problems with TTL on Av or Tv mode with my Canon 5DII

I recently upgraded to a Canon 5DII dslr setup with Sea&Sea housing, TTL converter and strobes (250pro's)... i took it to my first dive trip a few weeks ago and discovered i was having problems with exposure under either Av or Tv modes. In full Manual it was fine, TTL was reading and strobes were firing appropriately. However once i switched to Av or Tv the camera was functioning as if there were no strobes and would adjust the shutter accordingly, which made for some seriously blurred pictures with the the long slow shutter. I've been trying to look for information online and a few sites have mentioned that this is normal for EOS cameras with external strobes as the light metering is not based upon a external flash as the primary lighting source but ambient light (in Av and Tv). Does anyone have any insight into this? i'm new with Canon products, and this is my first dslr underwater set up.. any information would be greatly appreciated. I don't mind shooting in Manual most of the time but i would like to resolve this issue in the event i choose to use Av or Tv mode. thanks again.

I recently upgraded to a Canon 5DII dslr setup with Sea&Sea housing, TTL converter and strobes (250pro's)... i took it to my first dive trip a few weeks ago and discovered i was having problems with exposure under either Av or Tv modes. In full Manual it was fine, TTL was reading and strobes were firing appropriately. However once i switched to Av or Tv the camera was functioning as if there were no strobes and would adjust the shutter accordingly, which made for some seriously blurred pictures with the the long slow shutter. I've been trying to look for information online and a few sites have mentioned that this is normal for EOS cameras with external strobes as the light metering is not based upon a external flash as the primary lighting source but ambient light (in Av and Tv). Does anyone have any insight into this? i'm new with Canon products, and this is my first dslr underwater set up.. any information would be greatly appreciated. I don't mind shooting in Manual most of the time but i would like to resolve this issue in the event i choose to use Av or Tv mode. thanks again.

Your camera is working as it is designed. Use manual and as you say it works fine. In AV mode, the attached flash is supposed to function as a fill flash only i.e. to add some fill light only. Look at

http://photonotes.org/articles/eos-flash/

for a description but in AV and TV mode you get only fill flash.

Bill

Your camera is working as it is designed. Use manual and as you say it works fine. In AV mode, the attached flash is supposed to function as a fill flash only i.e. to add some fill light only. Look at

http://photonotes.org/articles/eos-flash/

for a description but in AV and TV mode you get only fill flash.

Bill

Thanks for the help Bill... yea i did read that site about fill flash in AV and TV, was hoping that there might be something i could do to change that setting somehow when i take it diving.. but manual it is then.

You can change the characteristics somewhat.

EG: If you use - Exposure comp, so it darkens ambient conditions then use + Flash EC to moderate the flash output, you can control the lighting somewhat in Tv mode if you want to maintain a higher shutter speed and still have semi-decent ambient light. Av mode is a bit more problematic as it'll choose to move ISO first before shutter speed if you have it in AutoISO mode.

I'd use it in Tv mode for fast moving subjects with changing light conditions, when you don't have time to meter, adjust exposure etc, and hope the eTTL will do it right.

Is there no way to use Av mode and dial in a slowest allowable shutter speed? Many cameras have this.

Is there no way to use Av mode and dial in a slowest allowable shutter speed? Many cameras have this.

Of course you can use AV mode, but in AV mode, the camera sets the shutter speed for whatever exposure you choose. The problem is then that the camera (designed this way) will only put in as much flash as you need fill. There are lots more wedding photogs than underwater guys so this makes sense. That's why most folks shoot manual, pick your shutter, pic your aperture, then hope your strobe has enough oomph to light the scene.

Bill

The poster's problem was not the exposure ratio, as I read it, but just long exposure times, leading to motion blur.

Every camera has a shutter speed limit, in Av mode, when the flash is on, then it will not go longer than 1/60th (or some fraction) of a second.

Many cams have a way to set that shutter time limit. So set it to 1/100th, and see if that works better.

The 5DMKII has a custom function to set the shutter speed in Av to 1/200.

Right. Or you can set it to 1/60 - 1/200, which at least gives a little wiggle room for the Av to function.

I'm not sure that's what the OP is complaining about. In Tv mode, shutter speed is fixed yet the OP is experiencing slow shutter blur. So it is the shutter speed set in Tv mode that is an issue as well. Or the mode selection is wrong as Tv mode, the shutter speed is fixed.

One other explanation is when in Tv mode, one can sometimes see double exposures of a fast moving subject as the exposure is set to ambient. The motion of the subject is illuminated by the strobe then by the ambient light. Perhaps that's what he's talking about?

