Possible configurations

AF Switch (next to the lens mount)

Autofocus – CSM 02

AF-area mode – CSM 03

AE-L/AF-L (AEFL) button (next to the viewfinder, on the right) – CSM 15

AE Lock – CSM 16

Usage

"Prosumer camera"

AF

AF-S

Single area

* I have used this mode almost exclusively from the 1^st day I purchased the camera, and suits my needs well.

AE Lock only

* The camera locks exposure whenever this button is pressed. Auto focus activation remains at the default, that is by half-pressing the shutter button.

* Before I became accustomed to the pros and cons of the various settings, I used this value, which allowed me to lock exposure by keeping this button depressed.

+ Release bttn (On)

* I'm not too sure what the factory setting was for this CSM, but with this value chosen, half-pressing the shutter button does 2 things – it activates and locks AF, and also calculates and locks exposure.

* Pressing either the AEFL button, or half-pressing the shutter button will lock the exposure. Exposure will NOT be recalculated if you press the other button while keeping the first button pressed. There is no "higher" precedence or priority assigned to either button where exposure locking is concerned.

Variation #1 – AE and AF calculated / set on different portions of the scene

1)       Set exposure by composing the scene, then pressing the AEFL button – this locks the exposure

2)       While keeping the AEFL button pressed, focus on the subject by pointing the active AF bracket at it, then press the shutter button half-way. The camera autofocuses and locks on the subject.

3)       At this point, you're pressing 2 buttons. Recompose the frame as in Step 1, then press the shutter button all the way. This captures the shot.

Disadvantages

• Not convenient to use AF-C in tandem with recomposition. The reason is the only way to focus on a subject is to press the shutter button halfway, and when you recompose, the active AF bracket would just pick up another subject

Variation #2 – AE and AF calculated / set on the same portion of the scene

1)       Select an AF bracket. Usually the center AF bracket is used for this variation. If the subject to be focused happens to fall on one of the other AF brackets, you can use those brackets, but please see the disadvantages of this method below.

2)       Place the AF bracket on the subject, half-press the shutter to lock focus and exposure, then press all the way. If you're in a hurry, just fully press the shutter button all the way in one smooth action

Disadvantages

• I have found that with my Sigma 18-50mm lens set at 18mm, AF accuracy is very poor in very low-light situations if you use any of the AF brackets other than the center one, and then attempt to AF using that bracket. The lens tends to go all the way out to infinity. At 50mm the accuracy is vastly improved. I have not verified if AF-C would show any improvement. It is for this reason that I use the center bracket almost exclusively now, due to it's higher accuracy. Unfortunately, the use of the center bracket doesn't allow for easy AF-Lock, AE-Lock and recomposition, which is why I don't use this configuration anymore.

Continuous AE, with option to lock exposure (settings are the same as for "Prosumer Cam", except for AE-Lock – CSM 16

AF

AF-S

Single area

AE Lock only

AE-L button (Off)

* This is a curious value, which gives added exposure-setting flexibility in the D70 compared to other prosumer cams (well, at least in the case of the Nikon Coolpixes)

* If this value is chosen, half-pressing the shutter button does only 1 thing, and that is to activate and lock AF. Exposure is NOT locked. The only way to lock exposure is to press the AEFL button

In my opinion, I think this combination offers much more flexibility than the "Prosumer Cam" combination, because both variations of usage documented for that combination can be used here!

In addition …

Variation #3

1)       Place the AF bracket on the subject, half-press the shutter to lock focus only, then recompose. If you're in P, S or A modes, you will notice that values for Shutter Speed &/or Aperture will continuously change as you recompose, the degree of which is subject to the variation in lighting and whether the camera is on Auto ISO. I can't emphasize this enough – half-pressing the shutter button locks focus only, NOT exposure. If you want the exposure to be locked at any time, just press and hold the AEFL button. When you're ready to take the picture, press the shutter button all the way down. This feature would work great in situations where the subject is stationary, but the lighting conditions keep changing very quickly, for example in pubs / discos / stage performances or outdoors, if the sun keeps appearing from and disappearing behind moving clouds.

Continuous AF and AE, with option to lock exposure

AF

AF-C

Single area

AE Lock only

AE-L button (Off)

I'll come right out and say it – this setting does not allow for the traditional approach of locking focus on a subject, then recompose. The reason is due to the use of AF-C and also because as long as the shutter button is half-pressed, the camera will continuously focus the lens.

Which is one reason why I don't use this setting.

Still …

What 's good about this configuration is that you're able to, with a single-finger, half-press the shutter button, aim at your subject which is on the move, and track the subject. As long as the center bracket is on the subject, the camera's focus will cling on to it. BTW, it's best to use the center bracket on account of its higher accuracy. The other AF brackets can be used if the lighting conditions are fine, and the subject has high contrast.

Setting CSM 16 to AE-L button (Off) also means that the camera continuously recalculates exposure if the lighting conditions change, even while the shutter button is half-pressed.

When you're ready to capture the picture, just press the shutter button all the way down. One practical application of this configuration is if you're tracking a mobile bug at a close distance, or a racing car, for example, and if it's OK to have the subject in the center of the frame – this setting is then the Mother of All Convenient Settings – one finger's all that's required.

If you need to "lock" the focus and recompose, one workaround is to half-press the shutter, and then set the AF switch to M (manual) – don't forget to switch it back to AF once you're done.

Trap Focus

AF

AF-S

Single area

AF-ON

* This setting completely removes the AF capability from the shutter button. It means that to activate AF one actually needs to, and can only press this button. Interesting possibilities arises with this setting, and is something that is difficult to appreciate initially, since the majority of cameras on the market do not offer this option.

