Autofocus

OK WP gurus, I need some help!

I've got a problem. I use manual focus. Always. Every time I try to use autofocus I have to fight to get the camera to do what I want. I end up going postal and go back to MF!

Yet, some people here NEVER use manual focus and they get awesome shots.

So how do you do it ???

What camera settings?

What techniques?

And how do you know you've got the shot nailed - or are you happy to miss a few, c'est la vie ?

Leander

I never use manual focus. The focus mode I use depends a lot on what I want to do. If I am doing wide angle, I use the multipoint focus. If I have a specific feature I want to focus on, I use spot focus on the center point.

You aim the center point on the feature, half press the shutter release to lock the focus, recompose, and then full press to take the image. Sometimes if I anticipate a subject moving, say, from right to left, I will use the left point, etc.

When I am doing macro with my 100mm+macromate, the autofocus is way too twitchy. In that case, I use the Canon custom function 4-1 to map the * button to focus lock. Then I lock on something that is approximately the correct distance and then move the whole rig in and out to fine tune to focus. Since the focal depth is only a few mm, this works pretty well.

Like Steve, I never use manual focus. My eyes just aren't good enough. I need glasses to read or see anything close, but can't dive with glasses or I wouldn't be able to see most things.

I have been using a Nikon D70 for a couple of years and just started using a D300. On the D70 I only had the choice of a single focus point (from a choice of 5) but with the D300 I get up to 51. So far I have still only used one of the 51. I always have the camera on AF-C. I tried AF-S once, but the camera will not refocus after it has already acquired focus so that if there is any surge, or the subject moves, focus will be lost.

use only the center point for maximum focus speed and controlling where the camera is focusing

set up the camera (if possible) so focus and shutter release are independently controlled

use a lens that autofocuses reasonably well - my Canon 100 Macro does not

if the lens autofocuses well, then the Canon AI servo works pretty well on moving subjects

in low light, use a flash with modeling light or a flashlight on a bracket to provide enough light for focusing

I should point out that the AquaView viewfinder magnifier on my Aquatica housing makes judging the quality of the focus MUCH easier. It was expensive, but worth every penny.

My technique on small critters is fairly standard. I have my camera set to use the desired focus point. My camera is set to AI Servo focus mode, which causes the lens to continually focus as I move closer to or further from my subject. From a distance (where I can easily find the subject in the frame), I place the portion of the subject that I want in sharpest focus (e.g. the eye, or rhinophore) at the active focus point. Once focus is established, I slowly move towards the subject, keeping the desired focus point positioned. My camera continues to keep that point in sharp focus. Once I have reached the distance where the composition is what I desired, I release the shutter. I find this method to be far more successful at yielding sharp photos than manually focussing, rocking in and out, or than getting focus lock and recomposing. The other benefit I have found is that I can take the first photo from further away, then try a second photo closer, and then a third photo from quite close. With skittish critters I will at least get the first photo, and often all three shots since they seem to become used to it.

I've got a problem. I use manual focus. Always. Every time I try to use autofocus I have to fight to get the camera to do what I want. I end up going postal and go back to MF!

Use a powerful focus light with AF - often, the camera can't "see" well enough in low light to achieve AF.

Shoot at the highest F-stop you can, to maximize DOF.

read the previous posts for additional tips.

I almost always use AF. But the mode depends a great deal on the subject, the lens, the camera, the conditions and the composition. It is tough to make hard and fast rules with so many variables.

For example I generally shoot my D2X with AFC, diamond pattern type 2 (closest subject priority) AF when shooting wide angle and fish portraits. However I have tried this system on the D200 and it does not work well at all. The D200 AF is not good enough for this method. Annoyingly the D300 and D3 do not have this option in their AF settings - although I was very impressed with the 3D tracking. And that is comparing the current/recent top Nikons!

The most important thing about AF is to help it. Learn what it likes to lock on to and then aim those sensors at what it likes.

