How do I meter when using flash?

[cmosdos]

I feel so stupid for not being able to figure this out. I shoot in manual mode 95% of the time and when in a dark situation where I need to use my 420 speedlite I have to keep taking 'test' shots to find the right ISO/shutter speed/aperature. Is there any good general rule to follow? The in camera meter system tells me to use 1/8 second or something slow like that when obviously 1/125 is correct. But I can only figure that out by practicing over and over and draining my batteries.

I will usually set my apearture based on the DOF I want. I try to keep the ISO at or close to 100 to prevent noise. From there, I just keep flashing till I get the right shutter speed. There must be a better way.

[d'homme]

If you're shooting manual, the shutter and fstop are exposing for the background or ambient light, the flash is exposing your subject.

Personally, I like a good mix of ambient and flash. Try starting with 60/5.6 and adjusting until you get the right mix of flash and ambient light that you like.-

[scottbergerphoto]

As I understand your question, you have the camera in Manual Mode and the 420EX in ETTL as it has no manual mode. In that case, the aperture and shutter speed only control the exposure of the ambient light and not the flash as long as you stay under the max sync speed of the camera. There shouldn't be any need to tinker with the f sop and shutter speed toget a correct flash exposure. Can you be more specific as to your technique and results?

[CyberPet]

Flash photography is really hard! Sometimes I wonder how I get the results I get... I have no clue! Recently I've actually been shooting in Av and Tv mode and tried to keep the shutter speeds fast, mainly due to the fact that when I shoot with the magic drainpipe I want about 1/350 sec, and then I let the camera/flash do the rest. Same as if I want a special aperture, I use Av and let the camera/flash figure out the rest. Why, how and all that, have no clue. So anyone explain it in simple words that I understand, it'd be appreciated. :D

[gasrocks]

There is such a thing as a flash meter. Most any studio has one. Great for checking light distribution as well. Wein make an inexpensive one. Of course, this is with the flash in manual mode, not auto.

[photofinish]

I use "P" mode when using my flash. This way I let the camera figure it out since I'm usually too busy composing. For the most part, this mode does a decent job for the typical indoor shots. Since I obviously can't chew gum and photograph at the same time, the world is a safer place if I don't have have to think alot. :-)

[scottbergerphoto]

Just to clear up two statements on this thread:
1. Using an incident Flash Meter serves no purpose in ETTL. The camera/flash will readjust itself to produce what the camera thinks is the correct exposure regardless of what you set the f stop and shutter speed. The 420EX does not have a manual mode.
2. You can't use a shutter speed faster then your camera's max sync speed, which is no greater then 1/250 sec, unless you switch your flash to High Speed Sync. That markedly reduces the flash power because it is really giving a series of low power pulses of light.

A really good basic understanding of flash photography never hurts. Take a look at the EOS Flash Sticky in the Small Flash section.

[CyberPet]

Scott, then the plot thickens. Honestly, I tried to read that thread about flash. Either my english is lacking or I'm just too blond. I just don't get it how to use *my* flash. In any event, the exposures when I did what I did turned out fine. So maybe I shouldn't try to fix it or I'll just confuse myself even more? :D

[cmosdos]

Sorry if I was confusing... I've read through the Flash FAQ and here's something I've pulled:

Keep in mind that the camera meters for ambient (existing) light conditions and flash illumination independently.

P (program) mode keeps the shutter speed between 1/60 sec and the maximum flash sync speed your camera can handle. It does this so that you shouldn’t need a tripod, even if light levels are low. It then tries to illuminate the foreground using flash.

Av (aperture priority) and Tv (shutter speed priority) modes set the shutter speed or aperture to expose for the existing light conditions correctly. They then fill in the foreground using flash. If light levels are low you will need a tripod to avoid blur.

M (manual exposure) mode lets you set both aperture and shutter speed to be whatever you want. The camera then automatically controls the illumination of the foreground subject using flash.

So my problem here is that when I try to meter in M mode, it is metereing for the ambient light. It expects the flash to provide fill flash. In P mode it will do the oposite... meter to provide hand holding ability by using no slower than 1/60 shutter speed and the correct flash. Obviously that can result in very dark backgrounds which isn't very desirable. Using M mode I can get an idea of what the abient light should be metered to. But, many times this results in a very over exposed photo if I choose to use the abient light metering. I

So what I have been doing is setting my apreature to DOF I want... lets say f4. I'll set my shutter speed to something like 1/125. Then, take a photo and see if its under/over exposed. Then adust the shutter speed to achieve the exposure I want.

If I were to use AV mode and set f4, it may end up using 1/8 shutter speed resulting in a VERY over exposed shot. Is there supposed to be some sort of pre-flash to help the camera know how to meter? Or is the pre-flash just for the flash to know how much to 'fill flash'. Should I be using my camera's flash exposure compensation for any of this? I obviously have a lot more to learn about flash photography. http://photonotes.org/articles/eos-flash/ is a wealth of information, but it can be a little confusing to me.

