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Learn to Use It!
Photo: Rainer Ebert used under CC license
The following post is from Australian photographer Neil Creek who just launched a free background image site featuring his photography, and is developing his blog as a resource for the passionate photographer.
Welcome to the sixth lesson in Photography 101 – A Basic Course on the Camera. In this series, we cover all the basics of camera design and use. We talk about the ‘exposure triangle’: shutter speed, aperture and ISO. We talk about focus, depth of field and sharpness, as well as how lenses work, what focal lengths mean and how they put light on the sensor. We also look at the camera itself, how it works, what all the options mean and how they affect your photos.
This week’s lesson is Shutter.
Here’s What We’ve Covered Previously in this Series:
Lesson 1: Light and the Pinhole Camera
Lesson 2: Lenses and Focus
Lesson 3: Lenses, Light and Magnification
Lesson 4: Exposure and Stops
Lesson 5: Aperture
In previous lessons we have talked about the basic theory of how a camera works, including some basic optics, and introduced the idea of exposure and how we control it with the exposure triangle. In this lesson we will be drawing upon what we have learned to understand the second point on the exposure triangle – shutter – and how it works to create your photo.
The Shutter
The shutter’s function in the camera is simply to block light from getting into the camera, unless a photo is being taken, and then to allow light in only for as long as needed to achieve a correct exposure. The name shutter is a little misleading, however. Rather than being a door that opens, and then closes at the end of the exposure, it is more like a gate, with a pair of doors that slide together across the sensor. This arrangement allows for much shorter shutter speeds than could be achieved by moving a single door. The animation below explains this more clearly:
For the sake of clarity, the above diagram excludes the mirror and all other camera mechanics, only showing the sensor, shutter and some representative surrounds to give a context for the illustration.
When you press the shutter release on the camera, a complex sequence of events occurs, including setting the aperture in the lens, flipping up the mirror of an SLR and a lot more. We’ll just look at the shutter however. So referring to the animation above:
- The rear of the two shutter “curtains” as they are called, opens behind the front curtain, and stays up out of the way. At this stage no light has entered the camera, as the front curtain is still closed.
- The front curtain drops away, revealing the sensor behind, and allows the light to enter the camera, beginning the exposure.
- After a period determined by the set shutter speed, the rear curtain now drops to close the camera to light and end the exposure.
- To prepare for the next exposure, the front curtain returns to its normal closed position.
There is an outstanding interactive movie of the inside of a Nikon D3 showing the complete process in incredible detail. I highly recommend taking a look.
Fast Shutter Speeds
When the shutter has been set for a very short exposure period, such as 1/200th sec or faster, the twin curtain system comes into its own. A single “door” shutter wouldn’t be able to open and close this fast. For such short exposures, the rear curtain starts to fall, covering up the sensor before the front curtain is even fully open. The result is a moving open slit passing in front of the sensor. See the animation below:
This method of exposing the sensor (or film) is important when shooting with flash, but the topic of flash sync speed is best covered in another post. In the very early days of photography, when films had poor sensitivity to light, the rolling gap effect of this kind of shutter led to problems with moving subjects, but today there is no disadvantage at all. Most high end DSLRs can achieve incredibly short shutter speeds, such as 1/8000th sec with this shutter design.
The Shutter’s Effect on your Photos
It may seem like your camera is capturing an instant in time, but in reality, it’s capturing a duration of time equal to your shutter speed. This is especially noticeable with long exposures. Anything in the image that is moving while the shutter is open will appear blurred. This also includes the camera itself. Accidental movement of the camera during an exposure is called camera shake and has the effect of smearing the image in the direction of movement. This can be done deliberately for artistic effect, but in most circumstances you’ll want to avoid this.
A good rule of thumb to minimise camera shake is to set the shutter speed at a minimum of one second divided by your focal length. So for example, if you are using a 50mm lens, then to minimise camera shake, you should shoot at 1/50th sec at least. If you are shooting at 200mm, then set the shutter to 1/200th sec. The reason for this is that as we know, longer focal length lenses magnify the image, but they also magnify the camera shake.
Some examples of how choosing your shutter speed can affect your photos:
- Choose a high shutter speed to freeze motion or action, for example in sport photography.
