Why is there a dark halo or shadow along the edge of my subject on a reflective surface?
Asked 9/9/2013
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2 answers
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I’m new to photography and was experimenting with tabletop macro shots on a reflective surface using a tablet. In my photos, a dark halo/shadow appears along the back edge of a battery, especially near the copper-colored end. The effect becomes more obvious with a longer shutter speed, and if I rotate the battery, the dark area follows that side of the object.
Setup: Nikon D3100, 60mm macro lens, f/5.6, ISO 100, about 1 second exposure. I also noticed the issue does not appear the same way when working from RAW files.
What is likely causing this dark edge, and how can I test whether it’s a real shadow/reflection issue or an in-camera JPEG processing artifact?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
12y ago
2 Answers
3
It appears to be a JPEG processing artifact of some kind based on the diagnostic steps you have taken. Most likely some heavy sharpening is being applied to try to deal with some of the blur that occurs as a result of the really small depth of field. If you want to try narrowing it down further, you could try using Nikon's NEF processing software (which should replicate the behavior in camera) and tweak with different parameters until you identify the exact factor that is causing it.
When you shoot RAW, it is capturing the exact sensor data prior to processing which is why you end not seeing the issue since it is JPEG processing related. Interestingly, this is one of the other more subtle advantages to shooting RAW. The often quoted reason is the expanded dynamic range and exposure recovery capabilities, but you also sometimes get weird stuff like this from how the image processing is applied to form the JPEG. Raw lets you fix such issues.
Originally by user11392. Source · Licensed CC BY-SA 4.0
user11392
12y ago
0
Generated from our catalog & community — verify before relying on it.
Two likely causes came up:
-
A real shadow/reflection from the setup. Since you’re shooting on a reflective surface, the dark area may simply be the battery’s actual shadow or a reflection effect. A quick test is to place the battery on a matte, non-reflective surface and see whether the dark edge remains.
-
JPEG processing artifacts. Because the effect seems to differ when using RAW, the halo may be caused by in-camera JPEG processing, especially sharpening. RAW files contain the sensor data before that processing, so they often avoid this kind of edge artifact.
To narrow it down:
- Shoot RAW and JPEG of the same setup.
- Turn down or disable in-camera sharpening/processing if possible.
- Test on a matte surface instead of the tablet.
If the halo disappears on RAW but appears in JPEG, it’s probably processing. If it stays on a matte surface and follows the lighting geometry, it’s more likely a real shadow/reflection effect.
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