It sounds to me that the OP needs to understand the features of Av, Tv & M. As already stated, Av lets the user set the aperture and camera decides on shutter speed, so when you're underwater and have lost anywhere from 2-10 stops of light from the surface ambient...the camera will select the correspondingly low shutter speed to render the proper 18% grey exposure, turning on a TTL strobe simply tells the camera to put out enough light to match that calculated exposure (i.e. strobe/flash fill). Same goes for Tv, just in reverse, select the shutter speed and camera sets the aperture, if you get a blinking Fstop value, that means that the camera can't open the lens' iris wide enough for the set speed/aperture value. Manual TELLS the camera what you want to shoot and the strobes will then fire to that exposure.

Won't matter if your underwater or topside, try out the camera, learn it, get a book (manual helps in this case). The camera is only doing what it's designed to, render an even exposure, it doesn't know what the shooter wants, it doesn't know you're 60 feet underwater and want that piece of coral to be properly lit with the sun in the back.

5dmk1, EF15mm FE, Manual Mode, ISO 100, f22, 1/160th, Twin S&S YS120s at full power

Stu

The 5DMKII has a custom function to set the shutter speed in Av to 1/200.

I don't think you mean "set" but rather "set the default or set the maximum". My understanding is that in AV mode, you set the aperture and the camera sets the shutter and fires the strobe as fill flash. At least that's what the manual says.

I am so confused.

Bill

It sounds to me that the OP needs to understand the features of Av, Tv & M. As already stated, Av lets the user set the aperture and camera decides on shutter speed, so when you're underwater and have lost anywhere from 2-10 stops of light from the surface ambient...the camera will select the correspondingly low shutter speed to render the proper 18% grey exposure, turning on a TTL strobe simply tells the camera to put out enough light to match that calculated exposure (i.e. strobe/flash fill). Same goes for Tv, just in reverse, select the shutter speed and camera sets the aperture, if you get a blinking Fstop value, that means that the camera can't open the lens' iris wide enough for the set speed/aperture value. Manual TELLS the camera what you want to shoot and the strobes will then fire to that exposure.

 

Won't matter if your underwater or topside, try out the camera, learn it, get a book (manual helps in this case). The camera is only doing what it's designed to, render an even exposure, it doesn't know what the shooter wants, it doesn't know you're 60 feet underwater and want that piece of coral to be properly lit with the sun in the back.

 

5dmk1, EF15mm FE, Manual Mode, ISO 100, f22, 1/160th, Twin S&S YS120s at full power

 

Stu

Stu:

Very nice.

thanks

Bill

From the 5dmk2 manual

"C. Fn. 1-7, Flash speed in AV Mode.

Auto: The camera will provide the proper fill flash

1: 1-200-1/60th se. When the flash is in AV mode, this prevetns a slow flash sync speed from being used in low light conditions. Effective for prevent subject blue and camera shake. The only problem is that while the subject will be properly exposed with the flash, the background will come out dark

2: 1/200 fixed: The flash sync speed is fixed at 1/200. This better prevents subject blue and camera shake with setting 1. However the background will come out darker than with setting 1."

while I see the settings above possibly helpful in macro mode, there will be no way the camera will do a proper TTL exposure with my sunburst image as the camera will determine that there is enough light and will just fire for fill, leaving a very dark subject.

Stu:

Very nice.

thanks

Bill

Thanks Bill, I was with a mutual friend, Kelly B in Tubbataha when I shot that.

Seeing how the OP hasn't visited WP in 1 1/2 mths, I think it's all academic now

From the 5dmk2 manual

 

"C. Fn. 1-7, Flash speed in AV Mode.

 

Auto: The camera will provide the proper fill flash

 

1: 1-200-1/60th se. When the flash is in AV mode, this prevetns a slow flash sync speed from being used in low light conditions. Effective for prevent subject blue and camera shake. The only problem is that while the subject will be properly exposed with the flash, the background will come out dark

 

2: 1/200 fixed: The flash sync speed is fixed at 1/200. This better prevents subject blue and camera shake with setting 1. However the background will come out darker than with setting 1."

 

while I see the settings above possibly helpful in macro mode, there will be no way the camera will do a proper TTL exposure with my sunburst image as the camera will determine that there is enough light and will just fire for fill, leaving a very dark subject.

 

 

 

 

 

 

Thanks Bill, I was with a mutual friend, Kelly B in Tubbataha when I shot that.

I'll tell her hello, tonight is the LAUPS banquet.

Bill