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I am new to photography and use a Nikon D3200 to shoot jewelry in a light tent. I use the original 18-55mm f/3.5-5.6 lens with Xit XTETN Auto Focus Macro Extension Tube for macro shots.

I have this problem where I would be shooting perfect images under a certain setting, then all of a sudden the light drops even though nothing changed (none of the light, settings, objects changed). See below two pictures taken a few seconds apart; and I took a third picture with a slower shutter speed but the picture came out even darker. This happened to me a few times already and I can't figure out why. Any advice?

First Picture - perfect light Second Picture - same setting,

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    Is your flash in manual or automatic mode? – Philip Kendall Mar 5 '17 at 8:03
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    That used to happen to me with a cheap flash that couldn't recharge fast enough. First shot bright, then count to ten between subsequent shots; they would then be equally bright to each other, but dimmer than the first shot. If I shot any faster than 10s intervals each one would be darker than the last... I bought decent flashes eventually ;) – Tetsujin Mar 5 '17 at 8:16
  • I do not use the flash. All the light comes from the LED light stripes within the light tent. So like I said,the lighting condition has not changed between the shots. It's almost like the camera all of a sudden cannot pick up the same light. Could it be because of the extension tube? – JoD Mar 5 '17 at 18:28
  • Where is the "third picture" with the slower shutter speed? – Michael C Mar 5 '17 at 19:42
  • I can't figure out how to upload the third picture. I couldn't upload all three in my original post since my "reputation" was low. Any tips? I am learning everything, :D – JoD Mar 5 '17 at 22:01
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I do not use the flash. All the light comes from the LED light stripes within the light tent.

LED lights flicker. Your shot-to-shot inconsistency has nothing to do with your camera. It is about the variability of the lights.

Assuming your camera is solidly mounted on a stable tripod, the best way to deal with it is to increase the exposure time (reduce the shutter "speed") until the flicker is no longer evident. I'd start at ISO 100 and 1/50 second and go from there.

  • true to that. Almost all LED lights are intensity-modulated by flickering them. You can google "pulse width modulation" to learn more. – aaaaa says reinstate Monica Mar 5 '17 at 20:31
  • I started using LED bulbs because I liked the white light. The flickering is definitely giving me trouble, I am also getting "banding" (light and dark stripes in my photos) due to using LED. What kind of lights and bulbs would you recommend for economically-priced home studio for shooting simple hand made jewelry? – JoD Mar 5 '17 at 22:02
  • Cheap LED lighting uses a half-wave bridge rectifier, so the lights are lit only half the time. Better LED lighting uses a full-wave bridge. The most consistently lit LED lighting contains proper capacitors to filter the resulting pulsating DC into proper DC, but that approach is fundamentally incompatible with the use of dimmers. The best approach would be to use a proper DC power supply with a high-frequency PWM dimmer to drive the LEDs directly (say 60 kHz). I doubt anybody builds them, though. :-) – dgatwood Mar 8 '17 at 2:28
  • Incidentally, the only reason you don't see this with incandescent lights is because the filament retains so much heat that it continues to radiate a decent amount of light even while the power is off... but you can actually see the effect if you point a camera right at the filament. Fluorescents are notorious for this, hence the development of high-frequency ballasts. – dgatwood Mar 8 '17 at 2:31
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I ended up taking off the extension tube, or replacing the previous extension tube with another one with a longer lens, viola, problem resolved! I can only assume the problem lies with the extension tube. Go figure...

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