Digital SLRs have a really cool feature that’s often overlooked by novice photographers, but is heavily-used by professionals. It’s the histogram, and it can tell you a lot about how well your image is exposed. I’ll be writing more about it soon.
This histogram came from Photoshop, but your camera should provide you with a similar though probably simpler display on the LCD.
Do you ever use the histogram? Do you know how it works? Have you even noticed that it’s there?
I’ve touched on this briefly a couple of times, but it bears a little bit more discussion.
Bulb mode is kind of a special manual mode on your camera. On some cameras there’s a B mode on the exposure mode dial, but on others bulb is just a shutter speed– set the camera to M mode, change the shutter speed to 30 seconds (not 1/30, but half-a-minute 30 seconds) then go one step further. Once you’re there, set the aperture that you want to use.
Now what? Press the shutter button, and the shutter opens. Let go and it closes. You can keep the shutter open for as long as you want to, until your finger gets tired or your camera runs out of battery.
In order to make effective use of bulb mode, you really need another piece of hardware– a remote shutter release of some sort. I’m pretty sure that there are wired shutter releases available for all dSLRs and probably all film models too. In the simplest version, you plug the cable into the side of the camera, and when you press the button on the cable it activates the shutter. (This works in all camera modes, not just bulb.) In bulb mode, holding the button down holds the shutter open. Slightly fancier models have a shutter lock so that you can activate the shutter and then walk away for a while.
Many cameras also have wireless shutter releases available. These basically function the same way, except that they sometimes have two-press operation– press the button once to open the shutter. Press it a second time to close it. If you have a Canon Digital Rebel (original, XT, or XTi) the Canon RC-1 is a valuable addition to your kit. It lives on your camera strap and is completely unobtrusive when you don’t need it. If you want to release the shutter remotely, you just pop the RC-1 off of the strap and it’s ready to go. When you’re done, pop it back onto the strap and it’s out of your way. It’s not just for long exposures– it’s valuable whenever you want to be away from the camera, such as when you want to be in the photo. When I used a Rebel XT all the time, I was always reaching for the RC-1.
Some cameras may require you use the self-timer setting in order to use a remote shutter release. Consult your manual for the details of your specific model.
Why would you want to use bulb mode? Mostly it’s for very-long exposures of over 30 seconds, but it has other uses too. I use bulb mode a lot when I’m shooting fireworks– I try to open the shutter just as a rocket is going up, and close it as the explosion fades. You can set the camera on a tripod at night and shoot the path of stars moving across the sky, or capture blurs of cars driving through the city. Though I have no first-hand experience, bulb mode is also used for taking pictures of lightning strikes. I’m sure there are plenty of creative uses that I can’t even imagine.
Another cool technique that uses bulb mode is light painting. Light painting involves taking the camera into a darkened room, opening the shutter, and then using light sources (LEDs, flashlights, whatever) to paint light onto an object or just onto the sensor itself. While it didn’t use bulb mode, the image at left was taken by opening the shutter in a dark room then moving an LED glow ball in front of the camera. As you might have guessed by now, I like playing around in front of a camera with bright objects in a dark room– you just never know what kind of cool image you might wind up with.
Bulb mode is a specialist tool, but it’s a really useful one to know about. You probably won’t need it very often, but sometimes it’s the only real choice for getting the shot you want.
I’ve extended the April homework assignment through the end of May. Have fun!
The March homework assignment worked out so well that I’m doing it again.
We all know that photos are static representations of the world– a moment frozen in time by the camera’s shutter. However, photos can also be dynamic, and show both split-second and slow changes.
This month’s homework assignment is both very simple and much harder than last month’s– capture something in motion. It can be a golf stroke, cars whizzing by, the blur of a bird’s wings, anything you choose, but I want to see some nice motion blur.
Like last month, the idea here is to plan the image before you capture it, not just shoot a bunch and hope you get lucky. You can use aperture priority, shutter priority, manual, or bulb modes at your discretion. Bulb mode isn’t something we’ve talked much about, but it’s really very simple– rather than using a fixed shutter speed, the shutter stays open for as long as you hold the button down. Bulb mode is typically used with a remote shutter release of some sort, so that you don’t shake the camera by pressing the shutter button. It’s most commonly used when you want exposures longer than 30 seconds. You probably won’t need it for this, but you can use it if you want to.
One thing to be aware of is that longer exposures are much easier than shorter ones, since it can be easier to get the timing right.
