Lightbeam Photographing Calibration

Can we come up with a simple lightbeam photographing method that we can use among ourselves as our guide to photographing lightbeam.

This probably will compose of;

1) flashlight - must be the type commonly available in a household or store, need not be the expensive type.

2) digital camera setting - shutter speed, white balance, resolution

3) lightbeam & camera setup - (a) distance of flashlight and position of lightbeam against blank wall or target paper, color-shade of wall and type/form of target paper to be agreed upon (b) distance, height, and position of camera to capture lightbeam

4) Software image editing rules

With so many types of flashlights out there it is probably impossible for one of us to photograph every type of lightbeam there is.

The benefit is anyone using this method to photograph a lightbeam can come up with lightbeam's photo that all of us agree to be close to the actual lightbeam. Example: calibrating a lightbeam photo of Maglite-2AA in England to look as close as can be to the calibrated lightbeam photo of Maglite-2AA from CPF. Once setup is calibrated other lightbeam photos are acceptable as close to actual lightbeam as seen by the eyes and we can exchange with confidence photos for comparing lightbeams of different flashlight.

If manufacturers won't get together and come up with a standard to rate flashlights lightbeam, this is a cheaper and effective method for us to at least have a photographing standard to lightbeam photos.

Manufacturer can label its flashlight with any number of lux, candelas, or lumens they want to and we won't be confused because our lightbeam photographing method is calibrated to show photo as close to actual lightbeam at a set distance.

How about it guys. What do you think? Share your thoughts.

Darn! Another one of my crazy wild ideas.

- verge -

It sounds like a good idea. I think the best improvement we have made is comparison shots, say using a 2AA Mag or 3D Mag next to the light in question. Taking a bunch of shots all at the same time with the same setting on the camera gives us similar results. I really don't have a point here, oh well.

You're getting the point Brock.

Take a series.. say 12 photos of 2AA-Maglite or Arc-AAA lightbeam,

1. position camera 24 inches above the flashlight and 36 inches away from the wall
2. use different camera settings and note (ex: 50mm lens setting, 0.5 sec exposure, white balance=off, flash=off, red-eye=off)
3. lightbeam setup (flashlight 12 inches away from the wall, target wall marked (bold black "X" on piece of masking tape) every 6 inches vertically and horizontally to show size of lightbeam at that distance.

* This is just an example, we'll find the best setup for best result.

and I'll do the same. We'll compare pictures.. select and agree on photo that comes close to the actual lightbeam.

When a photo is selected that will be our "Calibration Photo" using the setup details used to take that photo for our lightbeam photography of other flashlights.

Much like adjusting our monitor so that the pictures and colors you see is the same pictures and shades of colors that I see using a picture that we both agreed to be true.

We're getting there! Gotta save money to buy the Canon-D30 or Canon-G2 I've been eyeing for some time.

- verge -

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by 2d_edge:
If manufacturers won't get together and come up with a standard to rate flashlights lightbeam, this is a cheaper and effective method for us to at least have a photographing standard to lightbeam photos.

Manufacturer can label its flashlight with any number of lux, candelas, or lumens they want to and we won't be confused because our lightbeam photographing method is calibrated to show photo as close to actual lightbeam at a set distance.
<HR></BLOCKQUOTE>

This all will not come close to any measurement.

There are already enough standards about how to rate light sources.
Technically correct: make just a light distribution polar diagram, best in more than one axis (horizontal, vertical). You may add the luminous flux and the light temperature, maybe the CIE rating.
A photo (but not with a standardized exposure) may complete this data.

In this case some data (diagrams) will say more than thousand photos.

If you use a 'standardized' exposure, brighter flashlights will overexpose your photo in the center. They will look like having an even light distribution, which they have not at all. For example, 1000lx may look like 10,000lx.

What is your camera's dynamic range? How many EV?

Don't get me wrong: Of course a photo is easy to make and better than no data at all.
(to be continued)

If you want to use an (especially incandescent) light as a reference, be shure to have it at a very well defined voltage (regulated power supply).
If you shine your light at a test target (wall?), it will be fine when you mark it in angular degrees from the center. If you also include at least one 'brightness' reading, even better. Better make several measurements at 0°, 10°, 20° halfangle or whatever is appropriate for the specific light. A Luxmeter is not expensive and gives a rough idea. And always run also your test sample from a regulated power supply (also a regulated power supply is not expensive and should be available at hamfeasts for a couple of bucks). You have to agree at which voltage, of course.