I need to understand ETTL better.

[e.rose]

Yup.

It's true.

I kind of understand what's going on, but I never really quite FULLY... figured it out.

I don't shoot on camera flash 90% of the time (I always have it off camera and use them on Manual with triggers), so I never... REALLY quite worried about it.

But the fact of the matter is... I really should understand it better.

SO. Does anyone have any SUPER CLEAR, and awesome resources explaining ETTL?

We're talking "Understand Exposure" level of clear... Like, I really need it super dumbed down for me so I can make sure I 100% understand this, and can make it work for me without having to think about it too much in a pinch.

THANKS.

 

[Derrel]

This might be one of the better, clearly-written sets of explanations I've ever seen related to Canon flash. It is very clearly-written stuff. It's presented in 3 good segments, with bullet point headlines, so you can really see what there is to know, ahead of time, then just dive in.

Flash Photography with Canon EOS Cameras - Part I.

 

[e.rose]

Thanks, I'll take a look at it

 

[vimwiz]

Lets take a trip through the history of Canon TTL metering:

To begin with - The T90 was the first Canon camera to support through-the-lens (TTL) flash metering. Metering was performed by the spot metering photocell beneath the main morror, allowing for off-the-film (OTF) TTL metering. This works by measuring the reflected light off colour film itself. It shipped with the Speedlite 300TL (Which also did Advanced TTL (A-TTL) which is the same except distance is calculated using a preflash infrared pulse and sensor on the flash body.). This allowed it to provide X-Sync at up to 1/250, and the T90 is the only non-EOS body compatible with current Canon flashes.

E-TTL (Evaluative-Through The Lens) was the version uses on EOSes. It uses a visible pre-flash before the main flash in order to obtain a more correct exposure. It uses the normal, internal, evaluative metering sensor, as well as another external one fror the pre-flasn. More modern EOS bodies do everything in the body, and, like the T90+300TL did, uses distance information in its algorithm, and calculates where the subject lies in the scene itself, rather than relying on the AF points. This fixes issues early EOS bodies had with tricky seans featuring hotspots

 

[Overread19 7]

My experiences are that it generally works well for fill lighting, where you're just using it to bump up the shadows it will generally work without much trouble. The only really important thing to keep in mind is that the cameras meter isn't going to take into account the flash light, so if you're using a semi-auto mode you're going to need decent ambient exposures or a lot of exposure compensation.

It can do decently well as the main light contribution as well, but you've got to be shooting in manual mode to force the camera settings you want. I also tend to find there is sometimes a little fiddling around with exposure compensation here as well and you might find you need to push it up or down depending on the lighting (adjusting how it meters might also help although I'll admit to not tinkering with this aspect that much).

I typically find that in bright/sunny conditions a little flash exposure compensation helps as well, dialling in a little negative exposure on the flash itself helps counter blown highlight problems (although in harsher lighting its hard to avoid them all). Remember flash exposure compensation is compensating the flash component of the lighting only.



I find it pretty useful for general shooting and can be a bonus when your working distance to subject and ambient lighting shift around a fair bit (something I find with macro shooting). With more experience you might be able to get to akin levels of accuracy with manual power settings on the flash itself; its always a shame, in my view, that the flash won't show the power output its used when in ettl on the back for reference*.


*though its also my understanding that it selects a lot of in-between power ratio settings when in ettl mode.

 

[Big Mike]

In a nutshell...

E-TTL uses a preflash to determine how much light/power to use. Before the shutter opens, it pops a small flash and reads how much is reflected back Through The Lens (TTL). By doing that, you can shoot straight, bounce and/or use diffusers & filters etc., and the process will account for that.

Note that E-TTL metering doesn't use the camera's primary metering mode...it's completely separate. So if you are in say, spot or partial metering mode, the E-TTL metering is still going to be 'Evaluative'. You can change it to 'Average' but the recommended setting is 'Evaluative' for most scenarios.

So the camera receives the light from the preflash and determines how much power it should use, to expose what it thinks is the subject, to a middle grey level. In other words, just like the camera's ambient light meter, the flash metering will only expose correctly when your subject is the same tone as a grey card. If the subject is brighter, the metering will under expose it. If the subject is darker, the metering will over expose it.

This is why you have FEC...Flash Exposure Compensation. So when you are shooting someone like a bride in a white dress, the metering will naturally under expose, so in order to get proper exposure, you must dial in positive FEC. It's pretty much the same principle as getting proper exposure with ambient light. You can dial it on either the Camera or the Flash, I've always liked using the camera controls.

The main issue with E-TTL, is that it's still an automatic function. It tries to determine what your subject is, and tries to give you enough light to expose that subject to a 'middle grey' level. It's metering will change when the brightness/reflectivity of the scene/subject changes. For example, if you go from shooting a bride in a white dress, to a groom in a black tux, the TTL metering will give you different amounts of light.
In other words, it can be inconsistent.

But if you know and somewhat expect that it will sometimes be inconsistent, then it's still a great tool.

 

[KmH]

You might find some of the info in this Canon specific book helpful:
Speedliter's Handbook: Learning to Craft Light with Canon Speedlites

 

[runnah]

I am going with witchcraft and voodoo.

 

[e.rose]

In a nutshell...

E-TTL uses a preflash to determine how much light/power to use. Before the shutter opens, it pops a small flash and reads how much is reflected back Through The Lens (TTL). By doing that, you can shoot straight, bounce and/or use diffusers & filters etc., and the process will account for that.