Upload your photo to a photo sharing site (I recommend Flickr but any one will do). Leave a comment on this message with the settings that you used, a link to your photo, and anything else you want to say about the image.
At the end of April 2008, I’ll pick one commenter at random and send them an 8×12 signed print from my flower porn collection. If at least 20 people submit entries, I’ll give away a second print to the submitter of the best image. You can enter more than once, but don’t get carried away.
Have a field day! This one should be fun.
Small print: void where prohibited by law. Anyone who clearly violates the spirit of the rules will be disqualified. Don’t put that in your mouth… you don’t know where it’s been. Please make sure your images are worksafe. You can post more than one photo, but you’ll only get one chance at the drawing. It must be a photo that you took specifically for this assignment, not something pulled out of the archives. Play nice. Judging is at my discretion, and is final. SSA might want to show your image in a future entry, but we don’t want any other rights to it– if we want to use it for anything else, we’ll play nice and ask for your permission first.
Congratulations to Tyler, who won the drawing for the March homework assignment. For being favored by my computer’s random number generator, he wins a signed print from my Flower Porn series.
I was impressed with the submissions– you guys really understood what it took to blur your backgrounds. There were adorable dogs, jewelry, walls, lots of flowers, and plenty of other interesting subjects. The bell was a fascinating and slightly nontraditional composition. Of all of the submissions, I think the bouillon was my personal favorite for moodiness and interesting lighting.
Everybody seemed to understand that the right way to do this was to use a very wide aperture, and almost everyone shot in aperture priority mode. Several people mentioned changing the ISO to get a better shutter speed. A couple of you even mentioned moving closer to your subject in order to get a more desirable depth of field– that’s an excellent technique!
If you learned just one thing from this assignment, I hope it was this: visualize the image before you shoot, and then figure out how to use your camera to capture the picture that’s in your mind. Digital cameras make it very easy to just shoot lots and lots of images until you get lucky, but just a little bit of skill and forethought will do much better.
A print of this image will be in the mail to Tyler soon. And get ready, because the April homework is on its way. It might be a little bit more challenging, but it will also allow a lot more creativity. I’m really looking forward to seeing what you guys do with this one, since the March entries were all great.
Thank you all for contributing!
There’s an old saying among photojournalists– f/8 and be there. Sometimes the technical details of a photograph really matter, and sometimes they don’t. Perfect technique won’t help you if you don’t have your camera ready to go when the moment happens.
As you may have heard, the Olympic torch made an appearance in San Francisco today. In fact, it was scheduled to pass just a block from my office. I normally just hop in the car and drive to work, but I was worried that parking would be expensive and the neighborhood would be a zoo, so I opted for public transit. I took the ferry across the bay to San Francisco (and snapped some fun pictures, but accidentally erased them… I don’t function well in the morning), and encountered lots of protesters near the ferry building.
I knew this was likely, so I already had the camera ready to go. In particular, I put the camera in aperture priority mode, set the aperture to f/8, picked a lens that I was happy with, and made sure that autofocus and image stabilization were turned on. f/8 is the perfect middle-of-the-road aperture, since it will give you enough depth of field to compensate for minor focus mistakes, and will let in enough light to get decent shutter speed in daylight. I also put the camera in multiple shot mode, so that if something was changing quickly I could just hold down the shutter button and hopefully get one of the shots timed perfectly.
Later in the day, I increased the ISO to 400– I was shooting a lot of stuff that was in shadows, and I wanted to make sure I had plenty of latitude in my shutter speed.
(I made one mistake in camera settings, but I was able to work around it OK. Can you spot what it was? It’s hiding in the photo’s exif data.)
By spending a little bit of time up-front thinking about how I would be shooting, I was able to just forget about the mechanics of the camera and pay attention to what I wanted to shoot. The picture above is one that I almost got right, but not quite… if only the bloody video guy hadn’t walked in front of me just as I pressed the shutter button. Still, if I didn’t tell you that you might think he was another protester, and I’d almost be off the hook.
When shooting fast is really important, think about your camera settings in advance and figure out what you need in order to be able to forget about them. In typical broad daylight shots, that’s probably aperture priority mode and f/8.
I wrote a little bit about bracketing earlier, but it’s an important concept and it deserves its own entry.
You’ll often hear photographers talk about bracketing an image. Bracketing sounds pretty technical, but it’s really just a fancy term for taking multiple shots of the same image at slightly different exposures. With some scenes, it’s really hard to know whether you’ve gotten the exposure right, and it’s worth taking a few extra shots to make sure one of them will be good.
