EOS 420 EX flash question....

[jason_wolters]

I posted a previous question with regard to a problem I'm having with

my speedlite. Indoor photos with low light are coming out grossly

underexposed. This is from as close as 10 feet away with the camera

and flash set to automatic mode.

I have checked all settings and they are correct, but I just noticed

something when going over my instruction manual.

It indicates that a "pre-flash" should fire automatically, just prior

to the full flash, in order to obtain the correct flash metering.

Well, I set the camera on timer mode with the camera pointed at me

from 10 feet away just to watch what the flash does, and I did not

see any "pre-flash" fire....just the one single burst when the

shutter was tripped.

Could this be my problem? If anyone has any knowledge of what the

pre-flash actually should look like, (how long, brightness, etc...)

please comment.

Thanks,

Jason

[mark u]

There are two ways of proving that the pre-flash happens:-

 

a)Set 2nd curtain sync on the camera, and select a slow shutter speed,provided your body supports this. Mirror lock-up would also separate the two flashes.

 

b)Use flash exposure lock - this actually is the pre-flash manually advanced.

 

You do not mention which body you are using, but if it is a digital body then you should be aware that flash exposure is strongly biassed to the "in focus" focussing point(s). If these cover a light subject, flash output will be greatly reduced. For further guidance, read

 

http://www.photonotes.org/eosflash/

[hans_eckelman]

Jason, I've tried to detect the preflash on my 550EX and I can't see it either. I have some strobes that can, however. I tried triggering them with my flash but without the flash set to manual. You get very dark pictures that way because the studio flashes would have already fired before the curtain opened, PLUS the light from the studio lights tell the camera that there is a LOT more light out there than there really is.

[jim_strutz]

First off, you need to identify what Camera body you are using this with. If it is a type B camera body (something introduced prior to the Elan II or Rebel G (EOS 50 or 500N)) it will never fire a pre-flash since these cameras are incapable of E-TTL flash metering.

 

If it is a type A camera body, normally the pre-flash is about 1/20 second prior to the main flash. It's very difficult to see, but if you look through the viewfinder and see a flash just before the screen blacks out, that was the pre-flash.

 

But as has been suggested, press the FEL button (the one with the * on it). If it doesn't flash then, you have a problem, or a type B EOS camera.

[PuppyDigs]

"Indoor photos with low light are coming out grossly underexposed."

 

I use the 420EX with my Elan 7E and 10D and exposures are usually dead on. However, under dim conditions in P and Auto modes the CPU favors hand holdable shutter speeds and, thus, allows the background to be underexposed. The subject, however, is correctly exposed by the flash. If you need correct ambient exposure, use a tripod and Av or M mode.

 

Another shot in the dark... You can dial in up to minus 2 stops flash exposure compensation on the body. If you accidently set it and forgot...

[chuck_dowling]

Simple answer: The preflash is too fast for you to see, but it's happening. In "P" mode, the ETTL system will expose for your subject, NOT the background. If you want more background exposure, drag the shutter, say 1/30th sec. Handholdability becomes an issue at these slower shutter speeds, so consider a tripod. Experiment, and see what your camera can do for you in aperture or shutter priority modes.

[caroline_cooper]

Hi Jason

 

I am having massive problems with my 420 EX flash right now, including (but not limited to) the problem you mention. I am using it with a 300D body and I am getting gross underexposure (pre flash fires but not main flash), gross overexposure - practically a whiteout (flash fires at full power unnecessarily), flash does not fire at all, flash does not charge, zoom lights blink, pilot flash does not work, pilot light comes on instantly on power on, tone does not sound, flash is not recognised at all by the camera. Occasionally I even get a correct flash exposure, but if I do the next one is always wrong even if I don't change any settings on the camera.

 

I have tried this on all creative mode settings as well as green square, tried new batteries, cleaned contacts etc. Mine is going into the dealer tomorrow, my first ever malfunction in 18 years as a Canon customer!

 

Caroline

[frank_liu2]

Hi Jason (to Caroline too)

 

Caroline's flash may not have problem. The problem is the Canon E-TTL system. It's too sensitive to the brightness of the object your camera points to.

 

I've used a Canon 10D digital camera with 420 EX flash for 9 weddings. I used manual settings on the camera and E-TTL on the flash. When the camera pointed to the bride who was dress in white, The picture turned out to be very dark because the camera lens told the flash gave less power. I keep the same settings and pointed the camera to the groom who was dress in black right next to the bride, the picture turned out to be too bright because the lens told the flash it needs a lot more power. I compare a friend's Nikon D100 in the same situation, the Nikon TTL seems not too sensitive weather I pointed to white or black object as long as they are in the same lighting situation. In this case, I really like Nikon. I think Canon needs to solve their 420EX E-TTL's problem. They may not know or think they have problem. I have been using Canon camera for five years since I bought Rebel 2000. But if they don't fix the problem, I might consider Nikon in the future especially if I continue doing weddings.

 

Since I still have to stay with Canon now. I have tried many ways such as flash compensation and FE lock to get the right exposure for each picture. FE lock works fine but I have to lock the flash exposure every time before I take the picture. I don't have time to do that during the wedding. Now I'm buying a Vivitar 850AF. This flash has both TTL and manual power settings as 550EX but less expensive. If I could turn off the TTL and set the flash power manually, I'll be able to solve the problem.

 

Frank