billroach2717

I'd appreciate help understanding this. I had believed that when using BBF, you left the camera set to servo mode. That way you could just push and release focus button for stationary subjects. For moving subjects you would just keep your finger on the BBF button.

Today I was shooting in a darker environment and my camera would not focus while using Servo. A friend suggested I switch to single shot and viola the camera began to focus.

Can someone help me understand why this is. And which mode I should be using.

Thanks so much.

CHG_CANON Loc: the Windy City

You should always be in Servo. Others can guess why the camera would not focus in your dark situation. I have it sometimes. I just scout for something of contrast in the neighborhood of where I want the focus (nearest to the desired subject), obtain focus there, and release BBF and recompose on the desired subject.

Longshadow Loc: Audubon, PA, United States

If I have AI Servo set and release the back button, does the focus stop (lock) at the last focus?

billroach2717

Thanks so much. That affirms what I thought. I appreciate this forum and I often find your particular comments very clear and helpful.

billroach2717

Yes, that is correct. Thanks.

Longshadow Loc: Audubon, PA, United States

Howard5252 Loc: New York / Florida (now)

Steve Perry on BBF
https://www.youtube.com/watch?v=FzqQskGoURE

gvarner Loc: Central Oregon Coast

"Available dark" is always a problem for Auto focusing. Use manual instead.

cschonwalder

Hold on and let's clarify. Steve Perry shows BBF setup to be AF-C. Folks in this discussion reference his videos but say to use AF-S. I've been on AF-C for years, and when I release the BBF (AF-on with D4), it seems to lock just like I want. So, does BBF work with both AF-C and AF-S? If there is a difference, please give a detailed explanation. Thanks!

gvarner Loc: Central Oregon Coast

The problem is shooting in poor light. I’ve never experienced that with AF-C and BBF.

aphelps Loc: Central Ohio

What is Servo mode?

SuperflyTNT Loc: Manassas VA

Don’t let the S confuse you. On a Nikon AF-C is servo mode. As long as you press the back button it will continue focusing. As soon as you let go it locks, essentially giving you both options with one setting.

lautenk2

In Nikonese you might say AF-C (a.k.a. Continuous-servo AF mode)

amfoto1 Loc: San Jose, Calif. USA

Just to clarify, Canon and Nikon have different names for the focus modes...

Canon AI Servo and Nikon AF-C are essentially the same thing.... focus will run continuously as long as you maintain pressure on the back button or a half-press of the shutter release button (if set up to work that way... BBF removes AF control from the shutter release button). This mode is used for moving subjects, but can also be used for stationary subjects (in a somewhat limited way if BBF is NOT used). Focus can be maintained when the subject moves.

Canon One Shot and Nikon AF-S are essentially the same thing. Focus will only run until it's achieved, then will stop and "lock". It can be done with either back button or shutter button half-press. This mode can usually only be used with stationary subjects. If the subject moves after the focus has been achieved, it doesn't update and correct for any change in the distance until the user causes the camera to re-focus. When a subject is moving and distance between them and the camera are changing, you cannot re-focus quickly enough and virtually all images taken will be a little to a lot mis-focused.

One of the primary benefits of BBF is that it allows the camera to be left in AI Servo (or AF-C) mode for both moving and stationary subjects, so that you can be "ready for anything" and don't have to pause to change camera settings, probably missing some shots, should a subject start or stop moving.

Normally both continuous focus and single shot focus should perform the same. There should be no difference in sensitivity under any particular lighting condition. The difference the original poster saw were likely due to other factors, such as using a more sensitive type of AF point or focusing upon an edge or higher contrast area after switching modes. Both forms of focus... continuous and single shot... use the same phase detection sensors in the same way. It's simply not possible for there to be a difference in performance, without some other factor causing it.

One difference is that in single shot focus mode you can get "focus confirmation". The way it's confirmed might differ a bit in different manufacturers' cameras, from model to model of one brand, or even depending upon how the user has it set up. For example, some Canon flash the AF point itself red to indicated focus has been achieved. Most Canon DSLRs also have a green LED in the viewfinder that lights up to confirm when One Shot focus has been achieved. Further, on many Canon DSLRs you have the option for the camera to give an audible "beep" to confirm focus is achieved.

Because continuous focus is continuous, there is no "focus confirmation". If you stop and think about it, there can't be. Some Canon show "AF" in the viewfinder or flash AF points to indicate that AF is working, but this isn't "confirmation" that it's been achieved. (Note: I keep the "beep" enabled on my cameras because it immediately alerts me if I'm in the wrong mode for moving subjects, not that I often use One Shot. I am always surprised how many peoples' cameras I hear beeping when we're photographing sporting events. That means their cameras are in the wrong mode and that most of their images of moving subjects will be mis-focused. And I bet a lot of them will blame the camera, rather realizing and correcting their own mistake!)

It takes a bit of practice to work without focus confirmation. But, it can be done. You have to develop a "feel" for how long your camera and lens typically take to focus under various conditions and rely upon what you see in the viewfinder to tell you, as best it can, whether or not focus has been achieved. Some viewfinders are bigger, brighter and better for this than others. It also can help to get in the habit of starting focus while tracking the subject for a short time, before taking the shot. That's more easily done with subjects that are moving predictably and subjects you're most familiar with.

Finally, some cameras have adjustments you can make in the menu, that might help. For example, my cameras have several settings where I can prioritize focus versus shutter release. Basically this lets me set the camera so that it will delay shutter release until focus has been achieved. I set that strongly biased toward focus accuracy, because I have little use for mis-focused images. Someone like a photojournalist might make the opposite setting, to insure they don't miss a fleeting moment waiting for focus to be achieved. But I rarely see any sort of delay in spite of my settings, largely because a lot of my shooting is with fast-focusing lenses (Canon's USM or "ultrasonic"... similar to Nikon's AF-S or "silent wave"), and because I tend to use only a single AF point, work at keeping that on target and usually start focus well in advance of tripping the shutter to take a shot, allowing plenty of time for AF to "do it's thing".

A common cause of missed focus is using too many AF points. The more points that are enabled, the greater the chance the camera will focus somewhere other than you wanted. While there are times that multiple points are necessary and helpful, they have to be used carefully. For example, if a bird is flying past you and you've got multiple AF points enabled, the camera is likely to focus on the closest wing tip, rather than the bird's body, head or eye. (Some mirrorless cameras have face and eye focus... some DSLRs do too, but only in Live View, which isn't practical for a lot of shooting and may be slower than viewfinder-based AF.)

I try to use as few AF points as possible.... often only a single one. This is more work for me, because I have to keep it right where I want the camera and lens to focus.

Another thing that can help... stop your lens down when you don't need max apertures and strong background blur effects. A stop or two smaller increases depth of field, which can efffectively hide minor focus errors. I really love large aperture "fast" lenses with all that gorgeous glass... But they are the hardest ones to focus accurately. They're the most demanding and the least forgiving! They can make truly wonderful images, though!

foggypreacher Loc: Dickinson, Texas

If I remember correctly, Perry uses AF-C most of the time because he is a wildlife photographer and does not want to miss a shot changing from AF-S to -C. I leave mine in -S most of the time because of the type of photos I take most. However, if I am concerned about action I will move to -C. If I am in error, I apologize in advance.