Painting with Laser

in Tutorials
By hrebic/Richard (5,692) This user is a Premium Member Send mail to this user on January 4, 2006 7:02:15 PM CST

Introduction
Equipment
    Camera
    Tripod
    Room
    Laser Pointer
    Safety Glasses
The Subject
Camera Settings
    Shutter Speed
    Laser Speed
    F-stop and ISO
    Focus
Technique
    Laser Direction
    Laser Motion
Post-processing
Conclusion
Appendix: Determining Exposure for Painting with Laser

Introduction

Painting with Laser is a photographic technique inspired by and loosely related to Painting with Light. In both cases the illumination on the subject is controlled dynamically during the exposing of the film, print or digital CCD. However laser painting differs from light painting in that the purpose of the laser light is not to illuminate but to sculpt the subject.

In this article I show how to create striking images using Painting with Laser. I also point out some interesting variations which should get you thinking about the flexibility of this technique and hopefully get you to create novelties of your own.

Equipment

Camera

The Painting with Laser images and examples in this article were done with a 35mm digital SLR. However almost any digital or film camera may be used provided that the camera has a shutter speed control that allows long exposures of up to 10 to 20 seconds or more. Your camera must be able to focus on the subject manually or have the ability to disable the camera's auto-focus. It is also strongly recommended that you use a remote shutter release or self-timer function if your camera has this feature.

Tripod

 Obviously you will want to use a tripod, particularly if you are working alone. Even if you have an assistant working with you who will hold the camera while you move the laser, the long exposure times required make using a tripod essential.

Room

Because of the unique properties of laser light, the painting technique should work over a fairly broad range of distances. However the wider the set, the faster the laser will need to move, and this will affect the aperture and ISO settings. (These settings and their relationship to laser movement are discussed later.) The photos in my "Painting with Laser" portfolio on PhotoSIG were produced in a small 5 meter x 5 meter room.

Laser Pointer

The key piece of equipment for this technique is the laser itself. I recommend not using the cheapest laser pointer. You will want something that throws a well-defined beam over a good distance. The laser used in my portfolio is a Class IIIa laser purchased from Radio Shack which can easily throw a visible beam 75 to 100 meters. Also important is to keep a set of spare batteries handy.

Red light laser pointers are the most commonplace, but green laser should work as well. I have not tested blue lasers but I suspect that it will not produce as good an effect for this technique.

Safety Glasses

Before going further I need to discuss safety. The use of laser light with human subjects can be harmful to the model if there is direct eye contact with the laser light. Although some people have suggested to me that conventional laser pointers pose no health risk, I strongly recommend staying on the safe side and investing in a pair of laser safety glasses which are designed to the frequency range of the laser you are using. The laser safety glasses I use were purchased from Phillips Safety Products (http://www.phillips-safety.com/ps/)

The Subject

The subjects used in this article are nudes. The advantage of using nudes is that they have fairly good reflectivity for laser light and result in an image that is easily recognizeable. A person wearing dark clothes would probably not produce as distinct of an effect. But there is no rule; any subject will product satisfactory results provided that 1) they have high, uniform reflectivity to the laser color used, and 2) the subject must not have a lot of fine detail, such as a shrub. Small details will almost certainly get lost in the end result. Simple abstract or geometric shapes such as spheres, cones and blocks would be ideal.  

Camera Settings

Painting with Laser does not require extremely tight control of camera shooting parameters, particularly if you are shooting digital and even more so if you shoot in RAW format. You should be able to get decent results in post processing even if the original appears too dark.

Shutter Speed

You will be shooting in total darkness, except for the laser light. The time setting will therefore be several seconds long, but not because of the darkness. In fact, the Painting with Laser technique doesn't really depend on the duration of the exposure. This may appear confusing at first, but think of it this way: If you were taking a photograph of a stationary point of light, then shutter speed, aperture and ISO all must be factored in for proper exposure. But if the light is quickly moving across the camera's field of view, then the level of exposure really depends on the speed at which the light source is moving, not the amount of time the shutter is open.

