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Slr Autofocus
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In focus objects in a digital photo is a very basic requirement for high quality photography. There are two different ways to focus on such objects: manual or automatic. There are a few automatic focus methods one of them is known as active auto focus.

High quality sharp and crisp digital photos are a result of many optical parameters that need to be set right. One of the most important optical parameters is focus. When objects in a digital photo are out of focus they look blurry and are missing details and clarity. When objects are in focus they look sharp and crisp.

While focus can be set manually by the photographer in most cases using the digital camera's automatic focus feature is much easier and faster. There are many different algorithms and methods that digital cameras use in order to automatically determine the right focus for a specific scenario. One of those methods is knows as active auto focus.

Active auto focus

Setting the digital camera focus to its right position can be easy if only you knew the exact distance between the camera and the object or objects that you are trying to focus on. If you know the lenses that you are using, the aperture and all the other optical settings then by simply by knowing the distance to the object or objects in the digital photo the exact focus can be calculated and set.

This is exactly how active focus works. Digital cameras that are equipped with an active auto focus system use distance sensors that measure the distance from the camera to the objects in the scene. Usually the camera measures the distance to the object or objects around the center of the photo.

There are a few techniques to measure the distance. One of them is by using an ultrasonic sensor. Such a sensor transmits an ultrasonic signal toward the object. When the signal hits the object it bounces back and some of its bounced energy is received back by the digital camera sensors. The digital camera measures the time it took the signal to reach back the camera and since the speed of such an ultrasonic signal is known the distance can be calculated. Other methods use infrared signals. Once the camera determined the distance to the objects the focus can be set by calculating the exact position of the lenses and by moving the lenses to that position.

Active auto focus has the advantage of working in complete darkness. Since the camera does not rely on measurements done on the captured photo the camera sensors can calculate the distance to the object in complete darkness and in focus high quality digital photos can be taken in scenarios where otherwise focus would have been impossible.

Since the active auto focus method requires extra sensors it is more expensive to implement and is usually found in higher end digital SLR cameras. Active auto focus can sometimes fail. The reasons can vary: some objects tend to absorb the transmitted signal energy instead of bouncing it back while other objects actually radiate similar signals (for example candles radiate infrared energy) and can confuse the digital camera sensors. When the auto focus fails you can either try to focus on other objects in the same distance from the digital camera, lock the focus and pan back to the original objects you wanted to capture or you can revert to old fashion manual focus.

Ziv Haparnas is a technology veteran and writes about practical technology and science issues. This article can be reprinted and used as long as the resource box including the backlink is included. You can find more information about photo album printing and photography in general on http://www.printrates.com - a site dedicated to photo printing.

Canon Xsi Rebel – Inconsistent Autofocus And Busy Indicator

I wanted to love this camera so much. It takes great pictures and the colors are vivid WHEN THE AUTOFOCUS work properly. I would get 6 shot of unfocused pictures out of 10. I tried all the settings (Manual, P, ATV, AV, A-DEP) and the results are the same. One would think that by setting the camera to AUTO MODE you would at least get consistent good pictures but it's not the case. Also, there is this BUSY indicator which appears for no valid technical reason. I was taking picture of the San Francisco BAY at around 4:30 pm. It was slightly cloudy and the sun was just peeking through the clouds. I set up the ISO to 200, shutter speed to 1/1250 (I was also focusing on the small waves and that's why I went for the faster shutter speed) and sometimes to 1/50 , wb to daylight, and also cloudy. There were a several shots where I got the BUSY indicator when I didn't even use the flash. The BUSY indicator delays your shooting significantly, and it performs like a P&S camera.

I have P&S digital cameras (sony, panasonic, and Canon) and their autofocus are dead on.. no problem whatsoever. For a DSLR, although entry level, one would assume that the autofocus will be accurate on auto mode. I am disappointed with this camera. I think canon cameras are great unfortunately, I probably got a defective one. I also ordered the Nikon D40 last month. It was a great camera but focusing was bad as well. It is just frustrating. By the way, I have very steady hands so camera shake is not an issue. I hope Canon will fix this problem soon, or at least during production so it will be fixed when the camera is out for sale.

Canon XSi Rebel – No Eexpert, But a Great SLR Camera for a Noob

My first SLR camera and I really like the feel and the large LCD screen on the back. I find it is very user friendly. Has a lot of automatic features so you don't have to be a expert to take some good quality photos. You can grow with the camera as you learn more of it's basic features. I picked up a couple of lens to go with this camera and can't wait to explore more of what it has to offer. I'm so glad I choose this model. I've been wanting to get a SLR camera for years and finally I got one and I couldn't be happier!

Canon XSi Rebel – Very Good Camera

This review comes from a novice looking to learn more with a good camera. I really do like this camera but I gave it 4 stars because the automatic setting does NOT allow you to use the display screen to view your shot, you have to use the viewfinder. I do not know why Canon did this. In this way it does not function like a typical digital camera - in auto mode. I believe you can use the display in manual mode, but I am not competent enough (yet) to use that mode. It is a nice view finder though and accurate.

Canon XSi Rebel – Reviews

This is the first camera I've ever owned - including point and shoot cameras...yes, i popped my cherry with a canon Canon XSi Rebel.

This camera has me wishing that I could relive some moments of my life just to be able to capture them with the Canon XSi Rebel. The best advice I got was to steer clear from the automatic modes and dive headfirst into the different settings to get a feel for what they can accomplish. The pictures are remarkable to say the least, especially the close of shots of inanimate objects. Enough of the objectivity-

price - very good value - a deal ! 8/10
comfort/handgrip/ease-of-use - 8/10
design/layout of buttons - 8/10 (never used a camera before, but for a beginner, pretty decent)

zoom - limited by use of lens....i.e. buy a zoom lens - for the kit lens I'd say 7/10
replication of real life - 8/10 - RAW format is amazing
Canon software - I'm very new to it, initial 5/10.

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Can some one send me a link to get an instruction manual for a Canon EOS Rebel 2000 35MM SLR Autofocus, please

I know nothing about cameras, my daughter is signed up for photography class next year. We got her a used camera for her class and it didn't have one.

it didn't come with one?
here's a link to a semi-manual:
http://photonotes.org/manuals/eos-rebel-2000/

hope your daughter gets into photography, it's a great sport to become a part of. Oh, you also need to buy her a variety of films
( 100-3600 ), and more lenses, as a part of class. Oh, and later down the line, she might need a DIGITAL SLR. God Bless you.

Sony fuses portability with DSLR lenses
Sony’s next generation of compact DSLR cameras, the NEX-5 and NEX-3, let users select the right lens for the job — bringing the flexibility and quality of a high-priced digital SLR camera to users that don’t want to lug around a big, heavy camera on their next photographic outing.

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