30D + 580EX & shutter speed

When I use my 30D + 580EX, I sometimes have trouble with the shutter speed in AV. Here's what I do: Let's say I'm shooting inside. The camera thinks that the lighting is low, even though the flash is turned on. If I don't have the sync speed dialed in to 1/200, I may end up with a very slow shutter (often around a full second or so, ISO 100 typically--I know I could boost it but why?) Now, if I go outside, and maybe I did set the sync speed to 1/200. Now all of a sudden, my pictures are way overexpsed because 1/200 is way too slow. So I have to go back through the menus and reset the sync speed to auto and make sure I have high-speed sync enabled on the flash. It would be nice if there was a setting that set the sync speed to "AT LEAST 1/200" That way if I was using the flash as a fill flash, it would happily use a higher speed. But if I went inside, it would go no slower than 1/200. Of course, if I shoot on "M", then I won't have this problem (and I often do shoot on "M", but sometimes I just feel like shooting pictures. like a family get-together or something). Is there another easy workaround?

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I think the only way is by using exposure compensation since the meter is working on exposure for ambient light

Wow, you sure were fast.
I don't think exposure compensation would work (EC or FEC). The difference between the two places (inside/outside) would be well over the 2 or 3 stops that EC and/or FEC can give you. Or did you mean something else?

On my 5D the swing is 4 full stops but if that's not enough I think your stuck doing the current adjustments or changing the ISO.

It just occurred to me that there is one other option: TV instead of AV. I don't know if I've ever taken a picture on TV. But I don't see why it wouldn't work.

readthe manual again.
but i think you can set the shutter speed to be constant 1/250 with flash installed on camera, maybe i misunderstood that but why you can't use manual instead?
I love manual more than Av or Tv or P, it gives you more Full control on your camera then half or semi-Auto.

First bit.... the max sync on the 30D is 1/250

Second bit... when in Av mode, the shutter is set for ambient lighting, NOT taking the flash into account. When using flash, you're really taking two exposures in one shot. You've got an ambient light exposure which is determined by your shutter speed and a flash exposure which is determined by your aperature and flash output. Assuming you're taking advantage of ETTL autoflash, you have to keep in mind that the flash metering system is looking for 18% luminosity, Just like the ambient light meter. If the flash hits a surface that lighter than 18% gray, it will dial the output back to make it 18% and the results can be underexposure. You have to either take this into consideration and dial the FEC up to the level where underexposure doesn't occur, OR do an FEL on a 18% gray target before taking the shot to get the right exposure. For me it's easier to do the previous since it's not always convenient to find an 18% gray target near the subject. If I am inside, in order to get a good balance between ambient light and flash with Av mode, I'll set my EC to -1 to -2 stops and the flash will fill in the rest.

Third bit... Outside you may have more than enough ambient light to use and when the camera sees this, your shutter speed will most likely bump out at max. You can either dial back the ISO to 100, use a slower aperature to get the shutter speed down, or if you want to use a fast aperature, either an ND filter on the lens or us FP flash which the 580EX happily supports. Using the FP flash, you'll reduced the effective range, but you'll be able to use any shutter speed you'd like.

There's also P mode; if it's dark it'll let the flash do its thing; if it's bright, available light will be allowed to dominate.

My bad. 250, not 200. (I was remembering my 300D, which is 1/20). But my flash has a high speed sync button. I have used that to take pictures with the flash outside with shutter speeds much faster than 1/250. What's going on then?
I have noticed that when shooting on AV, the shutter speed is determined before taking the picture (AV, of course), not taking the flash into consideration. I hadn't thought of taking the EC down a stop or two to get better results. I will give that a try.
How does the flash decide how much.... ummm... "flash" when shooting with the camera on M, and the flash set to E-TTL? Does the flash still use the camera's light meter to determine how bright to fire? And then use the dialed in FEC to determine the final brightness? I'd rather put the flash on M, but I have no idea how to calculate the proper power for a given picture.
Overall, I usually like shooting on M, but sometimes when I am going inside and back outside pretty often, sometimes it's just easier to shoot on AV, but I can usually dial in a good exposure pretty quickly on M, so maybe it will be better to just go that way. As for using P (or the green square), that's just leaving too much up to the camera. Perfect point, I like to use the flash a lot outside for a good fill light.

