How do I film high shutter speeds in a gym?
 

I am sure this question will show my real lack of knowledge when it comes to filming, but I'm willing to RTM, if I know the right questions to search for in these forums. Here's what I'm trying to do.

I'm a volleyball coach who gives private and group lessons. I find it very helpful to tape a spike or serve or pass, then replay it in a TV for the girl to see what they are doing. Many times my telling them what they are doing wrong doesn't register in their mind until they actually SEE it on the screen. I had a personal camera that I taped with and tried doing a frame by frame advance showing the girl what happened in each step. My problem was the image was pretty grainy and I was never able to get a clear picture of their arm swing and contact with the ball.

So I invested in a Canon GL-2 camera so that I could put the camera in frame mode, then also change the shutter speed of the camera to capture the frames clearer. As I've played with the camera settings, I've discovered some strange things...namely, that the lights in the gym are not always "on" so to speak. My background would be bright and clear, then a couple of frames later, it would go yellow and dark, then light, then dark.

After additional research and playing, I found out that as I increased my shutter speed above 1/100th, this is when the lighting "strobing" showed up. If it's 1/100 or even 1/60, no visible changes--but I'm not able to catch a clear enough picture in the frames when replayed on TV.

I'd LOVE to be able to film at 1/500 or even 1/1000 indoors in the gym, but what can I do? It's not my gym, so asking the owner to change out his lighting to something non-"pulsing" is not an option. Is there a way I can bring in additional lighting from Home Depot or wherever to do the job? If so, what kind do I need that won't do the pulsing or strobing effect? If I spent $100, what could I do? $500? $1000? If it gives me the results I'm looking for, maybe I'll start saving up now.

As I mentioned at the beginning, I have no problem at all reading a manual or book or article that would help me nail this down better. My background is not in photography or videography, so it would need to be a little dumbed down for me.

Any help? Anyone ever done this before?

Mucho thanks in advance!

-Dave

Dave,
There is almost nothing you can do to easily tackle this problem. You need to light the gym with a steadier source of light which is going to be on for the 500th of a second or a thousandth of a second you are looking for. The sun comes to mind. Outside is not a bad idea. Fluorescents and other sources used for large areas often cycle with the electric current frequency of 60Hz which is why it is hard to get above 1/100 without the light changing to the sensor of the camera. It is really taking the picture in the gaps of the light turning on and off . Tungsten work lights might not flicker but the amount of light you need to get up to 500th of a second is about 8 times the light you need at a 60th of a second if I am doing my math correctly. You might be able to light one area where people can practice but to light the whole gym is why the lighting guys bring in trusses. Also if you end up leaving the other gym lights on they will still cause some flicker in the rest of your image.

Hi Dave:

Since you cannot really change the lighting, I would suggest looking into a camcorder like the Panasonic HVX-200 or the Sony EX-1. Both cameras shoot 60fps video that would look leagues better than anything any HDV camcorder can do to tape. You would be recording twice the number of frames and if you were playing back at 24p, you would have butter smooth two and a half times slow motion.

I shoot about 40% of my b-roll at 48 and 60 fps because it looks so good.

Dan

I never found myself in such situation but theoretically if you double the shutter speed such as 60-120-240-480 it would still remain synced to the 60 cycles of the current. The shutter on most broadcasting cameras can be adjusted to any speed for this specific reason. I'm not familiar with your camera but perhaps you can borrow or rent a better camera. Keep experimenting with all the shutter speeds.

All great comments, I thank you many times over. Here's what my camera can do when I put it into manual mode.

Shutter speeds - 1/8, 1/15, 1/30, 1/60, 1/75, 1/90, 1/100, 1/120, 1/150, 1/180, 1/210, 1/250, 1/300, 1/360, 1/420, 1/500, 1/600, 1/720, 1/840, 1/1000, 1/1200, 1/1400, 1/1700, 1/2000, 1/2300, 1/2600, 1/3000, 1/4000, 1/8000, 1/15000, CS

F Stops - 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3.2, 3.4, 3.7, 4, 4.4, 4.8, 5.2, 5.6, 6.2, 6.7, 7.3, 8, CLOSE

Gain - 0dB, +6dB, +12dB, +18dB

Given that I need to experiment with the camera, there are only 31*20*4 = 2480 different combinations I could try. Not wanting to go thru that many just to see which would be the best combos, perhaps you lighting gurus could point me in the right directions to start testing? Even narrowing it down to "only try those shutter speeds divisible by 60" is helpful. Or saying "I would only mess with F stops between 2.4 and 4.4"

Where's the sweet spot likely to be found?

There are no rules, only best practices and compromises.

Shutter speed - fast enough to freeze the action to the extent you want, but it cuts exposure down. Eg. 1/120th gives half the light to the sensors than 1/60th does. So, just fast enough.

F-stop - Open enough to allow maximum light... (lower numbers represent a more open iris). Nothing wrong with shooting at f1.6. The compromise here is that a wider f-stop means comparatively less depth-of-focus aka. depth-of-field. This isn't usually a problem for small cameras, they usually have lots of depth-of-focus. If you don't have enough d-o-f you can use a smaller aperature (higher number), but this cuts down on the light too. When your lense is more towards the telephoto you have more d-o-f, but you have to move the camera further away to get the same field of view.

Gain - magically electronically boosts the amount of light the sensor sees. On your camera a gain of +6 will help increase exposure. Above that, the compromise is that grainyness increases. You may find +12 acceptable.

So, what you should do with the above information is shoot some tests and see what compromises work best for showing your team what you want them to see. Try some shutter speeds from 1/120th to 1/500th, try gain at +6 and +12, keep that iris open and see if you have enough exposure, enough depth-of-field, sufficient resolution, and sufficient freezing of the action to work.

As a side note, this sort of situation is where automatic exposure really doesn't work too well, the grainy image was probably from the camera boosting the gain to +18.

The problem with flickering discharge lighting sources has been around for a while now, and real video/film lighting has special ballasts that smooth out the flicker. The sodium style discharge lamps in sportshalls - very popular here in the UK are just grim for anything where you have an effective exposure time shorter than 25fps(30 in the US). In fact because of our 50Hz mains, we suffer a little more. The old problem with shooting CRT tv/monitor screens was solved to a great extent by the adjustable shutter speeds in the camera menus, but modern cameras are very stable timing wise, but mains frequency varies around it's nominal figure - so the camera capturing an image at the same time the lighting is out really common. Fluorescent tubes are better, but if the only lighting is sodium or other similar discharge sources then the good advice given on using the longest open shutter speeds is the only real way to reduce the flickering

Dave:

Gain and exposure have nothing to do with the flicker, it is the sole domain of the shutter speed/angle.

If you cannot afford a camera that shoots real slow motion, I would suggest using a camera that has clear-scan. This is a feature that lets you adjust the camera's shutter angle in .01 degree increments, it is really made for shooting CRTs without flicker but would be helpful in reducing the discharge flicker you are experiencing.It's simple to use, dial in the shutter speed and exposure you want. Then duplicate the same shutter speed/angle with the clear scan, then, looking at the camera's output on a decent monitor, adjust the clear scan in tiny increments until the flicker is reduced or eliminated. Simple.

Does your camera have a clear scan function built-in? If not, you may want to look at upgrading your camera. Slow motion would be the best tool for motion analysis but may be out of what you can or want to spend. Those lights may be scanning and discharging at 60.396 Hz (for example) and the only way to mitigate that is with clear scan. As ballasts age, the flicker rates change so no matter what you do, you may be hosed. I once shot in a store in Memphis that had about 30 flicker rates all in the same room because all of the ballasts for the ceiling lights were different ages and had been replaced at different times. Was shooting S16 slow motion that day and there was literally nothing that could be done about it, short of killing all of the lights in the store and lighting the whole store from scratch (was not even a remote possibility). I recall sitting in telecine, transferring that film and cursing the stupid flicker.

Dan

There are all kinds of things you can do in camera. But the honest truth, is you need more light. You don't need "pretty light", you just need to blast some light at the athlete. Fortunately, this is not so hard. I am a coach also and have done some recording work to show athletes mechanics.

The cheapest way to do this is to go to Home Depot, and get 2-3 of the 1200 watt construction lights. Set up the athlete on the baseline. Place One set of lights near the camera aimed at the athlete. Place another set behind the athlete aimed at the net. Place another set (if you have it) on the far side of the athlete on an angle facing the lights behind her. Now you have enough light to shoot at 1/250 which should give you the freeze frames you need for a teaching tool. You can set this up for $150-$200. At 1/125, the jump and backswing will be clear, but you'll lose the hand position to ball, and the wrist snap on top of the server. At 1/250 you should be able to freeze the entire thing cleanly.

Alternately, you can purchase a nice 2k Fresnel light. This is a "pretty" light, and you can et it used. It's focusable and you can stand the light off 10ft from the athlete and light them very nicely for your purposes. The light used, plus a good stand will cost you around $400. But it will be near bulletproof and you can use it the rest of your career.

I would take the time to film the athlete in profile on the serve arm side, from directly behind, and from in front with the camera placed up high on a ladder at the far baseline and zoomed in. This will allow him/her to see both the hand as it strikes the ball, and the follow through. It will also allow you to show any spin motion on the ball and the trajectory can be tracked.

Just my thoughts coach to coach.

It seems to me that what you really are after is slow motion. That has little to do with shutter speed. Somebody mentioned the HVX200, which does allow you to shoot up to 60 frames per second. But at the same time, that's going to probably cause you lighting problems, not flickering but you'll need more light. You should, however, be able to shoot at a standard, 1/60, shutter speed and load the footage and step through it frame-by-frame and see what you want to see. The GL2 isn't going to be as sharp as a camera with bigger chips, but I don't see that the faster shutter speed is going to do anything for you in terms of giving you sharper frames. It's video, not still photography.

I'm going through the same frustrations right now with the soccer field at our college. Perrone's answer re: the home depot lighting or the fresnel is probably going to be your best bet for a solution in a gym. Out on the soccer field i'm basically screwed... There's literally no way to re-light that properly at night!

Having done a lot of dancers both still camera and video, the problem in capturing the action is shutter speed.

A 1/60 shutter speed will be nothing but a ghostly blur of fast movements.

The coach above has the best solution, I believe. To stop the motion properly 1/250 or higher is needed.

One simple solution, if you need a special setup anyway, is to do some video outside in the daylight. You can capture individuals one at a time. Obviously this is not the answer for using an actual practice indoors for the stop-frame study.