Either the + Release bttn (On) or AE-L button (Off) setting can be used (please refer to the notes for the ealier configuration on the distinction between the two, however, see the next point)

* Trap focus emphasizes the AF aspect of image capture, not AE, so any setting can be used – it's entirely up to you. However, because the AEFL button has now been set to AF-ON, you effectively cannot lock exposure if you set this value to AE-L (Off) – please bear this in mind.

This configuration was brought to light by Thom Hogan, and discussed in this thread:

http://forums.dpreview.com/forums/read.asp?forum=1034&message=9479603

Essentially the word "trap" simply means that one prefocuses the camera to a certain distance by pointing the center bracket at an object, pressing the AEFL button to activate AF, then releasing that button. Point the camera at another part of the scene (to gain an understanding of this feature, point at a subject which is farther or nearer than the original subject that you focused on), press the shutter button all the way down and hold it down, and what you'll notice is that the camera doesn't initially capture the image! Well, with the shutter button still held down, move toward or away from the subject, and the camera will fire the shutter only when the subject is at the same distance as the subject you initially focused on.

That took more words to explain than necessary, so, try it out for yourself! Those who like this feature say that it makes AF at macro distances quicker, by prefocusing on a subject at the desired approximate distance, say, one's finger held 6 inches away from a macro lens, then moving closer to bug on a flower, for instance, and the shutter will fire when the lens comes to, well, 6 inches away from the bug – virtually solves the problem of AF-hunting which happens all too often when focusing at macro distances.

Again, do try this out for yourself!

My all-time favourite setting

AF

AF-C

* This means the lens will contune to be focused until the AF button is released

Single area

* I have yet to test the usability of other modes such as Dynamic Area or Closest Subject

AF-ON

* In addition to the points made above, we need to be aware of the impact of using this setting in combination with AF-C. Pressing this button down will activate the Autofocus mechanism, and as long as this button remains depressed, the camera will continue to autofocus. To stop, or effcetively "lock" the focus, release the button.

+ Release bttn (On)

* Based on the notes for this setting under the "Trap Focus" configuration, choosing this value is a no-brainer for me.

So, why is this my favourite setting?

Because, it caters for both advanced and basic usage of the camera.

The basics first

Ever tried handing your D70 to someone else to take a photo, especially if that someone else is a tourist holding a point-and-shoot camera, or for that matter, any non-D70 camera? It's apparent that one doesn't have all the time in the world to explain to that person how to focus and compose the shot, correct?

Well, this is what I do. I stand at a spot, point the center AF bracket at an approximate location where I will be standing to have my photo taken, press the AEFL button until I see the AF confirmation light come on in the viewfinder (no beep when AF-C is used, unfortunately), release the button, recompose, take a test picture to see if the exposure comes out right (remember that the exposure is continuously calculated until the moment the shutter button is half-way down whereupon the exposure is locked), if not satisified, adjust the EV up or down, retake, if satisfied, smile at the tourist and say "… Miss / Mam / Sir, hi! Would you mind taking a picture for me? It's really easy, just stand right over here where I'm standing, and I'll stand over there, and all you have to do is take the picture by pressing this shutter button here – everything's been setup real nice already, if it's not too much trouble, please include the entire Sequoaia tree behind me in the picture – thanks so much! …"

Hmmm, was everything really set up so nicely? Yes. Because the focus is already set when you pointed, pressed the AEFL button, and then released it, which means that we don't have to worry about AF being activated when the tourist presses the shutter, (s)he could be pointing the center AF bracket anywhere, it doesn't matter – the camera does not activate AF when the shutter button is pressed – beautiful. We do have to take care of exposure though, so it's normally best to set exposure mode to Matrix or Center-Weighted, take a test pic, and adjust EV if necessary – you would have included the Sequoia tree in your composition, and hopefully, the tourist would just do as you requested and include that same Sequoia tree. If you need to lock exposure, then it's down to using your favourite M mode.

What about advanced usage?

Let my wife, Kellie, tell you about advanced usage. We were at an ostrich farm, where they let you ride on an ostrich for a few rounds. My wife said she'd like to take some photographs of me. I was thinking, hmmm, take a picture of me – on a moving ostrich? How's she gonna AF (she hasn't tried AF-C before)? What about exposure? What about … well, with any of the other configurations, it would have been difficult to teach her. But with this combo, it was … Honey, can you see the center AF bracket? Yes? Well, just keep that pointed at any part the ostrich's or my body, and hold down this (AEFL) button down – this causes the camera to continue to automatically adjust focus – yeah – do you feel the lens focusing when you point at different objects – OK, now whenever you feel like taking a pic, just press the shutter button all the way down, then you may release the shutter button, but don't release the (AEFL) button, just keep it held down. With any luck I'll survive the ride and the ostrich won't trample on me (OK, I made that one up). Guess how the pics turned out? I couldn't have done better myself – sharp and focused. She did accidentally activate one of the other AF brackets, so it's probably wise to lock the AF point using the AF lock slider switch first.

What about this sequence (1) Focus and lock focus (2) Exposure locked on a different portion of the scene (3) Recompose (4) Shoot the picture? This is how I would do it à (1) Point the AF bracket at the subject, activate AF by pressing the AEFL button, release it (focus is "locked", and this is the greatest part J, take your hand off the camera, reach for your coffee, have a sip, set the cup back down, hand back to the camera (2) Point the camera at a portion of the scene to set exposure, and press the shutter button half-way down (remember that pressing the shutter will have no effect on AF now), (3) Recompose, and (4) Shoot by pressing the shutter button all the way down.

The AF-C mode works very well for macros of active bugs too. And should work well for sports.

Just remember: Release the AEFL button once focus has been achieved (little green AF light in the viewfinder) and before you recompose, otherwise the AF might grab some other point. A little practice with this configuration, and you're all set.

Do this often enough and you'll probably understand why this configuration is my favourite.