? about 10D and onboard flash.

[JoeCanon10D]

I don't use flash much, and when I tried to use it last week I got a surprise I didnt know how to work around. I was in a drizzling forest, shooting a pic of my boss and his wife at the base of a redwood tree. With the flash off, the exposure was 1 second at F4 with the 17-40mm. With the flash on, guess what, it was still 1 second at F4. Why didnt the flash raise the shutter speed to the point I could have gotten the shot?

[Morden]

I don't use flash much, and when I tried to use it last week I got a surprise I didnt know how to work around. I was in a drizzling forest, shooting a pic of my boss and his wife at the base of a redwood tree. With the flash off, the exposure was 1 second at F4 with the 17-40mm. With the flash on, guess what, it was still 1 second at F4. Why didnt the flash raise the shutter speed to the point I could have gotten the shot?
In some modes, the 10D will expose to get the "background" right, even when using the flash. Try (M)anual mode with a shutter speed of 1/200 and f4/f5.6 or so. The ETTL will (should!) get the exposure right.

[Jim Larson]

Um, NO. 1/200 is way too fast if ambient light calls for 1 second.

Av and Tv modes: exposure is set for ambient light regardless of flash. Background will be properly exposed. Flash will expose subject *under the focus point*.

P mode: Exposure at 60 F4 regardless (well, usually) Flash will expose subject.

M mode: you set exposure. Suggestion: Set shutter based upon your ability to handhold. Set aperture based upon desired depth of field. Set ISO so ISO is not *too dark* (I don't like using more than ISO 400)

[Morden]

Um, NO. 1/200 is way too slow if ambient light calls for 1 second.

Av and Tv modes: exposure is set for ambient light regardless of flash. Background will be properly exposed. Flash will expose subject *under the focus point*.

P mode: Exposure at 60 F4 regardless (well, usually) Flash will expose subject.

M mode: you set exposure. Suggestion: Set shutter based upon your ability to handhold. Set aperture based upon desired depth of field. Set ISO so ISO is not *too dark* (I don't like using more than ISO 400)
Bear in mind that, whatever the chosen shutter speed, the flash illuminates for a tiny fraction of a second. I use the settings that I suggested with very good results.

[robertwgross]

Um, NO. 1/200 is way too slow if ambient light calls for 1 second.

You want to explain that? I don't think that is what you meant.

---Bob Gross---

[Jim Larson]

Um, NO. 1/200 is way too slow if ambient light calls for 1 second.

You want to explain that? I don't think that is what you meant.


If the camera meter says you want a 1 second exposure, that implies that the area is fairly dimly lit. If you set the camera to 1/200th second, the flash will fire to ensure proper exposure of the subject. The background, however, would be basically exposed ONLY be the flash (since the shutter is open only 1/200th and not 1 second). If the background is far away, the background will not be lit by the flash and will be DARK.

By setting the shutter speed to 1/60th (what you can hand hold), the shutter will be open three times as long and the surroundings will show more "natural" illumination.

In fact, since the flash pulse is quick, many can successfully "drag the shutter" (shoot very slow, say 1/15th) since the flash will stop subject motion. The only reason to set a 1/200th shutter in this case is if you are trying to stop some serious subject movement.

For indoor shooting, I generally use 1/45th or so. I set aperture based upon subject (2.8 for portrait, F5.6 or F8 for group shots). If the light sensor shows gross underexosure, I bump up to ISO 400 (but not higher=> I don't use neat image) and fire the flash. Note if I am using F8, the backgrounds begin to look dark because the ambient exposure is going to pot.

The key (I have found) is to use FEL on a skin tone before focusing recomposing. That really helps flash exposure. Camera on "auto focus point selection" is a evil, since one can never really predict what the camera will meter. (or focus on, for that matter).

[Morden]

Each to his or her own, I believe.

[robertwgross]

Um, NO. 1/200 is way too slow if ambient light calls for 1 second.