- Create the appearance of motion in your photo by choosing slower shutter speed and deliberately controlling camera or subject movement during the shot.
- A longer exposure on a tripod can make moving water fluffy and white.
- Very long exposures on a tripod at night can capture very dim scenes, and even stars in the night sky fainter than you can see.
Examples
 Panning with the subject during a long exposure blurs the background and gives the impression of motion. Photo: indywriter used under CC license |
 A slow shutter speed with the camera on a tripod turns river rapids misty white. Photo: Neil Creek all rights reserved. |
 Exposure of 30 seconds or more can capture striking night sky images. In this case, several 30 second images were “stacked”. Photo: Neil Creek all rights reserved. |
Homework
- Find a fast moving subject – a water fountain is ideal. Photograph it at different shutter speeds, from slow to fast (adjust your aperture to maintain correct exposure), and see what affect it has on the appearance of the subject in the photo.
- Set your camera to a variety of slow shutter speeds – for example between 1/16sec to 1/2sec – and experiment with moving the camera during the exposure in different ways. Take note of how the different speeds affects the photo, and try exploiting this creatively.
- Find a moving subject such as cars, or kids on bikes, and shoot them at the same slow shutter speeds – you’ll probably need to do this at dusk or indoors. Pan the camera to keep the subject sharp, and see how the background blur changes at each setting.
- At night, grab a tripod, or find a stable surface for your camera, and experiment with longer exposures, from one to 30 seconds. Try this with moving subjects such as people at a busy street intersection.
- Shoot the stars! Take your camera and a tripod away from the city, under some darker skies and point the camera up. A moonless night is best. Use the self-timer or a remote shutter release to minimise camera shake. Set the shutter to 30sec and shoot the stars. Focus can be a challenge, so try auto focusing on a bright star, or use live view zoom to focus if you have it. Here are some of my recent astrophotos.
Resources
- Aperture and Shutter Priority Modes – At DPS
- Nikon D3 Shutter Release in Super Slow Motion – At Jeffrey Friedl’s Blog
- Camera Works: shutters, flashes, and sync speed – At penmachine.com
- Focal plane shutter – At Camerapedia
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Didn't know exactly where to put this but while shooting the moon I have found the right exposure - easily if you have a spot meter in your camera. Might try 'Manual' Mode or do an exposure compensation for the shot - treat it like you would a beach scene, take the spot exposure of the moon and then change the exposure by 2f stops (darker) and you will probably get a pretty good shot. Go ahead use a slow non grain ISO you will be surprised at how little it takes. I also use manual focus and look for the highest contrast plus clarity. Oh you might just try 'Beach' and spot exposure. Happy shooting.
Phillip
My Super Moon - http://www.flickr.com/photos/vietvet67/5541557477/in/photostream/
LookISO = 100, exposure = 1/180th and aperture = f9.5 with - 1/2 ev. So fast I did it hand held - would have been sharper if on a tripod since the focal length was 200mm.
Very nice artice. Probably best way to explain shutter mechanism via graphics. Cant get simpler than this to understand. Thanks a lot.
i think that this website is terrible and it sucks
Thanks for this series. I find your lessons easy to comprehend and they're helping me really get a handle on my new DSLR.
Photography is a self orientated job opportunity. Learning is associated with one’s keen interest. I am fond of photography that’s why you collection emphasize me to say kinds thanks to you. #
Thanks for this education, just read all 6 articles.
Although I already knew the theory, the diagrams and animated gifs are veeeeery explanatory and things got clearer now!
Keep up the great work!
I am a graduate of Graphic Design in one of the Popular Art institute (Institute of Management Technology IMT) Enugu, in Nigeria, And in one of our courses way back in school we had similar course in photography which geared my interest in your Course Photography. Though I am afriad I can not aford your cost for a course in your school. If not I will like to enroll in your online lessons. currently work in a small firm as Graphics Deisgner/Visualizer.
I like your teaching approach to Photography and I know how much i just learnt from my little time in your site "Photography 101.6 Shutters"
Thanks
A. Paschal.
another great lesson Neil. I had a basic understanding of how modern shutters worked (well I was familiar with the terms front and rear curtain in any case) but to see it pictorially really makes things very clear.
Love the example photo's. I hope you do a tutorial on capturing those night images.
