CUSTOM SETTING a4 “Lock-On®” – DOES IT WORK?

There are many reports floating around the internet about Custom Setting a4, however no explanations about how come turning it off could sometimes make the Nikon D2x focus better than before.

"Flying V" by Oliver Kuerten (inselney)

If you read posts or even articles proclaiming that it’s best to turn off a4, and they offer nothing more than a mystery as to why, just re-read the above reasons for not turning it off. In fact, turning off a4 will “dumb down” your otherwise smart Nikon D2x, and actually cause some of the problems people are trying to prevent by turning it off.

But, I must add that many people have written me with experiences that seem to indicate that they have personally had better results with a4 turned off. I have thought about this a lot, and have come to some conclusions (opinions) why this might be true for them, or you. Read my opinions, test for yourself, and you decide.

Does a4 slows down the camera? I think this is a strong possibility, since it makes the camera “think” harder as it is tracking your subject. You’ll have to judge for yourself whether that small speed decrease affects YOUR photography. If it does, turn a4 off.

Dynamic Area AF is designed to use multiple sensors to track a subject that is "moving erratically." ALL SENSORS ARE ACTIVELY SEEKING A SUBJECT AT THE SAME TIME, but only ONE is doing the tracking. (see manual page 73) Since we have Predictive Focus tracking, and Tracking with Lock-On, the D2x will tend to stay with the subject, unless it’s having problems due to the subject blending in with the background.

If the subject is rather low-contrast, enters a dark area, etc. it is entirely possible that the Nikon D2x will switch focus points to a higher contrast area. I think that this has been well borne out by many actual users who are trying to photograph birds flying in a confusing background.

It is also true that many animals have colorations that tend to blend in with their environments. If they didn't their life spans would be much shorter. If an animal’s fur or feathers looks like grass and trees, how successful do you think any camera will be at picking it out from the background? Not very, I’am afraid. And the problem is compounded, I am afraid, by the big size of the AF sensors in the Nikon D2x. They exceed the edges of the AF sensor points in the viewfinder by at least 50% surrounding the sensor.

If you are focusing on a rapidly moving bird, colored like the background, and only covering part of a sensor, it is going to be VERY difficult, or impossible for the Nikon D2x to track it well. So, it can be hard to keep the subject in focus even using all the technology that Nikon can throw at it.

I think that the good results some are having in tracking a bird against an open sky, and less accurate tracking against trees and such shows that NO autofocus system can be as accurate as the human eye. The camera’s autofocus system is contrast based, and if contrast gets weak or everything is of similar contrast autofocus does not work well.

I once read an article about the first computer that they were able to program to use a video input to identify objects. They set up a series of objects like blocks, teacups, and such, on a rotating table and passed the objects one at a time in front of the camera. The computer was supposed to identify the object. They finally got the computer to identify an object ... the teacup. Everyone was very happy. The only problem was the computer had to study the object for TEN MINUTES to do so. Of course, technology has improved a thousand-fold since then.

The article interviewed the scientist conducting the artificial intelligence experiments, and asked him what the main problem was in getting the computer to recognize the object. He said, "Well, it has a hard time figuring out where the object ends and the background begins." Does that sound familiar?

Today, we have a computer (D2x) with a built-in lens, which is basically doing object tracking. But, sometimes it has a problem figuring out where the object ends and the background begins.

We all know that CONTRAST is king here. If we shoot birds flying against a blue sky, then, OF COURSE there will be a better response from the camera if a4 (Lock-On) is turned off. With a4 off, the camera/computer is simply not concerned with staying locked-on to a particular subject, and since you are giving it an easy to follow subject with high contrast, the camera will react faster with a4 turned off. Less processing is involved.

But, put that same subject in a low contrast environment, like a bird flying in front of trees, and whooeeee the processing requirements just exploded. In this case, a4 (Lock-On) may do better, since it’s smarter at staying with the subject. But, if the contrast between the subject and background is too low, even a4 won’t help!

The reason that Nikon lets us turn a4 off, is because in some instances we simply don't need it. YOU have to be the judge of when you need it and when you don't. There’s no magic here, just common sense. If the contrast between your subject and the background is not very good, NO COMPUTERIZED CAMERA CAN HANDLE what your eye EASILY can. There is no point in arguing about this. It’s simply the way computers work. They are very fast, but they are NOT as smart as a human brain. Anything that will sit and crunch math problems for hours with no complaint is not smart. And that’s what your camera’s computer is doing, processing math algorithms endlessly.

My advice to those who are having problems with autofocus is this. Examine your subject. If it looks a lot like the background, or is far enough away that it does not cover a sensor, your $5000 camera is going to have problems following it no matter what mode you put your autofocus in. That's why they left a MANUAL switch on our cameras.

Listen, the Nikon D2x and cousins have some of the best autofocus technology in the world. They’ve added all sorts of little improvements like Predictive Tracking and Lock-On, but they all have SERIOUS limitations in low-contrast environments.

YOU know this, but it’s great fun to complain and whine and feel sorry for ourselves. (I am including myself in this!) Maybe the D3x or D5x will have enough processing power to track a bird by the contrast between its eyeball and beak. In the meantime, we may have to help our cameras focus. (GASP!) It’s a partnership. If you spent $10,000 for your camera, it still would not focus and track low-contrast subjects very well. I think Nikon is to be commended for providing powerful technology that works MOST of the time. No one else is doing it better for the money.

Use the technology when it works well, and when it doesn't...turn it off and use your eye. How did we all survive without autofocus for so many years?