Need help with 7Dmk2 and 600EX-RT Tv settings

I was out shooting this past weekend and I had the flash on camera and I was in
Tv mode with shutter at 1/500 and flash on high speed synch
The issue was with Auto ISO....I had it set to auto iso and it would always revert to ISO400 when I would use the flash.
Any idea why I could not shoot in Tv with the flash at a higher ISO??
Do I have something set wrong??

Yes, the setting of Auto ISO was wrong. You should have changed it to the ISO value you really needed.

The light was changing drastically and quickly. How come you cant leave it in Auto ISO with the flash on? It would function fine in Auto ISO except for when you turned the flash on and then the camera would revert to ISO 400

Because Canon's flash metering system is based on metering ambient light well before the photo is taken, and flash right before the photo is taken. If ISO was allowed to vary, then it may be that what the camera found useful for ambient light is not at all useful for flash. But when that's found out, it's too late, since the user has at that time already been told what time and aperture will be used. If the camera would change the ISO at the time of flash metering, this data wouldn't be correct, but it's too late to find out then.

Hence the camera converts Auto ISO to ISO 400 as soon as you use the flash, to give you a consistent set of data for your picture. The user's guide would tell you this, but I don't think it tells you the technical reason for it.

Use the camera's ability to vary flash output, time and aperture instead.

Ok Thanks for that explanation

I remember something like this on my 5D3, if you were shooting with flash in av or tv and auto iso it would always set it to ISO400 for some reason before even shooting. Manual ISO is the way to go.

TV mode? never you should have used AV using auto ISO, and set your 600ex to manual mode and do the adjustment from from the camera.

Yes. If I use anything other than manual I will use AV. Never TV.

Just in case a warning about using AV indoors. Because it us aperture priority the system will set the shutter speed to whatever is required to maintain your selected aperture. Often because the ambient light is so dark shutter speeds can be as low as 1/15.

Sometimes people do that on purpose to bring in more ambient. The flash will freeze the subject and if there is little movement in the background IS and or a steady hand can compensate for what the flash can't illuminate enough to freeze.

The only way around this is to shoot with a wide open (or close) to aperture and crank the ISO up until the shutter speed becomes acceptable. 1/60 is good. Some people don't like to shoot with high ISO's.

I remember a thread where a person was asked to shoot the company xmas party and ran into this which frustrated him and struggled all night. He was about to give up photography.

Setting the camera on manual when shooting indoors is the preferred method as you can set both aperture and shutter speeds to your liking. The flash takes care of the subject exposure.

Indoors I use manual and set my ISO to 400-800 depending on lighting with a flash.
My subjects were moving all around that day and Av wasnt cutting it as the shutter speeds were way too low with flash and the subject movement

gqllc007 wrote in post #17716078
Indoors I use manual and set my ISO to 400-800 depending on lighting with a flash.
My subjects were moving all around that day and Av wasnt cutting it as the shutter speeds were way too low with flash and the subject movement

Cool. I will take my 5D3 up to 6,400 but prefer a max of 3,200. One of the called smorter that we have not seen in a while shot exclusively in AV indoors. You are pretty much bringing in the correct amount of ambient to start with and flash finishes it off. Of course you achieve that in M.

On my cameras, and I'm sure it should be in all EOS DSLRs, there is an option in the flash menus that will limit the shutter speed to 1/60s when using ETTL flash in Av mode. This is useful as you can then still set your preferred aperture in Av mode, and the flash acts as only fill light, until the light drops below the point where the shutter speed would fall below 1/60. At this point the flash output will start to be boosted to at least maintain exposure on the subject, and the background will start to become darker.

Alan

Yes that is true.

The option BigAl mentions is on all reasonably recent EOS cameras. You have to go back to models like the 40D for this particular setting not to be there. It had only floating or locked at shortest flash sync time.

I use the 600 RT and I shoot with the camera in manual, underexposing the background by 2/3 of a stop, the flash in ETTL and set the ISO at 100 or 200. My shots come out perfect every time.

So you set your 5Dmk3 to -2/3 exp compensation? I did this all the time -2/3 exp compensation and ISO 160 and Flash ETTL. I did not do this on my 7Dmk2