D200 Continuous AF on catwalk

[imagestreet]

I just tried a catwalk show for the first time under what I think

was tungsten lighting. Selecting tungsten WB settings gave very

cold colour balance so I picked flourescent WB as this seemed a bit

warmer. I was shooting on a brand new D200 with a 70-200 Vibration

Reduction lens at f2.8 ISO 400 on Continuous AF and I was very

disappointed with the results. Almost every shot was blurred (1 in

20 hit rate with over 600 shots). All of the shots where the models

were walking were clearly out of focus. Continuous AF just didn't

seem to judge the focus correctly. Also the metering didn't seem to

be able to cope with the lighting with either over or underexposure

occuring. An example is attached(this is one of the better ones!)

 

Any idea what the problem is? I think it is one of or a combination

of the following:

 

(1) DOF issue - her legs seem sharper then her obviously out of

focus face. This is confusing as even at 2.8 I would have expected

DOF to pick up her features as well as they are not that far off the

plane of focus. Anyway most of the other shots were so blurred

there was nothing in focus at all.

 

(2) Technique - could be, but I was balancing a 70-200 VR lens wide

open using my knee as a support and at shutter speeds between 125

and 500th sec I feel I should have got a higher % hit rate(based on

previous use of the 70-200 VR on a D100 shooting at lower shutter

speeds at a wedding!)

 

(3) The continuous AF setting doesn't work well under flourescent

light settings (when the lighting is tungsten), doesn't work well

with the 70-200 VR lens, or doesn't work well on catwalk models at

walking pace

 

Anyone else suffered this problem? I've been happy with the D200 in

all other respects so far (ie. daylight static portraits).<div></div>

[imagestreet]

Closeup of centre model<div></div>

[chris_leck]

Did you give the AF time to lock-in? In AF-C, the shutter will fire regardless of focus status.

 

Was VR turned on? It takes a moment to settle-in when first activated. If your hands are steady, it may be better to shoot this without VR.

 

Which AF sensor or group was activated? Did you have 'closest subject priority' turned on?

 

Did you try any shots slightly stopped-down?

 

Was the lighting level constant? If so, you can spot-meter a face and shoot manual.

 

I haven't had the best results under artificial lighting either, especially when it is mixed. A gray card or similar is helpful to fix WB after the fact. An ExpoDisc can help with setting a custom WB up front.

[michael_bradtke]

Ok the lights that they are using are quartz halogen and burn much hotter then tungsten. The last concert I videoed had a lot of the moving lights like you have in the background of your shot. We WB by them and it came up around 5800K. That's much closer to daylight then tungsten (3200K)

I would have done a custom WB for them

You are sitting with the camera balanced on your knee shooting up.

So there could be as much as three feet between your point of focus and her face. (Depending on how tall she is)

 

Itﾒs not a shutter speed issue or nothing would be sharp Itﾒs a point of focus, DOF issue. That's why you focus on the eye when you are shooting portraits. It makes sure the face is in focus.

 

I honestly think it was more OE (Operator Error) then camera error.

 

Michael

[lex_jenkins]

Practice, practice, practice.

 

I've had my D2H for about 10 months. Its autofocus capabilities are one of the primary reasons I bought the thing. But I still routinely experiment with the various options to determine which is most appropriate for a particular situation.

 

I don't know about the D200 but the D2H allows choosing between focus priority and release priority. I typically choose release priority because I'm usually banging away at the maximum framerate when using AF-C mode, so I know that at least some frames will be in focus. But focus priority will ensure that the camera fires only when focus is locked.

 

Keep in mind that the camera decides when focus is locked based on the active sensor. If the active sensor is on the subject's clothing, the face may be out of focus. Group Dynamic AF and "Dynamic Area AF with closest subject priority" (that's a mouthful) are great for unpredictable, rapid movement, but less precise than the single sensor options. You might also find out whether the camera offers choices between "closest subject" and "center area". All of these options can strongly influence how effective AF is in a given situation.

