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Canon 600EX


Hello all. I wanted to know if there is a way to turn down the brightness of the flash. Say if I am in a dark setting and I just want a little bit of light to fill in the subject.


Also what  does the setting that change the flashes 50mm to 100mm do?  That's not the power level is it?


Also if you have a diffuser on the flash is it still better to take the diffuser off and bounce the flash instead?



The diffuser is _only_ for use when using a very wide angle lens.  Otherwise do not use the diffuser.  It's point is to make the light scatter wider.  You are only supposed to use the built-in diffuser when the flash is pointed straight ahead (you'll get an error message if you try to use the diffuser while bouncing.)


If you are shooting in E-TTL mode then the camera and falsh work together to find the correct flash power and it sets the power level automatically.  However... you can tell it that you want either less or more power than the flash metering would otherwise use.  Your camera (and I don't know which camera you have) will have a setting that lets you control the flash exposure compensation.  It can be adjusted -- usually from -3 to +3 (each 1 unit is a "stop" meaning it either halves or doubles the power (depending on if you go in the - or + direction).  So -1 means you want the flash to fire at 1/2 power.  -2 means you want the flash to fire at 1/4 power (1/2 of 1/2) and -3 means you want it to fire at 1/8th power (1/2 of 1/2 of 1/2).  


You can also control the flash power in manual mode.


The flash has a reflector which is motorized and can slide forward or backward in the flash head.  This helps narrow or widen the spread of the light.  When narrowed, the flash carries farther.  When widened you don't get the same distance but it provides wider coverage.  The focal length numbers are intended to match the focal length of your lens.  The camera will AUTOMATICALLY move the head for you and it will set it to match the focal length of your lens (you can also put it in manual mode in which case you have to adjust it and the camera will leave it alone.)


You may want to watch this series of videos to learn more about your flash:



Tim Campbell
5D III, 5D IV, 60Da

Ok now I understand more. But, I meant to say a diffuser you put on the flash not the built in flash. What would be better to use the external diffuser or bouncing light??

The built-in wide-panel is just that -- not really a diffuser.


The little caps you put on the flash that they call diffusers are ... not exactly what they are marketed to be.


To "diffuse" light for purposes of photography, you want to cause the light to originate from a broad origin... not a pin-point origin.  This causes shadow transitions to be gentle... with a pin-point source the shadow transitions are abrupt.


The caps you put on a flash are good for feathering -- e.g. you bounce most light off the ceiling, but the diffuser causes some light to feather in from the front so that it fills the shadows in eye-sockets, etc. to avoid "raccoon eyes" from a bounced light source that was too close to the subject.


BUT... the 600EX has a built-in catch-light card / bounce panel which will kick enough light forward to handle that. 


If you want to diffuse the light for a better look, you'll need a light modifier that can create a broad source.  A shoot-through umbrella, a soft-box, etc.    It helps if the broad source is also close -- the farther away it is, the more it starts to seem more like a pin-point source.


Tim Campbell
5D III, 5D IV, 60Da


There are various, easy ways to adjust a Canon flash.


First, if you are using the flash in ETTL mode and any one of your camera's automatic exposure modes - Av, Tv or P - the flash will automatically act as a "fill" light. The camera will set exposure according to ambient light, then the flash will be fired around -1.5 or -1.7 stops, to open up shadows and add just a little light. You can further dial back the flash if you wish using Flash Exposure Compensation (FEC), which is what Tim was describing. This can be set on the camera or on the flash. The easiest might be to just press the button in the middle of the dial and turn the dial to -1/3 or more. That reduces flash output in one-third stop increments.


If you instead set your flash to ETTL and your camera to M or Manual mode, the flash will be "full". In other words the camera will treat it as if it's the only light source and will ignore ambient light. Once again you can dial the flash down in the same way. You can either balance the flash and ambient light manually, or reduce you can reduce the camera's exposure settings so that ambient light has little effect (which might be done to make a background go dark, for example). Note that this is still an auto exposure mode, even though the camera is set to M. ETTL is metering and adjusting the flash output for a "correct" exposure... i.e., auto exposure. Just as you can use Exposure Compensation to tweak the auto exposure modes when shooting without flash, you can use Flash Exposure Compensation to tweak the results when using flash in ETTL mode.


I disagree with Tim about using the wide angle flash panel. Feel free to override the automatic settings and set the flash's zoom manually to a focal length wider than your lens. This will spread the light more and make possible to shoot closer without blowing out the image. You will still need to dial down the flash if you want "just a touch" of light from it. But it can get you closer to the look you want.  Adding the wide angle panel can do this even more. I often use it, even with longer focal length lenses. Give it a try and see what you think.


