Focus with Shutter or * [AF ON] button? -READ ME-

I thought this thread became a "sticky" about two years ago! How many pages did someone have to go back to ressurrect this topic? In any case, 4-1-2 fan.

apersson850 wrote in post #10155602
P mode doesn't cancel any custom functions. Green box does, just like CA.

Sorry, I meant green box - don't get to that end of the dial often.

Way back when .... I was using my 20D. I used the CF # 4 to get the focus control onto the * button.

Now I use my 40D most of the time but I can't understand when and how to use the AF ON button. And because I can't understand this I'm missing out on a lot of additional options.

I have read and reread the manual but I'm still lost. I'm hoping that some of you very smart Photographers. Will help me understand this.

Sometimes when somebody else explains something in a different way. It helps you to understand it.

Thanks.

I assume it's the same as my 7D, in standard form pressing AF will stop the focusing, or if like me you have it set to back button focus, it activates focusing, leaving the shutter to deal with the metering. It will be one of the custom functions to set that up, to behave the way your 20D did.

I'm sorry but I still don't understand. What are the steps I need to take in my 40D to achieve the same settings you get in the 20D when you use the CF # 4 to get the focus control onto the * button?

Please can some of you 40D users tell me how to set this up on my 40D?

Post # 6 express precisely what I need.


The following came from Post #6
"Teaching on Old Dog New tricks
Text Copyright and Photography Copyright Arthur Morris©


On a crisp fall afternoon, dozens of Sanderlings scurried frenetically in search of sand fleas and other tasty invertebrates that live in the wet sand along the deserted beach at the very edge of the Atlantic Ocean at Stone Harbor Point, New Jersey. Occasionally, they would stop for a few seconds to preen or simply to stare at the crashing waves.

I was seated (with a wet butt) behind my Gitzo 1548 Carbon Fiber tripod, working with the Canon EF 600mm f/4.0L super-telephoto lens and a Canon EOS 3 camera body. The EF 1.4X teleconverter yielded the 840mm-f/5.6 combination that is my everyday bird photography rig. Before I came to realize the many benefits of Custom Function 4 (CF4), available on all mid-range and high-end Canon EOS camera bodies, I would have faced the following dilemma: Should I work in AI Servo mode so that I could easily track the moving birds, or switch to One-Shot mode so that I could focus on a momentarily still Sanderling, recompose, and make the image?

By opting to utilize Custom Function 4, I had the best of both worlds. When activated, CF 4 transfers autofocus operation from the shutter button to the exposure lock button, the left of the two small buttons on the top right of the camera back. With autofocus set to AI Servo mode (for moving subjects), I simply activated autofocus with my right thumb to track a running or a foraging bird, or tapped the button once to focus on the eye of a stationary bird. In the latter instance, I would quickly recompose and make the image by fully depressing the shutter button. I was able to enjoy the benefits of both AI Servo AF and One-Shot AF without having to toggle back and forth (by pressing the AF button and turning the main dial). In addition, when photographing static subjects, I did not have to keep the shutter button depressed halfway as is customary when working in One-Shot AF mode.

When a Royal Tern flew by, it was a simple matter to frame the shot and activate AI Servo autofocus with my right thumb. To boot, I was able to pre-focus manually before engaging AF. This allows the photographer to drastically reduce the time of initial focus acquisition, and is especially helpful when attempting to do flight photography with the 600mm-lens/2X teleconverter combination. (Focus manually until the bird is relatively sharp, then engage AF by depressing the exposure lock button; thus, the system does not have to struggle to "see" the subject.)

Referring to the use of Custom Function 4 in "The Art of Bird Photography; The Complete Guide to Professional Field Techniques," I wrote, " Many photographers rave about this function, but I do not." And in public lectures and seminars I expressed disdain for CF 4 by stating that those attempting to use it would surely wind up on a psychiatrist’s couch. (I felt that they would become extremely confused when attempting to activate AF--is it the shutter button, or is it the exposure lock button? Is it the index finger, or is it the thumb?) But oh, how wrong I was. Today, when photographing perched birds or those on the ground, I activate CF-4 so that I am always ready to make either static portraits or images of the birds in motion.

For in-flight only photography situations, such as those that often arise at Bosque Del Apache NWR, Socorro, NM, or at the Venice Rookery, South Venice, FL, I find it easiest to set CF 4 to the default setting (0) so that autofocus is activated in the traditional manner, by depressing the shutter button halfway. Additionally, I am often afield with a big telephoto lens and one of Canon’s lightweight, hand-holdable flight lenses, either the EF 300mm f/4 L IS, the EF 100-400mm f/4.5-5.6L IS, or the "toy lens,� the EF 400mm f/5.6L. (FYI, the latter is still the world’s best for photographing birds in flight.) When I carry one of these lenses on a shoulder strap, mounted on a lightweight EOS A2 camera body, I always set CF 4 to the default setting, as these lenses are used almost exclusively to photograph birds in flight or in action. Thus, I simply depress the shutter button to activate AF. The body on my big tripod mounted super-telephoto is, however, set with CF-4 activated, as this lens is used primarily to make portraits of birds at rest. In reality, I do not have any problem switching between shutter button AF activation and exposure lock button AF activation as the shooting situation demands. And, I have not, as I once predicted--needed to undergo psychotherapy.

Though the owners of the newest Canon Super Telephoto Image Stabilizer Lenses have full time manual focus available, (hey--the folks at Canon Japan sometimes do read my product critiques!), they will still benefit from activating CF 4 when photographing perched or standing birds. They will then--as described previously--have the option of working in either AI Servo AF, or, effectively, in One-Shot AF, without having to keep the shutter button depressed halfway. To attain One-shot AF while utilizing CF 4, simply tap the exposure lock button to focus on the bird’s eye, then release the button, recompose, and shoot. As I said, the best of both worlds.

With EOS A2, Elan II, and 1N bodies, activate Custom Function 4 by toggling from CF 4-0 to CF 4-1. EOS 3 users may wish to note that there are two ways to activate CF-4, either by choosing CF 4-1, or CF 4-3. The former locks the exposure when the shutter button is depressed halfway after focus has been set, the latter yields real time exposure. I almost always choose the latter so that I need not keep the shutter button depressed to hold the exposure when photographing static subjects.

To Chuck Westfall, Canon technical representative, who has suggested for years that I give CF 4 a try, I say, "You were right. I was wrong, big time wrong. I wish I that I had listened to you sooner." I guess that you can teach an old dog new tricks. "

If you want the AF on the * button, you will need to change two Custom Functions. I'm not sure about the 40D but on my 1D3 they are C.Fn IV-1 to switch the AF to the AF ON button and then C.Fn IV-2 to switch the AF-ON function with the * button.

Make sure you read the descriptions of the various choices in IV-1 -- they give different results.

I'm a little confused. I have the 7D. I use the AF-ON button instead of the * button. Is there a difference?

I use the * button because, well, I'm used to it -- I have two bodies with no AF ON buttons so the habit is also to use the * with the body that does have the AF ON button.

Umm I just bought a 7d used (barely is 4 month old) but it is set up with the * doing the focusing......

How do set it back????

Thanks

I actually figured it out. By Clear All Custom Functions

I tried the AF-On button method and I didnt't like it. But mostly because of one reason: If AF is set to Ai-Servo I don't get any confirmation when focus is achieved (on 5d MarkII). Of course I could asign the Focus to the AF-On Button and set focus to One Shot. But this way I would lose the biggest advantage of asigning focus to the AF-Button: Instant switch between One Shot and Ai-Servo.

Or is there any workaround that I have overlooked?