Daylight focusing issues and solutions

Photophun

So there I was, hot tallented model with sunlight streaming through some dense treas in the back ground. My model standing in the shade with the reflection from a window to highlight her hair. Add in some fill flash with a soft box and whos feeling like they nailed the shot, ya me. So I get home and from that shoot half my shots are out of focus. I was using a single point that was basically nailed to the models forehead/eyes and shooting at 2.8 to 3.5 at 7 meters distance.

Whats the deal with how Nikon cameras decide what is considered in focus and how do you get around the problem of a bright background throwing off the accuracy of the cameras focus.

FYI I shot 2.8 and then did extra shots at 5.6 just in case my artsy whim didn't pan out. Yay

Msmoto

Provide camera body, lens, settings, shooting mode, focus program settings and someone might be able to help.

Thanks

Photophun

D7100 24-70 2.8 & 50 1.4 Manual mode with single point nailed to the models head. There was a fair amount of back light but no direct light hitting the subject.

JJ_SO

@Photophun why should somebody take the time to guess, how those photos in question look like? Can you post a picture which shows the chosen focus point and gives the idea of how much backlight you're talking about? Was it AF-S or AF-C, what Msmoto already asked? Did you adjust AF before or not? My post with questions already is longer than your reply to Msmoto. That shows while you're asking for help, you still provide not enough information. Just imagine to explain to somebody who wasn't there...

Photophun

D7100 is a AF-C camera and it was more of a general question. Wish I could show you a photo but the client was 17 and I cant release any photos with out the moms auth. At that point the photo would be edited or not given auth to use.

Think of it as more of a general question as I have no idea how a Nikon camera determines what is in focus and what could confuse it.

Paperman

You can start by selecting AF-S ... Camera keeps searching for focus at AF-C.

And the release mode ... Was the shutter set to release priorty or focus priorty ? ( Release priorty might be the default @ AF-C ) . At release priorty, camera will shoot even though focus is not acquired.

You can't expect to find get more help without sample photos as others have correctly indicated ... But you can check yourself where the AF point was at those shots - most editing softwares will show it if the photo is not touched.

Photophun

No worries then and thanks for trying to help.

JJ_SO

...Think of it as more of a general question as I have no idea how a Nikon camera determines what is in focus and what could confuse it.

Actually, I don't know either: I don't know how different the contrast has to be, which kind of lines or edges the sensors need and what the cam decides, when you aim at forehead/eyes. Meaning, I could not explain to somebody who never had a DSLR in his/her hands, which kind of objects should be aimed at and at which point.

Sometimes those rectangle markings for focus points are too huge and cover different 3-dimensional objects. To which of them I should direct the cam?

I would expect sharpness given your distances and apertures. Often I guessed the wrong point and used an aperture too wide open. Also, I made better expereinces by using AF-C all the time shooting without tripod, because not only the object is moving, I'm too. I know, AF-C is not the most precise mode - but it handles the fact that my body isn't a tripod better than AF-S, at least wide open. Best thing ist shoot more and get a feeling/experience for focuspoints and substututional objects (with better contrast, clearer lines, but at the same distance as the subject you wnat to photograph.

sevencrossing

Just a suggestion

before doing the real shoot

fire off some test shots and use the magnifier in preview

with a D800 I found AUTO focus is better than spot ( don't know why it just seems to be so)

More and more I am using auto setting settings ( I have been a photographer for 50 years and grew up the manual everything era )

Golf007sd

@Photophun: A couple things for you to consider...not sure of your skill lever so please don't get offended if what I recommend sound elementary 1) Use Spot metering when your subject is in the shad with harsh light in the background. 2) Consider getting a good Light meter (Sekonic L-758DR), 3) USE AF-S /w single AF point. 4) A reflector will help directing some of light coming from behind to your models face...an assistant will come handy in such a case. If you cannot get one a wireless shutter release one ( I use RFN-4s by SMDV...for your D7000 you will need the ). 5) Pop some fill-flash if you don't want to use a reflector 5) Use a tripod in taking the shot.

Good luck and happy shooting....cheers.

FlowtographyBerlin

1) Use Spot metering 2) Consider getting a good Light meter 4) A reflector will help get a wireless shutter release 5) Pop some fill-flash if you don't want to use a reflector

Golf, I think the TO was asking about focussing issues, not light metering issues. Although there is a connection if the light is too low, I think @Photophun was happy with the light setup, from what I understand from the description.

