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New Contributor
Posts: 1
Registered: ‎07-09-2013

E-TTL on 6D+600EX-RT

Hi Everyone,

         my current setup is the 6D (24-105 F4) and the 600EX-RT speedlight. the issue i'm having is with the E-TTL exposure.

 

         yesterday i noticed that any subject further than 10feet gets under-exposed (this is indoor testing). But any subjects within the 10feet (estimate) get's a very good exposure.

 

         Exposure Settings

 

         Camera : 160/1 @ F4  ISO800  Avg Metering Mode

         Speedlight : E-TTL Mode (Eneloop Batteries)

 

Regards

   Chris

Esteemed Contributor
Posts: 3,807
Registered: ‎06-11-2013

Re: E-TTL on 6D+600EX-RT

Is the flash zoom mode set to automatic "A" so that the flash zoom follows lens zoom?

 

Also... did you adjust flash exposure compensation by chance?  You can do that either on the flash OR on the camera, but if you do it on the flash then it will lock you out of changing it using the camera controls until you set the flash back to no compensation by using the controls on the flash.

 

There's an 8-part video on the 600EX-RT by Syl Arena (author of "The Speedliter's Handbook") in the Canon Learning Center.  See:  http://www.learn.usa.canon.com/galleries/galleries/tutorials/syl_arena_speedlite_600exrt_seminar.sht...

 

In E-TTL II mode the flash is pretty clever and you should definitely NOT be having this problem.  Through your on-camera menus you may want to clear all flash settings to return it to factory defaults.  

 

Tim Campbell
5D III, 5D IV, 60Da
New Contributor
Posts: 1
Registered: ‎03-24-2015

Re: E-TTL on 6D+600EX-RT

[ Edited ]

hi, i am having the same problem. 6D+24-70L f4is and another 6D+17-40L. Both camera tend to underexpose when using 600rt with ttl function on both direct flash and bouce. Comfirm flash EV 0, zoom auto, both front and rear cutain firing. shooting both using Av and Tv modes with EV 0 and exposure time lower than 1/160s. I will update the firmware to latest 1.1.6 and see if the problem solved. For note, using iso4000, even the non flash photos look better than with flash. Its underexposed and the camera AWB getting really warm, like 10000k warm. No problem when using M flash. My initial suspect, the flash trigger later than the shutter curtain. And this problem occur with subjects within 2 meter and 5meter.

Esteemed Contributor
Posts: 4,952
Registered: ‎06-25-2014

Re: E-TTL on 6D+600EX-RT


@tomramzul wrote:

hi, i am having the same problem. 6D+24-70L f4is and another 6D+17-40L. Both camera tend to underexpose when using 600rt with ttl function on both direct flash and bouce. Comfirm flash EV 0, zoom auto, both front and rear cutain firing. shooting both using Av and Tv modes with EV 0 and exposure time lower than 1/160s. I will update the firmware to latest 1.1.6 and see if the problem solved. For note, using iso4000, even the non flash photos look better than with flash. Its underexposed and the camera AWB getting really warm, like 10000k warm. No problem when using M flash. My initial suspect, the flash trigger later than the shutter curtain. And this problem occur with subjects within 2 meter and 5meter.


The designers of ETTL speedlights were almost pathalogically averse to blown highlights. ETTL will always expose for the highlights; if there are no highlights, it wiil expose for what is nearest the camera. My way of dealing with that is to treat all direct (non-bounce) flash as fill flash. Often this means turning the ISO up higher than you'd like; but if the camera supports it, the results can be quite good. Under normal circumstances it avoids the old "flashcube" syndrome, wherein the subject was well lit and the background dark. An of course, if fill flash is what's needed, ETTL is exactly the right solution.

 

If you really have to use flash as your sole source of light, you should probably set it to manual mode.

Bob
Philadelphia, Pennsylvania USA
Highlighted
Super Contributor
Posts: 246
Registered: ‎11-11-2012

Re: E-TTL on 6D+600EX-RT

[ Edited ]

ETTL is a good tool but it is ball park. It can get you through most sitiations quite well but it is still just a computer, making it's best guess on the inforimation it gets back from the pre flash. The pre flash is so fast you cannot see it unless you look through the viewfinder. It happens just before the actual flash exposure. If you look through the viewfnder and shoot in ETTL you will see a flash. This is the pre flash becasue the mirror is stil down. After the pre flash the mirror locks up during the acutal exposore. If you put the flash on manual and shoot you won't see it. This is because there is no pre flash and the mirror is locked up during the flash exposure.            

 

The sytem reads light reflected back from the closest object/s pre flash and make's a decision for the correct flash exposure. The light reflected back influences the exposure. Forget about the flash for a moment and think about your camera only. If you shoot pure black tar your cameras metering system will try to bring it to 18% gray and overexpose the shot. If shooting pure white snow it will underexpose to bring it to 18" gray. A scene with 50% tar and 50% snow will produce a balanced esxposure without input from the user. For the tar shot you need to under expose and snow you need to over expose.

 

Although the flash has nothing to do with your cameras ambient meter it works the same way. When you press the shutter half way the system takes an ambient reading. When you press all shutter all the way the pre flash fires. The system compares the ambient reading to the reflected light from the pre fash and isolates the closest object/s which is usually your subject/s. A bride alone in a white dress, a groom alone in a black tux and the bride and groom together all reflect light back differently thus you will need to compensate flash power based on the scene. This is done via the FEC adjustment.

 

There is no way to predict flash exposure. You can only check after, adjust the FEC and shoot again. A handy tool is the histogram and your whites are your best friends. Compensate for them and the rest falls into place. Check out the gent with the white towel in hand. 

 

http://super.nova.org/DPR/Histogram/

 

Bouncing and all types of factors also effect flash exposure in ETTL. The best way to shoot is in manual and having a flash meter is even better. I will always choose manual if I can but when in a busy changing envrironment I switch to ETTL, shoot, check, adjust FEC and then shoot again. I have long ago stopped trying to figure it out and just work around it and it usually just needs a tweak or two.    

 

If your camera allows it (not the flash) you can switch the flash metering system from Evaluative to Average and give it a try. This is done via the camera menus but again has nothing to do with the cameras ambient light meter. In average the system does not isolate the subject, it averages out the whole scene. So if you take the bride alone example there will usually be darker areas around her. People like to use it indoors but it is not so good for outdoors. Outdoors go back to Evaluative.             

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