how take pictures of reflective surfaces (pictures painted with acrylic ink)

Ron Wolpa · Feb 7, 2015

In the attempt to soften the light to take pictures from acrylic ink paintings ( very reflective surfaces) I built 2 low cost makeshift reflectors (as seen on attached pict).
It improved very little , chiefly regarding the darker pictures , after all the external natural illumination proved to be softer with some blinder control.
My question is what do you suggest me to improve the light ?

tirediron · Feb 7, 2015

Without seeing the images of the "paintings" it's difficult to offer too much help. If the distance between the subject and softbox is representative of how you were shooting, then move the light closer. A LOT closer, and drop the power accordingly. I would crosslight these with each light on a 45 angle to the subject, and as close to the "paintings" as I could possibly get them.

If that doesn't work, and it may not, then you are likely going to have to read up on cross-polarization. Essentially a technique where you place polarizing film on your lights and a polarizing filter on your lens. This will take care of pretty much all of the all of your specular highlighting issues.

BTW, nicely done on the D-I-Y softoxes!

Ron Wolpa · Feb 7, 2015

So many thanks for posting your reply , I tried different distances from the softboxes to the surfaces (angle 45 degrees) , used white light lamps ; the picts you saw is from the 2nd softboxes , the 1st one the reflector box was smaller.
I was thinking to encircle the paintings around a white fabric "tent" and light it externally. Perhaps this will give me a little bit more control (?)

KmH · Feb 7, 2015

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AKUK · Feb 7, 2015

The only thing that is going to soften the light, is a larger light source. A lot of people make the mistake of thinking that placing diffusion material directly over the front of existing light sources will make a difference. It doesn't. It may make the light less specular but, other than that you'll still have hard light. You've got the right thinking here in making some softboxes but, they may not be large enough for the level of contrast you want. If you are on a budget, get a couple of silk screens or voile curtains and fire your strobes into this.

Reflections are a PITA to deal with sometimes but the thing to remember is angle of incident = angle of reflection. So long as you keep the lights off axis from the camera, you should avoid the majority of problems. As @tirediron mentions, a circular polariser will take care of most unwanted reflections, but will reduce your exposure slightly.

If you have a boom arm and a means of rigging it, you could put a strobe directly over the top (90°) of the paintings, with the painting facing the camera and fire the strobe directly down on top of it. If placed on a large white table top, the light will bounce all over the place and illuminate the painting. Due to the angle of the light, any reflections should return in the direction of the strobe and not in the direction of the camera.

TCampbell · Feb 8, 2015

These lights appear to be too close to the position of the camera. Push them farther out to the side.

Imagine you take down the art and replace the art with a glass mirror. Would you be able to see the lights from the camera's point of view... as it's looking at the mirror? If the lights are close to the camera, the answer will be yes. But if the lights are off to he sides, then the answer will be no.

The acrylic paint is reflective surface and will behave "like a mirror" -- so treat it like a mirror and move the lights to a position where you wouldn't be able to see them.

There's also an issue with light "fall off". Each time the distance from a light source to the subject increases by the 1.4x (it's actually the square root of 2, which is about 1.4142... but "1.4" is close enough) the amount of light will be halved.

Suppose you have a painting which is 2' wide (left to right) and you've placed a light source 5' away from the "right edge" of the painting. This makes that edge 5' away... but the "left edge" is 7' away from that light. The light fall-off rule (which is really the "inverse-square law" -- see: Inverse-square law - Wikipedia the free encyclopedia ) says that since 5 x 1.4 = 7 then that 7' distance will get precisely half as much light as the 5' distance and your image will have a noticeable drop off in lighting (the "fall off" problem.) But if you place ANOTHER light not he opposite side (and at the same distance) then it will provide supplemental light to the left and fall off to the right. This balance gives you even lighting across the image.

While this makes it sound like balancing the lights at equal distance from left to right should cancel out the fall off... not necessarily. Suppose you have a 9' wide piece of art and the lights are 5' away from the left and right edges respectively. Think about the math....

If the light is 5' away from the "right edge" then by the time you reach 5' in from the right (nearly the mid-point) the light fall-off is now down to 1/4 of the light. So you've got a bright outer edge but a dim center area. And unfortunately the light on the opposite side is ALSO unable to reach the mid-point. Increasing the power of the light won't help because the fall-off distribution is the same. If, however, the lights where moved back to about 20' (instead of 5) then the problem remedies itself.

Lastly... bumps and textures in the paint may be reflective EVEN with the lights far off to the side. But it turns out a circular polarizer is particularly good about handling reflections from light sources that originate from the side. If moving the lights to the side does not solve the reflection problem on it's own... invest in a circular polarizing filter (and preferably a good filter that doesn't create a color-cast).