JJ_SO

...and it's Sekonic for people who want to google it.

I too don't think, the TO was calling for gear battle and as well, I think spotmetering is as long no solution as one doesn't know how to use it. Fill flash was already mentioned and a tripod doesn't help focusing in first place although it could be worth a sidelook to the shutter times. Blurred images don't have to be caused by focussing.

No offense, @Golf007sd, but first you were talking about skills, afterwards recommending things to buy. to me, these two subjects, skill and gear, are not coupled together. without skills all gear is useless.

Ade

A strong backlight will significantly reduce the subject's contrast especially in the presence of flare. All AF systems (even phase-detect ones) depend on good contrast and will struggle in strong backlight regardless of the AF mode used.

Using a lens hood may help reduce flare. If there's sufficient DoF (with smaller apertures), then maybe put the focus point on the edge of the face or some other high-contrast edge instead of trying to focus on the eyes.

But with very strong backlight and shallow DoF, manual focusing might be the only sensible option.

Photophun

Ade, your reply sounds consistent with what another friend of mine said.

FB I will be packing a flashlight as I usually don't have an assistant.

So from what I can tell, the camera decides what is in focus by. A: Magic B: Infrared C: Contrast Who cares, i am an expert on lenses.

I noticed there was a large number of photos that the center of the depth of field was approximately 1 ft behind the subjects face that I was spot metering on. I have taken my camera and lenses to Nikon and they did not need any adjustments. My feeling is a low contrast scenario with indirect glare from the side may confuse the camera and cause it to degrade the accuracy of its focuse selection.

In post, the photos were washed out and I had to darken the shadow details. This would make me think I was metering incorrectly but I was metering in spot mode. Oh, and to or not to use a light meter is a topic/debate for a different thred. I metered for the dress of my subject in manual mode, did a test shot, added fill flash as needed.

JJ_SO

I never had problems with backlight or sidelight focusing. I had problems when there was only unstructured or low contrast surfaces to focus on.

And as I said, spot metering without being able to interprete the measurements can cause problems, too. Mind you, the exposure meter is adjusted to give a proper result to a graycard with 18% light reflection. Every subject brighter or darker than this value will be shown under- or overexposed in the picture. If you just point the spot meter to a caucasian face, not very tanned, you need to correct the value +1.

SquamishPhoto

As Ade mentioned, shading is key. However, as I've discovered on a number of backlit shoots it helps to have an assistant block the sun with a white board and leave enough room for you to shoot under it. Thats how I got the shot below.


D800 • 200mm f2 @ f2 • 1/320 • ISO 100

Photophun

I think you guys nailed it. In post i had to darken my shadows by 1.5 EV just to get the image from washed out to clear. Lost some crispness but the client wont be printing more than 8/10 so life is good and its a good problem to be aware of.

I picked up a camera 9 months ago and am now shooting portraits 2 to 3 times a week and spending time in the west coast mountains shooting landscape, stars, glaciers, ect. This is so addictive and what I thought was a masterful shot 6 months ago I wouldnt now dare show to anyone. LOL

fatrascal

For me in harsh backlite pictures, getting correct exposure has been more of an issue than focusing. Nothing that cant be fixed in postprocessing. Then again I shoot sports so clients are not so nit-picky, as long as you capture the moment.

Nice shot Squmish, like the light in hair. A bit strong on top and at the back for me, but does not bother me as much as the in-focus leaves on her right. May be its intentionally so?

TaoTeJared

This may help explain AF - All Nikon DSLRs have "Active AF system" where infrared light is bounced off of the subject and back into your camera. This explains it fully.

As for bright backgrounds throwing off accuracy, I have never experienced that and I shoot with strong bright backgrounds all the time. Maybe in extreme conditions but we are talking exposures of f/11 w/ 1/4000 at ISO 100. I have had really reflective surfaces throw the focus off like mirrored/highly polished outdoor artwork and windows. If light was coming straight into the lens (purposely creating ghosting) that could do it but it would have to be close to the same angle as the focus point.