 

The more I look at great action photography in sports and wildlife magazines, the more I'm convinced that the best photographers are those who have mastered all the permutations of autofocus. I'm sure some are still relying on manual focus, but I'll bet most of 'em are making the best possible use of AF.

[fistral]

It may be that the AF has not locked on properly, quite common when background colours merge eg, she is wearing similar colour clothes to face tones, as the models are moving it makes the AF lock more tricky, so I agree that the eyes would have been a good focus point.

I feel from studying the picture that the lines on the front steps appear to show a narrow DOF, yet the large light? in the background appears to be sharper? but I would say f2.8 may have helped get the speed up for handheld but may have been a bit narrow for front to back sharpness.

On the White Balance, I would have shot in RAW for such an event as you can easily alter the WB afterwards in your conversion, and lets be honest it`s one less thing for you to worry about at the time of shooting.

[bernard_frank]

I don't see how the WB settings could have any influence on AF, except for very low

lighting conditions, which doesn't seem to be the case. But then it's not an issue with WB.

 

Now, before accusing the camera AF system, I suggest you revise your technique (how do

you maintain half-pressure on the shutter release, or do you use the AF button, are you

sure you select the right AF point, or groups, etc...), your AF settings (dynamic or not,

closest subject priority or not, etc...) Nikon AF is highly sophisticated, and can sometimes

be tricky.

[ky2]

If the models are moving, then your AF may not be able to cope with the very thin DOF you're imposing on the shot with your long lens, shot wide-open. Retry this with a higher ISO, or possible add some strobe light of your own.

[imagestreet]

Some very interesting and useful pointers here thanks. I think that poor DOF management or focus zone issues is probably indeed the issue for the shot attached. For the other 500 odd rejects I think that I need to revisit the manual and experiment with different AF modes. I did use a SB800 flash for some of the later shots (see example) - what confused me was that even these were out of focus! The SB800 apparently releases pre-flashes prior to discharge to calculate the flash exposure - this might have allowed sufficient time for the model to move out of focus. I didn't actually try to focus on the model's faces as this would have led to rather boring compositions (I was hoping that DOF would be sufficient to cover the head). Do pro catwalk photographers use manual or prefocus on a spot on the catwalk to catch movement?<div></div>

[imagestreet]

Crop demonstrating out of focus face

[bruce_rubenstein___nyc]

For people walking, I never use Continuous AF. The AF is fast enough in single shot mode to lock on and almost instantly fire the shutter. In your first shot the models on the side are in focus. I don't know how you have the AF configured, but it didn't focus on the center model. (If you were in wide area and you had closest subject turned on, that would explain it.) From what I've read, Continuous AF works better with Lock On turned off. (I think it is on by default with the D200). If you want to make sure that the thing you want is in focus, use all 11 AF sensors (instead of the wide mode) and put a sensor on the thing you want in focus. FWIW, my D200 had not trouble nailing the focus (on the license plate) of a moving with a 18-70 lens, which is no ball of focus fire, in AF single mode.

[andy a.]

If you're using Af-C, you may want to check some the custom settings.

 

For example:

custom setting A1 - are you using plain fps priority, or fps+af?

custom setting A5 - lock on - this defaults to normal, you could try none. That will reduce the delay between refocuses.

 

These might not be any help, but they are worth a try.

[marcofrancardi]

For what I'm seeing the answer is easy: YOU were focussed on her legs, not her face nor her clothes! ;-)

[philippe_c.]

So the problem is a leg fetish ;o)

[sean_allen1]

Try turning off VR, you're shooting fast enough shutters where you don't really need it and VR can slow down focus locks. That's the first thing I'd do, then I'd try all the other suggestions.

[nino]

I went out to test my new D200 AF on some fast moving traffic the other day in late afternoon light with an 80-200 f2.8 set at around f4 and a shutter speed of 1/500sec; and was delighted with the results. I shot all the images at 200mm and tracked down to the cars number plates and got close enough to fill 1/2 the frame with it. I would say that 75 of 100 images were tack sharp. About 70% better than my d70 ever was.