E-TTL and Manual flash modes

MarcusM · Mar 26, 2008

I have been doing some reading using the search function, but I'm still trying to learn my 430EX and the basics of using external flash.

I read my manual but it did not explain E-TTL very well. According to Big Mike's quote from another thread, from what I understand, E-TTL is basically the Automatic mode for the flash. Is that an accurate statement?:

Big Mike said:
The more expensive flash units will 'dedicated' to work with your camera. They will communicate with the camera to give you E-TTL metering (Electronic Through The Lens). This means that the flash fires a preflash to meter the reflected light, the camera reads the light and tells the flash how much power to use for the actual flash. This all happens so fast that you can barely tell that the flash fried twice.

The benefit of a system like this is that it will set the flash power to the setting that you want to use. If you want to use F8, it will automatically meter and give you enough power for F8. If you want to use F2.8, the it will adjust for that. To vary the exposure from the flash, you use FEC (flash Exposure Compensation).

The cheaper flash units may not be dedicated. Instead, they might have their own built-in metering. They way these usually work is that they fire and measure the light at the same time, when enough light has reflected back to the flash's sensor...it quenches the light. These can actually work fairly well...but you have to make sure that you are using the same settings on the flash, as you are on the camera. And if you change the settings...then both need to be re-aligned.

Most flashes can be fired in a 'manual' mode...some only have a manual mode. In this case, you would need to calculate the correct aperture to use, using the flash's Guide Number and the distance to the subject.

There are some build quality issues. The more expensive ones will usually be built better. Also, there is wireless technology. Canon uses IR technology for it's wireless flash. You would need at least two units. One to be a master and one to be a slave. The expensive Canon flash, the 580EX, can be either a master or a slave. The 430EX can only be a slave.

I would recommend the 430EX, if you can afford it.

I did some test shots in Manual Mode varying the power of the flash and I could not tell a difference in brightness from one exposure to the next. Does anyone know why this might be?

I'm still having a lot of trouble grasping all the features of my 430EX even after reading the manual. Does anyone know any websites that explain external flash really well?

Village Idiot · Mar 26, 2008

What was in manual mode? The flash and the camera?

You have to keep the aperture static and adjust the flash power. You can tell a difference. When taking pictures with a flash, the aperture controls how much light the flash lets in, not the shutter speed. The shutter speed just adjust ambient.

Using a flash means you're getting two exposures in one.

Try again and post some examples. Take a picture at 1/250 @ f/5.6 with the flash @ 1/4 power then move the flash up to 1/2 and finally 1/1. If everything is in manual, you will see a difference.

Big Mike · Mar 26, 2008

I did some test shots in Manual Mode varying the power of the flash and I could not tell a difference in brightness from one exposure to the next. Does anyone know why this might be?

So you had the flash in manual mode (not just the camera)?

I just did a test with mine. I set the flash to manual mode (pushed the 'Mode' button). First I shot at 1/1...it was really bright. Then I tried again with the flash set to 1/4, and then set to 1/64....each time, the image was darker.

Now, if you had the flash set to E-TTL mode and the camera in manual mode....you will get pretty much the same results when varying the aperture or shutter speed. The flash (in E-TTL) will match it's output to the aperture that you have set. So if you use F2.0, the flash might use low power....if you set F16, the flash will have to put out a lot more power, but the exposure will be the same. That's E-TTL.
You can alter the flash exposure by changing the FEC (Flash Exposure Compensation).

I'm still having a lot of trouble grasping all the features of my 430EX even after reading the manual. Does anyone know any websites that explain external flash really well?

I've got the perfect link for you....it's often called the 'EOS Flash Bible' and it's got more info than you will want to read. http://photonotes.org/articles/eos-flash/

MarcusM · Mar 26, 2008

Village Idiot said:
What was in manual mode? The flash and the camera?

Both were in manual mode.

Village Idiot said:
You have to keep the aperture static and adjust the flash power. You can tell a difference. When taking pictures with a flash, the aperture controls how much light the flash lets in, not the shutter speed. The shutter speed just adjust ambient.

I think that really makes a lot of sense now. So shutter speed really has nothing to do with allowing the light from the flash in up to the camera's maximum flash sync?

Village Idiot said:
Using a flash means you're getting two exposures in one.

Try again and post some examples. Take a picture at 1/250 @ f/5.6 with the flash @ 1/4 power then move the flash up to 1/2 and finally 1/1. If everything is in manual, you will see a difference.

I will try this tonight and post the results. Should the camera and flash both be on manual? Thanks.

