Question about off camera flash & metering

BeardedChick

My setup is 7D w/ a 430 ex flash, 100L & various tubes used by a macro and flash newbie. I just picked up an L bracket, mini ballhead, and flash cord thinking it would be a nice setup.

I tried it today and every shot was badly overexposed, even with flash comp. turned down to -3 (using TTL setting on the flash). I also tried dialing down exposure comp, and could not get it low enough to prevent overexposing. I switched to M mode on the camera and worked out the settings through trial and error, but it's not easy as the metering from the camera is so far off.

If I leave the flash on the shoe the metering works like a charm.

So my question is why is the metering so far off - is the metering off because the flash is a bit closer to the subject? And is there anyway to get the metering to work properly with my L bracket setup??

Thanks for reading!

GOLDENORFE

HI THERE, i use the 430 ex , as does Brian
i always use manual on camera, metering never works in aperture priority, probably because flash-subject so short.
leave camera in Manual, iso 100/200 use f6- f14 range for sharpest images. i have the flip down flash diffuser down all the time .end of coke can diffuse approximatly level with end of lens.
just alter FEC by +-1 stop depending on subject/background light.
very rarely need to change from these settings.
phil

basflt

so , Phil , what you say is , you use a certain EV , regardless the meter ?
if so , you just answered the [same] question for me

GOLDENORFE

basically you learn through experiance what fec to change.
bright background you increase FEC, dark - reduce. +- 1/3 stop usually.
in manual, shutterspeed is always set at 1/200 , i leave apperture on f8 for 80% of my shots, just alter flash compensation on camera .
only other thing is to alter flash angle for some shots.

phil

basflt

i know that , but original question was about light-meter
do you just pick your known values [ which is what i asume ] and forget about the meter ?

GOLDENORFE

yes! my settings work 90% of the time .
but what mode was he originally shooting? auto? with flashgun on hotshoe. auto wont work with macro, you need full control of apperture, and shutterspeed will be set at cameras flash synq speed 1/250th on 7d
it is possible the off camera cord is faulty.
in apperture priority the cameras meter determines what it thinks is correct exposure, altering the shutterspeed acordingly, not at flashsynq so longer shutterspeeds will overexpose .

stick to manual with pre-determined basic settings
phil

BeardedChick

Thanks Phil!

She was shooting with shutter priority at 1/250 with flash gun in hotshoe :-)

It does make sense at that close of a distance & using flash, exposure might be very close to the same all the time.

I was really suprised there was so much variance with the corded flash off camera. I guess I could try using the remote flash feature on the 7D just to test what it does. It is possible the cord is faulty.

However, I am going to use your advice on using M mode & see how that goes.

- Michelle :-)

basflt

as for me , its clear now
thanks for reply

paddler4

I do pretty much what Phil suggests, with a 430 and a 50D, and it usually works just fine. I'm still a relative novice, but I can think of a couple of other possibilities:

--Did she have the flash metering set to evaluative? that's how I have mine, and I think it's what you want.

--is it a matter of glare and unwanted specular highlights, rather than exposure per se? I have found this the hardest part of learning to use flash at macro distances. It requires lots of diffusion. My current system is a 430 held near the front end of the lens, capped by a sto-fen (with foil around the sides), with an extra layer of diffusing plastic on top of that (cut from a lumiquest), and two layers of paper towel over that. And all of this is not always enough.

pathfinder

BeardedChick wrote: »

My setup is 7D w/ a 430 ex flash, 100L & various tubes used by a macro and flash newbie. I just picked up an L bracket, mini ballhead, and flash cord thinking it would be a nice setup.

I tried it today and every shot was badly overexposed, even with flash comp. turned down to -3 (using TTL setting on the flash). I also tried dialing down exposure comp, and could not get it low enough to prevent overexposing. I switched to M mode on the camera and worked out the settings through trial and error, but it's not easy as the metering from the camera is so far off.

If I leave the flash on the shoe the metering works like a charm.

So my question is why is the metering so far off - is the metering off because the flash is a bit closer to the subject? And is there anyway to get the metering to work properly with my L bracket setup??

Thanks for reading!

What aperture and ISO were you using?

I suspect you were using large apertures and higher ISOs perhaps.

I use my 7D with a 580ex hand held with the 7D controlling the remote 580ex as a slave frequently and the images are exposed correctly, when shot in Manual mode or Av mode. You MAY find you need to use High Speed Synch to allow higher shutter speeds than the native flash synch shutter speed on the 7D though - when you go to flash, no matter what shutter speed you dial in, the camera/flash will reset the shutter speed to 1/250th ( even in you dialed in 1/1000th ) if you have not turned on High Speed Synch.

This is a very common reason for "unexplained over exposure" with flash when shooting at close macro distances with the Canon system.

I assumed you were using a Canon ETTL off camera flash cord, but you do not say that in your post - that could be why the exposure was correct when the flash was in the hot shoe, and over exposed when the flash was used with the cord - if the cord was not ETTL capable.

BeardedChick

Thanks Pathfinder. I was not using high speed sync - will try it with that set. I tried using large aperature, and tried various ISO settings - from 400 down to 100, and in M got it working best with low ISO.

I am using an Opteka ETTL II cord. It is not the Canon cord, so I suppose it could cause issues, though the reviews for it were decent. I didn't realize that some cords were not ETTL, so thanks for pointing that out...

pathfinder wrote: »

What aperture and ISO were you using?

I suspect you were using large apertures and higher ISOs perhaps.

I use my 7D with a 580ex hand held with the 7D controlling the remote 580ex as a slave frequently and the images are exposed correctly, when shot in Manual mode or Av mode. You MAY find you need to use High Speed Synch to allow higher shutter speeds than the native flash synch shutter speed on the 7D though - when you go to flash, no matter what shutter speed you dial in, the camera/flash will reset the shutter speed to 1/250th ( even in you dialed in 1/1000th ) if you have not turned on High Speed Synch.

This is a very common reason for "unexplained over exposure" with flash when shooting at close macro distances with the Canon system.

I assumed you were using a Canon ETTL off camera flash cord, but you do not say that in your post - that could be why the exposure was correct when the flash was in the hot shoe, and over exposed when the flash was used with the cord - if the cord was not ETTL capable.

Lord Vetinari

As commented above - normal to use flash with the camera in manual and settings like ISO100, 1/200th F11 and flash in ETTL. I'd first check the off camera cord head and flash are both correctly seated on the flash shoes and then try a shot with above setting of a large mid green leaf. This should come out with the correct exposure.
Shooting in Av or Tv modes gives you fill flash. So the camera correctly exposes the scene without flash and then tries to add a bit of flash. I normally do this with something like -.66 EC set on the camera and -1 FEC set on the flash. Slightly difficult to tell from what you have said whether you may have a connection problem with the flash and it's not metering properly- this could result in the flash fully discharging each flash but you should then be able to hear the flash recharging after each shot.

Brian V.

BeardedChick

The followup is that I do have an issue with the cord - it's persnickity in the connection between the flash and the cord. It trashes the metering if I don't get it set in there just right before tightening it down.

And the other followup is that the advice about using a standard metering system like yours, Brian, or like Phils is working out really well. I set one of my custom functions with the basic settings so it's always easy to setup my camera and shoot without any fuss. I have been trying F/8 - F/22 when there's extra light bouncing around and for now, and am finding F/13 or so to be a happy place. :-)

Thanks again, all.

Cheers,
Michelle