July 16, 2018, 12:37:52 AM

Author Topic: Use autofocus or depend upon DOF in basketball videos?  (Read 1914 times)

stevelee

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Use autofocus or depend upon DOF in basketball videos?
« on: May 05, 2018, 04:18:07 PM »
Next month it will be time for my annual project of shooting some video at after-hours pick-up basketball games during the nearby college's boy's basketball camps. After the campers are through for the day, the main court in the arena is taken over by counselors and others around for the summer for some informal games. Returning players on the team, incoming freshmen, alumni who are playing professionally in Europe, sometimes a guy or two from another school, and an occasional prospect participate. It's been a few years since our guy in the NBA came back and brought his little brother who was playing at Duke, but he's been busy with championships and such more recently.

I have an appreciative audience in other parts of the country who can't get here. For the most part they are interested in the freshmen and sometimes a prospect, but it is always good to see alumni back on the court. The audience is not fussy about technical quality, but I try to do the best I can. I treat it as a learning experience, and I usually use my most recent equipment so I can practice on it and learn how to use it for video. In the past I have used an S95, S120, T3i, 4K on my iPhone 6S, and last year the G7X II.

So this year I will be shooting FF for the first time, and will have less tolerance for focus. I plan to use the 6D2 with the 24-105 STM. I might play around with autofocus options after I think I have enough basic footage. But mainly this is a social occasion for at least one or two of the nights, when I'm hanging out with a few other fans I don't see much of outside basketball season. So I don't want to be paying lot of attention to the camera.

I did the diagram below to approximate the distances. If I sit midcourt about 36 feet away, it looks like my shooting distances will be between 36 and 105 feet, and rarely if ever at either extreme. There is plenty of light, though the colors are a little off because they don't turn on the good TV lights for this. For my angle of view, I'll want to see most of the half court where the ball is. My diagram suggests that I will use between 50mm and 70mm on the zoom about all the time.

I'm inclined to use manual focus. I could have it track faces, but I don't know how well that will work at that distance, and the shooter could be facing away from me. Regular autofocus would probably be OK, but does risk that some footage might get lost from focus hunting. DOF calculators tell me that at f/5.6 60mm, if I focus about 70 ft. away, everything from about 35 feet to ∞ should be in focus, with a circle of confusion 0.03mm.

The rim of the basket will be around 75 feet away, so if I focus on that or a bit closer, I should have enough margin of error just to leave the focus on manual.

Any comments or suggestions or disagreements with my reasoning? Any suggestions for when I'm trying out other alternatives and learning more about the equipment?

As for color balance, the lights probably have gaps in the spectrum, but I've not had any trouble with flickering in the past. The mostly empty seats across from me, and thus the background, are red, and so auto white balance tries to compensate by making the light look even more greenish. I'm thinking of trying a custom balance from shooting a white piece of paper or a gray card. Is that a good idea? Does the video on the camera support that, as the manual seems to me to suggest?


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Use autofocus or depend upon DOF in basketball videos?
« on: May 05, 2018, 04:18:07 PM »

Mt Spokane Photography

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Re: Use autofocus or depend upon DOF in basketball videos?
« Reply #1 on: May 06, 2018, 01:22:51 AM »
You can use a wide angle such that you see half the court and let the DOF take care of it.  If you want to zoom in on a individual like they do on television, focus is important.

If you have a camera with dpaf, autofocus is pretty good, but watch out for the aperture changing and stepping the brightness up or down.  That can happen when zooming, because the lighting will change.

If you are happy watching a video without closeups, no AF should work, and you should lock the aperture and shutter speed as well.

sanj

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Re: Use autofocus or depend upon DOF in basketball videos?
« Reply #2 on: May 06, 2018, 02:16:40 AM »
Why would you not use auto focus? I would.

You concerned about camera not tracking or your technique? I would turn on servo focus, use point focus and get a lot of sharp focus photos. You will be at F4. No need to stress.

stevelee

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Re: Use autofocus or depend upon DOF in basketball videos?
« Reply #3 on: May 06, 2018, 02:00:37 PM »
You can use a wide angle such that you see half the court and let the DOF take care of it.  If you want to zoom in on a individual like they do on television, focus is important.