Big Mike · Mar 26, 2008

So shutter speed really has nothing to do with allowing the light from the flash in up to the camera's maximum flash sync?

That's exactly right. The flash fires very quickly...maybe 1/10,000 of a second...so the shutter speed doesn't affect the flash exposure. What the shutter speed does do, is affect the ambient exposure (as mentioned, flash photography is actually two exposures in one, flash & ambient). You can test this out by shooting (a person or something) in a somewhat dark room or outside before it gets really dark. Keep the aperture the same (& flash the same) and change the shutter speed and watch how the background changes.

I will try this tonight and post the results. Should the camera and flash both be on manual? Thanks.

To do your testing, yes...put both the camera and flash in manual mode.

MarcusM · Mar 26, 2008

Big Mike said:
I've got the perfect link for you....it's often called the 'EOS Flash Bible' and it's got more info than you will want to read. http://photonotes.org/articles/eos-flash/

Wow, thanks for the link. This looks like just what I've been needing. I've got some reading to do.

JamesF · Mar 28, 2008

I have a question which is kind of related...

Do Canon flashes offer an off-camera wireless TTL function like Nikons Creative Lighting System?

Village Idiot · Mar 28, 2008

JamesF said:
I have a question which is kind of related...

Do Canon flashes offer an off-camera wireless TTL function like Nikons Creative Lighting System?

Yes. You either have to have a 580EX on camera or attached via sync cable as a master or an ST-E2 ir transmitter on camera to control the flashes.

JerryPH · Mar 28, 2008

Yes, I believe so. Its called an ET-2 (ES-2?), or something similar? The only thing is that it is not integrated into the camera like the Nikon's CLS is.

Village Idiot · Mar 28, 2008

JerryPH said:
Yes, I believe so. Its called an ET-2 (ES-2?), or something similar? The only thing is that it is not integrated into the camera like the Nikon's CLS is.

Ha, beat you to it...and even got the model number right. :greenpbl:

Big Mike · Mar 28, 2008

Canon's off camera system uses an IR signal to trigger slave flashes with a master. As mentioned, the master can be either the 580EX (or 550EX) or the ST-E2. The ST-E2 is a master control only, and not a flash...and it's still a few hundred dollars...so I would rather have the 580EX.

The IR signal work fairly well when inside, where it can bounce around. However, it's known for being less than reliable when used outdoors and especially in the bright sun.
This is one reason why many photographers prefer to use radio triggers like the Pocket Wizards...as per the Strobist.

JerryPH · Mar 28, 2008

Village Idiot said:
Ha, beat you to it...and even got the model number right. :greenpbl:

solrac8126 · Mar 28, 2008

There is one new wireless devices that promes to have e-ttl over a wireless signal.
They are called :
RadioPoppers

you can read info on the strobist site.

Tiberius47 · Mar 28, 2008

To take a photo when both the flash and the camera are in manual mode...

Start with the flash turned off and the camera in manual mode.
Set one of your camera's settings to control the kind of photo you want. For example, if you are taking a portrait, you'll most likely use Aperture mode and set a reasonable wide aperture, such as f3.5. If you want to show movement, you'll have to use shutter priority and use a longish shutter speed, maybe half a second or longer, depending on the subject. (See note at the end about freezing the subject with the flash)
Then adjust the other setting. So, if you've set your aperture to get a certain depth of field, now adjust your shutter speed. Don't worry about the subject for the moment, this is just to expose the ambient light. The subject will most likely be terribly under-exposed by this. You may also need to adjust your ISO rating. Take a photo to see that the background is properly exposed. If not, adjust your settings. If it's fine, move on.
Turn on your flash. Aim your camera at a surface or a reflector if you are using bounce flash. Take a photo. if the flash has over-exposed the subject, reduce the power of the flash or move the flash further away from the subject (if you are using off camera flash). If the subject is underexposed, then increase flash power or move the flash closer to the subject.

This is just a basic walkthrough on how to do it. Remember, it's art, not science, so feel free to play around.

Regarding the use of flash to freeze the subject, this can work quite well. However, if the shot is a skateboarder and the shutter speed is long, you'll have a sharp skateboarder that has been frozen by the flash, but motion blur around him from where the ambient light has lit him up.

TCimages · Mar 28, 2008

I wouldn't invest in the ST-E2. Unlike the 550EX/580EX/580EX II the ST-E2 supports only groups A and B and A:B ratio control - it unfortunately cannot control group C. The ST-E2 also does not support flash exposure bracketing (FEB), and requires expensive lithium batteries rather than cheap and easily available AA cells.