New Studio Set up

[fwellers]

Sorry, I don't understand what you just said.
I had read the first few chapters of the 101 on strobist, and just now scanned the rest, and I can't find any reference to 2 exposures or anything about that.

Doesn't the shutter speed work with flash the same as without flash ? In other words, say you are in AP mode. If you use flash, the camera will know there is more light coming, and accordingly speed up the shutter, and that's why you would have a clearer picture ?

 

[Big Mike]

I had read the first few chapters of the 101 on strobist, and just now scanned the rest, and I can't find any reference to 2 exposures or anything about that.

That site is more about the equipment and the application of that gear, not really the fundamentals.

Doesn't the shutter speed work with flash the same as without flash ? In other words, say you are in AP mode. If you use flash, the camera will know there is more light coming, and accordingly speed up the shutter, and that's why you would have a clearer picture ?

As mentioned, every flash photo is actually two images in one. The first exposure is from the ambient light (just like any photo without flash). This exposure is a result of the aperture, shutter speed and ISO. The basic principle is that you get more light with a bigger aperture or a longer shutter speed.

The second exposure is from the flash. It is a very quick burst of light, much faster than the shutter speed. Because it's so fast, the shutter speed has no effect on the flash exposure...but the aperture and ISO still matter. Of course, the power of the flash plays a part as well.

The two exposures are made and usually, they layer over one another and you can't tell. If it's dark, the ambient exposure is probably going to be fairly dark, so the flash exposure easily overpowers it in the photo.

As for how the camera deals with it...it depends on what mode you are using. In auto, when it's gets dark enough, the camera will use the max aperture and a preset shutter speed (something like 1/60)...which isn't enough for an ambient exposure....and the flash will take care of the rest.
But if you switch to Av or TV, the camera will give you settings for the ambient light (probably a long shutter speed) and the flash will add to that but not be as dominant as in auto mode.

It's a bit of a mess to wrap your head around how it works, but you'll get it eventually.

 

[Village Idiot]

Sorry, I don't understand what you just said.
I had read the first few chapters of the 101 on strobist, and just now scanned the rest, and I can't find any reference to 2 exposures or anything about that.

Doesn't the shutter speed work with flash the same as without flash ? In other words, say you are in AP mode. If you use flash, the camera will know there is more light coming, and accordingly speed up the shutter, and that's why you would have a clearer picture ?

It's two exposures. You get the exposure from what ambient light hits the sensor and the exposure from the flash. This is assuming one is using manual mode and the camera isn't doing the exposing for you.

Like say you're inside. If you shoot at ISO 100, a shutter speed of 1/250 and an aperture of f/9, you'll most likely get a black photo, unless your lights are extremely bright. If you're using a flash, it's what exposes the scene in that case.

So ambient light creates no exposure because of the settings. The flash is what lights things up in this case. Small speed lights like the Canon 580EX can has flashes as short as 1/15000 of a second. That's how long the light last from beginning to end. That's what creates the exposure, provided settings are right.

Now, if you're shooting inside and you're shooting at ISO 100, a shutter speed of 5 seconds, and an aperture of f/9, you could probably get a properly exposed picture in the same situation as above. The problem is that a shutter speed of 5 seconds is not enough to freeze motion, in fact, it's probably not enough to show anything that moves infront of the lens. You may get trails, but that's it.

If you have a flash with the settings set to match the camera settings and you fire it with the above settings, you're going to have the ambient exposure of the room, along with the exposure created by a flash. So if you catch a cat moving infront of the frame with a flash that has a duration of 1/15000, it would be like you're using a shutter speed that fast.

In fact, you can do multiple exposures. Each time you pop a flash, it will show what ever it lands on, provided it's power is set to match your camera settings.

 

[Chris of Arabia]

Doesn't the shutter speed work with flash the same as without flash ? In other words, say you are in AP mode. If you use flash, the camera will know there is more light coming, and accordingly speed up the shutter, and that's why you would have a clearer picture ?

Simply put, no it doesn't. The only thing that the shutter needs to do is be fully open when the flash fires. It used to be that most cameras were only able to do this at a fastest speed of 1/60 sec or longer (1/30, 1/15, etc..). Now it's faster in many instances (haven't checked, but maybe as fast as 1/250 sec), but they are still nothing like the 1/6000 sec duration that a flash (strobe) may last. In order to get the correct lighting using a flash, you no longer need to worry about shutter speed under normal circumstances.

To get the correct exposure, it's now a case of balancing the aperture setting and the power output of the flash. When using the camera manufacturers' own flash products (e.g. Canon 350D + Canon Speedlite 580EX), they are usually designed to communicate with one another as the shot is taken. An aperture is set on the camera and as you press the button, the flash fires, but only for long enough to get a correct exposure at that aperture, at which point the camera tells the flash to stop firing.

As for the ambient/flash thing, there are ways of balancing any available (ambient) light with the output of the flash. Essentially, all that's being done is that the power output of the flash is being reduced to a point where it isn't the only light source that the camera sensor is registering. Under these circumstances, the shot you take is benefiting from two light sources. Take a look at this image of mine to see the effect:

Flash was used in this instance, as the camera wanted to expose for the much brighter background. Without flash, the subject would have been dark, positioned as they were in the shade. The flash has helped balance the lighting out - this is known as fill-in flash.

Is this any help?

 

[fwellers]

Thank you all !!
Very interesting how that works. I'm not too lazy to look things up, and have been reading a lot for the last month or so, but never came across that info presented that way before. First I've ever heard about the 2 exposure thing, the first I've understood about the shutter speed vs the flash speed.

I appreciate you guys.

 

[Chris of Arabia]

We do our little bit, you know... :blushing: