Need advice on focusing moving objects.

[Sonoma]

My wife and I went out to the game preserve yesterday to watch the Sandhill Crane migration start and I wanted some pictures. Most of the pictures I took turned out bad or worse.

The first picture turned out about the best because it looks like a silhouette, and I kind of like that. The second and third pictures are the ones I really wanted to turn out, but as you can see they are very OOF. I was using AI-servo for the birds in flight, but it is very difficult to keep a focus point on such a small target.

Any pointers on getting the focus on small fast moving objects such as these?
Thanks for the help!


1.)

2.)

3.)

 

[myftop]

I like the #1.

 

[Kaytlin]

Sandhill cranes are some very loud birds haha we have a few that live in the pond in our backyard. I like the second one, its my favorite, and I also like number three.

 

[HomelessBoy]

Well, you could try to pre-focus.

 

[KmH]

Unfortunately, the little focus point outlines shown in the viewfinder are only approximations of where the auto focus sensors actually are in the frame. When image elements are small in the image frame it can be very difficult to be sure the focus point is actually on the image element you want in focus.

Your T1i only has 1 cross-type focus point, and it's in the center of the frame. Cross-type focus points are more accurate than regular focus points because they can detect contrast horizontally and vertically. Regular focus points can only detect vertical, or horizontal contrast, but not both.

Auto focus needs edge contrast to work, though most DSLR's use a phase detection AF system that splits the image and compares their phase. In photo #2 the birds are in front of backgrond that is almost the same color as the birds, which diminishes auto focus performance because there is little contrast between the birds and the background.

Shutter speed has a lot to do with stopping motion, and can also impact focus sharpness. Consider that the birds wingtips are moving a lot faster than the part of the wing close to the birds body.

At any rate the better you understand how the AF system in your camera works, the better you will be able to use it effectively. Autofocus - Wikipedia, the free encyclopedia

 

[Sonoma]

I like the #1.

Sandhill cranes are some very loud birds haha we have a few that live in the pond in our backyard. I like the second one, its my favorite, and I also like number three.

Thanks for the comments, it's much appreciated.

Well, you could try to pre-focus.

I looked up pre-focus, even though it seems quite obvious what it is and how it works. This area at its peak during the year has some 20,000 to 30,000 birds nesting here at any one time and they come from every direction. I will try this and see how it goes. Lots of opportunities.

KmH- I read the information you posted and I will reread it so I fully understand how the camera focuses. I new that the T1i only had one cross type focus point and that is the one that I use almost 100% of the time. When I bought the T1i I was also contemplating the 50d, I believe it has 9 focus points and all are the cross type. Beggars can't be choosers! Also, I have read the manual many times and keep it close. I just read that the focus point selection should be set to auto for AI-servo. I had it set to manual.

Many things to learn!
Thanks