Question about photos with static objects and lights in movement

[Gabo]

Good morning, guys.

I have recently started learning about photography an I'm going through any photo effects that I like and try to reproduce them myself as part of my learning process. I have a Nikon D40.

I have seen a few pictures that have an effect that caught my eye and I would like to reproduce it. In this case, it's the following:

* https://scontent-a-iad.xx.fbcdn.net...0x720/263370_488620397855428_1409045995_n.jpg

* https://scontent-b-iad.xx.fbcdn.net...=c16203e26faba0fa73517941dd8e5a9e&oe=5445E0BD

* https://fbcdn-sphotos-d-a.akamaihd....0x720/317963_484622454921889_1971102938_n.jpg

In those pictures, we see the lights that come out of the equipment's buttons "stretches" ad moves in he pictures. My first thought was those pictures were taken with a slow shutter speed and then the camera was moved in order to obtain that effect with the lights, however if that was the case... then why are the rest of the objects in the pictures still? why was not movement captured within the other objects in the pictures?

If they would have only been taken with slow shutter speed, then every object in the pictured would be blurred, am I right?

So, my questions how to take those kind of pictures in which the only movement captures was from the lights emitted out of the buttons (that are in fixed still place) and the rest of the objects appear to be standing still (with no distortion or blur)?

I hope I explained myself correctly. I'm still learning.

Thanks in advance.

Regards!

 

[TCampbell]

If these are not your images, the moderators will likely ask that you substitute links to the images rather than posting the images inline.

As for how it's done...

The shots are likely mistakes -- I doubt the photographer intended this "effect".

When you take a shot with flash, the camera "meters" the scene and sets the in-camera exposure based on the ambient lighting... but then uses flash anyway. It's very important to remember that the exposure indicated by the camera's light meter is based on assumption of not having the flash fire.

This means the shutter speed will often be long... much longer than it would be if the shot were metered for the amount of light provided by the flash. When using flash in dim situations, you are often encouraged to "drag the shutter" -- meaning you should deliberately set a shutter duration longer than is necessary for the flash alone. This is desirable because it helps pick up ambient lighting and fixes the light "fall off" problem. Of course... since the shutter is open longer, you'll need to be steady with the camera.

But if you don't understand how it works and why it works, you can end up with problems like those in the images above. (yes... I regard those photos as being unfortunate mistakes).

Suppose the camera meters the scene and because the scene is dark, it decides it wants a long shutter exposure... lets say it's 1/4 second. But let's also say we're using flash.

Consider the lights in those images above... they're all small LEDs. They really don't light up the room in any meaningful way. For purposes of setting exposure, they can be ignored. That means what you're REALLY seeing is a scene lit entirely by the on-camera flash.

The on-camera flash is very fast. The amount of time in which the flash is actually providing light is just a tiny fraction of a second. That is the only time in which there would be enough light to illuminate the table, the people, etc.

If you are in a completely black room with an open camera shutter... people can walk in front of the camera as much as they want and the camera won't see a thing. The camera can only capture "light" and as there is no "light" the camera won't see a thing.

Pulse the flash for 1/1000ths of a second and everything will be frozen in place for that moment in time. You can continue to leave the shutter open. It won't matter because there's no more light.

But in the case of the shots above... the LED lights on the table are still emitting light. The camera can see those lights... but can't see anything around the lights. Since the camera was hand held, the lights created these streaks or blurs you see in the photo even though everything else is not blurred.

If shooting with iTTL (or any TTL system, I just used iTTL since you mentioned you have a Nikon camera) - you can manually set the shutter speed to the max flash sync speed (often this is somewhere around 1/200th second but will vary by individual camera model and I don't know what it is for a Nikon D40), set the aperture to whatever you'd like based on depth of field needs, and take the shot. The camera will figure out how much power it needs to pump into the shot to light the scene (assuming it's not more light than the flash can provide -- and for distant subjects it could be.) You'd get the same shot regardless of a fast shutter speed (1/200th) or a slow shutter speed (1 full second for example) and the difference would be how much those constant source of light (the LEDs on the table) will blur.

BTW, you can do something called "multi-strobic" flash... some better flash units are capable of this. The flash fires multiple times while the shutter is open. For example, I can configure the flash to fire every 1/4 second for 4 flashes. The camera shutter would be open for a second while the flash fires 4 times. You'd actually get 4 "ghosted" overlays of your subject as they are moving. It's a neat affect with moving people -- particularly with subjects in action.

 

[Gabo]

Thanks for the tip about posting the links instead of attaching the images, I have edited my post.

And, Tcampbell...

Let me tell you I have been trying to find an explanation for this since a few days now and I had not been able to completely understand how those pictures were taken, but your explanation makes complete sense. Even for a newbie (just like me), you explained it in a way anyone can understand it.

I can rest now knowing those pictures were most likely mistakes and understanding why that happened. With the information you have provided me with, I might just try to reproduce those mistakes. I'm sure that will be good practice material.

Thanks a lot for taking your time to read and answer my questions. I do appreciate it.

I'm sure I will be checking and posting on this forums as I continue learning about photography.

Kind regards!