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I think I love manual mode, but not sure why it works.
So I'm messing around with settings on my XTi today, trying to improve my flash shots, and I found the following:.

It's dark out and not alot of lights on in the house..

ISO200 - In Av mode, set to F/5.6, the camera selects shutter speed of like 1/2 second. Picture is blurry due to this, and is pretty warm..

ISO200 - In manual mode I set F/5.6 and roll the shutter speed all the way up to 1/200. Picture is much, much sharper, and still exposed well. Not warm at all..

What I don't understand is why the camera is auto selecting a much slower shutter speed when the picture still comes out at the faster one. This is my first real venture into manual mode. I guess I can tell that the picture is "whiter" when doing this in manual mode, and maybe in Av mode the camera is trying to get a more actual light capture. I will be playing with this at an outdoor party tonight, so I hope that the pictures turn out better than my friends wedding last weekend. I think they will. (Of course I got my 35mm F2 in yesterday as well, so I'm using that instead of the kit lens)  .

Any help explaining this phenomenon is greatly appreciated!! Thanks!..

Comments (7)

In Av mode the camera gave you the "correct" exposure based on the metering. It didn't know that you are hand-holding it (where the blurriness come from.) I bet that if you redo the shot with a tripod, the picture will be better than the one with 1/200 shutter speed..

The 1/200 will be sharper because you can handhold at that speed. But it isn't necessary the correct exposure. Something must have been sacrificed in the process, such as details in the darker area, etc..

Hope that helps. Johnnyhttp://tuxbailey.zenfolio.com..

Comment #1

Shutter speed makes no difference for the amount of light the camera sees from a typical flash at shutter speeds that are not faster than the sync speed. Only aperture and ISO speed impact that part..

That's because the flash burst is too short (it's usually around 1/1000 to 1/10000 second, depending on your other settings, distance to subject, etc.)..

The camera is just varying the flash burst length to control exposure from it...

Shutter speed is used to expose for ambient light levels..

So, more ambient light is being used to make up the total exposure at slower shutter speeds, and less ambient light is being used to make up the total exposure at faster shutter speeds, given the same ISO speed and aperture..

IOW, it sounds like your camera is going to expose for Ambient using Av mode (which is why shutter speeds are so slow), using the flash for fill..

JimChttp://www.pbase.com/jcockfield..

Comment #2

JimC is very correct, and I agree that shutter speed is not a factor for flash...

And even in Manual exposure mode, the auto flash power level is changing to give a good exposure for the aperture selected. You could select Manual level for the flash too, to prevent that from helping automatically..

And even if you turn off the flash, you could still get a similar affect (where either 1/50 or 1/200 might come out OK), if you had Auto ISO speed selected. It would just keep pumping up ISO speed so that the available exposure worked, within it's limits. ISO speed used should be reported in the Exif..

But, otherwise, if no auto flash, and no auto ISO speed, then different settings should give different exposures in Manual, as expected...

Comment #3

... but it is different.

If you are using the built in flash, or have an external flash mounted in eTTL mode, the camera modes work very differently from when you are shooting in ambient light. When using the Canon EOS flash system, Av and Tv are fill flash modes. The camera exposes for available ambient light and uses the flash only to "fill" in the shadows. This will cause slow shutter speeds in dim available light..

With the flash in eTTL (or with the built n flash) and the camera in M mode, the flash is used as the main source of lighting. You can vary the shutter speed and aperture as you want to allow more or less ambient light into the exposure. As others have pointed out, unless you exceed the X-sync speed, the shutter speed will not effect the flash part of the exposure because the flash duration is always less than 1/500 s..

M mode on the camera and eTTL on the flash is not a manual mode, it is a semi-automatic mode, not too different to Av and Tv modes when used without the flash..

Your camera manual briefly describes the flash shooting modes. (Yes, I know that no one reads the manuals, myself included, but flash shooting is completely different from ambient light shooting.).