I read your follow-up, so apparently this ("too slow") is not what you really meant.

---Bob Gross---

[Tom W]

Um, NO. 1/200 is way too slow if ambient light calls for 1 second.

You want to explain that? I don't think that is what you meant.


If the camera meter says you want a 1 second exposure, that implies that the area is fairly dimly lit. If you set the camera to 1/200th second, the flash will fire to ensure proper exposure of the subject. The background, however, would be basically exposed ONLY be the flash (since the shutter is open only 1/200th and not 1 second). If the background is far away, the flash will not be lit by the flash and will be DARK.

By setting the shutter speed to 1/60th (what you can hand hold), the shutter will be open three times as long and the surroundings will show more "natural" illumination.

In fact, since the flash pulse is quick, many can successfully "drag the shutter" (shoot very slow, say 1/15th) since the flash will stop subject motion. The only reason to set a 1/200th shutter in this case is if you are trying to stop some serious subject movement.

For indoor shooting, I generally use 1/45th or so. I set aperture based upon subject (2.8 for portrait, F5.6 or F8 for group shots). If the light sensor shows gross underexosure, I bump up to ISO 400 (but not higher=> I don't use neat image) and fire the flash. Note if I am using F8, the backgrounds begin to look dark because the ambient exposure is going to pot.

The key (I have found) is to use FEL on a skin tone before focusing recomposing. That really helps flash exposure. Camera on "auto focus point selection" is a evil, since one can never really predict what the camera will meter. (or focus on, for that matter).

Jim, I'm certain that you know what you are thinking (and I think I know as well), but I had a little trouble, as did Robert, with implying that 1/200 is slow compared to 1 second. What you're meaning, I think, is that the slower shutter in flash conditions will allow for a brighter background. I agree.

I'll add that I think that you depend on shutter speed selection as a tool to adjust the balance between the selected subject and the background when using flash. That, to me, is making use of the flexibility of your SLR.

In short, I'm not arguing with your reasoning, but I think you should have stated that 1/200 is too FAST to allow the necessary ambient background lighting to appear when the camera wants 1 second of exposure time.

[Morden]

In short, I'm not arguing with your reasoning, but I think you should have stated that 1/200 is too FAST to allow the necessary ambient background lighting to appear when the camera wants 1 second of exposure time.
That makes sense. For what I tend to (mainly) shoot I use the fastest shutter speed that I can - 1/200 with the flash. The background is seldom far behind the subject, and getting a sharp-as-possible picture of the subject is paramount.

Having said that, the argument for a slower shutter speed is almost certainly more sensible in most cases. I should have explained the reason for my chosen configuration when I posted it. :)

[Tom W]

That makes sense. For what I tend to (mainly) shoot I use the fastest shutter speed that I can - 1/200 with the flash. The background is seldom far behind the subject, and getting a sharp-as-possible picture of the subject is paramount.

Having said that, the argument for a slower shutter speed is almost certainly more sensible in most cases. I should have explained the reason for my chosen configuration when I posted it. :)

And I agree - I sometimes find problems with the standard 1/60 flash speed. A little movement can cause problems with pictures. I like to use 1/90 or 1/125 depending on the subject matter. The weakness I have is that my favorite lens isn't all that fast, so I lose ambient light and atmosphere sometimes when I use flash with faster shutter.

Its all in what effect you want, I guess. :)

[Jim Larson]

Um, NO. 1/200 is way too slow if ambient light calls for 1 second.

I read your follow-up, so apparently this ("too slow") is not what you really meant.

---Bob Gross---

Yeah, well, I claim "illiteracy" for my remarks. I saw your response, but did not closely reread my original post and failed to recognize the gaff.

Hey! I can edit my posts! I fixed the original.

[JoeCanon10D]

Thank all of you for your help, I was shooting Av, (my favorite since I like to control depth of field) I will go re-create the conditions and use manual at something handholdable.