d7000 unusual color on high iso / fast shutter speed
hi, just bought my camera last saturday and while testing camera on iso 6400 and even 3200 combi 1000+ shutter speed, i'm getting outputs that are not consistent, sometimes i'm getting pics that have this unusual horizontal strong yellowish color. it sometimes appear on top or center or bottom portion of an image. I took the pictures using auto white balance normal. When I tried returning the camera on the store, they said it's just the white balance and advised me to choose fluorescent (since i took the pics indoor with fluorescent lights on) - since the store also uses the same light (i think - also fluorescent but don't know what kind), i tried taking some pics but was not able to recreate it anymore however my friend is not convinced since he said if that is the case then the whole pic (not a portion) should be affected. need your advice for peace of mind I did not yet test the camera again using the f white balance indoor where i took the pics with the unusual color - to follow
please see my sample pics @ my gallery or this link :
thanks for your help
#2. "RE: d7000 unusual color on high iso / fast shutter speed" | In response to Reply # 1
#3. "RE: d7000 unusual color on high iso / fast shutter speed" | In response to Reply # 2wordwizrd Registered since 24th Nov 2010Thu 16-Dec-10 11:04 AM
fluorescent lights are not a steady light. you'll see that especially in the long tubes used in "shop lights." they flicker. i think all the gyms where i shoot use some sort of fluorescents. in a rapid sequence of shots, it is quite common to find a frame or two with shifted white balances and even exposure differences ... even though i normally shoot my indoor sports with the meter set to manual. as cameras get better, the effect diminishes. there was a particular gym near cleveland where the fluorescents were so bad that with my first d1, even though i always did a white card before basketball games, the kids always ended up with sickly green faces. thankfully, the papers that bought my pix were using them black and white, so the editors never saw the "martian kids."
#4. "RE: d7000 unusual color on high iso / fast shutter speed" | In response to Reply # 3grosda Registered since 18th May 2006Thu 16-Dec-10 06:49 PM
This color shift also can happen at outdoor sports venues (football, baseball) as the lights cycle.
I'm just learning my D7000 as well. It appears to be an amazing optical machine.
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#6. "RE: d7000 unusual color on high iso / fast shutter speed" | In response to Reply # 5km6xz Nikonian since 22nd Jan 2009Fri 17-Dec-10 03:52 AM
Both incandescent and florescent lights vary with the waveform and frequency of the mains source. Hot filament bulbs, incandescent, have as slower reaction to the waveform, and never completely go black but shift to the red end of the spectrum as the current passes zero. You can see that watching a bulb when turned off, the light lowers as the filament cools and for a moment is a dull red as it shifts out of the human visible spectrum into infrared.
Florescent lights light filaments react faster but the light is generated by lower energy photons striking powder phosphors that coat the glass tube. Those naturally emit light of a characteristic spectra for that phosphor when excited. The glow does not stop abruptly when excitation stops, it has a relatively slow decay that reduces flicker. Both florescent and incandescent bulbs are low flicker compared to other light types. LED light is much much faster in changing states so flicker badly with AC. Current. Area lighting using LED had driver circuits that change the 50 or 60 hz line frequency to several hundred kilohertz or megahertz, way higher in flicker rate than our rods and cone's response times. This all really fundamental to basic photography and is widely known, particularly by those interested in available light, interiors or sports. Being able to overpower available light for more consistent predictable color and balanced intensity is one of the primary functions of strobes and speedlights.
The higher the ISO, the greater the proportion of room illumination contributes to the total exposure, even when using flash. So the varying light color and intensity makes image results less and less predictable as the ISO, or exposure time is increased or aperture opened further.
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#7. "RE: d7000 unusual color on high iso / fast shutter speed" | In response to Reply # 6elec164 Nikonian since 15th Jan 2009Fri 17-Dec-10 11:27 AM
>Both incandescent and florescent lights vary with the
>waveform and frequency of the mains source. Hot filament
>bulbs, incandescent, have as slower reaction to the waveform,
>Florescent lights light filaments react faster but the light
>is generated by lower energy photons striking powder phosphors
>that coat the glass tube.
Actually I believe this is a bit inaccurate; the filament of the florescent bulb reacts similar to the filament of the incandescent bulb. But the glowing filament in the florescent tube does not provide the source of energy for the phosphors but provides free electrons and ions to start the plasma arc between the electrodes. Once the arc is established the glowing filament is no longer needed. That arc turns the liquid mercury into a gas and that process is what creates the energy to light the phosphor coating to produce visible light.
Thus the main difference is that the incandescent filament begins to glow at low voltages and the residual energy of the filament (heat) allows it to remain fairly steady in output given the frequency of the power source and never really every going dark (virtually imperceptible even by our cameras). Whereas the plasma arc in a florescent tube needs significant current for it to be maintained. Therefore the florescent tube does go dark causing the flicker.
Actually if things remain as they are this will all become moot with the issue passing into photographic lore. Current legislation in the USA and EU have for the most part virtually banned magnetic ballasts in favor of the more energy efficient electronic ballasts which work the same way as Stan described for the LED source lighting making florescent lighting virtually flicker free. The florescent tube still goes dark, but happens so many times a second that even our cameras will not pick it up.
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