Using the 550EX manual setting...

[dphoto]

Hello everyone!

I'm pretty stoked because I just got my new 550EX in the mail and it sure does liven up indoor shooting for my 300D! In fact, I just took some shots in a dark school auditorium awards ceremony and was able to get great exposures while leaving the camera at ISO 100. Anyhow, that experience led me to a question...

While I was shooting, I seemed to be getting some slightly underexposed shots. To compensate, I used FE Lock on a somewhat dark curtain on the stage. It worked great, but I noticed that the FE Lock "flash" itself could be interpreted as the actual picture flash and could confuse those on stage. One option would have been to use the flash exposure compensation, but that still wouldn't compensate for the fact that the focus point was sometimes on something light and sometimes on something dark. I was thinking that if all the action was at the same distance from me, it would be a perfect time to switch the flash into manual mode. It would be nice to be able to tell what power level the auto settings used so that I could use that as a starting point. Is there any way to do this? Can I tell for a particular exposure what power level was used by the flash? Or would I just have to use trial and error to start at say, 1/4 power, and just work my way up or down based on my histogram?

Thanks a lot for any help on this. I think the manual setting could really work well in a situation like that, but I'm a little scared... you mess up that manual setting on the flash and you mess up your shot! :D

Happy shooting!
-Deva

[slin100]

No, the flash unit will not tell you what power level it used while in ETTL/TTL mode.

When the flash is in manual mode, if you half-press the shutter button the flash will tell you the optimal distance for the selected aperture. As you adjust the aperture, you will see the distance displayed by the flash change. If you know the distance to the subject, you can, in theory, adjust the aperture and/or the flash power so that the distance displayed by the flash matches the distance to the subject. This should give you the correct exposure.

Of course, if you know the distance to the subject, it's probably faster to mentally calculate the required aperture by dividing the effective guide number at a given power level by the distance and setting the camera to that aperture. The devil is in knowing the distance. I'm a poor judge of distance, and the distance scales on Canon EF lenses are pathetic compared to the older FD lenses. Without a good estimate of the distance, either method above will at best only get you in the ballpark for the correct exposure. Also, neither method will work at all if you bounce the flash.

But perhaps this may be enough to serve as a starting point. The histogram can carry you the rest of the way.

OTOH, I suggest you first try enabling C-Fn 4-1, which remaps AF to the * button. The side effect of doing this is that, without an active focus point, ETTL switches to an averaging mode. This should make exposures much more consistent.

[dphoto]

Steven,

Thanks for answering my question about the power level. Also, you make a great point about using manual focus so that there will be no active focus point. I'm going to give that a try. Since I have the 300D, I cannot use the custom function that you mentioned, but I am getting used to flipping that AF switch on the lens! :D

Thanks again,
-Deva

[WestFalcon]

I use manual all the time on my 550 EX and it is trial and error. Once you get the distance down, I like manual mode. I use it a lot at weddings, especially on the aisle shots. Severe backlighting fools the 550 and often underexposes your subjects...this won't happen with manual exposure. Slight under and over exposure may be easily rectified with photoshop.I do a fair amount of histogram reading but the lcd screen is pretty accurate for under or overexposure...when in doubt ,pop up the histogram.

[dphoto]

Hey WestFalcon,

It's cool to know others out there are using the trial and error method. :D Yeah, I've noticed that the LCD does seem pretty accurate. I've got the setting so that the histogram comes up with the image so I can give it a quick glance as well... just to be safe. :D As you mentioned, slight under or over exposure can be fixed, so as long as my distances are close, I should be OK.

Thanks again!
-Deva

[Ballen Photo]

Hi Deva, Get a good book on photography, read the section on using flash manually, then make a cheat sheet that will always be handy while you're shooting(SHH! Dont tell anyone I do this. :wink: ). I did this, and it worked great! In fact, make several for the different power levels you can set the 550 to, ie; 1/2, 1/4, 1/8, etc. which will give you variable gain levels(I LOVE the 550 for this), which you will find useful when distances change. Example, lets say the flash's gain at full power is 180, then half power will give you a gain of 90, quarter power will be a gain of 45, etc.
BTW, the book I used for refference was "The Photographers Handbook" written by John Hedgecoe.
Dont be afraid to jump right in there and experiment with your settings. :D
.......Bruce

[dphoto]

Hey Bruce,

Thanks for the advice and thanks for the book reference! Maybe I'll know this after I read the book (if so just let me know... I'm going to the library tomorrow :D), but what exactly is "gain" when it comes to flash? When you say a gain of 180, what does that mean?

