Canon Flash Help

[racingpinarello]

Hello,

Now that I have a Canon EOS3 and the Canon 1Ds, which use the old E-TTL system for flash I am having a hard time.

I'm not sure what I am missing, but when I turn on the flash and set it to 1/60 or 1/125 for the shutter speed, it will always find the f/ stop for the ambient light. If it's low light then it will go to f/1.8 or f/2.8. This feels like it's always on slow-sync mode, even though I have it turned off.

In essence, I am always off on my exposure. When I shoot with the new E-TTL 2 system from Canon it's much better so this is a old flash system problem.


When I was shooting with Nikon it felt like the exposure was much better, and it would allow you to drag the shutter speed to capture more ambient light manually.

I try so hard, but I continue to struggle with Canon flash systems.

Loren

[Sebastian]

In shutter priority the aperture will go as far as it can and then it will under/over expose. In aperture priority it will use whatever shutter speed is necessary to expose the background properly.

Not much more I can say, you're really not giving many details here. What modes are you in? How can it seem like it's in slow-sync when you're setting the shutter speed?

Are you keeping the focus sensor on an area that you want to flash meter off of? E-TTL meters off of the selected focus sensor, not from the whole scene like Nikons, that's why you need the newer bodies to use E-TTL II.

[racingpinarello]

------------------
Are you keeping the focus sensor on an area that you want to flash meter off of? E-TTL meters off of the selected focus sensor, not from the whole scene like Nikons, that's why you need the newer bodies to use E-TTL II.--------------


I almost always use aperature priority for my photography using in-camera spot metering. It just seems that even with spot metering on the subject, it will use a shutter speed that is way to slow. To make sure that I am using a fast enough shutter speed I use Shutter priority, but the aperature setting is too shallow. Although it should meter off the subject, it still seems that it doesn't expose right.

What techniques do people use when using flash with Canon?

[Sebastian]

Well of course it will use a shutter speed that's too slow, it's exposing for the ambient light. When the flash fires, it meters off the focus sensor to see how much flash output is needed to match the ambient light.

The only way to override that is to set the exposure for ambient light manually, or if your camera has it (my 10D does, I'm sure the 1Ds's do too), set the custom function to lock the shutter speed at a certain value when in aperture mode with the flash on. The 10D's function let's you lock it to 1/200, yours might give you more control than that. I wish the 10D did.

[racingpinarello]

[QUOTE=Sebastian]Well of course it will use a shutter speed that's too slow, it's exposing for the ambient light. When the flash fires, it meters off the focus sensor to see how much flash output is needed to match the ambient light.QUOTE]

Thanks Sebastian. I guess I was hoping that the camera would set the exposure to the flash output to make sure that the subject was properly exposed. The Canon system works great during the day when you are using fill flash, but in low-light it lacks.

I will look into the custom menus, and just use Manual exposure from now on.

Thanks again,
Loren

[racingpinarello]

Long story short, you're not alone.

Thank you for that!! I've been going crazy, and the manuals didn't help.

Loren

[Sebastian]

That's actually the same way the Nikon system works, it tries to match the flash output to the ambient exposure. But, the Nikons don't let the shutter speed drop below a certain value. I think with my D100s it was 1/40 or 1/60th, don't remember exactly. So I would shoot aperture priority and never have to worry too much. The Canons just choose whatever shutter speed the camera pleases, which also really screwed me up initially.

Long story short, you're not alone.

[drg]

[QUOTE=racingpinarello]

Well of course it will use a shutter speed that's too slow, it's exposing for the ambient light. When the flash fires, it meters off the focus sensor to see how much flash output is needed to match the ambient light.QUOTE]

Thanks Sebastian. I guess I was hoping that the camera would set the exposure to the flash output to make sure that the subject was properly exposed. The Canon system works great during the day when you are using fill flash, but in low-light it lacks.

I will look into the custom menus, and just use Manual exposure from now on.

Thanks again,
Loren

Loren,

I saw this post late last night and wasn't awake enought to be coherent so we'll try it now!

Canon flash is not historically as fine tuned, it has been about sheer power. So it is not just you.

The 1Ds has a pre-flash system that with the FEL button and custom settings (fN16 I think, I'll look it up if you can't find it) will set the exposure based on AF and metering settings. This way it doesn't meter on the ambient light and should hold the setting for several seconds or you can program a One-Shot value and it will hold until after firing.

There is the paired AF point settings that can play tricks. This is the one where the camera chooses between two subjects to focus the 'scene'. This one works great in the proper lighting but otherwise it will 50-50 as to whether it picks what you want.

Some more Canon gotchas in the camera. The sRGB chroma setting is one that is worth setting with a meter as the response curve in an attempt to make it more 'transparency' like has some 'notches' in the response curve that for me always produce what look like hot spots if I'm not careful with the exposure. Lots of light and slightly underexposed seemed to work well

The 1Ds has FEB (flash exposure bracketing). A handy Canon feature that if nothing else may help determine more quickly which way to change compensation. The usually +/- values can be set in a range and so on.

The one thing I hate in digital cameras is when White Balance fools me into believing something that isn't true. I don't know if you shoot much high/low key type situations, but use the WB bracketing along with your flash/strobe setups to make sure that a mixed light phenomena isn't occuring. Back to the chroma setting, it will look improperly (and it is!) exposed in hi/lo key if the camera locks onto the wrong light! The WB balance will produce 'test patches' that you can kinda of evaluate in the camera but I prefer to just pop the Flash card in notebook and see what the software says if its particularly critical.

Until the 550 and now the 580EX as a real fix (for cameras that fully support it), I usually used a flash meter and color temp analyzer and a MecaBlitz and manually tweaked everything when I needed real portable light.

There are also some interactions mentioned with the Multi-Spot mode metering buried in the manuals, about reseting to a default value important parameters like compensation or shutter curtain priority etc. I'm doing this off the top of my head this AM.


Oh, and the sync speeds default to 200 or 250th of a second! That always fooled me for along time. That's part of the reason I went to an external PC synced flash a lot. More power and longer flash duration. If I set the aperture perfectly, if the shutter and the flash don't agree, well you know the story.

Good luck!!

[racingpinarello]

Thank you for your detailed reply. I will put that help to good use.

Thank you again,
Loren

[Lemming51]

http://photonotes.org/articles/eos-flash/ is a comprehensive and invaluable resource explaining the EOS flash system(s). Canon should include it in their user manuals.