Need even stronger flash reduction? A really simple diffuser is some white gauze bandage over the flash head, held in place with a rubber band. You can add layers to the gauze as needed, to further reduce the flash output or increase diffusion. I often use this trick when shooting macro, to allow using a single, non-macro flash that's technically way too powerful for very close macro distances...


Here's how I set it up, in this case with a single 580EX II flash on an off-camera shoe cord....


Flash with gauze diffusion.  


And here is an example of the results...


Praying mantis macro


Study up on Canon flash and experiment. There's a lot that can be done with it. I mostly use ETTL and work within that, making modifications and adjustments as needed. I have studio strobes, too, which are fully manual setup.... So I appreciate the automation of ETTL whenever I can use it.



Alan Myers

San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories



I have been using the diffuser from the link below to soften the light. I have been trying to learn more about the flash unit. I notice when the head is adjusted upwards to bouce the light, coverage in mm turns off and I have no idea how to increase or decrease the brightness of the light.  From what both of you have told me, correct me if I am wrong, ETTL mode control the light brightness automatically? If I want to make the light brighter or dimmer, I should use the exposer compensation?


In manual mode. I assume, I have full control over the light brightness and coverage? I am trying to figure this out because my bounced photos always seem to be underexposed. Of course I take off the diffuser when I try to bounce the light.



If you want more flash, dial up the flash exposure compensation (FEC), not exposure compensation.

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Why do so many people say "FER-tographer"? Do they take "fertographs"?

When using manual flash, you can tell the flash to cut back the power (full, 1/2, 1/4, 1/8, 1/16, etc. I think the 600EX goes down to either 1/64th or 1/128th) Another way to control flash power is to simply stop down the aperture on the camera (so it allows less light).

When using E-TTL, the camera and flash work together to establish the correct exposure. As you fire, the camera evaluates the metering (with no flash), then fires the flash at a low power level (by default I think it's 1/32nd power but it can be changed) -- while simultaneously metering again. Using evaluative metering, it's looking for areas of the image which hardly change at all (indicating a light source in the image -- e.g. a lamp, etc.) and also looking for areas which changed drastically (indicating a reflection -- e.g. a mirror, window, or other highly reflective surface). Lastly... if the flash happened to be pointed directly ahead and for lenses that support it, it reads the focused distance from the lens and the guide number of the flash and uses that as part of the flash calculation. After all of that... it figure out how much flash power *should* be needed to take the shot, the shutter opens and the flash fires.

This all happens so fast that if you weren't watching carefully, you'd swear the flash just fired once.

There is one more thing... you can set "flash exposure compensation" (sometimes just called "flash compensation") which tells the camera that you'd like it to use a little more power or a little less power than what it calculates.

When I'm shooting outside, I like to use my flash as "fill" flash... rather than being the key source of light, the idea is to use a weaker power level so that it helps fill in the shadows. You still have shadows.. but it weakens them. It's a nice look. I typically set flash exposure compensation to -1 (each "1" either doubles the power or cuts the power in half depending on whether you're on the plus side or minus side... so -1 says you'd like the flash to fire at half the power that it would otherwise have used.)
Tim Campbell
5D III, 5D IV, 60Da

OK. Great explaination. This stuff that you can't find in a book.  So going back to boucing flash, since the flash does meter when the head is tilted up, is it best to just practice bounce in flash manual mode? I was in a situattion where I was taking pictures in a place with high ceilings. I wanted to use bounce and increase the flash brightness to be my primary light source.


In E-TTL it will increase it's brightness on it's own. In manual you either have to adjust the power level on the flash (and the power levels are described as fractions of full power... e.g. 1/1, 1/2, 1/4, etc. where each level is half as much power as the one before.) or you adjust the f-stop on the camera to control how much light the lens will collect.

When you bounce, it's not just the distance to the ceiling (or wall) and back... it's also a question of how reflective the surface is. Some surfaces will eat more light than others.

You can use modifiers such as soft-boxes, shoot-through umbrellas, or reflectors to soften the light as well -- that's less preferred if you are on-the-move because it's gear you don't want. I have a Lastolite EzyBox (speedlite version) that I can use on an off-camera hand-held mono-pod.. portable... but bulky.
Tim Campbell
5D III, 5D IV, 60Da
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