Laser pointer focusing ... ?

[Matus Kalisky]

Hi,

we offten talk how hard it can be to focus our (mostly) wide angle lenses in low light and wheter to swap the f/8 version for f/5.6 or even f/4.5. Here comes my idea (though I am sure somebody had to think of it already) - what about using a lasr pointer? At least for shots or architecture or so - when there are no peole in the scene.
I have a personal experience shoooting inside (with fujinon 125/5.6) an old grape-pressing room wehre my exposure was ~ 16s at f/22 and when I got the film from the lab I could clearly see I miss-focused the picture. Then I got the idea of using a small on camera (or tripod) fixed laser pointer via some semi-stiff arm (or micro-ballhead) that would alllow for different directions setting and then using the little spot for foccusing.

A laser pointer for $10 should be plenty.

What do you think?

matus

[poco]

I tried this and while it worked for getting the intended shot, it wasn't as helpful as I thought it would be. It's surprisingly difficult to focus on an undifferentiated tiny red dot as opposed to even a pen light placed in the scene. But if a penlight isn't an option, then the laser is better than nothing.

[Uusilehto]

A paper focusing target (preferably made of thin paper) between a flashlight and the camera works wonders.

[Don Hutton]

Those super powerful new flashlights with lithium cells work well. I have one which is tiny, takes 2 CR123s and is brighter than a big maglite. Just buy one and leave it in your camera bag - very handy.

[Ed Richards]

I have a small high intensity LED pen light in my bag. You can get these from the police suppliers. It will throw enough light to focus for 30-40 feet.

[Greg Lockrey]

I haven't tried this since I don't have a laser light but what if you shine the laser light through the ground glass onto the target you wish to focus. Would you be able to see that?

[John Powers]

I have had great luck with a trick taught me on APUG. In the dark of the deep woods, place two small flashlights. One at the furthest spot you want in focus, another at the nearest point. Mark the spots on your focusing scale if you have one or spot on the camera. Use the rule of 1/3 in focus toward you, 2/3s away. Some say it should be 1/2 and 1/2. You may have to tape the lights in place. Don't forget to remove them before you shoot. Obviously there are some places you can't reach with the lights. At that point move to plan B.

John

[Lazybones]

At that point move to plan B.

Great. What's Plan B?

[PViapiano]

To make Plan A work!

[Dirk Rösler]

I have had great luck with a trick taught me on APUG. In the dark of the deep woods, place two small flashlights. One at the furthest spot you want in focus, another at the nearest point. Mark the spots on your focusing scale if you have one or spot on the camera. Use the rule of 1/3 in focus toward you, 2/3s away. Some say it should be 1/2 and 1/2. You may have to tape the lights in place. Don't forget to remove them before you shoot. Obviously there are some places you can't reach with the lights. At that point move to plan B.

John

Does this still work when using movements?

[RDKirk]

Putting the two flashlights out is what works for me. Better, are the small lights that have a cluster of LEDs. Point them back at the lens, and it's easy to see that the light is in focus when the LEDs resolve.

I tried the laser (even different laser shapes), but the spots were just too small to see. I do this especially when using movements.

[Robert Fisher]

Putting the two flashlights out is what works for me. Better, are the small lights that have a cluster of LEDs. Point them back at the lens, and it's easy to see that the light is in focus when the LEDs resolve.

I tried the laser (even different laser shapes), but the spots were just too small to see. I do this especially when using movements.

Would somebody please give a URL for the "cluster of LEDs" that RD just mentioned?

Thanks!

[John Powers]

Does this still work when using movements?

It has for me. You are still adjusting to get an object sharp on the gg. The small light is just a brighter target than a rock or a tree in the "Deep Dark Woods".

Besides being cheap and readily available, I like tools that serve more than one purpose. They give more bang for your packing, carrying, buck.

John

[Matus Kalisky]

- Greg -

that is not a good idea. Imagine you get some 20% reflected back into your eye. It happened to me once at university. One of young post-docs made a mistake during simple difraction experiment and threw very shortly the laser beam across the audience (small pencil - sized laser for basic experiments at school). I was the only one with the bad luck - the beam hit my eye directly. I could see a red spot for an hour .... though I could not focuse on it ;)

- all -

sounds like a small LED based torch is a better solution - will give it a try next time. Still I have to find a way how to attach it on the tripod to have the light steady and my hands free.

[Greg Lockrey]

- Greg -

that is not a good idea. Imagine you get some 20% reflected back into your eye.

How? I wouldn't be looking through the ground glass while shinning the light through it. :eek: I would be placing the light at the ground glass and shinning it through the lens onto the subject. Then focus the light on the subject with your eyes looking at the subject and not through the ground glass, it should indicate a sharp focus at the film plane. It would have to be a pretty low light situtation to see the red dot I would imagine. Probably any LED light would work this way. Again, it's just a theory.

[Helen Bach]

Probably any LED light would work this way. Again, it's just a theory.

And more theory: I think that a laser would work better than 'any LED light' because the laser will tend to act more as a point source at the ground surface of the ground glass. Any other small light will tend to act as two sources, each in a different plane: one at the lamp (with the size of the lamp) and one at the ground surface (with the size of the area of ground glass that is illuminated). If you wanted to use any light, then the old trick of shining a light through a small aperture at the location of the film plane could be the thing to do, if it was bright enough.

Best,
Helen

[Greg Lockrey]

And if Helen says, it's probably true. ;)

[Alan Rabe]

"Would somebody please give a URL for the "cluster of LEDs" that RD just mentioned"

Don't know about a url but any Home center or camping supply store will have several small flashlights with mutiple leds. Also the led style head lamps will do the same trick

[M Salhuana]

I have used the small lithium based flashlights that are more powerful than a maglite. They work great and are about 3-4" long and 3/4" wide. I usually shine it on my subject as I am focusing either in ny hand or an a clip somewhere. Of course it helps if you have a second pair of hands. I used the surefire brand of lights, since they are designed for a tactical envrionment, they can take a massive beating and still work. Of course you do pay a premium on these. You can find them online or at your local gun/sport shop. They make both bulb and LED models. The on I use is listed at:

http://www.surefire.com/maxexp/main/co_disp/displ/prrfnbr/198/sesent/00

Here is a smaller version of it

http://www.surefire.com/maxexp/main/co_disp/displ/prrfnbr/803/sesent/00

and an LED version of their lights:

http://www.surefire.com/maxexp/main/co_disp/displ/prrfnbr/24263/sesent/00

I have had mine for over 5 years and dropped it many times and it still works. Hope this helps.

They also make less expensive plastic models of their lights for about $36.00 here ia link to one:

http://www.surefire.com/maxexp/main/co_disp/displ/prrfnbr/878/sesent/00

Regards,

Miguel