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09-16-2012, 10:45 AM   #1
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Anecdote: Auto-Focus Nightmare

I was doing a family shoot of a couple with their baby. I had the perfect location and time of day. There was an ever so pleasant, meandering brook with a magnificent tree on one side of it extending its branches all the way over to the opposite side. On that other side, in the background, the sun was setting over a wonderful combination of undulating rock formations and historic buildings which featured a colonial period church and ruinous adobe structure. The sky had just the right amount of clouds to catch the varying orange and yellow light but still leave patches of rich blue. Right next to the brook, also in the background but only a few feet away, was a weathered fence with twisty-tangly vines running up and along parts of it creating a series of perforations for the low sun to pierce through. I had so many fantastic options of how to frame the shot, it was like a dream come true. I knew ahead of time I'd be shooting during the golden hour and would want to use my shoot-through umbrella to balance the exposure between the family in the foreground and the brighter background, which to my pleasure had many colorful features that were being beautifully lit up by the sun that was about to dip under the horizon. The shoot-through umbrella was perfect for this job because while being used mostly to light up the faces of the family it would also drop some needed light around them without creating a harsh and unnatural separation line between the shadowy and lit areas as the sharp fall off from a more directional light source, such as softbox, especially a gridded one, would cause. The effect was going to be such that the light from the strobe in the umbrella would appear to be a blend of ambient light and sunlight reflecting off the water. I had the couple standing in the water, about up to their shins, holding the baby but I could move them and myself in a whole slew of ways allowing me to frame any number of compelling compositions. The family could also sit up on the river's edge leaving their feet dangling. Simply put, the setting was magical and I was prepared.

The tree was large and its many sweeping branches cast a wide shady footprint. This, combined with the sunlight quickly dropping, made for some pretty dark subjects to try to focus on. I got the family in a spot and in a loose pose that I liked, framed up the shot and fired off a few. Something was wrong though. I wasn't getting focus confirmation. I chimped right away, as I always do with the first few shots to make sure the exposure is where I want it, and the exposure looked great but sure enough the focus was way off. I was shooting at about 24mm, f/8, ISO 200, and 1/120 shutter speed, so too shallow depth of field, motion blur or noise would not be presenting any kind of issue to mess with the sharpness of my image. I framed up my shot in the viewfinder again and tried locking focus. Again, I couldn't get confirmation. I was getting worried but didn't want to reveal this to the couple. I have them reposition themselves while casually talking to them, telling them how great they look, how wonderful the lighting is, and how I plan to take shots of them in a few different positions in order to take full advantage of all the great background features. They are happy and really feeling how good the location is, it was the furthest thing from the kind of location and light that only a photographer would appreciate. To cover my bases, before composing the next shot how I actually want it, I try focusing on the much better lit and more contrasty background. That doesn't work any better, and it's not where I want my focus to be anyway. I can't get focus confirmation. The focus is going back and forth hunting all over the place.

I'm using my hitherto trusty K-5 and DA*16-50mm. For a second I worry that I've been hit by the focus failure that has plagued other owners of this DA* lens. But that wouldn't make sense as the focus motor was clearly still doing it's thing. I didn't want to change my lens because I'm standing in the water as well, so using the weather sealed lens is giving me a little bit of reassurance in case I lose my footing or something. Then I remember, I'd turned off the AF assist beam the other night because I didn't want it shining right in the faces of my friends who I was trying to take candids of in a dimly lit pub. So I go into the camera menu and activate the AF assist beam. "Problem solved," I'm thinking. I bring the camera back up to my eye, give the couple a little bit of direction, compose a nice frame, press the shutter half way down and... damn it! The same problem still. Was my camera broke? What the hell was going on? I haven't ever had much trouble focusing in low light before with my K-5 and even then, I'd still get confirmation though not always on the right spot.

