AV Mode Flash Query

[MDJAK]

Two days ago, right after the big rainstorms in the northeast, I went out at dusk to take some pics of my 13 yr old daughter who still has lots of kid in her. She put on rubber boots and went romping in a large puddle caused by a small river overflowing its banks. The light was getting dim. I put my 1dsmkII in AV mode, had my 580ex on, and began to snap away, 40 pictures in all.

Only one:oops: :mad: picture came out sharp. I did notice the shutter speed was at around 40, but I thought the flash would freeze her jumping and antics. I was using the 24-70 F2.8 canon lens anywhere from 20 to 30 feet away.

Any ideas why?

Here's the only that came out decent:
http://upload.pbase.com/image/41698036

[mbze430]

yep, AV will cause the flash to only fill in flash. It will still open the shutter for a duration to keep light getting in for "proper" exposure. If you plan on using AV, in dark area, with lots of action. Make sure when you read your meter you get above 1/125+. You can do this by openning up or increase ISO.\

also might want to use high FP mode on the flash.

[Hellashot]

From what I've heard, 1/40 isn't fast enough to freeze jumping motion. Also, as with my Drebel, your camera might not take into account that you have the external flash mounted in Av mode. I use manual exposure - disregarding the exposure meter, and snap away choosing an appropriate shutter speed and appeture for good image quality and worry about how bright it was recorded later.


Her body was not moving much, you can see motion in her arms and her feet were slowed down by the water. And I didn't know your camera was so noisy at ISO800. Gives me new respect for the 20D/XT.

[MDJAK]

Thanks. Please look back. I edited my post and posted a picture.

Here's an example of a picture that came out blurry, as most of the rest did.

What should I have done?
(Warning, large size photo. I'm still learning how to upload pictures of the right size.)
http://upload.pbase.com/image/41698073

[Hellashot]

Thanks. Please look back. I edited my post and posted a picture.

Here's an example of a picture that came out blurry, as most of the rest did.

What should I have done?
(Warning, large size photo. I'm still learning how to upload pictures of the right size.)
http://upload.pbase.com/image/41698073


Focus seems to be just beyond her in the weeds. Wrong AF point by mistake if it was dark?

[MDJAK]

I actually have just changed one of the custom functions and placed the focusing on one of the rear buttons. But I'm still learning, so maybe I did have the wrong point on, or perhaps had it on single shot, though I don't think so. You do appear to be right, however; the weeds do seem to be more in focus. Now, if only they were my subject.:oops:

[mbze430]

umm, we looking at the same picture? cuz the focus seems to be at the knee cap, which happens to be the same distance as her head (since it's tilt forward). Looks fine.

Ah I see there is a 2nd link. Yes, this one is wrong focus point.

You can always check your EXIF data to find out if you used One Shot or AI Servo.

you can also use EOS Viewer to find out which AF point it locked into.

[MDJAK]

People here usually post such beautiful photos that I'm truly embarassed to post such lousy ones, but I'm doing it to learn. Here's another example: (warning: large photo again, sorry).


Help. http://upload.pbase.com/image/41698580

(Usually when I upload to pbase, it gives choices of photo sizes. I'm now left only with the original. I don't know why.)

[mbze430]

Not to put you any more down....but besides being out of focus, there is also camera shake in the last link. 1 and 1/3 stop slower than your focal lenght.

[MDJAK]

Please tell me how you can tell that.

[mbze430]

its fairly easy. Specially being so large. Look at your forground subjects. Look at the edge of each of the subject. Your pictures has a bit of a "ghost" to it, meaning its a camera shake.

example, look at the trampoline, the legs to be exact. noticed that the left side of the legs seems to be ghosting? Now look at the greenish area of the trampoline. Noticed that there is this ghosting on the top side of the greenish area, and it looks like it's going at 300 degrees? That tells me its the camera shake. Just look for stationary subject in a frame, if they start to ghost its because of camera shake.


Unless the wind was blowing really hard :)

[robertwgross]

Camera shake is hard to tell for sure, but there is something kind of vague and indistinct about the sky/tree branch area. Maybe it is just underexposed, since it was not the subject. The different exposure modes will surely give you very different flash results. That much is a given.

---Bob Gross---

[MDJAK]

Don't think I can blame it on the wind. That's why I like my IS lenses best; really helps me out holding steady.

My 100mm F2.8 macro I can't hold steady if someone held a gun to me and ordered me to.

[mbze430]

just try to get close to the FOV millimeter and your shutter speed that will eliminate the shake.

Here is a sample taking with a 180mm + 2x TC II, on a moving boat. Manual focused.

http://mysite.verizon.net/turbo2/album/Nature/Animals%20&%20Insects/slides/Seagull01.html

[MDJAK]

Nice shot. You really know how to hurt a guy.:o

[MDJAK]

Here is one between the puddle shots and the boot dumping near the trampoline. The flash failed to fire on this one and it originally was very dark. I used heavy level adjustment. I think this one is pretty good, at least for me. And she was swinging, not just posed upside down.

http://upload.pbase.com/mdjak/image/41699690/large

[mbze430]

yes that's looks great.

