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How to Prevent Image Blur
April 29, 2008
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Digital SLR Q & A
Question: What do some digital SLRs cost so much more than others?
AnswerInstead of digital SLR cameras, let's talk about cars for a moment.
When you're in the market for a new motor vehicle, there are a lot of factors to take into consideration.
If you're buying budget, then really all you need is something with 4 wheels, an engine, a driver's seat and a steering wheel - everything else is just extra fluff.
But for many, the convenience and comfort of power windows, air conditioning and a sunroof all make the driving experience that much more enjoyable.
Digital SLR cameras aren't all that different: the cameras priced below $600 offer the ability to take photos with the two main benefits a digital SLR has over a compact digital camera (speedy response times and better image quality in low light).
Cameras in the $600 to $1,000 price range have a bit more: extra features like dust control, built-in image stabilization and live view LCDs, paired with higher megapixel sensors and more customized control over how the camera captures color.
SLRs between $1,000 and $2,000 are the "luxury" models. Like BMW and Mercedes cars, these cameras are a step above the rest in terms of speed, performance and reliability. They also allow photographers to adjust every camera feature and setting so that each camera can be tailored for a different shooting style.
Any digital SLR above $2,000 is designed for a professional. The car world equivalent would be a Formula One race car or any vehicle from the NASCAR circuit. The features available on these cameras are there for only one purpose: to perform reliably under extreme circumstances and extensive use.
So there you have it - the reason why there is so much price variation amongst the different digital SLR camera models. Which one is right for you?
Perhaps the car that you've been driving around in will offer up some hints.
Common ProblemsFor more digital SLR camera techniques and common problems, browse through the back issues of this newsletter.
This month's common problem is: I can't stop my photos from looking blurry.
When it comes to blurry photos, there's one main culprit and two causes. The culprit in this case is shutter speed. The cause that I'll be discussing in this newsletter is camera shake.
Let's talk about shutter speed first. The shutter speed is the amount of time the sensor is exposed to light every time you take a photo.
Think of your digital sensor like a sponge: in order to capture a decent photo, it needs to absorb a certain amount of light. The amount of light the sensor is exposed to is a combination of three different settings:
For every photo you capture with your camera, the shutter speed selected will depend entirely on the other two variables AND on the amount of available ambient light.
Imaging that you're trying to soak a sponge under a faucet. If you turn on the faucet full-force, the sponge will get soaked pretty fast. But if you only turn on a trickle of water, it's going to take some time for the sponge to become saturated.
In this case, the flow of water is the amount of available light. If you have plenty of light (a bright sunny day) then your sensor will suck up all the light it needs while using a fast shutter speed. But it you are working with dim light (indoors at night) then your shutter is going to have to stay open a LONG time so that the small trickle of light can saturate the sensor.
Key Point: as your shutter speed slows down, you run the risk of capturing a blurry photo.
Shutter speeds faster than 1/125th of a second are usually fast enough to prevent blur, but as you drop below this number the risk of capturing a blurry shot increases significantly.
I mentioned at the beginning of this section that one CAUSE of blurry photos is camera shake (really it's camera shake in conjunction with a slow shutter speed).
How can you tell when the blur in your photo is due to camera shake? Simple: EVERYTHING in the photo looks blurry (see below).
Now that we know the culprit - slow shutter speeds - and the cause - camera shake - let's find out what we can do to reduce and/or eliminate this type of blur entirely from our photos.
Solution #1: Stabilize the camera
The most sure-fire way to completely eliminate camera shake blur from your photos is to stick the camera on a tripod and then activate it using a remote trigger so that you're not even breathing on the camera when it captures the shot.
With this setup, you can use any old shutter speed you want - even if the shutter is open for 10 seconds or more - and you should still be capturing crisp, clear photos. You can't have blur caused by camera shake when the camera is perfectly stable.
But hauling out your tripod every time you want to take a shot with a slow shutter speed is not terribly practical. Sine that's the case, let's talk about a different way of reducing the effect of camera shake.
Solution #2: Keep the shutter speed faster than the focal length of your lens
This solution is a bit harder to grasp than the previous one, but helps when you don't have a tripod and are trying to get some decent shots in dim light without having to use your flash. This last point is key: once you introduce light from artificial flash into the mix, all of the rules change (plus, it's a topic for a different newsletter).
For those taking photos without a flash, here's how to apply the shutter speed/focal length rule.
But what if the light is so dim that it doesn't let you select a shutter speed faster than the focal length? You must leverage your ISO setting to make the sensor absorb light faster.
Gradually increase the ISO value (to 200, then 400, then 800, etc.) until you can select a shutter speed that's faster than the focal length.
Using this principle means that the more telephoto the lens, the faster the shutter speed you'll have to use. Example: with a 55mm focal length, I can use a shutter speed of 1/60th of a second, but if I change to a 200mm focal length, then my shutter speed must increase to 1/250th of a second to eliminate camera shake blur.