Also get to know your camera in the conditions you dive, with the lenses you use and the subjects you favour - and see which AF modes work best.

I'd love to say "do this and everything will be great..." but I don't think there is a simple answer to this one. To many variables - perhaps the biggest of which is personal differences in shooting style.

Alex

Lots of great advice so far. I am like most, I almost always use AF, and I tend to set a specific focus area so I know where it is and once I achieve focus, I can quickly re-frame my shot if required.

A lot of course will depend on your specific setup and the environment you're shooting in as well. If you're in water with relatively little light, focusing is going to be more difficult and having a focusing light might help.

Lenses with wider maximum aperatures will also be a benefit to autofocus as more light allowed into the sensors, the better.

I have an article on autofocusing here:

http://www.photosafariindia.com/articles.html

Scroll down and click on "Art of Autofocus"

This is primarily written for land photography, for shooting things like birds in flight and so on, but the concepts also apply to underwater photography.

First practice on land. That will give you the tools you need to handle virtually any AF situation. Then apply as you see fit for underwater shooting.

For topsides shooting, I always autofocus using the "*" button on the back of the camera (what used to be CF4-1/3 on the earlier Canons). For underwater WA, however, I often switch to One Shot Focus and shutter-activated AF, relying on "lock focus/recompose" - this works well with non-moving objects. The reason for this is that I find focusing with the * key to be a little less than ergonomically comfortable with my rig.

Point is - you need to figure out what exactly the AF problem is, and then apply some of the tips from that article to solving it. Feel free to PM me if you have any questions.

Regards,

Vandit

My style is like Canuck in that I get the camera focused early and then move in, taking shots continuously. I set my D200 to focus priority so it won't fire when not in focus. I use a single center focus point and don't worry about repositioning the camera. I simply crop later. This way I usually get multiple shots of skittish critters from varying distances, usually with the eye well focused.

When I spot the critter I set my F/stop and place the strobe accordingly based on what I consider the perfect shooting distance. Then I try to move in. I tend to keep my single DS-125 well out to the side ( 2-8" arms) to provide a wide angle of strobe coverage. The Ds-125 is using Ikelite iTTL which appears very accurate for macro. The Ds-125 also recycles quite quickly which allows me to click off a huge number of shots as I move in.

In summary, I am trying to get lucky. I am hoping that one of the zillion shots I take (all with the same strobe angle, F/stop and shutter but NOT the same camera position) will turn out to rival professional shots. Naturally, if I get to the proper distance an position and the critter is still there I will vary everything just like a professional. However, that usually only happens with Flamingo Tongues (;

If the light is very poor I simply turn on the Ds-125's targeting light. Typically the D200 won't get a focus lock in very low light until the edge of the targeting light lights the subject.

The advantage of this approach, as Canuck says, it that I will usually get SOME picture of the critter with the eye in focus though not maybe the perfect picture. I think a lot of one's personal shooting style depends on what constitutes a great picture. I am an amateur. If I took my best shots (The ones where I got lucky) and placed them in a collection with a professional like Alex, my pictures would belong but they would not be among the best pictures in that collection. Alex's best would always be better than my best.

Another variable not usually discussed is how do you intend to display your shots? In my case I either print on an Epson R2400 or display them on a Panasonic 65"1080P plasma. (I have a 1080P screen for my computer) Very different pictures work for the different media. The flatscreen displays billions of colors at 2K by 1K pixels. The color depth makes relatively complicated backgrounds quite pleasing. Not so on the printer. Single subjects with black or dark blue backgrounds look best.

Someone who shoots for a magazine or for a web-based photo gallery might have very different criteria. Also, someone shooting to win a contest might have very different standards.

Regards,

Tom

Lndr, if you're happy with MF, why change? Julie does almost everything in MF and she gets awesome shots. I tend to use AF a bit more, but i mix and match between AF and MF. I can usually tell beforehand if AF is going to work or not, it's just a matter of getting to know how your camera and lens behave like Alex said as well.