For high speed sync, your flash fires a lot of short (less than full power) bursts, like what you see when you press the DoF preview button with flash on. As a result, it's less effective than when you're in normal X-sync mode.

MrGibbage wrote in post #2315329
How does the flash decide how much.... ummm... "flash" when shooting with the camera on M, and the flash set to E-TTL?

That's what the E-TTL preflash is for. It measures the light from the preflash to determine the required output.

With direct flash, look at the distance scale on the back of the flash unit.

There's no point in even considering Av or Tv mode for flash shots unless you want the ambient light to contribute to the exposure.

I think you would benefit from reading the EOS Flash Bible.

I understand about the pre-flash. But when you are shooting with the camera on "M", what is the "required output" of the flash? As for shooting with the flash on "M", of course distance would make a difference, but what about reflectivity of the subject? Doesn't that make a difference? It is starting to make sense that using AV (or TV) on flash shots really doesn't make sense.

Btw, I found the EOS flash bible. I'm in the middle of reading it now. Based on the detail it offers, I think it will probably answer every flash question I've ever had.

MrGibbage wrote in post #2316401
when you are shooting with the camera on "M", what is the "required output" of the flash?

With E-TTL the flash will figure this out for itself. That's what automatic flash metering is all about.

In technical terms, no.

MrGibbage wrote in post #2316401
I understand about the pre-flash. But when you are shooting with the camera on "M", what is the "required output" of the flash? As for shooting with the flash on "M", of course distance would make a difference, but what about reflectivity of the subject? Doesn't that make a difference? It is starting to make sense that using AV (or TV) on flash shots really doesn't make sense.

I'll expand on the great info Curtis is giving you...

The exposure mode you choose (M, AV, or TV) has NOTHING to do with flash exposure levels. Think about it logically... when the exposure level is determined (as indicated by the moving pointer on the scale) is there any flash going on? Nope. The exposure meter is for the ambient light ONLY. Enter ETTL. After your ambient exposure is determined, your flash will operate to expose what's left over to create the level of 18% luminosity or 18% gray much like the ambient meter. In fact, I think the same sensors are used in some camera systems, just used in a different way.

Even color can be deemed 18% gray... because the metering isn't looking for color. It's color blind. If you take a color image and convert it to grayscale.. you'll see that skin tones vary in shades of gray.

If you meter on light skin people... you'll find that images tend to underexpose. If you meter on dark skinned people, you will find that images tend to overexpose.

Now, understanding that the internal ambient light meter and the flash meter are both looking for this 18% gray value, you'll know that if you get close to this value in ambient light, you'll receive less output from the flash. This means the flash will act as fill. Some will say that the flash acts as fill in Av or Tv modes only, but I'm telling you that the reason the SLR systems do not have a "fill mode" setting for the flash is because with any TTL flash metering, the level of flash used is directly dictated by how well you nail the ambient exposure regardless of WHAT mode you're in... EVEN manual. The reason they say it's operating in fill mode by default in Av or Tv is because those modes attempt to nail the exposure with ambient light by default... so logic dictates that the flash will act as fill, by default.

If you nail the exposure (18% on whatever surface you're metering) the flash output will be minimal. The reason I suggest 1 to 2 stops underexposed with ambient light is because indoors you will tend to get shutter speeds much lower than you should be using for a given focal length to correctly expose the image and even with flash, which at this point is just filling in shadows you can't get away from motion blur. If you are 2 stops under... the flash will be more of a motion stopping force and your BG although acceptably exposed, could be a bit blurred, but your subject should appear crisp. I think outdoors you can end up with fast shutter speeds so closer to 1 stop to 1/3 stop under is fine there and should provide a VERY nice ambient/flash blend. IE. your photos will not look flashed!!!!

The EOS flash bible will teach you that a flash photo is really two exposures in one shot. Hopefully after reading it, and this post, you'll be off and running with flash.