Laser for photography equipment testing

[ericbowles]

Hi - I'm new here and relatively new to lasers.

I'm looking to use a laser mounted to camera lens to test for vibration caused my camera mirror slap, shutter release, etc. I'll be testing different camera bodies, lenses, and tripods. This is a one time project primarily for personal use. I'll probably have other uses but none that are really worth a large expense.

I expect to measure results by using longer exposures in order to see movement of the laser point rather than a sharp point.

I expect the results will allow me to understand how long it takes between raising the mirror and shutter release for the vibration to settle. I expect lighter and physically longer lenses will have longer vibration periods and need more time to settle.

I don't know the distances involved, but expect it will range from 5-6 feet to 150 feet or more. I want enough distance to show motion so a more precise beam will let me use shorter distances or more easily see evidence of vibration.

I plan to use gaffer tape to attach the laser to the lens hood. I'll use shims if necessary to make sure it is properly aligned. The target will be an appropriate photo target to achieve sharp focus.

I think I should buy an Altair Series 532 nm Green Focus-Adjustable Laser Pointer. It's about $59 which seems okay for a reasonable quality pointer. The 3-4.0 mW version is $59 and the 4-5.0 mW version is $79. It produces 532 nm light which the camera sees well, and allows focus adjustment for different distances. Power of <5.0 mW seems to be adequate.

What do you think? Is there a cheaper option that I should consider? Do I really need adjustable focus?

 

[DrSid]

It would really depend in the distance. Any laser pointer will increase dot size linearly with distance. For a start let's estimate divergence of your laser to 1 mRad. It may better, but also worse. Hard to tell without knowing the specific model. 1 mRad would mean at 1000 feet the dot will be 1 feet large .. at 100 feet it will be 0.1 feet. Question is if that is OK for your setup. In other words, at distances like hundreds of feet you won't gain much sensitivity by increasing the distance. Yes, the dot will move more, but it will also be larger, in exactly same ratio.

To get dot small at a distance, you would need beam expander. Dot size is inversely proportional to the 'aperture size', which is basically beam width at the laser. Thick beam focuses better at a distance, it might seem counter intuitive for some people.
Beam expanders are sold separately, and are sometimes quite expansive. They could be built, but so far I haven't met anyone trying it. Well except me, and I mostly failed, so I can't really recommend it.

I don't clearly understand that method of yours. If I was to measure camera vibration, I would slap a laser to the camera .. and take high speed video of the dot with ANOTHER camera, while the first camera is taking a shot. Instead of high speed camera you could use still camera as the second one, and rotate it in horizontal plane during the shot with long exposure, so the dot will spread to line, capturing vertical movement of the dot.