Using Screen as Camera Flash

That's good thinking. I never thought of redirecting the back light of the LCD to use for flash. I'm sure it would work, but probably not as effective as LEDs; especially the dual LED flash systems in place in many cell phones today. And with the right app to make the LEDs stay on, it makes a great flashlight in a pinch! Just don't leave it on too long.

A multiplying effect? Like 'Free Light'? No.

Multiplying effect? Multiplying effect?

That could be dangerous. Put too many mirrors in the circuit and you could melt them when the light intensity gets too high. Plastic camera would vaporize if it got in the path.

Say, is there a weapon to be developed here?????

I resisted telling our anonymous poster about our Light Compression technology. Sales of the LynDoor™ Supervelocity Arrest Nanomechanical Device With Individual Condiments-Handheld^® (SANDWICH^®) (which can be reconfigured to decompress the light) have been brisk, and I doubt we could handle another order at this time.

Even the R & D at LynDoor™ Industries is having trouble with multiplying light... we cannot make photons simply appear... Yet!

Good call partner, you can't be too careful with our high powered mmilitary grade stuff equipment.

We wouldn't want this technology to fall into the wrong hands. Especially that guy Anonymous Poster #1 and his minions Anonymous Poster #2 and Anonymous Poster #3.

How he comes up with all those goofy questions all the time, I just can't figure.

BTW, we need a safety switch on the SANDWICH^®. I had mine in my back pocket the other day and sat on it and it took out half of my couch and the wall behind it. Kids thought it was great!!!!!!

Still haven't found Fluffy though.

You two are fun to watch - from a nice safe distance, of course.

There once was a guy in northern NJ who would peep into the windows of cars parked at the local drive-in movies. He chose not the cars filled with families of children but those cars who had no heads visible above the bottom of the windows. When he found a car with appropriate subjects paying attention to other than the movie on the screen he would have his girl friend hold a mirror about 1 ft sq in any ambient light available (car headlight, movie light, overhead light, etc) and shine the reflected light onto the otherwise indisposed couple.

When he was finally caught he stated that a flash was too bright and got too much attention. He chose to use high speed film with low reflected light to illuminate the couple. He was then banned from local drive-in theaters. No use though, he hid in the trunk of his girl friends car and she drove in.

Yes, I am old enough to remember drive-in theaters and that they were nick-named "passion pits". I also remember when there was only 102 known elements.

The original poster's theories are clearer as to their viability when applied to a drive-in movie! Also more fun I'm sure.

Good Luck, Old Salt

Yeah I'm sure LED's would work better. But as my phone didn't have one I was just curious what would happen.

As for 'Free Light', it wouldn't be free. It would be coming from the LCD screen... What was meant by multiplying effect was the process from going from a minimum brightness to the max allowable by using the screen as your light. When the light from the screen is first directed in front it would still be relatively dim, but as the now brighter object is seen and captured by the camera it's screen will light up a little bit more, and then that'll be redirected around and so on... Until a sort of Max is reached and the screen can't get any brighter.

I'm assuming here that you're using a webcam fixed to the lid of a laptop, or some similar arrangement. Rather than trying to get the light round behind the screen, why not bring the subject and camera in front? A webcam with a USB lead is very cheap these days.

And as for the brightness - you won't do any better than a white screen (say a blank document) with the backlight control turned up full. Frame the subject, then shrink the camera application so that it reveals as much as possible of the white.

There are a couple of issues. The intensity of the LCD screen is very low compared to a normal flash.

The camera's ISO will need to be adjusted very high. Your camera probably does this automagically, but there is a limit as to how well it will perform in low light conditions. Generally, the lower the light the more noise that is introduced and you could have focus issues.

You can increase the exposure time and open up the aperture to gather more light. The downside is that longer exposures lead to blurring and camera shake focus issues and wide apertures change the depth of field (the point of focus) to a very narrow depth range.

The color (or temperature) of the screen may also yield a color cast with the photo. It will depend on how well your camera interprets the light temperature and adjusts its white space to compensate.

The idea of using mirrors to redirect the light will not actually amplify the total lumens that the screen generates, but you could focus the light onto a smaller area and get some gain with a concave mirror. You will also need a diffuser so the light is evenly dispersed over the subject.

The easy solution is to simply buy some cheap photography flood lamps and light up the subject that way (or turn on the room lights). If you ever watch a professional photo shoot in the dark you will be surprised at how much light they use to get a good picture. Modern digital cameras are getting better at low light photography, which helps remove some of the need for flash or external lighting.

This concept is based on a positive feedback loop, but still, the starting point i.e the light your LCD emmits in it's dark state, will decide if it will amplify or not. For an older LCD with bad contrast ratio it propubly will. OSD characters, emmiting light even at 'darkness' signal from CCD also increase your chanses along with optical help suggested above. S.M.

Don't you have a cellphone? Even the cheap ones emit a fair amount of light when you activate the screen. They also make a good emergency flashlight.

It's not clear to me if AP#1 is using a lap-top or cell phone for this picture. If it's a cell phone & it's one that you can add applications to, there are various programmes available that will turn the LCD screen into a torch. This would make the screen go straight to maximum brightness instead of relying on feedback from the subject. I use an add-on called 'best torch' on an old Nokia E50 so this is not restricted to iPhones & the like.

Why not simply use a cheap wildlife camera? They shoot well in the dark and are triggered by movement.

Not enough light from a screen. Have you looked at the screen when you are focusing on a dark area? If the focus works at all in the dark (maybe ultrasonic, contrast focus, led or infrared), the screen is also dark if the subject is in the dark: no much light on the screen because all the camera sees is dark, right?

Flash intensity is 100s of times higher than a lightbulb, or 1000s of an LED screen.

In absence of a flash connection get a good LED torchlight and use that, better still: get a camera with flash, unless you plan to photograph something you should not be photographing in the dark, eh?

If you have no problem spending several 1000$ get a Leica with an f0.7 lens and shoot what you see in real colour, or a camera with an infrared light amplifier.