Single AF verses Continuous AF Underwater

[peterbkk 110]

Single AF verses Continuous AF Underwater

 

I am just migrating to DSLR from Nikonos V. I have never used auto focus before, neither above or below water.

 

Can someone please advise me on the two main focus options: Single AF (S-AF) verses Continuous AF (C-AF) in underwater photography. I understand how they work but I'd like some suggestions on how to apply it best works underwater.

 

My gut feel tells me that, for most underwater photography, I would be better off with a standard setting of C-AF.

 

The C-AF should be applicable to long-range and mid-range fish shots where there is the potential of subject movement.

 

Is it also useful for macro shots where potential camera movements could move the focus point out of narrow depth-of-field range or will the auto-focus jump around too much to be useful?

 

What about diver shots if there is any current action or movement?

 

Is S-AF more applicable for wide-angle static reef and wreck shots when I want to tell the camera "focus on that object there"?

 

I am on the right track? Any tips and techniques gratefully received...

 

Regards

Peter

[MikeVeitch 0]

i use AF-C exclusively. i found i had a lot of trouble with AF-S as it would focus on particulate etc or not fire when i thought it was actually in focus....

 

got very frustrating to be sure, i switched to AFC after only a few dives.

[frogfish 5]

Same here. AF-S is fine some of the time, but it can be a problem in murky water. I routinely set the autofocus to AF-C, for pretty much all situations, macro and wide-angle.

[peterbkk 110]

Same here. AF-S is fine some of the time, but it can be a problem in murky water. I routinely set the autofocus to AF-C, for pretty much all situations, macro and wide-angle.

 

Thanks for the advice. I'll set my underwater settings to Continuous Auto Focus.

 

Regards

Peter

[derway 2]

I guess if you are going to keep the subject in the focus frame afc is ok.

 

But AFS is better, in clear water, for doing "half press - focus, recompose, then shoot'.

 

If you are using other than a single focus spot in the center of the frame, it may not be an issue.

[CeeDave 0]

Howdy,

 

I've used both:

 

On macro:

AF-S misses some shots

AF-C sometimes gives unfocussed shots

 

Me, I blast away with AF-C (dynamic area) on a 4GB card and review and reshoot if I must.

 

On WA:

I use AF-C, or the focus lock tricks discussed by Berkley White in a recent Fathoms mag. The AF/AE lock button rocks!

 

Chris

[scorpio_fish 5]

I use AF-S. I hate AF-C. Too many out of focus shots. To each his own. Try both. Choose the one that works best for you.

[expatdiver 0]

I also started with AF-S, but quickly switched to AF-C.

 

I found that AF-S would not lock, therefore you couldn't take a picture, even though you could see that the image was in focus.

 

If you still need single focus for composition, like CeeDave said, "the AF/AE lock button rocks."

[davidrodkeller 0]

Can someone please advise me on the two main focus options: Single AF (S-AF) verses Continuous AF (C-AF) in underwater photography. I understand how they work but I'd like some suggestions on how to apply it best works underwater.

I think AF-C is applicable to most close stuff, in particular skittish subjects like anemonefish, but there are some critters that I get more reliable focus with in either manual or AF-S, like pygmies or the small squat lobsters that you find in soft corals. AF-C in these cases always seems to bounce a bit. For wide angle I almost always use AF-S or manual, except in cases of human foreground subjects where the eye is critical to the image.

 

For me the bottom line is that, like diopters and color correcting filters, each type of focusing situation is special and requires the application of the right component, technique or capability. Filters and diopters have limited application, and so does any single focusing mode. Though I think AF-C has a broader range of application.

 

If you have been shooting nothing but manual until now, I suspect you will end up using all three types of focusing as they are applicable to your need. The "auto" modes will drive a person used to manual.....crazy

[Lionfish43 0]

I use AF-C 90% of the time for macro. For wide-angle I often use manual. What I do is: at the beginning of a dive I will set the camera on AF-S and focus on a subject about 1-1 1/2 ft away. Once I have the focus locked I use the MSC switch and set it to M (manual) and leave it there.

[davidrodkeller 0]

"the AF/AE lock button rocks."

I just use a half-push on my shutter to lock the focus. On occasion I use the AF/AE button topside, but since my exposures UW are manual and I don't need AE lock, the shutter is easier for me to lock focus with.

[CeeDave 0]

When I use it, I have the AF/AE on AF only, and set to AF-S. Then I focus on something at my target distance, and then either blast away (wide angle) or move the camera (macro). In the first case, it gets rid of time lag or possible failur for focus lock in dim settings, and in the second case it get rids of hunting. Berkeley White's Fathoms article addresses the first case ... and I think he's dead-on, especially when using huge (sharp) DOF lenses like the Nikon 16mm FE that he favors at f8 or so.

 

If I choose to re-range, I find a high-contrast target (like my yum-yum yellow fin against water) or my hand, and bump the AF lock button. Or even re-range on one shot, with the hope that it will reccur.

 

For me, it's much to do with style. I tend to "pre-visualize" shots and go after them. I am less concerned with flexibility (have yet to shoot a zoom UW). The AF lock is *ideal* for this style of shooting, and won't work as well for more spontaneous styles.

 

Goodbye, focus-lag. Hello, a few more blurred shots. Your decision.

 

All the best,

Chris

[peterbkk 110]

focus lock tricks discussed by Berkley White in a recent Fathoms mag. The AF/AE lock button rocks!