I'm looking at the back of my camera, and really starting to worry. I spout out a couple of BS reassuring words to the couple so they don't also get worried. Then I look over at my wife, whose helping keep the lightstand stable, and whisper that the camera isn't focusing. She flashes this serious look at me then mutters, "you have to at least get one good shot". I mutter back, "I know, I'm trying". I look at the couple and with a forced smile say, "just changing some settings here". My brain is running in circles and I ask myself, "what am I doing or not doing that I should be?" Then I think, "well, manual focus is always an option". I say to hell with the AF, bring the viewfinder back up to my eye, get a good composition, and do my damndest to manual focus. It's not easy to manual focus at 24mm on APS-C, nearly six feet away from your subject, on a fairly short focus throw zoom lens, with less than perfect vision. After taking the shot and flipping the camera over to peak at the LCD, the difficulty of what I'm trying to do is confirmed by the blurry image in front of me. Despite being barefoot and almost knee deep in very cool brook water, I'm starting to sweat bullets. I'm at the verge of meltdown. I don't have a backup camera to use. By this point I'm already needing to drag the shutter at 1/90 to keep the background from being too dark and will have to drop it even slower if I want to better my chances of getting a sharp image by going with a smaller aperture. About my only option is to try changing lenses. I'm really hating the idea of putting my FA31 on the camera but know that I'll have better luck at manual focusing with it.

Just as I'm about to step over to the riverside to dig in my camera bag, I wake up to find myself in my small dark bedroom feeling clammy and a little jittery. Oh god, it was all a nightmare. I lay there scrolling through the images still fresh in my mind and was truly upset that none of them were in focus. I couldn't shake the idea that if I could just find one shot on the SD card in my mind that was in focus then I would be okay and have something to feel good about.

Maybe I have a problem. An unhealthy photography obsession, perhaps. Well, I see two obvious lessons to take away from this nightmare experience. One, I need to keep working on my manual focus technique to always have on hand as a poor man's backup. And two, I clearly need another camera body and probably even another lens, you know, just in case.

09-16-2012, 11:10 AM   #2
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My experience is that AF-C is not useful for still subjects. I'm convinced that AF-S is more reliable, although I don't do a lot of photography of moving subjects and rarely have a need for AF-C. I can see why it would be useful, but when I use AF-S, the lens takes a few movements to get the focus right and it stops there instead of continuing to look for focus points. It's very reliable, however you need to confirm that it has chosen the right subject.

I like to use the AF-IF button for focusing so the shutter button won't interfere with your composition.
09-16-2012, 12:54 PM   #3
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Solution 1: Use live view. A K5 may be able to lock focus in those circumstances, and if it does it will be spot-on.
Solution 2: Use PDAF with AF-C and select one appropiate focus point , use lo for drive and keep the shutter button down for at least 3-4 shots at a time. Your first shot will be blur but everywhone that follows will be perfect or nearly perfect since the camera re-focuses between shots.
This is a mysterious and little known behaviour in Pentax dslr:s through generations. I've always wondered what keeps them from making the first focusing run correctly since it manages every consequtive one.
The main problem with this method is that your flash goes off with the first frame. Keeping your finger on the trigger gives it a chance to catch up at one of the later ones.
09-16-2012, 02:19 PM   #4
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QuoteOriginally posted by Kameraten Quote
Solution 1: Use live view. A K5 may be able to lock focus in those circumstances, and if it does it will be spot-on.
Solution 2: Use PDAF with AF-C and select one appropiate focus point , use lo for drive and keep the shutter button down for at least 3-4 shots at a time. Your first shot will be blur but everywhone that follows will be perfect or nearly perfect since the camera re-focuses between shots.
This is a mysterious and little known behaviour in Pentax dslr:s through generations. I've always wondered what keeps them from making the first focusing run correctly since it manages every consequtive one.
The main problem with this method is that your flash goes off with the first frame. Keeping your finger on the trigger gives it a chance to catch up at one of the later ones.
Regarding #1 -- I find with slow lenses or low light the K-5 in live view will often "lock" but be focused on nothing at all. Can't trust it.

I never have the trouble others seem to with the PDAF though -- the only thing is I make sure it does focus rather than just confirming it is already focused with a beep but no lens movement -- I always focus on something much closer or farther away than my subject to start. Since it shows you which point it is picking (although I usually use select) and you can see in the viewfinder what is in focus (I use S-type screen) I've just never had trouble hitting the spot I want.

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