Strange grunge on photos

[Cinka]

Hey all, I'm working on some product photos for my sister and noticed this strange grunge on my photos.

ISO is set at 100, so it's not ISO grain. I have 3 lights - at the moment, I think two (Alien Bees b800) were just off to the side and one Canon 580exII behind the white paper. I'm using a 35 mm lens. I'm shooting inside and when I took this one the overhead chandelier was on. Even when it's off, it still shows up. I inspected the lens and it looks clean. Note: I picked a random photo out of the bunch, this one isn't especially exposed or lighted well. 5D Mark III on a tripod.



Never seen anything like it. I can figure out what the issue is. Anyone know?

 

[480sparky]

Is it the texture of the paper?

 

[Cinka]

@480sparky - That's definitely on my list of maybes. It just standard issue "pure white" seamless. Seems like a strange thing to happen, even if it is the paper. Never in all my years seen something like this.

 

[480sparky]

If the light is hitting it obliquely, it will show up like that.

 

[Cinka]

@480sparky It's showing up even when the light is 45 degree angle. Possibly it's the 580exii in the back. I'll check.

 

[dennybeall]

The appearance is of the structure of the paper. The lights you are using are perhaps causing the reflected light to come back at different angles or wavelengths.
Take a set of photos with one light, then 2 lights, then 3, then add chandelier, etc and see if the reflectivity of the paper changes.

 

[Cinka]

@dennybeall I'll definitely do some tests today and experiment with the lighting. It's so bizarre. I've been using white seamless forever and I've had these lights for about 7 years. Just weird. I'll post results.

 

[Buckster]

Definitely the paper/light arrangement. I can even line up the reflection of it from the surface to the paper behind it with my eyes. Notice how it's not on the label or bottle.

 

[runnah]

Yeah if the flash is behind the paper this is likely the cause. Backdrops like that are design to reflect light and you are projecting the light.

 

[Buckster]

Yeah if the flash is behind the paper this is likely the cause. Backdrops like that are design to reflect light and you are projecting the light.

AHHHH!!! I didn't even notice in the opening post that one of the lights was BEHIND the paper!!! That's totally it!!!