 

Can you please tell me which issue of Fathoms magazine. I will try and get a back-copy from the publisher.

 

Is "Fathoms" a magazine worth subscribing to? Most dive magazines seem to be pitched at the beginner diver.

 

Regards

Peter

[peterbkk 110]

When I use it, I have the AF/AE on AF only, and set to AF-S. Then I focus on something at my target distance, and then either blast away (wide angle) or move the camera (macro).

 

For a beginner to digital SLR (30 years of all-manual film cameras is hard to shake out of my head), can you please clarify the "AF/AE on AF only". Are you talking about the AF lock button? I thought that it was only active while it was pressed and held? Does it set the lens focus at whatever distance it focuses on and keeps it there until the lock button is pressed again or until the camera is switched off?

 

Would this be the same on the E-330? I guess I'll have to experiment and see.

 

My first experience last week with AF-C underwater was a bit hit and miss. Albeit the water was murky and everything was moving in a current. But, I would like an easy technique to fix the lens' focus distance and then adjust the camera-to-subject distance to control the focus point in the image. This is how the Nikonos worked best and it'll help me to take one more complexity out of the DSLR setup.

 

Regards

Peter

[Cerianthus 55]

that depends on the camera brand, you have to check the manual for that. The halfpressing of the shutter button and the ae button (the one for your thumb, that is mostly standard on "Keep this lighting") can both be programmed.

 

somehwere in the menu..

 

if you use AF-C, and have switched to AF-only, then you can stop and start AF by pushing that button (more or less what you want, I suppose)

 

Gerard

[peterbkk 110]

that depends on the camera brand, you have to check the manual for that. The halfpressing of the shutter button and the ae button (the one for your thumb, that is mostly standard on "Keep this lighting") can both be programmed.

 

somehwere in the menu..

 

Gerard

 

I have figured it out for my camera. At first it looks quite complicated but once you boil it down to what you want to do, it is not too bad. Fortunately "www.wrotniak.net" has a more logical explanation of the E-500 settings (similar to the E-330) than the Olympus manual.

 

On the E-330, you can save all the settings as two separate master settings, Reset 1 and Reset 2. So I can have one set for normal photography and one set for underwater.

 

In the underwater setting, I have now set the AF-S mode to only focus when the AFL button is pressed and to keep that focus distance setting until changed. This will enable me to set a focus and then move the camera until the subject is at that distance. This will be useful when the visibility is too poor for effective auto-focus. But I have left AF-C at its default setting to do continuous auto-focus from when the shutter is half-pressed until it is fully pressed. This would be useful when there is a lot of movement or when the subject is very clear and easy to auto-focus on. Switching between the AF-S and AF-C modes is quick and easy.

 

The biggest challenge will be remembering which mode I am in...

 

Regards

Peter

[CeeDave 0]

Can you please tell me which issue of Fathoms magazine. I will try and get a back-copy from the publisher.

 

Is "Fathoms" a magazine worth subscribing to? Most dive magazines seem to be pitched at the beginner diver.

 

Regards

Peter

 

I don't have the number here, but it was two issues ago. I'll try to remember to get the number when I get back home. I thnk Fathoms is quite good, with lush photo spreads and good info on *different* dive destinations (although it seems a bit more conventional lately, in my opinion). The writing style is quite different: irreverent, brash, often amusing, and sometimes irritating.

 

All the best,

Chris

[scubaboy1 0]

Can you please tell me which issue of Fathoms magazine. I will try and get a back-copy from the publisher.

 

Is "Fathoms" a magazine worth subscribing to? Most dive magazines seem to be pitched at the beginner diver.

 

Regards

Peter

 

 

It's issue no 17. www.fathomsmagazine.com

[peterbkk 110]

It's issue no 17. www.fathomsmagazine.com

 

Thank you. I'll see if they will include this back issue when I subscribe.

 

Regards

Peter

[davidrodkeller 0]

When I use it, I have the AF/AE on AF only, and set to AF-S. Then I focus on something at my target distance, and then either blast away (wide angle) or move the camera (macro). In the first case, it gets rid of time lag or possible failur for focus lock in dim settings, and in the second case it get rids of hunting. Berkeley White's Fathoms article addresses the first case ... and I think he's dead-on, especially when using huge (sharp) DOF lenses like the Nikon 16mm FE that he favors at f8 or so.

I guess it depends on what you are looking for. I am usually very disappointed in my shots that are not in focus on critical components of the image. Berks' shot of the tiger taking the bait shows a very soft eye. The composition is great, the balanced exposure super nice, but how much more of an impressive image would that have been with it tack-sharp at the eye?

 

Now I recognize that mag print isn't perfect and I certainly don't want to criticize anyone's work, particularly in this case, because I think Berkeley's's article was more about composition than it was about tack-sharp-focus anyway (the notion that pre-set focus allows one to concentrate on composition). But I think this shows that "in focus" from 2' to infinity doesn't mean tack sharp at the specific points many photographers determine to be mandatory to their satisfaction. The Nikonos 15 and 13, and Sea & Sea 15 were the only lenses that ever gave those results underwater, and all were water-contact.

 

Personally, outside of intended softness, I don't see any way around paying attention to critical focus. These hi-res sensors we use are simply harsh and unforgiving if we fail to do that correctly. And how do you manage critical focus unless you place critical focus, whether it's auto, manual or pre-set?