drebel flash questions

[bballboy30]

I was playing with the rebel and something odd happened. When shooting in the green square mode the flash fired and the aperture was about 3.5 and the shutter was 1/60. Then I changed the mode to Av. I set the aperature to 1.8 hit the flash button and took the picture. However, the camera set the shutter speed to 1/4. This didn't make sense. Shouldn't the shutter speed be faster? I should mention that the flash looked a lot less bright in the Av mode compared to the automatic mode. I used the canon 50mm 1.8 len.

[cmM]

in AV mode the camera meters for ambient light, meaning it'll disregard the flash and set the shutter speed as if there was none, and use the flash as fill.
In automatic mode it won't go below 1/60 or so... I think, I've never used automatic mode :)

[bballboy30]

Thanks cmM.

If you never use the automatic mode what do use use for nightime photography?

[PacAce]

Thanks cmM.

If you never use the automatic mode what do use use for nightime photography?

Funny but nighttime photography is the ONE time I never use auto-anything. It's strictly "M" mode for me. That's because metering gets very difficult at night and I need to be able to control both the aperture and the shutter speed.

[Hellashot]

In green square it could have changed the ISO to a higher value. The ISO used in manual, Av, etc. is not used for green square. Green square manages all settings exposure settings.

[scottbergerphoto]

P mode is good if you don't care much about the exposure of the ambient light and you don't want to worry about camera/subject movement with a slow shutter speed. It won't go lower then 1/60. In low light, your backgrounds will go black. If you like to have some natural light to compliment the foreground, use Manual Mode on the camera and depending on your lens and hand holding ability drop the shutter speed to around 1/30. Don't overexpose the ambient light. Keep an eye on the camera meter. Leave the flash on ETTL.
Scott

[cmM]

Funny but nighttime photography is the ONE time I never use auto-anything. It's strictly "M" mode for me. That's because metering gets very difficult at night and I need to be able to control both the aperture and the shutter speed.
Exactly ;) .

[intechpcx]

Thanks cmM.

If you never use the automatic mode what do use use for nightime photography?

I'm with PacAce on this one, night photography is the one time I'd never use any of the basic mode settings. The internal meetering on the camera does not handle extremely low or no light settings (no light defined as less than 1 lux). You've got to be able to set the exposure settings manually. I was also taught some time ago that the key to night photography is trial and error (since even many handheld meters can't properly meeter such dark environments). An expensive proposition on my 35mm SLR, hence one of many reasons that I bought the dSLR. Many times I even switch to manual focus for night shots. Especially if I'm shooting stars or other predominantly dark scenes, the AF doesn't find enough contrast to focus on.

[bballboy30]

Thanks everyone for your help. I am still not confortable enough to shot in M mode. I have been playing around somemore and the manual says that in Tv mode the shutter speed can be 1/200 or slower when using flash. I interpreted this as the flash adjusts brightness to match the shutter. I tested this and sure enough the images looked almost exactly the same. The aperature was 1.8 but I changed the shutter to 1/200, 1/160, 1/125, and 1/100. I also shot in automatic mode for the heck of it and the image looked the same even though the aperature was 2.8 and shutter 1/60. My question is will this happen all the time? Will the camera always have enough flash to properly expose a shutter of 1/200 no matter the lighting (or lack thereof).

[scottbergerphoto]

The shutter speed has absolutely nothing to do with controlling the flash exposure. The flash exposure is occuring at about 1/10,000 sec. ETTL is controlling the flash exposure, or the Manual controls on the flash. The shutter speed is only controling the ambient light exposure. You need to keep your shutter speed below 1/200 so that the entire frame can be illuminated by the flash as the shutter opening travels across the sensor.
Scott

[robertwgross]

I agree with the words that Scott used, but I would re-arrange them slightly to improve readability:

As long as you keep the shutter speed at 1/200th or slower, the shutter speed has absolutely nothing to do with controlling the flash exposure. The flash exposure is occuring at about 1/10,000th sec. ETTL is controlling the flash exposure, or the Manual controls on the flash. The shutter speed is only controlling the ambient light exposure. You need to keep your shutter speed at 1/200th or slower so that the entire frame can be illuminated by the flash as the shutter opening travels across the sensor.

