5 FPS - With different exposures?
I shoot a lot of Hockey, D700 - 80-200 F2.8 Zoom.
Exposure: Manual - ISO 4000-5000, F 2.8 Shutter 640 - 800 - 8 gig Lexar CF Card 233x. Autofocus 51 point.
The problem I am having is even with completely MANUAL exposure, I am getting variable exposures within a 5 or more frame burst. It can be as much as 2 stops (index equivalent).
I have turned off most of camera aids, ie: Auto ISO etc, but can't seem to eliminate the variations in exposure. Is this normal?
To expand on this issue:
I'm shooting regularly with AUTO White Balance however I have shot using a calibrated WB with similar results. Also, I have shot at more than 10 different indoor venues with the same result, outdoor tests are next.
#1. "RE: 5 FPS - With different exposures?" | In response to Reply # 0aldewitt Registered since 16th May 2008Tue 17-Feb-09 01:18 PM
This has been discussed in multiple places, but as I understand it, the changes in exposure result from the light that your sensor sees at the moment of the exposure, and often that is different than the image your eyes see. Most commercial lighting systems are on 60 cycle systems and so effectively cycle on an off 60 times a second. The human eye cannot see any variation. However, your camera, taking a series of shots over 5 frames per second, does catch the image at a point where the light can be waning.
I do not personally vouch for this theory, but it does make some sense.
A. L. DeWitt
Jefferson City, MO
Cameras allow us to share the beauty in God's creation with others.
Visit my Nikonians gallery.
#2. "RE: 5 FPS - With different exposures?" | In response to Reply # 0Tue 17-Feb-09 05:10 PM
A.L. DeWitt's explanation is probably right on this. Maybe you would do better with either aperture priority or shutter priority, but even then I'm not sure the camera would keep up with the lighting cycle. I shoot a lot of basketball, and while I don't notice much variation in exposure, I do notice a substantial difference in white balance in a series of shots in burst mode regardless of whether I use auto white balance or set the white balance myself. I also notice a substantial difference in lighting characteristics from one facility to another, so you may have that problem in one location but not somewhere else.
Indoor lighting (unless it's incandescent) is tough with high shutter speeds, and I'm pretty confident the problem isn't the camera, but rather a result of the lighting where you are shooting.
#3. "RE: 5 FPS - With different exposures?" | In response to Reply # 0Tue 17-Feb-09 05:16 PM
Another thought on this: you may be using a higher shutter speed than you need. Your 640-800 is picking up just a tiny slice of the 60 cycle variation in the lighting. Try lowering your ISO to 2000 or 3200, which would lower your shutter speed to 320-400. I suspect 1/400 would be fast enough to stop the action, and you'd get twice as much of the lighting cycle, which may lower your exposure variation.
If you were shooting at 1/60 you'd pick up an entire cycle of 60 cycle lighting and your photos would like as your eyes see, but obviously you can't have a shutter speed this slow for action sports.
#4. "RE: 5 FPS - With different exposures?" | In response to Reply # 3Tue 17-Feb-09 05:31 PM
I appreciate your input, However I do need higher shutter speeds, hockey is a VERY fast game, especially up close.
I had thought about the lighting frequency, the lights are typically Sodium based and definitely could be contributing factor. However, I've spoken to a few Pro Hockey Shooters who occasionally shoot college or lower level hockey (without strobes) and they don't seem to have the same issue.
This is my first DSLR and I never had the issue with film.
The quest continues...
#5. "RE: 5 FPS - With different exposures?" | In response to Reply # 0
Are you sure you have not accidentally engaged bracketing?
My Nikonians Gallery
"Nikonians membership - My most important photographic investment, after the
Retirement is a gift of time - Don't waste it!
Old age is a special gift that very few receive. Be thankful if you get it.
#7. "RE: 5 FPS - With different exposures?" | In response to Reply # 0
Unfortunately, it is the lights, and you just have to live with it. Some shots end up duds because of the precise timing associated with the lights at bottom output and the shutter flying. If it's any consolation, it's even easier to find the problem with an 8-fps, 9-fps or 11-fps body...
You can verify this by setting things to manual everything (exposure, white balance, etc) - and it will still happen.
Brian... a bicoastal Nikonian and Team Member
My gallery is online. Comments and critique welcomed any time!
#8. "RE: 5 FPS - With different exposures?" | In response to Reply # 7Tue 17-Feb-09 08:53 PM
I'm sure you're right, and it is the lights. But I wonder what would happen if the OP switched to aperture priority. Would the camera be able to adjust the shutter speed quickly enough to compensate for the fluctuating brightness? I don't know, but I can tell you the camera doesn't adjust the white balance fast enough, so auto white balance will give a different color cast from frame to frame.
It would be worth a try to experiment with aperture priority to see if it can lessen your exposure problem.
#9. "RE: 5 FPS - With different exposures?" | In response to Reply # 0
As others have stated the lights fluctuate due to the Alternating Current of the power. In North America the AC frequency in 60 Hz, in most the rest of the world the frequency is 50Hz. This actually means that the lights cycle at twice the frequency of the power, i.e. 1/120 or 1/100 of a second.
In most athletic venues lighting uses some sort of arc discharge lamps. The light is produced by arcing inside the lamp. This arc starts and stops at twice the power frequency. This is very much like a flash unit, put pulsed at 120 or 100 times each second. Thus you have pulses of light, not continuous output. Also because all the lights get their power from the same source, this pulsing is synchronized.
The exposure problem comes from the fact that the exposure determination is not made during exposure. It's made before the shutter opens. The metering time is also slow compared to the time the shutter lets light reach the sensor or film. The meter probably averages the light from several cycles of the lamp. For example 8fps is 15 cycles of a discharge lamp; many but not all of these cycles are averaged by the meter. The shutter opening is only 1/2 of a cycle. The meter averages several cycles but the image sensor sees only a fraction of a cycle. At high shutter speeds, the shutter action is a slit that sweeps vertically across the sensor. This could lead to exposure variation from top to bottom of the frame.
Note that manual exposure setting does not change the problem. The manual exposure can be correct for one portion of the light's cycle and incorrect for another portion of the cycle.
Gary in SE Michigan, USA.
Nikonians membership - My most important photographic investment, after the camera.
D4, D810, D300 (720nm IR conversion), D90, F6, FM3a (black), FM2n (chrome)
YashicaMat 124, Graflex Speed Graphic 4x5
My Nikonians Gallery & Our Chapter Gallery
#10. "RE: 5 FPS - With different exposures?" | In response to Reply # 9markscamera Registered since 05th Aug 2006Wed 18-Feb-09 12:40 AM
This is normal. It happens to me even when I'm outdoors with my D2H shooting long 8fps bursts, and even more so indoors such as basketball.
USN, retired ...GO Navy!