For moving subjects I usually try AF first, and generally that works fine, but the D2x is particularly good at AF so YMMV. For stationary subjects, or when Im looking for a very specific shot, i use AF to get close, and then move my housing to get fine focus. My shutter release does not do focus, so it doesnt unintentionally refocus.

Just practice with it, you should get the hang of it soon enough.

Cor

Lndr, if you're happy with MF, why change?

Cor, I'd starting to play with some teleconverters, which will mean I am dependent on AF until I work out which route to take with them and then come up with the MF options.

Plus I do sometimes feel that I miss stuff because of relying on MF, but maybe I'd miss just as much because of it ??? besides as a geek I have to make the tech work for me ;P

With TCs i always work as follows.. AF until im close to the image i want, then move the housing to fine focus. AF with TCs will make your head explode from anger

Cor

I never use manual focus. The focus mode I use depends a lot on what I want to do.

very true, i'm sure like all things there's no one setting for all situations

If I have a specific feature I want to focus on, I use spot focus on the center point.

Steve, Andrew & others. (Maybe because I'm a control freak) but i find the centre focus point is never where I want the focus to be, and esp when the camera is set up for wide with stobes out wide I find it quite difficult to move the rig with the shutter button half depressed. I'm going to try to use the lock button more, but I have small hands (its a girl thing!)

Its interesting that some folks swear by AFS and others AFC ... I'm more comfortable with AFS and use it topside. The camera and I never seem to agree of AFC mode - I missed so many shots when I tried that on my new 105 last year

With TCs i always work as follows.. AF until im close to the image i want, then move the housing to fine focus. AF with TCs will make your head explode from anger

 

Cor

ha ... that's what its done without a TC!

Would you say that for wide angle or fisheye lens?

I'd love to say "do this and everything will be great..." but I don't think there is a simple answer to this one. To many variables - perhaps the biggest of which is personal differences in shooting style.

Thanks Alex, I'm hoping like anything there are some better places to start than others. It interesting that you say the closest mode sucks is not good in the d200 - because I had tried it with my 10.5mm and wasn't impressed. I have gone back to multipoint as this has given me better results when a close subject fills the frame.

Still I find the point of focus tends to be the edge of the foreground subject (where obviously the camera is finding better contrast) and I if I'm using a big aperture in (darker) temperate conditions that can mean the very front of the subject isn't sharpest ?

The other day I was playing with AF. Now this is not a great shot, but in terms of AF nearly everyone of my shots ended up being crispest on the edge of the gorgonia.

What settings might have made my d200 do its best in this scenario?

another situation is where I am using both hands to control moving the housing and I have a moving subject.

again I'm trying AF, and it is in Jervis Bay ... so lots of crud in the water and not the best light or vis ...

Thanks for all the posts so far ... I'm trying to digest it all and come up with a plan of attack for this week

cheers

I use MF exclusively when I use teleconverters, except perhaps when I am racked all the way in or out and need to get to the other end. In that case, I just hold down the focus button until I feel the lens hit the other end (I can feel this through the handles).

During shooting: As I move in, I focus out. As I move out, I focus in. A large viewfinder will allow you to judge critical focus on the eye.

If you don't have a large viewfinder, I suggest using a combination of AF and moving in and out (per Cor's method). I'd rather do this than try MF with a small viewfinder.

With the exception of getting in real close on macro shots, where I’ll switch to manual focus if required to get in tighter, I most always use AF with excellent results. I most always use Canon One Shot AF mode using the center AF point to achieve focus lock. A good viewfinder like the AquaView is of great assistance. A good aiming light such as the Fix Light HG 20 DX is important when working with macro shots.

With TCs i always work as follows.. AF until im close to the image i want, then move the housing to fine focus. AF with TCs will make your head explode from anger

 

Cor

Cor-

Not sure what you mean by move to fine focus? Are you saying you switch to manual and then move the camera in or out until you get the exact focus you want?