This makes sense when you realize that telephoto lenses enhance camera shake. You can take perfectly clear shots at 18mm even if the camera is jittering all over the place, but if you're using a 600mm telephoto lens, the slightest twitch of the camera can result in a blurry photo.
The good news here is that you can SEE this effect when you have a telephoto lens attached to your camera. If you have a 300mm lens attached to your camera and look through the viewfinder, you'll see the image in the viewfinder moving all over the place. If you then zoom out (or change lenses) to 70mm the image in the viewfinder will stabilize and the camera shake won't be as apparent.
What Do You Need?This month I'll be answering the question: Do you need a live view LCD?
The first generation of digital SLR cameras had just one way for you to take photos: in order to see the shot you were about to take, you had to look through the viewfinder.
This was in stark contrast to every compact digital camera on the market, which allowed you to use the camera's LCD screen to compose your photos (which was mostly due to the fact that - unlike SLRs - compact viewfinders don't show you an EXACT view of the image you're about to take).
When a digital SLR finally did include the capacity to compose photos with both the viewfinder and the LCD, it was dubbed a "live view LCD".
The first camera to include this feature was the Olympus E-330, and ever since the release of that camera, live view LCDs have been popping up on many of the new digital SLR cameras of 2008.
Today, you can buy Canon, Nikon, Olympus, Pentax and Sony digital SLRs that have live view LCDs.
But how useful are they?
The answer to this question depends a lot on how you take photos and what you want to photograph. Action photographers will find little use for a live view LCD, since many of the live view systems don't leverage the full power of the camera's autofocus system (except for the Sony A300 and A350).
The live view mode becomes more useful for portrait photographers, because it means you can maintain eye contact with your subject while still getting the right composition. However, if you're working with portrait subjects who can't stay still - children and pets - then not being able to use the autofocus once again becomes a problem.
Live view modes work very well for anyone who takes photos of static subjects (plants, still life, etc.) where it's not always convenient to peer through the viewfinder.
For example, if your favorite photographic subjects are plants and flowers, you'll find many times where you can't capture the image you want AND look through the viewfinder due to the subject's proximity to the ground (especially if you don't fancy lying down in the dirt to get the shot).
Live mode also works well for landscape photography, where you can set the camera up on a tripod and then make adjustments to the composition using the live view LCD.
Live view LCDs really come into their own when they are paired with an LCD screen that articulates away from the camera body: this allows you to see the LCD easily from high and low angles. If the camera is above your head, you can tilt the LCD down, and if the camera is near your waist, you can tilt the LCD up.
For those interested in live view LCDs that also flip out from the camera body, there are currently only three models for you to choose from: the Olympus E-3, Sony DSLR-A300 (to be released in May) and the Sony DSLR-A350.
Photo FunSince no new digital SLR cameras have been announced recently, this month I'll turn your attention toward a new way to engage your photographic creativity.
There's only one catch to the technique: you can't use a digital SLR camera to do it (I'll explain why in just a moment).
A new type of "image" has showed up recently on several different web sites, and it's already been given a name: the Long Portrait.
A Long Portrait sits somewhere in between a still image and a video. Essentially, it's a short video clip of a person/place/thing where the ambient sound helps to set the tone for the image. The video may either be motion, or just a still frame with the audio in the background.
Here are some examples of Long Portraits:
The trick here is to keep things short. Don't think of these as video segments, think of them as moving photographs with sound.
Long Portraits are a great way to get your creative juices flowing, and help you pay more attention to the micro-events happening around you each and every day.
The only problem...you can't use your digital SLR to capture them, since no digital SLR camera has a movie mode (the closest that I've found is the burst mode on the new Pentax K20D).
So now you have a fantastic use for that old compact digital camera, even though you have a brand new SLR. Keep the SLR around for any high-quality still images that you want to capture, and permanently set the compact camera to video capture mode, to start taking some Long Portraits to go with your other static images.
Here are some examples of Long Portraits that I've taken: http://www.flickr.com/photos/croberts/sets/72157604643847791/
I'm just starting out and am getting a feel for what works and what doesn't. To see a significantly larger collection of Long Photos check out Heather Powazek Champ's 10-second collection: http://www.hchamp.com/10seconds/
LinksThe following collection of links will help to keep you posted about what's new at the Guide and in the world of digital SLR cameras.
Recent Updates to the Digital SLR Guide
Other Photography Sites
In ConclusionThat does it for this month's newsletter.
Coming up in the next month: how to prevent SUBJECT image blur, the return of the marketplace (with more SLR gear for sale), and the usual grab-bag of tips and new camera information.
Until then, happy picture taking!
--Chris Roberts, Your Digital SLR Guide
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