Canon 20D fill in flash

[gerolamo]

Can I use the 20D onboard flash as fill-in flash?

I tried searching for this in the manual, and played with my camera for a while but can't figure it out.

Another flash is on my list, but it's a long list so it will have to wait for a while, and I would really like to be able to use the onboard as fill in flash in the mean time.

If it can be used this way, can someone let me know how?

Thank you

[jimlp]

Can I use the 20D onboard flash as fill-in flash?

I tried searching for this in the manual, and played with my camera for a while but can't figure it out.

Another flash is on my list, but it's a long list so it will have to wait for a while, and I would really like to be able to use the onboard as fill in flash in the mean time.

If it can be used this way, can someone let me know how?

Thank you

The onboard flash can be used as fill, just pop it up and you should be set. It will operate with auto fill-reduction unless you disable it using custom fuctions. If I am wrong someone more knowledgable will be along to correct me.

[CyberDyneSystems]

Turn your cameras mode dial to either AV TV or M
Your flash will now function as a fill flash,. otherwise all settings made in exposure ignore the flash completely.

You may need to use the FEC flash exposure compensation setting as well to get the results you want.

[gerolamo]

thanks for the replies guys, that's great.

I'm just getting to know the ways to use the flash, and my camera, still have a lot to learn :)

[scottbergerphoto]

Turn your cameras mode dial to either AV TV or M
Your flash will now function as a fill flash,. otherwise all settings made in exposure ignore the flash completely.

You may need to use the FEC flash exposure compensation setting as well to get the results you want.
I contradict CDS with some trepidation ;) as he is a very knowledgeable fellow, but all exposure modes other then Manual are designed for automatic fill flash. If you really want fill flash, where ambient light is the main source of light and you are only looking to lighten some facial shadows or create catch lights in the eyes
with the flash, then I suggest you put the camera body in Manual Exposure Mode, the flash in ETTLII, and dial in -1 to -1and2/3 FEC. Set your camera body's Manual Exposure settings to correctly expose the ambient light. This way you aren't mixing your settings with auto reduction by the camera. This is also covered in the EOS Flash Sticky.
Regards,
Scott

[RJSorensen]

I have been looking for this answer in my book as well . . . so my thanks to all.

[Bob_A]

Hi Scott,

I've been emailing Canon about this (fill flash), and it appears that ALL modes, including manual, are designed for fill flash. The first response I got from them was a bit strange ... telling me that at 1/60s or faster in all modes supporting flash it will be "fill-flash". I've sent a second email asking to confirm that fill flash is used for all modes (basic modes other than "sports" and creative modes including Manual), and asking if EV is really what determines when fill flash reduction takes place, not shutter speed.

I'm also not sure if Canon uses EV=log2(Av^2/Tv) ... or if they have a different approach.

Also, jimlp commented that fill flash reduction can be disabled using custom functions. I didn't think a custom function to do this was available on the 20D, and the only choices we have is to take test pictures and use FEC ... or use a non E-TTL flash. Any idea if a custom function does exist?



Regards,

Bob

[jimlp]

Hi Scott,

I've been emailing Canon about this (fill flash), and it appears that ALL modes, including manual, are designed for fill flash. The first response I got from them was a bit strange ... telling me that at 1/60s or faster in all modes supporting flash it will be "fill-flash". I've sent a second email asking to confirm that fill flash is used for all modes (basic modes other than "sports" and creative modes including Manual), and asking if EV is really what determines when fill flash reduction takes place, not shutter speed.

I'm also not sure if Canon uses EV=log2(Av^2/Tv) ... or if they have a different approach.

Also, jimlp commented that fill flash reduction can be disabled using custom functions. I didn't think a custom function to do this was available on the 20D, and the only choices we have is to take test pictures and use FEC ... or use a non E-TTL flash. Any idea if a custom function does exist?



Regards,

Bob

I was mistaken in saying that fill flash reduction could be disabled by a custom function. Sorry for the misinformation.

[Bob_A]

No problem at all! You got my hopes up ... :)

Bob

[scottbergerphoto]

The 10D has a Custom Function that disables Auto reduction of fill flash. The 20D doesn't.
The 550EX Manual states that Tv and Av are fill flash modes and M is not.
Scott

[Bob_A]

Hi Scott,

I can't find anything in my 420EX manual clearly stating that fill flash is only used for certain modes and is defeated for Manual. Reading the manual I get the impression that for the 420EX flash is handled the same for all modes, except that Man gives you full control of the aperature for flash and aperature/shutter speed for background.