WOW-Now that was a great way to explain it.
I had learned some basics of photography about 18 years ago, but it is not unitl now that I have been reading and experimentig with all the tips I have read here that I am getting a better understanding of how my DSLR works different from my old SLR and how much better pictures I have been able to take. All this is great and extremely usefull, especially now that I will venture into the Events photography field.
I have been lulling around for a project to shoot, and your Shutter assignment was just the thing I needed.
Looking forward to the next lesson, Thanks!
Thank you for putting in the time to teach people like myself, who haven't a clue but want to learn. I am following you "class" and learning lots. Please keep 'em comming.
I'm going to use this series as a way to train new editors. Clear and consise. And best of all, already written (so I don't have to). Thanks
PS: Already did my homework:
http://photobooster.blogspot.com/2007/03/give-movement-to-action-shots.html
Panning can be a lot of fun with kids in the shot.
Dan
i never knew that there are 2 curtains. thanks for sharing these valuable info.
explanation is very easy to understand.
Neil:
After reading your weekly tutoring, it's helps me to understand the basic of control FOTO... also indepth of the camera it self (mechanism), very interesting!. I have had sharing the art of "foto" to a friend and finaly he's in it, he just got the Canon 5D to start-out w/ lense 17-40mm f4/L, by the time I'm ending this typing, he's prob. getting another one (long range), he's hook! -:). Anyway, THANK YOU for for the site that keep us busy with the world of FOTO!. Keep up the good work, Neil.
David
Thanks for sharing. Great article. It's great to have graphic explanation to see what is inside.
Well-explained. I gained something from it. Thanks.
Thanks for sharing this! I might want to try out the suggestions in the homework section.
I'm glad you're finding the article useful! Look forward to the next one which will discuss ISO.
@john - Focus during a slow shutter pan is just as important as with any other photo, it's no different here. So use the focus techniques you'd use in other sports photography, such as prefocus. The difference with the slow shutter is that you're trying to keep the subject in the same place on the sensor. For most shots like this, a moderate shutter speed, like 1/16sec for example, will be enough to blur the background, and should make it fairly easy to track the subject. Experiment with different speeds, and get lots of practice, and you'll soon get the results you're after.
@chas - Great examples! Thanks for sharing.
@dcclark & @ george kravis - Indeed, aside from motion blur, flash synch is the most important issue associated with shutter speeds. I've deliberately left that for a later lesson, as I think it's a bit more advanced topic than I want to cover at this stage in the series. However, I am very happy for anyone to provide more information in the comments, as you have. So thank you!
I'm loving this series and devouring every bit of it. Thank you.
You are probably aware of the fact that the original focal plane shutters traversed the film plane in a horizontal direction. This worked well when flash bulbs were used but limited synch speed for electronic flash to only 1/60th sec. That was until the introduction of the "Copal" shutter, that changed the direction of the curtain travel to vertical, as you've shown in your illustrations. As a result of this shorter travel, flash synch speeds could be increased to as much as 1/250th sec. in digital SLR's. Geo.Kravis
How closely/accurately do you have to be focused on your subject when you pan?
For example, when I want to take pictures of a bicyclist going about 15-20 mph in daylight?
I'll have to practice the panning method when it gets warmer out.
I always saw those 'fast motion' looking pictures and wasn't quite sure how the subject could be in great focus and the background be blurred to look 'fast'. I knew it had to do with shutter speed, but I didn't know the technique.
Thanks for the help!
Oh, I went to a Roller Derby recently and took some cool slower shutter speed shots while panning. The crowd gets blurred while the skaters are in focus. If you haven't been to one of these events, see if there are any in your area. Very interesting. http://blog.chaselliott.com/?p=35
Awesome article! Thnx.
YEAH! Neil's back. I love this series. Most well-written articles on the fundamentals of photography that I have seen anywhere!
Great job...again.
The curtain illustration also gives a good understanding of "Front Curtain" flash vs. "Rear Curtain" flash -- the flash goes off at different times depending on which mode you select. "Front" means the flash lights things up just as the sensor is exposed, while "Rear" means the flash lights things up at the very end of the exposure.
Very nice illustrations.
Wow... I never knew there were two curtains...
Great explanation, you learn something new everyday.
Thanks!