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by Aditya

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I'm completely new to photography, and was attempting to shoot on a reflective surface (using a tablet for experimentation). I get some good results (to my untrained eye) but on my latest attempt, I get some weird shadow around my subject. I do not know the correct terminology to try and google the problem, so I figured I'd ask here.

If you notice the back edge of the battery, there is a shadowy (dark) spot that is more prominent near the top corner of the battery...

All shots are taken with a Nikon D3100, 60mm macro lens, F5.6 aperture, ISO 100, and a shutter speed of 1" (so that the problem becomes obvious).

This is a new shot of the problem. The slower the shutter speed, the more prominent the dark area becomes. example

If I rotate the battery by hand, the dark area follows the copper colored side of the battery. example rotated

This is how my setup looks like (I followed a tabletop photography tutorial on Flickr): Setup Top Setup Bottom

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That's fascinating. Can you do it again? If you can, please take another shot without the battery. –  Stan Sep 9 '13 at 7:59
    
You can upload the picture as part of your post. That way it's not necessary to click on a link, and the picture does not get lost in case you remove it from Dropbox. –  feklee Sep 9 '13 at 9:12
    
both are useful as the imgur strips the EXIF info which is still present in the dropbox link. –  Matt Grum Sep 9 '13 at 11:23
2  
Can you describe how the image was processed? It looks like some form local contrast enhancement artifact (like the halos you get in the sky with tonemapped HDR images). Was this shot RAW or JPEG, did you enable Nikon's auto lighting optimiser? –  Matt Grum Sep 9 '13 at 11:25
    
Where are the lights in the room / how was the shot lit? –  Patrick Hurley Sep 9 '13 at 12:45

2 Answers 2

up vote 3 down vote accepted

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.

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I think that's the actual shadow of the battery. Place the battery on a matte surface and see if you have the same effect. I bet you will see the same dark area.

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The thing that's weird is that if I rotate the battery in place without moving the lights, the 'shadow' seems to follow the copper end of the battery. Thanks for the input though! –  user2636834 Sep 9 '13 at 19:39
    
To me it looks like it's following the "far" side, not the copper part. Try it on a matte surface - if it's a real shadow, that should make it show up better. If it doesn't show up better, then it's probably a processing error, or an actual "halo" caused by internal reflections - for which the only solution I'm aware of is to use dimmer light, or better lenses. –  Jasmine Sep 9 '13 at 19:44

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