If you have a camera with dpaf, autofocus is pretty good, but watch out for the aperture changing and stepping the brightness up or down.  That can happen when zooming, because the lighting will change.

If you are happy watching a video without closeups, no AF should work, and you should lock the aperture and shutter speed as well.

Yes, I don't particularly want or need closeups. I want to show what is going on all around and on shots show the shooter and the trajectory of the ball to the basket as well as some of the defenders. If I want a little tighter composition, I can do that in editing, so I won't play with the zoom very much if any. Final output doesn't need to be more than 720p, and I can enlarge the 1080p original by 150% without it getting blocky. (With the iPhone, I shot 4K and output to 720p to compensate for the wide-angle view. It looked surprisingly good.) The lighting is even and consistent enough that I don't think fussy exposure changes will be a problem. They never have been. At 60fps I trust the camera would choose 1/120 and adjust aperture and ISO accordingly.

My experience with the 6D2 and the STM lens has been that autofocus is excellent and fast for stills. I should probably trust the autofocus the first night of shooting, and if it does some hunting, I can just edit that out. I usually come up with about 15 minutes of highlights for each evening I shoot.

DSP121

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Re: Use autofocus or depend upon DOF in basketball videos?
« Reply #4 on: June 15, 2018, 01:44:20 AM »
Both actually, depending on the situation!

stevelee

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Re: Use autofocus or depend upon DOF in basketball videos?
« Reply #5 on: June 15, 2018, 05:05:12 PM »
Both actually, depending on the situation!

I’ve tried both this week. On Tuesday I used autofocus. It didn’t look bad, but I could see that other things were in better focus than the players. I guess they are too far away for face tracking to kick in. Perhaps there are better settings than the ones I used.

On Wednesday I used manual focus. Once I set the zoom to something between 35 and 40mm for the angle of view I want, I focused on the rim of the basket. I was about the same distance from both baskets, but confirmed visually that both were in focus. I used the OVF rather than magnifying live view since I don’t have reading glasses along. The players came out looking sharper.

I turned on the image stabilizer, and that worked really well, even when I coughed. I got a flicker warning, so I turned on the compensation for that. I shot at 60 FPS in case I wanted to do some slow motion.

They don’t turn on the arena’s TV lights. There is plenty of light, but the colors never look quite right in my videos. Last year I shot with the G7X II and the color seemed worse than usual. So I tried taking a photo of a piece of paper in the light and using it for custom white balance. That made everything too orange and too saturated. So I went back to AWB. I think there must be gaps in the spectrum of the lights. I’m not great at color grading in FCP X, on top of that, but I did save a set of color and exposure settings as a preset.

Three of the Charlotte Hornets showed up to play on Tuesday night. They were the darkest of the African-Americans on the court, and two of them were dressed all in black and the third wore a black shirt. The corner scoreboards have a bright lighted white area that fools the camera into under exposing. Once I posted the edited version on YouTube, it looked a lot worse. Their software seems to get fooled even more than the camera. If I knew what I was doing and had time for making tests, manual settings all around would be the way to go.

So Wednesday night I used 2/3 stop exposure correction with AWB and auto exposure. That gave me a lot more to work with in FCP X, and results were better. It still looked bad after YouTube mangling. There was a possible recruit playing who wore bright orange shoes. On YouTube they look pink.

The challenges of this little project have made it a good way to learn to use new camera equipment each year. Fortunately I have an eager audience who don’t care about technical quality, so I can experiment. They mostly want to see how the incoming freshmen stack up and the returning players have continued to progress. Watching them on the court with alumni who are pros in Europe and even occasional NBA players is a lot of fun. And I try not to let shooting video get too much in the way of my watching the play and socializing with other fans. Then I edit to try to make something watchable for fans who live out of the area.

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Re: Use autofocus or depend upon DOF in basketball videos?
« Reply #5 on: June 15, 2018, 05:05:12 PM »