It is always ambiguous to speak of "below 1/200 second". Which way is below? Faster is less time. Is less below or above? That gets further ambiguous when you look through a viewfinder and the shutter speed is shown as "200" and the user is forced to understand that means 1/200th.

---Bob Gross---

[scottbergerphoto]

I agree with the words that Scott used, but I would re-arrange them slightly to improve readability:

As long as you keep the shutter speed at 1/200th or slower, the shutter speed has absolutely nothing to do with controlling the flash exposure. The flash exposure is occuring at about 1/10,000th sec. ETTL is controlling the flash exposure, or the Manual controls on the flash. The shutter speed is only controlling the ambient light exposure. You need to keep your shutter speed at 1/200th or slower so that the entire frame can be illuminated by the flash as the shutter opening travels across the sensor.

It is always ambiguous to speak of "below 1/200 second". Which way is below? Faster is less time. Is less below or above? That gets further ambiguous when you look through a viewfinder and the shutter speed is shown as "200" and the user is forced to understand that means 1/200th.

---Bob Gross---
I'm not sharing my salary with you Bob, so forget about it! ;)
Scott

[Redbird_xo]

The shutter speed has absolutely nothing to do with controlling the flash exposure. The flash exposure is occuring at about 1/10,000 sec. ETTL is controlling the flash exposure, or the Manual controls on the flash. The shutter speed is only controling the ambient light exposure. You need to keep your shutter speed below 1/200 so that the entire frame can be illuminated by the flash as the shutter opening travels across the sensor.
Scott

Is it true that setting the D300 at 1/200 sec in M mode in order to stop action (say a toddler) is okay (meaning it won't affect the overall exposure) if an external flash is used?

Thanks for helping.

[scottbergerphoto]

Is it true that setting the D300 at 1/200 sec in M mode in order to stop action (say a toddler) is okay (meaning it won't affect the overall exposure) if an external flash is used?

Thanks for helping.
I'm sorry but your missing the point. The shutter speed isn't stopping the action, the flash is. Even at 1/200 the shutter is much slower then the flash at 1/10,000. Use your shutter speed to regulate the amount of ambient light you want in your picture. Flash pictures are really a combination of 2 exposures, the flash which you can let be controlled by ETTL which exposes your subject and freezes the action, and the ambient light exposure in the background, which you control with aperture and shutter speed.
Scott

[robertwgross]

I'm not sharing my salary with you Bob, so forget about it! ;)
Scott

I think Pekka pays you about the same as what he pays me.

---Bob Gross---

[Redbird_xo]

I'm sorry but your missing the point. The shutter speed isn't stopping the action, the flash is. Even at 1/200 the shutter is much slower then the flash at 1/10,000. Use your shutter speed to regulate the amount of ambient light you want in your picture. Flash pictures are really a combination of 2 exposures, the flash which you can let be controlled by ETTL which exposes your subject and freezes the action, and the ambient light exposure in the background, which you control with aperture and shutter speed.
Scott

Crystal clear. Thanks.

[bballboy30]

Thanks for all you help. However I am still just a bit confused. When you say that the flash stops action does that mean that the action is stopped at 1/10,000? Thus no matter what the shutter speed is you wont get blurry pictures due to subject movement?

Thanks.
Alex

[robertwgross]

Let me take a shot at this.

As Scott suggested, a flash image is a result of two exposures that happen at about the same time. The flash pop is relatively bright, but it is extremely short in duration. If you measure the amount of movement of the subject in 1/10,000th of a second, it should be next to nil. However, your shutter may be open for 1/200th of a second, or slower. It is likely to be gathering ambient light, which is much dimmer than the flash pop. So, ambient exposure is a normal result of the shutter and aperture. You may get a certain deal more movement of the subject during the 1/200th, but that movement is likely to be lit up much less than the flash pop. So, you'll likely get a very crisp image (due to the pop) and just a tiny bit of ambient light and very little ambient light movement visible.

---Bob Gross---

[bballboy30]

Thanks Bob!!

Had to read it twice but now I get it!!!!