If your camera has a time-delay feature for the shutter release, this can be a convenient way to give you time to turn off the room lights and getting into position with the laser pointer before the shutter trips open. If you don't have this feature, then simply add a few seconds of time to the exposure.

Laser Speed

s long as you move the laser wand at the same speed, a 10 second exposure will produce the same result as a 60 second exposure (assuming you don't have any background light leaking into the picture.) The speed at which you move the laser will determine how bright the light traces will appear on the photograph. For most people, simple trial and error is sufficient to get a feel for how fast to move the laser. For those who want a more theoretical explanation, a more rigorous analysis is provided at the end of this article.

F-stop and ISO

As is the case with laser speed, trial and error is the simplest and probably the quickest way to determine a satisfying combination of ISO sensitivity and f/stop. But consider that shallow depth of field, which might be desirable for conventional portraiture, is useless and even detrimental for Painting with Laser. So smaller apertures are generally preferred. Again, those who want a more specific technical discussion of these parameters should refer to the section at the end of the article.

Focus

Cameras don't focus well in total darkness. It's best to focus on the subject manually with the lights on. If you prefer using auto-focus, then focus on the subject and then disable the auto-focus, taking care not to move the camera, the lens and of course the subject. Another advantage of using small apertures is that the deeper depth of field makes precise focusing unnecessary.

(Surprisingly, slight movements by the model during the long exposure will produce very little noticeable motion blur, especially with quickly moving laser scanning. This is because the very short duration during which each part of the subject is illuminated has the same kind of freeze-action effect as using a flash.)

Technique

The two most important factors in producing successful laser painting images are 1) selecting the direction of the laser with respect to the subject and the camera, and 2) how you move the pointer over the subject during the exposure.

Laser Direction

You do not want to stand next to the camera with the laser pointer. It will produce flat and uninteresting photos. You want to use the laser light to sculpt the model, to give the photo a 3D impression. The human eye interprets the light patterns and re-creates the shape of the subject based on visual cues, such as the way the light streaks bend around curves or corners. Other shape-cues are shadows that one part of the subject casts upon another.

I recommend placing the laser at a point that creates a nearly 90-degree angle between the subject and the camera. Pose and orient the subject in a way that best exploits the placement of the light source relative to the camera.

Laser Motion

The most interesting effects I've gotten have resulted from trying to control the laser to get nearly parallel back and forth motion, wide enough to completely cover the subject, and gradually progressing across the subject until the shutter closes. I try to cover the subject evenly. It may seem easy but it really takes practice to get the desired effect.

I have tried other patterns but have found that circular, or random laser movements tend to camouflage the subject. Straight lines, or nearly straight lines, make it much easier for the viewer of the photo to identify what the subject is. Of course you may actually like the results from random motion better. Or you may come up with a totally different pattern which becomes your favorite.

Post-processing

There are an unlimited number of things one can do with laser paintings in post-processing. Obviously, brightness and contrast adjustments can bring out the laser in dark photos and add punch to the effect. I also tend to erase out the ?spill? if it occurs in distracting areas of the photograph.

You can change the color of the laser in post processing by adjusting the hue, or by adding a color layer with a hue-based blending mode. You can even overlay multi-colored patterns or gradients with this blending mode. Use your creativity.

Conclusion

In Summary, Painting with Laser is a surprisingly easy and relatively inexpensive technique for creating distinctive, stunning images. I hope you find this article useful and are able to create beautiful images of your own.

Appendix: Determining Exposure for Painting with Laser

The optimal settings for Painting with Laser technique begins with selecting the desired laser speed (how fast you move the laser dot across the subject), A series of exposure tests are performed on a stationary laser dot, and the results of these tests will determine the best combination of f-stop and ISO sensitivity.

By practicing with a laser, you can get a feel for how fast you can move the wand back and forth while maintaining control of the painting pattern you prefer. Begin by standing in front of a wall or background at approximately the same distance that you will be from the subject. The wall should have markers approximating the field of view of the camera. Using a back and forth zig-zag motion, move the laser dot between the markers on the background. Move with the speed you desire to use for the photos. Count the number of "zigs" and "zags" that you are able to complete within a second.

Now a bit of math. Knowing the distance between the markers and the number of "zigs" and "zags" we can estimate the speed. Let L be the distance between the markers and N be the number of zig-zags in a second. The average laser dot speed S is then

S = N x L

For example if the markers are three meters apart and you can do 4 zig-zags in one second, then the dot is moving at an average speed of 12 meters per second (4 x 3 = 12).

Next we need to measure the diameter of the laser dot on the background. Again holding the laser at approximately the same distance as you will be to the subject, shine the laser at a stationary point on the background and measure the approximate diameter of the dot (it doesn?t have to be exact). Let's call this diameter D.

Now I?m going to talk about a concept that I call the effective shutter speed. This is not the actual shutter speed you will use in the laser painting photos. It is a shutter speed you will use in your test shots to determine ISO and f-stop. The effective shutter speed T is the amount of time that a point on the background gets illuminated by a laser dot of size D moving at speed S.

For a given point on the background, the effective shutter speed starts when the leading edge of the laser dot arrives at the point and continues up until the trailing edge of the laser dot passes over it. Therefore this time can be calculated approximately as:

T = D / S

In our example, if the laser dot diameter is 5 mm (.005 meters) then T= .0004 seconds (.005 / 12 = .0004). (Shutter speed will be 1/.0004 = 2500.)

Now set up the camera to take a series of photos of a stationary laser dot at a shutter setting of 2500. This should expose the same as if the laser was moving at speed S and the shutter remained open. Start with ISO 100 and a moderately small shutter (say, f/11) and take a series of shots with progressively different f-stops. (Remember to turn off all other lights!) The photo which gives the best results will have the f-stop and ISO settings that you need. If you don?t get satisfactory results, then think about changing the speed with which you move the laser pointer.

What are "satisfactory" results? In my opinion this would be any photo which reproduces the color of the laser without getting washed out. But even settings which produce darker versions can be effectively reclaimed in post-processing.

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From charlesheckel/Charles (2,271) Send mail to this user on January 13, 2006 8:17:20 PM CST

Including hrefs to your folder of laser nudes would have made the article clearer and helped to sell the methodology. Your browser probably has a "page source" mode allowing you to inspect other tutorials to see how this is done.

Other possibilities: using gels on the pointer to get more than one color in the image, combining it with traditional "painting with light" techniques or perhaps a very underexposed flash image, using standard on-axis lighting and using the result as a bump map in PS, and so on ...

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From hrebic/Richard (5,692) This user is a Premium Member Send mail to this user on January 15, 2006 11:55:26 PM CST

Thanks Charles.

I didn't include hrefs to my portfolio in order to keep my article more accessible to the general public, some of whom might object to viewing nudes. But it's a good suggestion.

Regarding color gels, it won't work with color lasers, which are pure in color. A red laser for example, can only look red. Placing a blue gel (for example) in front of it will only yield a weaker red laser light or it will yield no visible light at all. However if you could get a white laser (if such a thing exists) then color gels might work. But I don't think that white lasers exist because lasers produce a stream of photons with identical wavelength, hence a single color.

As for your other ideas, all I can say is, give them a try!

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From aymx/Aymx (1,691) Send mail to this user on February 16, 2006 9:49:15 PM CST

I made a picture using lazer pen. You can see it HERE. Regards, Aymx

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From hrebic/Richard (5,692) This user is a Premium Member Send mail to this user on February 19, 2006 2:23:53 PM CST

Yes. I see that your images were submitted at least a year before mine. It's not a new technique, and certainly not one that I invented, but it is relatively easy to produce once you understand the way laser pens work. Thanks for your comment!

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From knol/Shawn (1,122) Send mail to this user on February 18, 2006 7:37:41 PM CST

very good information... laser light can be fun to work with, but at the same time, it can be very difficult to work with...

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From hrebic/Richard (5,692) This user is a Premium Member Send mail to this user on February 19, 2006 2:24:44 PM CST

Thanks Shawn!

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