Thank you for any help you can provide!

[scottbergerphoto]

The camera meter is always doing one thing and one thing only, measuring ambient light. In P mode, the camera is programmed to not let you go under 1/60 to prevent you from choosing a shutter speed that will result in camera shake affecting your image. Certain cameras also have something called Auto reduction of Fill Flash, that reduces flash output in bright ambient light in P mode. Some cameras allow you to turn that off in the Custom Functions. Check your camera manual to see which features your camera has. The most reliable method of flash is to set the camera to Manual Mode, so you decide how much ambient light to include in your picture and set the flash to ETTL. Take a picture and dial in FEC to get the fill flash effect you want. Traditional Fill Flash is usually -1 to -1and 2/3 FEC. It is just supposed to fill in some shadows. If you are using more flash then that, then you are not using fill flash, you are using the flash as a primary light source.

[CyberPet]

Ok, but the P mode never sets itself faster than 1/60 (the 420EX that is). So this might change if I'd change it to High speed sync?

Also, please explain why Av or Tv mode would not work... honestly, I'm *that* blond! :D

[scottbergerphoto]

Ok, but the P mode never sets itself faster than 1/60 (the 420EX that is). So this might change if I'd change it to High speed sync?

Also, please explain why Av or Tv mode would not work... honestly, I'm *that* blond! :D
No. Program Mode doesn't let the camera go SLOWER then 1/60 sec. It is set up that way so that if you are in a dimly lit room, the camera doesn't automatically set the shutter speed to some speed like 1/8 of a sec and you get a blurry background from camera movement. In P mode, the available shutter speeds are between 1/60 and 1/200(1/250) max sync speed.
High Speed Sync mode is when you need some fill flash and the shutter speed is greater then the max sync speed 1/200 (1/250). In HSS mode, the flash is actually a series of pulses of light approaching a continuous light source. It is much reduced in power over a single flash.
You can use Av or Tv modes, you just have less control then M.

[CyberPet]

I've never seen shutter speeds faster than 1/60 sec in P-mode. Maybe it's just one of those things, it does actually use faster shutter speeds, but looks like it's only 1/60. I dunno.

Ok, I'll continue with Av... and then when I get brave I go over to Manual. Still a bit nervous about Manual, even if I should just take a peak at the historgram to know I'm on the right track. I'm a mess, have a wedding in 12 hours. Still not gone to bed yet (over 3 am).

[scottbergerphoto]

Put your camera in P mode and point it at a bright light source. If it doesn't go faster then 1/60, it's broken!

[ksmattfish]

Put camera and flash into manual mode. On the camera the shutter affects ambient background light exposure, and aperture affects both flashed subject exposure and the background exposure.

Your flash has a guide number that represents it's light output at full power; it's usually listed for ISO 100 in feet and meters. Guide number divided by distance to subject equals f/stop for "proper" exposure; adjust for the ISO you are using. Keep in mind that "proper" is an opinion. Most of the fancier Canon flashes show you the effective range when in manual mode anyway.

Practice some. It's easier than it sounds. Digital makes it easy, because you can do a test, and see how it turns out.

[CyberPet]

Scott... did shoot in P-mode today, just to check out the flash output... nothing is broken... got 1/200 sec with the flash mounted in broad daylight. *phew* Just me that is a bit of a blonde (well a lot). So, thank you!! :D

[u02bnpx]

After commiserating with the many who find the 550 to be much like an unpredictable child, I've succumbed to the lure of the Metz 54 MZ-3 and have just bought a new one that I expect to receive next week. By all accounts, it's virtually flawless in manual (auto?) mode...much, I suppose, like the Vivitar 285, only with the added feature of optional ETTL with the Canon EOS module.

By the way, the other day I mounted a 285 on a Stroboframe bracket and ran an appropriately-tipped cord from the flash to a Wein safe-sync that was mounted on my 10D. Chose an appropriate color (i.e., distance range) on the Vivitar's dial, used different combinations of manual camera settings, and, voila, a series of beautiful histograms on a sequence of well over a dozen shots. However, since the question of the Vivitar-Wein combination's safety hasn't been satisfactorily resolved (I have an old 285), I'm afraid of possible cumulative damage to the 10D, even with the Wein. So...enter Metz into the mix.

I'll try to post again re the success (or lack thereof) with the Metz...on both the 10D and the Rebel...and maybe even on my 1D. My daughter's wedding is coming up on the 23rd, and she's asked me to do "informal style" pix. But I guess I shouldn't be too worried. This is her third marriage!

Floyd Lawrence