My guess is that you didn't have some setting set to the best selection for that type of shooting. Paperman has some great suggestions - release priority or focus priority and as others say use AF-S especially if you are reframing the shot. The things to look at is the Focus lock/release with shutter, AF assist... basically check the whole AF menu list. It is good to have the manual at hand to understand the choices.

D800 - ISO 100 - f/5.6 @ 1/1600 - 2 speed lights (Box left slightly higher, Bare flash right 6 feet high, reflector low front right.) This was taken mid morning on an extremely bright and hot day.

Msmoto

There seems to be some focusing issues when a single line is selected vs. a pattern such as an eyelash. My D4 will sometimes hunt when looking only at a pattern which is like a simple line.

Ade

@TTJ:

In the Nikon implementation, speedlight active AF is only enabled in low-light situations (as opposed to low-contrast situations). So active AF is actually disabled when outside in bright daylight conditions.

TaoTeJared

In practice Ade, my Sb-900s will trigger it when a subject is strongly backlit and other situations where I never expected it. They are smart systems, they know when they need to light up. On my shot above it was lighting the little dude up every once in awhile.

Ade

Well the morning rain just stopped here in Chicago and with the sun coming out I just tried an outdoor backlight test.

Although it's not yet very bright out, I can't get the speedlight AF beam to trigger even once in backlight, regardless of where I was pointing the lens. It always reverts to phase detect, and fails to focus when pointed to a low contrast subject rather than turning on the AF beam.

I can only conclude that speedlight AF doesn't seem reliable in outdoor/daylight backlight situations, if it works at all.

If anyone would like to try the same test: 1) attach speedlight with camera in AF-S mode, center focus point, and verify indoors that the AF beam turns on; then, 2) take the camera outdoors, point it to backlight and see if you can get the AF beam to consistently turn on (or in my case, turn on even once).

Further testing indoors, I also observed something interesting:

With all the room lights on and window shade open, I pointed to camera to the white ceiling and the camera failed to focus (AF beam did not turn on) -- as you'd expect, there's nothing on the ceiling to focus on. But if I turn all the lights off, the AF beam triggers and the camera was able to lock at the featureless ceiling.

So in this case, the camera can focus when it's dark, but can't focus when it's bright (opposite of normal situation). This test seems to confirm that speedlight AF beam gets disabled when there's adequate light for phase detect AF.

Feel free to try for yourself.

Edit: forgot to add, SB-900 on D800e. Might be different with other speedlight/camera combination, I guess.

Ade

Hmm, further testing makes me question whether Nikon cameras have "Active AF" at all, or if the speedlight AF beam is simply an assist light for the (passive) phase-detect AF.

Nasim Mansurov (the author of TTJ's link) usually knows what he's talking about; but so far I can't confirm via testing that Active AF is actually implemented. (I can't definitely rule it out either). I'll try to email him (and maybe Thom Hogan as he's an expert re: Nikon flashes) to see if they have any further info.

(Sorry Photophun to stray a bit from the topic).

TaoTeJared

Hummm. I need to dig deeper into what settings I have set up in camera & flash. I think there is something in the flash setting as well. (I have SB900 & D800) The blank wall example is why I set it up to fire all the time since it needs lines to snap focus. I set this stuff up and leave it when I have it working the way I want it too, so I forget all the settings.

I do know Nikon's is an active system. Always has been. I think phase detect is only for Live View and I assume video?

I have to get a job I'm finishing up out the door so maybe I have time to test it this evening to dig through it. Probably time to write the settings down as well .

FlowtographyBerlin

Hmm, further testing makes me question whether Nikon cameras have "Active AF" at all, or if the speedlight AF beam is simply an assist light for the (passive) phase-detect AF

It totally is. What else would it be? It projects a pattern (bars, actually) that helps the AF.

I do know Nikon's is an active system. Always has been. I think phase detect is only for Live View and I assume video?

You guys definitely know more on this stuff than me, but this would appear very strange to me. To my knowledge, active AF systems (as in: measuring the actual distance to something, this "something" being exactly the problem because it's not neccessarily what you wanna focus on) are totally old school. And most of all, the focus would work no matter what light you have. Which is exactly what it doesn't do, as you just confirmed with your tests. Nevertheless, active AF is not very accurate.

Maybe you guys are referring to phase detection vs. contrast detection? Because in Live View, the AF uses contrast detection.