Exposure Variation on High-Speed Burst

[george_prescott]

<p>I was taking some pictures at a JV football game the other night and noticed that there appears to be a variation in exposure from one frame to the next in a single burst, looks like about a half stop. I was shooting in manual, 1/320 sec, f2.8 ISO 3200 (the light was really poor), using a 7D and a 70-200 2.8L zoom. The exif data indicates no change in shutter or aperture. Typically, the first frame was darker and subsequent 2 were lighter (I seem to shoot a lot of 3-shot bursts). I tried to duplicate this phenomenon the next day with no luck at the same ISO and lens, although in the daylight. Anybody ever seen this?</p>

<p>George</p>

[randallfarhy]

<p>Is it possible that your subject was changing position relative to the light source during these bursts? When I shoot race cars under the lights (while it's twighlight), I tend to "lead" with the first shot in the burst, and that this sometimes results in an image taken just before they hit the area of best overhead lighting- yielding a slightly underexposed capture. (Manual settings).</p>

[george_prescott]

<p>No, there was very little subject movement in most of them, the shots are almost identical except for the exposure difference. Also, the background changed as well.</p>

<p> </p>

[nathan_meador]

<p>What you are most likely seeing is the effect of the field lights themselves, many types of floodlights on high school fields will show a shift in color/brightness that isn't noticeable to the eye but will show up in your pics. I'm not sure if that is due to the power current or the type of lightbulb specifically, but have had fields where I get brown or green 'flickering'. I've had that also happen in some small college gyms.</p>

[bob_sunley]

<p>Most field lights are arc lamps and they flicker at a steady 60 cycles per second. Short shutter speed will capture the difference in light output. It is even worse in countries that use 50 Hz power. :(</p>

 

[serguei_fenev]

<p>Hi George,<br>

I've got the same question; however never asked. That happens to me all the time when I shoot ice hockey (1D Mark III). I correct it during post-processing.</p>

 

[frank_skomial]

<p>In fast bursts the exposure is evaluated only once, so the reason described by Bob is most likely causing it.</p>

<p>Try the same setting outside, where there is no 60 Hz flickering lights.</p>

[john_macpherson]

<p>Other cause is if you take your eye away from the finder you can get light coming in the eyepiece which will alter the exposure - I've had this several times depending on camera angle and strength of lighting behind me.</p>

[georg_s1]

<blockquote>

<p ><a href="../photodb/user?user_id=3902476">Bob Sunley</a><a href="../member-status-icons"><img title="Frequent poster" src="../v3graphics/member-status-icons/2rolls.gif" alt="" /></a>, Oct 09, 2011; 10:34 p.m.</p>

 

<p>Most field lights are arc lamps and they flicker at a steady 60 cycles per second. Short shutter speed will capture the difference in light output. It is even worse in countries that use 50 Hz power. :(</p>

 

 

</blockquote>

<p>That's it! It's really worse here in europe! But the variations are easy to correct in post-processing.</p>

<p>Cheers, Georg!</p>

[george_prescott]

<p>Thanks for the help. I thought there may have been a possibility that there was an issue like that going on.</p>

<p>George</p>

[phule]

<p>About half-way down the page on this thread at SportsShooter, there's a link to an animated GIF made by Guy Rhodes that demonstrates, particularly well IMHO, what's happening with the lighting.</p>

<p>http://www.sportsshooter.com/message_display.html?tid=20873</p>

 

[julien_henri]

<p>I experienced the same but not systematically with my new eos 1v shooting outdoor in daytime clear day so that had absolutely nothing to do with flickering artificial lights. Furthermore this was a landscape photo and the difference in exposure was all over the frame. I can only conclude that there is some kind of intermittent issue with the shutter design.</p>