets us shoot at small apertures (large f-stop) and still shoot handheld at fast shutter speeds. The diagram only shows a small portion of the shutter speed scale that ranges from 1/8000s to bulb (hours if necessary) for most SLR cameras. Polarizing filters reduce the brightness of up to two stops (depending on the rotation of the filter). Sometimes this is beneficial (blurring motion) but often it is an unwanted side effect to remember. The "Sunny 16 Rule"The light meter in your camera may fail or you might be in a hurry. Whatever the reason, sometimes it is good to know that at f/16 (an aperture with lots of depth) your exposure on a sunny day should be 1/(ISO Rating) to keep the highlights from clipping. If you have your camera set to ISO 100, this means your exposure should be 1/125 (the closest value to 100). One stop reduction in light due to a faster shutter (to 1/250) requires opening the aperture by one more stop (going to f/11 from f/16). In my next tutorial, I will show you how to play Shutter, Aperture and ISO against each other to control Depth of Field, Motion Blur and your inner artist. Bookmark/Search this post with: |
Determining the "correct" exposure for an image can be a challenging task. We could choose to simply let our camera decide for us, and use the fully automatic settings that are quite sophisticated and often do a reasonably good job. However, this also means to give away part of the creative process to your camera. I am writing this tutorial with the beginning photographer in mind. The principles outlined in this article should become a second nature to you. I encourage you to practice and to ask questions. In many ways, this is like riding a bike. Once you learned how, you can focus your attention on your surroundings.
I will be watching this site closely
Some very solid sounding logic there not over complicated by detailed enough.
I look forward to seeing what else you come up with.
"A wide-open aperture (large
"A wide-open aperture (large Depth of Field) often requires a tripod"
should be "small aperture" I guess
Correct
Nice catch!
Amazing
This is exactly what I've been looking for, with a visual aid. As a complete beginner to exposure, the chart really helped me understand roughly how it all works.
Do you have the spreadsheet still? If so could you help a newbie and send it to me please?
matthewpaver@yahoo.co.uk
Thanks in advance.
Matt
spreadsheet
Hello Matt,
I am glad that you found the help you were looking for. I generated the drawing with Gnuplot, a scientific plotter. It is just a sketch of a complex behavior that I drew to make things a bit clearer. I don't have a spreadsheet for it. I will just release the code for gnuplot if I can still find it.
error
"One stop reduction in light due to a faster shutter (to 1/250) requires opening the aperture by one more stop (going to f/11 from f/16)."
Wrong stop. It should be going from f/11 to f/8.
No error
I am going from f/16 to f/11 in my text (or to f/11 from f/16). That is exactly one stop wider, same as you. The only difference is the starting point. I started with f/16 because of the sunny 16 rule, you started at f/11 which is what I would expect for slightly overcast days. We both increased the aperture, only I wrote it down the other way around.
what is a bad exposure?
nice tutorial easy to follow. my only criticism is, start using your gut feeling, most cameras today (digital) only see correctly exposed images, and give all sorts of warnings if you are trying to capture a dark moody shot! learn to correctly expose and then learn to push the limits for better and more interesting shots.
Preventing camera shake.
Very nice article! I'm writting something similar for my blog (it's in spanish).
I might be confused, but I don't think that the crop factor has to be accounted for the rule "we require at least 1/(focal length) or shorter to avoid camera shake"
Because it's not that the lens is longer it's just that we see only a part of a bigger image through the cropping sensor, right?
True and not true
It also depends on the resolution (how much camera shake do you see) and on the pixel density, which is generally higher for crop factor cameras. Assuming that you blow the print up to equal size in the end, you DO have to account for the crop factor for equal blur. The smaller part that the crop sensor covers ends up being blown up more. It's just a rule of thumb that also depends on your resolution (pixel peeping at higher resolution requires a more steady camera) and it depends on how steady your hand is. Just try it and check the result to see how slow you can go.
Do you offer The Three Exposure Controls for Dummies!
I am brand spanking new to the photography world. I read this whole tutorial and I am still having a hard time with how to work them together. I am sorry, I guess my brain is wired differently. I learn by hands on I guess and by examples. Like what is an example of how one would set their camera settings for indoors...I know there are things to take into factor, but in general...or for a cloudy day, or a sunny day? I guess I need it broken down more. I am so frustrated that I cannot get this! I have a Nikon D60 and I want to be able to use the manual settings because I like being creative...can you help me?
Sure
Its actually not that hard. Here is the quick and dirty version:
-Aperture is the size of the lens opening. Small aperture (large f-number) means large depth of field, but since the opening is smaller less light comes in (peephole vs. panoramic window).