Is it possible that the 550EX works with E-TTL-II differently than the 420EX?

Bob

[Jim Larson]

All the EX flashes should work pretty much the same on a 20D (despite Canon propaganda to the contrary).

Av and Tv are stated as "fill flash modes" because in these modes the camera will *always* expose for ambient conditions -> even in pitch blach (be prepared for a long shutter time). "P" mode will act like Av and Tv in bright light, but if the light is below a threshold the camera will go to shutter 60 and aperture wide open -> and then rely on the flash to get proper exposure.

I suspect (but cannot confirm) that with ETTL-II auto-reduction-for-fill-flash is a moot point and is not implemented. Thinking this through, if you are using the whole evaluative meter area to figure out flash exposure, the camera can figure out the correct way to expose the frame.

With ETTL, which is AF point centric, if you put the AF point on a dark spot, the flash will fire HARD to expose the dark spot. And to blazes with the rest of the image. . . .which is why you need the fill reduction function on a ETTL unit.

Of course, if you are NOT specifically metering the dark spot, i think it would be real hard to properly expose the image in a fill flash situation. . .I suspect this is a really, really hard application to get right.

[scottbergerphoto]

.......if you are using the whole evaluative meter area to figure out flash exposure, the camera can figure out the correct way to expose the frame.


This is exactly why I use my camera on Manual Mode and flash on ETTL or ETTLII. The camera has no idea how I want my flash illumination to look. I may just want enough light to light up the shadows under someone's eye sockets on a sunny day. The camera doesn't know that.
ETTLII supposedly eliminated auto reduction of fill flash, but what isn't clear is if they replaced it with something similiar in the ETTLII algorythms.
Scott

[slin100]

I agree with Jim with regard to his interpretation of "fill flash". It means that the camera will balance ambient and flash exposure. The camera does this in Av and Tv modes at all exposure levels and in P mode in bright light, which I believe to be EV 10 (1/60 @ f/4). I do not believe, however, that the aperture will ever go wider than f/4 in P mode.

"Auto reduction of fill flash" is an entirely different beast. With ETTL-I, it provides automatic negative flash exposure compenstation in bright light. The amount of FEC is not officially documented but it is believed to range between -1/2 to -1 1/2 stops (some say -2 stops). In my experience, auto reduction occurs in all camera exposure modes (Av, Tv, M, P). As stated by Scott, C.Fn 14-1 cancels auto reduction. It is, AFAICT, the only way to cancel auto reduction on an ETTL-I camera. Switching the camera to M mode does not cancel auto reduction.

With ETTL-II, I have not been able to find any definitive evidence whether or not auto reduction is implemented. Back when the 1D Mk II came out, Chuck Westfall of Canon stated that it did not implement auto reduction, but a few photographers on another forum have since disputed that.

I checked the manuals for all ETTL-II DSLRs (20D, 1D Mk II, and 1Ds Mk II) and all mention the following about C.Fn 14-1:
The flash is averaged for the entire area covered by the flash. Since automatic flash exposure compensation will not be executed, you may have to set it yourself depending on the scene. This also applies if you use FE lock.
The bold text is my emphasis. It suggests the possible existence of auto reduction, referred to as "automatic flash exposure compensation," when C.Fn 14-0 is in effect.

I think the following experiment using an ETTL-II camera could provide an answer. Take the following exposures of a person outdoors in bright light (bright enough to require 1/250, f/2.8 @ ISO 100).


No flash
Av mode, C.Fn 14-0
M mode, C.Fn 14-0
Av mode, C.Fn 14-1
M mode, C.Fn 14-0

Set FEC to 0 for all exposures with flash.

Do the highlights in the images taken with flash look substantially brighter than the highlights of the image taken without flash? Should reveal whether Auto Reduction is being applied.

Do the shadow areas in all images taken with flash look identically lit? Should reveal whether Auto Reduction is affected by shooting mode and/or Custom Function.

I'm hoping a 20D, 1D Mk II or 1Ds Mk II can perform this experiment. The results would benefit us all.