Let’s say that you’re shooting a scene and the camera’s meter thinks that the right exposure is f/8 and 1/200 sec. Maybe it is, but maybe that will result in a little bit of underexposure or overexposure. If you wanted to bracket one stop on either side, you could take one shot at f/8 and 1/100 sec, one at f/8 and 1/200 sec, and one at f/8 and 1/400 sec. Alternately, you could take one at f/8 and 1/100 sec, one at f/5.6 and 1/100 sec, and one at f/11 and 1/100 sec. Either way, you’d wind up with three images and if the camera was anywhere close to being correct you probably will wind up with one perfectly-exposed image.
In the days of film, bracketing was often a necessary but expensive operation. Digital cameras have made it cheap to take multiple exposures, since there are no film developing costs. Flash cards are both cheap and reusable, and you can fit lots more images onto them than you could on a roll of film.
Bracketing sounds cool, but I bet it also sounds like a lot of work. Want me to make it easier for you? OK, piece of cake.
All modern dSLRs have a function called automatic exposure bracketing, or AEB. When you enable AEB, you tell the camera how large an increment you want to use, and then whenever you press the shutter the camera takes three images– one at what it thinks is the correct exposure, one underexposed by the amount you specified, and one overexposed by the same amount. Click click click. You can usually specify the size of the compensation in 1/3 or 1/4 stop increments up to two full stops, sometimes three
Look at the specifications for your camera, and you’ll see something that looks like this:
AEB: +/- 2.0 EV, 0.5 or 0.3 EV increments
That means that you can bracket plus or minus two full stops, and you can choose either 1/3 or 1/2 stop increments. EV means Exposure Value, and it basically means the combination of aperture and shutter speed for an exposure.
Voila! All you have to do is turn it on, and your camera will do the work for you. Consult your camera’s manual to figure out how to enable exposure bracketing on your camera.
In situations where the lighting is tricky, I highly recommend using aperture-priority or shutter-priority mode and then bracketing your shots. This will give you a much better chance at getting a perfectly-exposed image.
Now, go try it out! Put your camera into either aperture priority or shutter priority mode, and enable automatic exposure bracketing. Find something well-lit, and take a picture. You’ll hear three clicks of the shutter, and wind up with three images. (It’s like a buy-one get-two-free sale.)
For extra credit, put the camera in manual mode, set the aperture and shutter speed to what the camera thinks is the right exposure, and then manually take three shots, changing the shutter speed to bracket by one full stop. Look through the viewfinder and check the meter before each shot. For one it should be right in the center, for one it should be one stop to the left, and for the third it should be one stop to the right of center.
In Why are there spots on my picture? I showed several examples of sensor dust, and promised to tell you what to do about it. And then I procrastinated. No more! Here’s my simplified guide to cleaning your sensor.
Before I go very far, let me say this: whenever you clean your sensor, you run some risk of damaging it. If you’re careful and pay attention to what you’re doing that risk is very small, but if you’re not comfortable with the methods outlined here then you should take your camera to a reputable camera shop rather than doing it yourself. The author disclaims all responsibility for any damage you might do to your camera.
Have I scared you? Sorry about that. I’ll do my best to make you less scared. Some methods of cleaning the sensor are far safer than others, and those will do a good job on most dust. Occasionally you’ll wind up with really stubborn, sticky dust that can’t be removed without heavy artillery, but the vast majority of it is pretty wimpy and will go away when you tell it to.
Before we go on, there’s one tool that you’ll need for this project, and that’s some sort of a blower bulb. This is a small rubber gizmo that you will use to blast the pesky dust away from your sensor. The most popular one for this purpose is the Giottos Rocket Air Blaster, and I’m quite fond of mine. It’s powerful and works extremely well, and you get all of that wonderfulness for less than ten bucks. Another option is to go to the drugstore and pick up a bulb-style ear syringe. These cost a couple of bucks and will do a passable job, though the Giottos really is much better.
Before you attempt to clean your sensor, read your camera’s manual for instructions on sensor cleaning. My Canon manuals say to always have a fully-charged battery or have the camera plugged into an AC adapter when you clean the sensor. I don’t know much about Nikons or other dSLRs, but I’d imagine they’re the same.
Here’s a quick outline of what we’re going to do:
That doesn’t sound too hard, does it? OK, let’s go.
First off, read the manual and then look through your menus to see how to put the camera into sensor cleaning mode. You don’t want to put it into this mode yet, but you know where the setting is and be ready to go.