-Exposure time is how long we let the light in. If the hole is small, we need to increase the time to collect the same number of photons.
-ISO is the sensitivity. If we have less photons and less time to collect them, we need to have more sensitivity (better eyes). Technology limitations make it more noisy though (kind of like you don't see colors well at night).
Some Examples:
-If you cannot afford a long exposure (e.g. sports shots), you need to increase ISO and aperture. Large aperture isolates the sportsmen against the background (spectators) which is great (means small depth of field).
-If you need a great depth (nature) you need to increase exposure time (the numbers in your camera are seconds divided by the number, which means 125 is really 1/125 seconds, so 250 is shorter than 125).
Hope this helps, don't hesitate to ask again.
Exposure Cube Diagram
Believe me, you are not the only one who isn't getting this. And the whole cube diagram did nothing for my knowledge of exposure. I too learn by someone physically showing me but all the photographers around here are too stingy to give any help. They all think your trying to steal their gig or something. I am slowly getting it though and if there is one thing you should learn about it's metering. Definitely a huge process you must know about to get the right exposure. Good Luck.
Aperture, Shutter Speed and ISO
No, it didn't help...I cannot grasp the photography terms you are using. Like I said, we are all wired differently,... Photons?
Once I do get it, my first thing I will do with this knowledge is write a book in the simplest terms explaining how this all works. I am sure it will be a best seller!Lol☺
Dawn: Too bad, if you like,
Dawn: Too bad, if you like, contact me and I am sure we can figure it out together.
Anonymous: Not sure what you are saying. I am doing my best to help people and I do it without asking anything in return. Stealing my gig. Sure.
Hello, I think it would help
Hello, I think it would help the "hands on" people if you could explain an example this way (bear with me please)
I want to photograph my friend, we are out doors, it is sunny, they are about 5 feet away from me, use these settings because..
OR
I am taking my friends photograph indoors, the lights are dim because it is a birthday candle picture, use these settings because....
OR
My friend is racing their car, we are outside and it is partly cloudy out, use these settings because...
Does that make sense? if you could give a real world situation and explain the settings that you would use and why you are using them. Sorry if I confused anyone.. just trying to think how I need it explained to me.
Part 2
Hello Nick,
Thanks for the constructive feedback. I will take your suggestion and turn them into a new article, Part 2 of this series.
Glad to have people such as yourself as readers who have wonderful ideas and help me write about what readers want.
In my defense, I feel that a certain understanding and groundwork is necessary in order to cope with new situations. If you understand why I recommend certain settings, it may be easier to deal with a unforeseen case that doesn't fit any template that you memorized.
In any case, one example of what you asked for would be my response to this inquiry: Dog Photography Question.
Bear with me and give me a few days to write a new article.
Please understand that in order to become better photographers we must challenge the limits of our understanding and that we should not just follow simple push button rules.
Learning means you will have a certain failure rate, but from those failures you gain new knowledge. Following in the footsteps of others will get you as far as them at best.
I hope to lay the foundation for a deeper understanding in some of my articles, but I realize that not all articles are at the same level. This article and my article on diffraction are extremely technical.
Thanks! Your link to to the
Thanks! Your link to to the dog scenario was perfect. I understand what you mean about having groundwork vs. memorizing. But I do think the real world examples help some people grasp the technical side of it easier. Thanks for replying, I look forward to reading more of your writings, regards. Nick
Thanks again for the
Thanks again for the constructive feedback Nick. I have added another part to this series.
In the next version of the tutorial:
The Correct Exposure Part 2: Shutter Speed and moving subjects
I am showing you the camera settings you need to consider for moving subjects.
'Anonymous'
Hi,
I've been reading through the site and have found it immensely helpful.
Just thought I would help clarify what anonymous was trying to say when he/she wrote:
"I too learn by someone physically showing me but all the photographers around here are too stingy to give any help. They all think your trying to steal their gig or something."
I believe that when anonymous refers to 'around here', he/she means the physical area in which he lives - not your website! Also, in the second sentence, he is using 'your' in the same way that you(one) uses 'one'.
i.e. The photographers in the area where anonymous lives are unwilling to help him with his photography as they think that anonymous wants to 'steal their gig or something'.
You don't have to put this up on your site but it just doesn't seem that he meant to offend you with his comments.
Cheers,
Jamie
Thanks Jamie! You could be
Thanks Jamie! You could be right. I do so many things online, physical and virtual places are often the same to me.
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