Loyce Hood Photography
Photo Tip of The Month
Avoiding Auto-Focus Errors
Most modern cameras have auto-focus lenses or AF for short. These lenses work great to ensure our images are sharp. However, there are times when the AF fails, or focuses in the wrong place. Auto-focus lenses work by focusing on a spot with a high level of contrast. Sometimes our subject has less contrast than the rest of the intended image. The image at the left is a perfect example. Click on this image to make it larger. You will notice the flower in the front is out of focus, while the leaves in the back are perfectly focused.
Most consumer cameras have heavily center-weighted focusing areas. Sometimes all it takes is to focus on your subject in the center of the frame, then hold the shutter button half way down while recomposing your shot (remember the rule of thirds?). The exposure and focus will remain set for your subject. Check your LCD readout to be sure you've focused on your subject correctly. The flowers will be sharp while the foliage is blurred.
There are several other reasons the focus may fail. If subjects have extremely low contrast because the focus works by looking for a spot with high contrast, it won't know where to focus, or when there are both near and far areas. Take the photo at left, for instance. If you click on it to make it larger, you'll notice the flower is out of focus, but the leaf to the right of it is in focus. I focused on the stamen of the flower (so I thought). Yet, the camera missed it by a few inches to the right. The reason is that a camera sees green and red as the same color value, so the contrast is very low. In addition, the leaf is a bit closer to the lens. The only way to be sure is to check your viewfinder after you've shot the image. Be sure to enlarge it so you can see which area is the sharpest. Again, the only way to avoid that problem is to focus on your flower first by holding your shutter button half-way down; when you get the light that tells you the image is in focus, reframe your photo while continuously holding the shutter button half-way down and try it again.
You will also have to be careful of subjects behind bars, behind glass, and subjects with a very bright area in the center of your frame. If need be, reframe and shoot.
Watch out for these caveats and be aware of them. You'll see how much your photography will improve if you first think before you fire off that shutter.
Until next month, I hope you've enjoyed this session as much as I enjoyed writing it. Happy Shooting! ◊
This article is copyright and may not be used without the express permission of the author.
Previous Tips of the Month:
Choosing the Right Camera for You
Up Close and Personal
Calling Attention to Your Subject Part A
Calling Attention to Your Subject Part B
So You Got a New Camera
What do all Those Symbols Mean on my Dial, and When Should I Use Them?
Using Your Camera's Built In Flash - or Not
How to Photograph Children
How to Photograph Children Part 2: Back to School and Throughout the Year
Capturing the Season's (Autumn) Color
Creating Great Christmas Images
The Quality and Direction of Light ...and why it's important to you
The Art of Creating Great Shots at the Beach
Learning to See as a Photographer
If you missed these topics and would like a copy of them, please email me and I'll be sure to send it to you.
If you have any questions regarding this article, or any other photography questions, please email them to me at the address below. I will be including your questions, along with the answers in my next Photo Tip of the Month.
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