M mode is THE flash mode on Canon cameras..

For more than you probably want to know about the Canon EOS flash system:http://photonotes.org/articles/eos-flash/.

Brian A...

Comment #4

Actually, I used to be a "don't read the manual" type of person, but the last few years, I at least go through the manual for everything, or there are functions that I just won't know about, but probably would use. I've read the entire manual for the XTi, and it is very weak in describing how to use the M mode..

I took a bunch of pics tonight at the party in total night outside, and they seemed to turn out well on the camera screen. (going to wait until morning to look on PC) The exposure compensation is slid all the way to the left and blinking, but the pictures seem really good..

Thank you for the insight. It makes a lot of sense...

Comment #5

Hugowolf wrote:.

If you are using the built in flash, or have an external flashmounted in eTTL mode, the camera modes work very differently fromwhen you are shooting in ambient light..

Actually, the camera works exactly the same whether you use flash or not. The camera meters the scene exactly the same in all the modes regardless of flash (well, expect in P mode, where it limits the shutter speed to between 1/60 and x-sync, and in in all other modes where it limits max shutter speed to x-sync). Please note that the camera can't determine how flash will affect exposure until after the shutter button is fully depressed, so it can't factor in the flash to it's metering algorithm..

When using the Canon EOSflash system, Av and Tv are fill flash modes. The camera exposes foravailable ambient light and uses the flash only to "fill" in theshadows. This will cause slow shutter speeds in dim available light..

Actually, that is not how E-TTL (or in this case E-TTL II) works. In E-TTL and E-TTL II, the flash works the same in any mode. It determines the flash output (duration) based on the pre-flash. That is it. It is how the modes meter that determine whether the flash is main light source or if the flash is a fill. So, in generally, Av mode will be a fill flash mode, since the camera should expose the scene enough so that flash is not required to be the main light source..

With the flash in eTTL (or with the built n flash) and the camera inM mode, the flash is used as the main source of lighting. You canvary the shutter speed and aperture as you want to allow more or lessambient light into the exposure. As others have pointed out, unlessyou exceed the X-sync speed, the shutter speed will not effect theflash part of the exposure because the flash duration is always lessthan 1/500 s..

M mode on the camera and eTTL on the flash is not a manual mode, itis a semi-automatic mode, not too different to Av and Tv modes whenused without the flash..

Agreed..

Your camera manual briefly describes the flash shooting modes. (Yes,I know that no one reads the manuals, myself included, but flashshooting is completely different from ambient light shooting.).

M mode is THE flash mode on Canon cameras..

For more than you probably want to know about the Canon EOS flashsystem:http://photonotes.org/articles/eos-flash/.

Yep. It's a great site. See the following link on how flash and the different modes work together:.

Http://photonotes.org/articles/eos-flash/index2.html#confusion.

Hope this clarifies thing...

Comment #6

Dave_s93 wrote:.

Hugowolf wrote:.

If you are using the built in flash, or have an external flashmounted in eTTL mode, the camera modes work very differently fromwhen you are shooting in ambient light..

Actually, the camera works exactly the same whether you use flash ornot..

No it doesn't, in fact you state that is doesn't later in your post..

The camera meters the scene exactly the same in all the modesregardless of flash (well, expect in P mode, where it limits theshutter speed to between 1/60 and x-sync, and in in all other modeswhere it limits max shutter speed to x-sync)..

Yes it meters the same in most modes, but that is different from working "exactly the same". Metering is only one of many things a camera does..

When using the Canon EOSflash system, Av and Tv are fill flash modes. The camera exposes foravailable ambient light and uses the flash only to "fill" in theshadows. This will cause slow shutter speeds in dim available light..

Actually, that is not how E-TTL (or in this case E-TTL II) works. InE-TTL and E-TTL II, the flash works the same in any mode..

Hmm, I made no attempt to describe how eTTL works..

Brian A...

Comment #7

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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