[J Rabin]

I'll stand to be corrected, but EVERYTHING I've used about EOS E-TTL and E-TTL II flash says that using flash in low/moderate ambient light in Av MODE WILL ALWAYS KEEP SHUTTER OPEN LONG ENOUGH TO PROPERLY EXPOSE BACKGROUND. This some times results in shutter speeds that demand camera be on a tripod. Only in brighter ambient does Av work as "fill." You can over ride this with the custom function.
Ditto for Tv. P will expose foreground and let background go to black if it must.
Study Photonotes.org a FEW times.
So, you've got some overexposed foreground elements, and camera shake.
Some of best "candid people action" success I've had is:
1. Turn off flash.
2. Set cam in M and meter ambient light. Set shutter to either stop action or expose background and f/stop to expose foreground. In your case 125 or 160 would have worked good. f/5.6-7.1 would give enough foreground DoF. ISO rarely needs to be above 400 in daylight.
3. Turn on flash.
4. Get focus point on foreground subject.
5. Bang away, no matter what camera meter says.
6. Adjust via histogram
Hope this helps.

[Bob_A]

yep, AV will cause the flash to only fill in flash.

Hi mbze430,

I don't believe that this is always true with ETTL-II (not sure about the earlier version of ETTL though). According to some correspondence I have had with Canon support, flash works exactly the same for every single mode. Basic modes, M, Av, Tv, P-Auto, etc. only reduce the power of the flash for fill mode if the Ev>10 for the scene (with maximum reduction at Ev=13). This seems to agree with what I have experienced with my 20D.

Ev=10 would be a scene that can be properly exposed at Iso100 and 1/60s at f 4 to 4.5. As an example, typical room light would be much lower than an Ev of 10, so the flash would not be in fill mode if this were the scene.



Bob

[robertwgross]

According to some correspondence I have had with Canon support, flash works exactly the same for every single mode.

You need to interpret those words.

The flash unit works just about the same in every single mode, as commanded by the camera body. However, the camera body does very different things to its own shutter and lens aperture depending on which mode it is in. I guess you see how this gets very different results in the flashed image.

---Bob Gross---

[mbze430]

This is according to the manual of the 580EX

AV: Select this mode when you want to set the aperture manually. The camera will then automatically set the shutter speed matching the aperture to obtain a standard exposure. If the background is dark like a night scene, a slow sync speed will be used to obtain a standard exposure of both the main subject and backgournd. Standard exposure of the main subject is obtained with the flash, while a standard exposure of the background is obtained with a slow shutter speed.

* Since a slow shutter speed will be used for low-light scenes, using a tripod is recommended.

* If the shutter speed display blinks, it menas that the background exposure will be underexposed or overexposed. Adjust the aperture until the shutter speed display stop blinking.

So in his situation, as he mention it was fairly dark low-light situation. The camera used a slow shutter speed to get appropriate exposure, only to use the flash to properly expose the main subject (fill flash I call it). It's exactly doing what the system is program to do.

[tim]

I do all flash photography in M mode, shutter speed of 1/80th and the aperture set to whatever I want - F8 is my usual starting point. The shutter speed only really changes how bright the background will be, but if it's too long the main subject can come out blurry. The flash is really really fast, like 1/1000 or faster i've read, but if I understand correctly the camera won't let you set a shutter speed faster than 1/250th on a 20D - not sure about your camera. Try it out, it's easy - M mode, 1/80th, F8, shots should come out ok and you can work from there :)

(sorry if this has already been said, I only skin read the thread).

[blackviolet]

if i'm shooting skateboarding shots, i use ES2M-E flash (everything set to manual, enhanced by chimping and histogram ;))
otherwise, i generally shoot people, etc. in AV, which is exposed for ambient as everyone else here has stated. if i'm just doing 'snap shots', then P mode and E-TTL2

[Bob_A]

You need to interpret those words.

The flash unit works just about the same in every single mode, as commanded by the camera body. However, the camera body does very different things to its own shutter and lens aperture depending on which mode it is in. I guess you see how this gets very different results in the flashed image.

---Bob Gross---

You're right Bob. The camera adjusts aperature or shutterspeed to try to get the right ambient/background exposure. However, for no matter what mode the camera is in, the flash isn't in fill mode until the scene brightness is at or above Ev=10.



Bob

[Bob_A]

So in his situation, as he mention it was fairly dark low-light situation. The camera used a slow shutter speed to get appropriate exposure, only to use the flash to properly expose the main subject (fill flash I call it). It's exactly doing what the system is program to do.

This is exactly right, except that Canon support seems to not call this fill flash. They appear to reserve the term fill flash for the region where the flash power is reduced above a scene brightness of Ev=10 (i.e., for a "catchlight" in your subjects eyes).

Before getting a few emails from support about this I always considered flash to always be fill ...

It would be nice if someone from Canon would speak up and give their interpretation. However, I think we are all using the camera the same way and this is just semantics :D .


Bob

[slin100]

Bob,

My understanding is the same as yours. Exposure of the subject by the flash operates independently of the camera's exposure mode.

In low light, flash always operates as the main light. I believe it's a mistake to say that flash operates as fill in Av mode. To me, "fill" is defined as a secondary and usually weaker light to supplement the main light. The purpose of a fill light is usually to brighten the shadows. If you experiment, you will notice that direct flash in Av mode doesn't just lighten shadows, it eliminates them. Hence, it is not fill.

In bright light, flash power is pulled back to provide fill. Again, this happens in any camera exposure mode.

[robertwgross]

Steven, did you just agree with Bob 1 or Bob 2?

---Bob Gross---

[slin100]

Bob, I was agreeing with Bob_A.