10 Tips For Better Autofocus

Text And Photography By Rob Sheppard

Labels: How-To, Camera Technique

This Article Features Photo Zoom

7 Shenandoah National Park, Virginia

9 Working With Teleconverters And AF
Modern teleconverters that are designed for specific focal lengths are very good. They might not match a single-focal-length lens in absolute sharpness, but on a cost-benefit basis, a teleconverter’s value can be huge. The problem is that they significantly reduce light to the focal plane of the camera and that results in less light to AF sensors. Sometimes this means that the autofocus doesn’t work at all with a teleconverter and a lens. In this case, especially, you may be required to use a fast lens with a teleconverter to coax your AF system to work.

10 Help Out Your AF System
It sometimes can take a fraction of a second to find an object and lock focus. Give your camera and lens a head start by starting the autofocusing early. If you wait until the last minute, you may find that you can’t get the photograph you want because focusing will be trailing the action. This is especially important for moving subjects, such as flying birds. Start by pressing the shutter button lightly, which engages your autofocus. If your camera has a specific AF button on the back of the camera, use it to start your autofocus (the camera is only focusing and not setting exposure or setting off the shutter).

Lenses and systems that allow manual focusing at the same time that your autofocus is on can help, too. Do a little prefocusing manually before you need your autofocus to work. That way, the AF system doesn’t have to search for something to focus on as you have already given it that information.

Cross-Type Sensors

A number of D-SLR (and 35mm SLR) manufacturers point out that some (and with a few models, all) of the AF sensors in their cameras are cross-types. Early phase-detection AF cameras used line-type sensors, which could only read focus with subject lines perpendicular to them: A horizontal sensor could read vertical lines but not horizontal ones; a vertical sensor could read horizontal lines but not vertical ones. A cross-type sensor, as you might suspect, can read both horizontal and vertical lines and thus is able to focus on a much greater number of subjects than a horizontal or vertical line sensor. Some cameras even employ diagonally oriented cross-sensors, so that they can autofocus on diagonal lines in a scene or subject.

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14 Comments

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Jeff makes this comment

Monday, 17 August 2009

The AF button on my camera has brought autofocus to a completely differant level. It tracks extremely well and is a feature that I will be using frequently. Great Feature......
rebecca makes this comment

Wednesday, 12 August 2009

I agree with auto focus not always working. But I do need to explain how much I love all my film cameras. I have a Canon F-1, and and A-1, they are the split screen focus ring. I love it. I am in control of my picture not the camera. Remember it is you that is behind the camera and pressing the button not camera. I understand that digital can be crystal clear but the right film it also can be clear.
Ola makes this comment

Monday, 27 July 2009

Great article it just met me where i am Thanks
Outofocus makes this comment

Thursday, 23 July 2009

www.katzeyeoptics.com For those who miss split sceen manual focusing.
Jim Horne makes this comment

Thursday, 23 July 2009

Article
image masking services makes this comment

Monday, 22 June 2009

Extremely informative article, well researched and clearly presented.Thanks for the hard work.
Janis makes this comment

Saturday, 16 May 2009

The best advice I've ever seen about focusing is to use the back-button AF exclusively. I'm amazed at what an improvement that makes for me. In the menu I turned off any focusing by the shutter button method, and then put the switch on the front of the camera on C for continuous. As long as I keep the center AF point on a bird or animal and my thumb on the AF button, it tracks its movement very well. Then I take my thumb off the button to freeze the focus when the animal stops. Therefore I can keep the front switch on C at all times. This also works on flowers in the breeze, etc. Try it! You need to take a few dozen shots to get in the habit of always using that button but after that I predict you will never go back.
Mike Lysecki makes this comment

Monday, 13 April 2009

Just found out you had a newsletter. Joined in and within minutes found it to be helpful!!
George makes this comment

Friday, 27 February 2009

I agree with the person who advocates bringing back the split ring screens. It is almost impossible to have tack-sharp focus with the flat matte screens we have today, unless we are able to fully utilize the auto focus function. If we could always depend on auto focus it'd be great, but in low light situations it isn't dependable.
Frank makes this comment

Thursday, 26 February 2009

All good advice, but what I'd really like to see is a return to the old style split ring focusing screens. It is virtually impossible (for me) to manually focus, or manually adjust focus, with these new screens. There's nothing to go by other than whether the light comes on...well, the light comes on in auto-focus and it's not right sometimes. The only way to really see focus is to stop down the lens, and that's just too time consumming in most cases. Also my 2x is virtually useless because it must be manually focused. Please bring back split rings!
Ray makes this comment

Friday, 23 January 2009

I some times get the problem in darker areas with auto focusing. To overcome that, i did exactly what has been explained in this article. On my Olympus Camera E500 i can lock the AEL on the back of the Camera Body and it will stay on until pressed again. That way i keep the exposure metering value for that area and can still move to try to focus on something around the subject to get the camera to auto focus. Go back spot i moved from and press shutter all the way down to take the Photo. When taking night shots and i have the Camera on a Tripod, auto focusing often is a problem. I lock the AEL on the are i want to take the shot. Then i move my camera to something of similar distance or best equal where it will auto focus. I then take my finger off the shutter release, re aim the camera back to where i initialy wanted to take the shot. I then set my Camera to manual focus mode so that my camera does not try to re focus again and hence spoiling my focus. I then take my shot.
Michel makes this comment

Thursday, 22 January 2009

Great article that summarizes the key knowledge to autofocus. I'd like to mention that a lot of Canon camera's have a custom function. This function let's you use the AE button on the back of the camera to focus. When you release the button focus is locked. Pressing the shutter halfway will lock AE and pressing further will let you take the photograph. This is very handy since you can seperate the focus and composition steps without having to set the camera in MF mode. Don't know if other brands offer this option also?
Rob Schley makes this comment

Saturday, 13 December 2008

Great Article!
Auguste makes this comment

Tuesday, 25 November 2008

Intereting and usefull to step back and be reminded of the basics one has started to take for granted, also very useful for new(er) photograhers.

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10 Tips For Better Autofocus

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