Totally black background for Macro work

Hi, I am just returning to Macro work after a long absence, and have bought myself a Nikon 105mm and an R1C1 macro flash kit. The problem is that I want to get a totally black background for the target object to stand out against.

Here is a trypical scenario: I place the subject, a small figurine on a stand. I place the lens about 9 inches away from the subject and place the SB-200's at 12 o'clock and the other at 9 o'clock.

I want to get a totally black background but any board or material that I have tried so far give some reflection of the flash.

Once, when I was doing some macro work before I seem to remember reading, in a book which I have since "lent" and lost, that if I ensure that there is no object within a certain distance from the back of the subject, then it will produce a totally black background due to light fall-off and the inverse square law.
Can anyone help me with this problem, or is my memory wrong.

yeah, fall-off is the key. just put the black backdrop farther away from the subject.
use the full synch speed and a small aperture with the I-ttl in operation.

--
Member of The Pet Rock Owners and Breeders Association
Boarding and Training at Reasonable Rates
Photons by the bag.
Gravitons no longer shipped outside US or Canada
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if I mock you, it may be well deserved.

High speed sync will also help keep the bg dark

I use 'black velvet' (fabric store) it helps with the non-reflection of light. Let us know what you learn...Brent

There will be plenty of suggestion in the lighting forum, but here are my two cents worth.

A black velvet-like material makes a great background, even stretched over a sheet of foam core to ease handling.

Also, light spill is key. The background illumination should be about five (or more) stops darker than your subject. Lighting direction and, to a lesser extent, shutter speed will help tame that pesky background.

Multiple issues.

First, a material go with black velvet, it tends to absorb the the best.

Second you're correct about the distance and fall off. This is going to be the most important (even more so than the material of the backdrop). The general rule for a pin-point light source is that it falls off according to the inverse square rule. (note, a a macro light is not going to be a pure pin-point light source so the math won't be exact but it will give you a rough idea). Inverse square rule states that light is reduces by 1/(change in distance)^2 so if you properly light one object, and then have another object that is 2x as far from the light source it will have (1/2^2=) 1/4th the light of (or be 2 stops darker than) the main object. If the 2nd object is 5 times as far from the light source as the first object, it will be (1/5^2=) 1/25th as bright (or about 4 1/2 stops darker). So if you have something that is fairly black and 5 times father away from the lights it would be pretty dark, if you want pitch black, I'd probably shoot for at least 8 times as far which would theoretically give you 6 stops and if the black is 3 darker than middle grey, that's about 9 or 10 stops darker than middle, which unless you have an 18 stop dynamic range, shouldn't be an issue. Basically the further the background the better. Also keep in mind, if you can't move the background further, perhaps you can shorten the distance between the lights and the object. The closer the objects are to the light, the greater the difference from the object to the background.

Finally, make sure your problem is not ambient light. Take the same exposure (same shutter, aperture, and ISO) with no flash on. You should have an extremely underexposed image. If your background is not black without the flash, there's no way it's going to be black with the flash. If you're seeing details in the background with just ambient light, you can do a couple things: 1) try a faster shutter speed (if you're already at sync speed that will cause high-speed-sync will will significantly reduce the amount of power your flash can deliver) 2) try reducing the amount of light in the room (eg: turn off the lights) 3) if that is not possible, try "flagging" or blocking the light from hitting the background area using something like black paper.
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~K

Thanks for all the replies. So nice to have some good info as feedback. Its also nice to know that the inverse square law works just as I remember.

I suppose one lesson is that once you find a technical book that really explains a subject then NEVER, EVER lend it to anyone, not even your brother.

It also occurs to me that there are some gadgets to help control the light.
Honl's Grids for flashes work just like the big ones we use on a strobe.
they give a very tight beam compared to even a zoomed flash head.

wait, you are using a macro flash right? maybe you could rig some mini-snoots.

but remember that macro flash does not pack the punch of a system flash
so if the backdrop is dark an at least three feet away the may be no problem
--
Member of The Pet Rock Owners and Breeders Association
Boarding and Training at Reasonable Rates
Photons by the bag.
Gravitons no longer shipped outside US or Canada
-----.....------

if I mock you, it may be well deserved.

You can control the amount of light that is hitting the background in several ways.

• By changing the distance from the subject to the background
• By the re-positioning of the light(s)
• By varying the output of the light(s)
• By varying the shutter speed
• By varying the aperture

If you are dealing with even ambient lighting or a subject that's in the shadows, then one on the simplest ways, IMHO, is to kill the background light using the shutter speed, while using the flash to highlight the foreground subject. You can control the exposure for the ambient lighting very easily by utilizing the shutter speed. Here I exposed for the background ambient light and then used flash to highlight the foreground. Then by simply dialing in a higher shutter speed, I virtually killed the ambient light. The shutter speed has no effect of the flash output as long as you are at or below the camera’s max sync speed.







As others have said too, using a dark piece of fabric as a backdrop works very well. But there needs to be some reasonable thought put into the separation between the subject and the background in conjunction with the lighting. Use your knowledge of exposure (ISO, Shutter, Aperture) to effect how the lighting hits your background.

Here, I simply have a black piece of bed sheet draped in the background, and the lighting is a 580EX speedlight shooting from the 12 o’clock position, straight down.
1/125, f/11





Regards, Mike

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B.R.A.S.S. (Breathe, Relax, Aim, Sight, Squeeze)

Yup Mike, thats exactly the effect I am trying for. I follow what you have said and should have some fun.
Thank goodness for digital, instant feedback.

Took these just a little while ago, while it's still day light outside.

Just one other thing I didn't mention about my examples, but you probably already know; the light (580EX flash) was off camera and was positioned very close to the subject....between 12 and 18".

I used a 580EX on camera as a Master to trigger a 580EX off camera as a Slave.



Regards, Mike

BrianMoore4 said:

Yup Mike, thats exactly the effect I am trying for. I follow what you have said and should have some fun.
Thank goodness for digital, instant feedback.

Click to expand...

--
B.R.A.S.S. (Breathe, Relax, Aim, Sight, Squeeze)

One last question:

Anyone recommend a GOOD book on macro photography. I hate buying books on-line because you can't look inside like you can in a book shop.

Yes the inverse-square law for light fall off is a great way to get a black background.

In macro land you can really use this to your advantage.

This one surprised me, I left a bag at home before heading out that had all my flashes in it, so this was with the pop up flash in a d300s.

I was in filtered daylight and I did use FP to underexpose the ambient.

The image has issues, the fact it was done with the popup flash is the only reason I find it interesting.

Oops this one didn't need FP, it was the gallery upload using 10 as a divisor that confused me.

enkindler said:

Yes the inverse-square law for light fall off is a great way to get a black background.

In macro land you can really use this to your advantage.

This one surprised me, I left a bag at home before heading out that had all my flashes in it, so this was with the pop up flash in a d300s.

I was in filtered daylight and I did use FP to underexpose the ambient.

The image has issues, the fact it was done with the popup flash is the only reason I find it interesting.

Click to expand...