The next step is so obvious that it doesn’t require explanation– remove your lens. I make it a habit to always keep the opening of the camera body pointed down whenever I don’t have a lens on the camera– this utilizes an amazing force called gravity to help keep dust out of the camera. It probably doesn’t do all that much good, but every little bit helps.
Now, have your blower bulb handy, then put the camera into sensor cleaning mode. You should hear the mirror flip up so that the sensor is accessible.
Here comes the fun part: keep holding the camera so that it’s facing down, and use the blower bulb to blast air onto your sensor a few times. This should dislodge most of the dust that’s hanging around. If you keep the opening pointed down, that gravity stuff will help keep the dust from falling back onto the sensor. Work quickly, but don’t hurry… it’s better to have to repeat the process a second or third time than to work too fast and bump something you shouldn’t.
Now, turn the camera off to take it out of cleaning mode, or alternately do whatever your manual told you to do. Put the lens back on the camera so that you don’t let more dust in.
A few words of caution:
When you’re done, take another test shot and you should see that much of the dust is gone. You almost certainly won’t get all of it, but that’s OK– I don’t think I’ve ever had a completely dust-free sensor in my life. Small amounts of dust are impossible to see in most images, and when they do show up it’s almost always possible to get rid of them with a tiny amount of Photoshopping.
What if you have serious stuck-on dust that won’t go away? There are several methods at your disposal that require a bit more caution than a blower bulb but can remove even the most stubborn dust. Probably the best is wet cleaning. This is done with materials that are specially designed to avoid leaving residue on your sensor. (Please put that Windex down right now.) The kit I have is sold by Copper Hill Images, and I’ve been quite pleased with it. I do most of my cleaning with a blower bulb, and when that doesn’t work I resort to wet cleaning. Copper Hill has an excellent tutorial on using their products– it’s a bit chatty, but contains a lot of good information.
Another method that some people swear by is a specially-designed electrostatic brush. I personally haven’t had very good luck with cleaning brushes, but that may just be my incompetence with using them. Your mileage may vary.
The Dust-Aid kit is an interesting new product– it uses a special adhesive pad to clean the dust off of your sensor, sort of like a lint roller for your sensor. I haven’t used one yet, but I’ve heard mixed reviews. My guess is that they’ll be somewhat more thorough than a blower, and not quite as good as wet cleaning.
Sensor cleaning has been written about a lot, and everyone has an opinion about it. If you do a web search for “cleaning dslr sensor” you’ll find a lot of excellent advice and a wide variety of opinions. To my way of thinking, the blower bulb method is the least invasive and should always be tried before you go onto something more hardcore.
Many new cameras try to automatically clean the sensor by vibrating it every time the camera is turned on or off. I don’t have personal experience with those, but others have reported that camera self-cleaning will reduce the amount of dust you get, but won’t completely eliminate it. You’ll still need to clean your sensor by hand from time to time.
Do your best to prevent getting dust into your camera– always keep a lens or a body cap on the camera, and when you change lenses do it quickly with the camera pointing down, and in as clean an environment as possible. However, when the inevitable dust shows up and starts causing problems, it’s not the end of the world.
All of you slackers and procrastinators have lucked out. I don’t have much free time until this weekend, so you have until the end of Friday to do your homework. You guys have posted some really cool images… I’m impressed! This weekend I’ll be going through the entries and finding a winner or winners.
After that I’ll post a new assignment for April.
Hey you… yes you! Where’s your homework? Remember the homework assignment I gave you that’s due by the end of the month? Some of you have done it, and done quite a fine job, but the rest are still slacking. No, the dog dd not eat your memory card, and I won’t take a note from your mother.
If you need to review, here are some lessons that might help you:
And if you want to go through all of the lessons, walk through Exposure Lessons, in order.
Now go out there and do your homework. I don’t want to have to give you detention. Be sure to leave a comment on the homework entry with a link to your photo(s), along with exposure details and anything else you want to say about them.
I found this site while browsing a Flickr discussion today. It’s a camera simulator that lets you look at a high-light, medium-light, and low-light scene and then tweak the aperture, shutter speed, and ISO to see how the photo will change. You can put the camera into aperture priority, shutter priority, and manual modes and tweak all of the controls. (There are also a couple of other modes available– program and automatic– but they aren’t interesting to us anymore, are they?) There’s also a setting for exposure compensation, which we haven’t talked about before but is used for telling the camera to intentionally under- or overexpose a shot by a certain amount.
And when you’re done, grab your camera and try doing the same thing.
