Problem with D90 and 70-300 VR: Random Underexposure

<p>Hi All,<br /> I hope you can help me solve a new mystery. Last night I went to the local Golden Gloves tournament. My position in the balcony and the lighting setup seemed identical to previous visits. However, when I started reviewing my shots, a large majority were severely underexposed. I expected slight underexposure because I was at the ISO limit of 6400 and shooting the 70-300 wide open at approx. 130mm, giving f/4.8 or so. Not ideal, I know, but previous nights had yielded reasonable results for almost all frames. I was shooting manual at 1/500 sec for most shots.</p>

<p>However, last night I would get two frames shot within a second of each other, and one frame would be OK while the next frame would be really dark. I got this time after time, with no logical (to me) reason. I inadvertently had D-lighting on at "normal", but don't see that in the exif data. I have a pdf comparing exif data of the two shots, which I will try to attach (never did this before for a pdf.)<br /> I have included two photos as examples. I think we can ignore the red focus area. I added these in PS, but after looking at a bunch more examples, the focus was at the same point on one boxer for both good and bad shots.</p>

<p>Can anyone make a suggestion. An error in my settings or camera/lens makfunction??<br /> Thanks!<br /> Doug</p><div></div>

<p>Trying to upload pdf of exif data</p>

<p>What type of lighting is used in the arena? Many arenas use Metal Halide lighting which has a frequency of 60 Hz, or 1/60 sec...much slower than your shutter speed. This will cause odd lighting and "random" underexposure depending on when in the light's cycle your shot takes place.</p>

<p>RS</p>

<p>Make sure that exposure bracketing is not switched on unintentionally.</p>

<p>If you have bracketing such that 1 frame is at the right exposure and a 2nd frame at 1 or 2 stops below, you'll get the result you had, repeatedly.</p>

<p>Richard, That is a good suggestion, but odd that previous nights there didn't show much of this. I did shoot a little faster this time, typically 1/500 rather than 1/320 on previous nights.<br>

Shun, the examples were much more random. Like 4 bad frames, then two good ones, then three bad ones, etc.<br>

Thanks for your suggestions. Mostly I worry about a malfunction problem.</p>

<p>I thought you were talking about alternating correct/dark/correct/dark ... frames. If it is more random, check whether the aperture diaphragm is opening and closing smoothly; press the little lever at the lens mount.</p>

<p>What metering mode did you use? Depending on if you changed this or if the environment was "screwing" with your metering more than normal, I could see this happening.</p>

<p>Do this to test your lens: Find an environment with a pretty consistent lighting. Set your ISO, aperture and shutter all manually, then rail off a bunch of shots. If it is consistent, than more than likely I am guessing your metering mode was a problem. If it isn't then it was more than likely the lens.</p>

<p>Exposureis identical - could it be that you are "catching" someoen else's flash or that there is some other light that is variable (see Rich's above comment on the halide lamps - good point). You are on Manual Mode so your camera would nto respond to those changes....</p>

<p>I totally missed the EXIF data before I commented. Never mind what I said. Shun, Benjamin and Richard have a better idea than mine.</p>

<p>I have the same combo, it's never happened to me. Benjamin or Shun sound like they have something there. I bet it's the lighting.</p>

<p>Zach, your test was a great suggestion. I just went outside and shot 40 shots with identical settings to last night and they look fine (except for being blue becaues my WB was set to 2500K :)</p>

<p>Richard, I think you and Peter are correct. Something with the lighting. Not sure why last night was so different but I guess these things happen. Live and learn (again.)</p>

<p>Thanks everyone!</p>

<p>Were you using spot metering? If so, depending on what the spot was pointing to, it could significantly affect your metering.</p>

<p>Shun, I was shooting manual.</p>

<p>Ok, as long as you cannot reproduce the problem again under a different environment, your camera and lens seem fine; most likely it was the lighting then.</p>

<p>I think Richard is right I had the same situation when shooting HS football game and one of three shots looked just like yours.</p>

<p>I'd have to agree with Shun. You're probably not catching someone's flash, as that would cause a very noticible white balance shift. I've noticed similar effects shooting roller derby events. I remember there was this one arena that had some sort of cycling florescents (which I'm sure I've misspelled), and then a few incandescents hanging down here and there. When the girls were on the side of the track with more incandescents, I got great shots. When they skated to the other side, where it was mostly florescent lighting, they were much more hit-or-miss.</p>

<p>there is nothing wrong, this happens occasionally under florescent light</p>

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<p>I did shoot a little faster this time, typically 1/500 rather than 1/320 on previous nights</p>

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<p><br />Doug, i think this answers your question...<br />Faste shutter exposure increases the chance to catch "a dark moment" in the 60 hrz cycle of the lights, wherás slower shooting increases the chanc tha a part of the xposure hits a ( part of) a light period within the 60hrz cycle.. ( shooting slower than 1/60 sec would insure hitting a light part of the cycel always...).</p>

<p>Thanks everyone! Now I know a little more about lighting than I did before.<br>

Doug</p>