Demonstration of low-light center point AF with 6D and 85mm 1.8 wide open

Started Apr 9, 2014 | Discussions thread
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Timbukto Veteran Member • Posts: 4,988
Demonstration of low-light center point AF with 6D and 85mm 1.8 wide open

I honestly don't like most of these pictures because I pretty much botched the photos for my own daughter (while actually taking decent pictures of other kids for test photos). Problem was using flash and having too uneven subject vs ambient lighting when really natural low-light was the way to go. However when I look back of the sequence of photos and pay attention to file numbers, I'm pretty much quite impressed with the spot on AF rate I can get in low-light so I thought I'd share a gallery of frames to at least demonstrate some 6D AF. I probably deleted frames in between that I felt were pointless test shots or may have been misfocused. Regardless we do have motion and a low light particular the center-point AF sensor can only 'see' at f2.8 as well, and I'm shooting near MFD wide open at f1.8. No $2k 70-200 at f2.8 with extra AF chips or anything just the simple, cheap, and old 85 1.8.

No exposure tweak in post, a demonstration of light levels with the exposure settings shown as well as demonstrating motion blur of kids in chair when I am not panning.

From the first shot of the ride attendant this is the 3rd frame (i.e. I must have tossed two frames in between for whatever reason).

1 frame tossed between the last

Next frame, no deletes since last

Next frame, testing longer distance shot wide open

Next frame, my daughter ride is inactive

Ride still inactive, but I'm putting on my flash...boy what a mistake.

DOF is thin enough where hands are OOF, but face/eyes are in DOF, and this is not the closest shot...According to AF layout there is no way I could have used AF points to focus this so it must have been focus and recompose which we all know just doesn't work wide open!

Next frame, ride starts, flash is used, focus is nailed + red eye

Tossed 2 frames, you can see based on cable angle that things are swinging now.

100% crop, you can still see despite flash freezing, motion blur evident in steel cables. This is wide open closer to MFD than infinity on an 85mm 1.8 in low light. In AI-Servo mode the camera does not turn on or need AF illumination assistance from the flash. Lens is plenty sharp enough to show I should have wiped her face better after she was still recovering from cold and must have drunken milk recently.

Although shooting center point for movement is limiting, megapixels are plentiful and my biggest faults were the flash and not getting a better vantage point for composition, the initial shots of the other kids were actually better and if I improved upon those, I would have been happier regardless of getting tack sharp focused shots of my daughter. Many camera's even with far more advanced AF modules tend not to offer as good performance off center in low light with bright apertures. They may be quite good for f2.8 telephoto zooms of subjects at a farther distance, but IMO shooting f1.8 of motion at much closer distances in low-light would tax *any* system. As for mirrorless alternatives, I already know the Fuji's 56 1.2, or MFT's 43 1.2 would not be capable of nailing as many of these types of shots (I've tried with a 45 1.8). Sony's A6000 and 50mm 1.8 probably is questionable as well in low light. I do not know if the DF or D610 would perform as well without renting or trying it in similar situations...but they get enough complaints that I have my doubts.

6D is obviously still not for daylight sports where other wider coverage AF systems with higher FPS are better suited, but it offers such a good center AF point that with practice you can get a lot out of it for low light candids, etc. Besides focus and recompose there are plenty of situations where you can try to zone focus based on focusing on other objects you know will lie in the same plane of focus as your subject, etc. And when I'm *not* trying to track motion wide open near MFD in low light levels on Halloween, I find no issues in having wide variation of subject focus across the frame.

 Timbukto's gear list:Timbukto's gear list
Canon EOS M Canon EF 200mm f/2.8L II USM Canon EF-M 22mm f/2 STM
Canon EOS 6D Nikon D610 Nikon Df Sony a6000
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