Note that E-TTL metering doesn't use the camera's primary metering mode...it's completely separate. So if you are in say, spot or partial metering mode, the E-TTL metering is still going to be 'Evaluative'. You can change it to 'Average' but the recommended setting is 'Evaluative' for most scenarios.

So the camera receives the light from the preflash and determines how much power it should use, to expose what it thinks is the subject, to a middle grey level. In other words, just like the camera's ambient light meter, the flash metering will only expose correctly when your subject is the same tone as a grey card. If the subject is brighter, the metering will under expose it. If the subject is darker, the metering will over expose it.

This is why you have FEC...Flash Exposure Compensation. So when you are shooting someone like a bride in a white dress, the metering will naturally under expose, so in order to get proper exposure, you must dial in positive FEC. It's pretty much the same principle as getting proper exposure with ambient light. You can dial it on either the Camera or the Flash, I've always liked using the camera controls.

The main issue with E-TTL, is that it's still an automatic function. It tries to determine what your subject is, and tries to give you enough light to expose that subject to a 'middle grey' level. It's metering will change when the brightness/reflectivity of the scene/subject changes. For example, if you go from shooting a bride in a white dress, to a groom in a black tux, the TTL metering will give you different amounts of light.
In other words, it can be inconsistent.

But if you know and somewhat expect that it will sometimes be inconsistent, then it's still a great tool.

This actually makes the most sense to me.

Maybe it's the state of mind I'm currently in, but this made the most sense.

I'm mostly curious about it in the setting of a reception hall.

When I'm forced to use on-camera flash in other situations, I usually still switch it to manual to keep things consistent. However, in a reception setting, when I'm moving about in the middle of a very tight crowd, flash on manual doesn't work. Because if I set it to light someone well 6 feet away from me, but then I'm suddenly 3 feet away from someone else and catching a moment that's happening, they're SUPER bright. ETTL helps in that situation, but then I deal with the very opposite problem. When I'm lighting for someone 3 feet away from me in a reception hall, but I see something happening 6 feet away I want to catch, they're super dark. I notice a lot of the time that there's usually someone on the edge of the frame with a white shirt who is light brightly, which made me start wondering what exactly the "flash" is seeing when it meters, because I assume the reason the people 6 feet away were dark is because, even though I had my spot meter pointed at them... the flash somehow took into account the dude on the very edge of the frame, closer to the camera, that had a white shirt on.

Basically I'm trying to figure out how to speak this damn thing's language so I can make it do what I want it to do when I want it to do it.

I am going with witchcraft and voodoo.

I agree.

 

[table1349]

This might be one of the better, clearly-written sets of explanations I've ever seen related to Canon flash. It is very clearly-written stuff. It's presented in 3 good segments, with bullet point headlines, so you can really see what there is to know, ahead of time, then just dive in.

Flash Photography with Canon EOS Cameras - Part I.

Real nice..... steal the website I always recommend for these kinds of questions. :lmao:

 

[pgriz]

Put up a set of those ropes that is used to keep people in line, tell people they can only walk between those sets of ropes, and you've got the distance problem licked - then manual flash will work each time.

Oh, ok. Not a serious idea. :blushing:

However, with ETTL, you DO need to know your maximum range to get a decent shot, which is ISO dependent. So if you have a camera with high ISO tolerance, figure out the max. distance you can shoot and still get a good exposure, and then you know that its at that distance or closer that you've got to shoot. It helps if there is enough ambient to allow the flash to be more fill than primary - so that you don't get the ghasty direct flash look.

Another technique that I have used in some locations, is to put up a set of manual flashes so that they illuminate the perimeter of the room, and then shooting anything inside that perimeter is usually possible using the manual flash settings. Of course you have to be careful not to get the illuminated surface(s) visible in the picture, as it/they will show up as blown.

 

[robbins.photo]

Ok, well if you really want to understand ETTL - your going to need a live chicken, a red candle and a white candle, the eye of a newt and some paprika. Hmm.. wait.. that doesn't sound right. Oh.. sorry, that's for a voodoo curse. Nevermind.

 

[table1349]

Ok, well if you really want to understand ETTL - your going to need a live chicken, a red candle and a white candle, the eye of a newt and some paprika. Hmm.. wait.. that doesn't sound right. Oh.. sorry, that's for a voodoo curse. Nevermind.

Nooooo......that was not a voodoo curse, with the paprika in it that was a love spell to get e.rose to marry you. You need the feet of a frog not paprika for it to be a voodoo curse. Jeeze did you flunk basic Voodoo 101 or what?

 

[robbins.photo]

Ok, well if you really want to understand ETTL - your going to need a live chicken, a red candle and a white candle, the eye of a newt and some paprika. Hmm.. wait.. that doesn't sound right. Oh.. sorry, that's for a voodoo curse. Nevermind.

Nooooo......that was not a voodoo curse, with the paprika in it that was a love spell to get e.rose to marry you. You need the feet of a frog not paprika for it to be a voodoo curse. Jeeze did you flunk basic Voodoo 101 or what?

Ok, well technically I didn't flunk Voodoo 101 - I got an incomplete. The teachers eyebrows did grow back... eventually. I don't think there is enough Paprika on the planet to convince E.Rose to marry me, she doesn't strike me as being that foolish.. lol.

 

[weepete]

I just read the posts by vimwiz, overread and big mike as one continuous section. Great explination guys thanks!