Thanks again. Yeah, I've been experimenting, and I need to do some more. I love to pull that flash out every chance I get. :D

-Deva

[Ballen Photo]

what exactly is "gain" when it comes to flash? When you say a gain of 180, what does that mean?


Hi Deva, Gain is a term that indicates how powerful a flash is. For example the gain of a 550EX flash is rated 180, it means that this flash has sufficient power to work out to 180 ft for your exposure. This rating is based on having camera ISO set to 100.
If memory serves, gain is covered in this book quite well.
Enjoy. :D
......Bruce

[robertwgross]

Gain is a term that indicates how powerful a flash is. For example the gain of a 550EX flash is rated 180, it means that this flash has sufficient power to work out to 180 ft for your exposure. This rating is based on having camera ISO set to 100.
If memory serves, gain is covered in this book quite well.
Enjoy. :D
......Bruce

How do you throw out a definition like that without reference to aperture?

A flash with a range of 180 feet with an f/5.6 lens, or with an f/1 lens?

Are you referring to Guide Number?

---Bob Gross---

[Ballen Photo]

Gain is a term that indicates how powerful a flash is. For example the gain of a 550EX flash is rated 180, it means that this flash has sufficient power to work out to 180 ft for your exposure. This rating is based on having camera ISO set to 100.
If memory serves, gain is covered in this book quite well.
Enjoy. :D
......Bruce

How do you throw out a definition like that without reference to aperture?

A flash with a range of 180 feet with an f/5.6 lens, or with an f/1 lens?

Are you referring to Guide Number?

---Bob Gross---

Sorry Bob, I should have said GUIDE number(Brain Burp)
As far as refference to the 550EX GUIDE number, here's a link to Canons specs for this flash. http://consumer.usa.canon.com/ir/controller?act=ModelDetailAct&fcategoryid=141&mode lid=7270
As you can see, Canon advertises this as a maximum guide number without any refference to aperture. :shock:
.........Bruce

[dphoto]

Hey Bruce,

Well, I just finished taking a look at that book, and it did have a little on guide numbers. In fact, it was enough to get me to understand it! :D I'm pretty excited about this new understanding. :D So with a guide number of 180 (55 metric), if my subject is 20 feet away, then at full flash power and ISO 100 I should use an aperature of f/9 (assuming an "average" or "neutral" subject).

Likewise, if I cut the flash power to 1/2, then I should use an aperature of f/4.5 at ISO 100. Or, I could cut the flash power to 1/4 and use an aperature of f/4.5 at ISO 200. The possibilities go on and on. :D

Thanks again for the help. I will definitely use this as a starting point when using my flash in manual mode. In fact, I will probably be using the camera itself in manual mode when I do this. I'm going to be setting the aperature anyhow, and the shutter speed is there for the background lighting, so I will want to control that as well. I usually set it fast enough to avoid motion blur, so I think I'll continue to do that (unless I'm in a situation where I want blur). Very cool stuff! :D

-Deva (glad to be learning!)

[robertwgross]

Sorry Bob, I should have said GUIDE number(Brain Burp)
As far as refference to the 550EX GUIDE number, here's a link to Canons specs for this flash. http://consumer.usa.canon.com/ir/controller?act=ModelDetailAct&fcategoryid=141&mode lid=7270
As you can see, Canon advertises this as a maximum guide number without any refference to aperture. :shock:
.........Bruce

Yes, Guide Number has no aperture factor in it, but you threw us off with Gain.

Take the Guide Number (typically in meters at ISO 100), then divide by the aperture number like f/4, and that yields the distance that it will reach, in meters. Sometimes also there is a Guide Number for feet, and it works the same way.

---Bob Gross---

[Ballen Photo]

Hey Bruce,

Well, I just finished taking a look at that book, and it did have a little on guide numbers. In fact, it was enough to get me to understand it! :D I'm pretty excited about this new understanding. :D So with a guide number of 180 (55 metric), if my subject is 20 feet away, then at full flash power and ISO 100 I should use an aperature of f/9 (assuming an "average" or "neutral" subject).

Likewise, if I cut the flash power to 1/2, then I should use an aperature of f/4.5 at ISO 100. Or, I could cut the flash power to 1/4 and use an aperature of f/4.5 at ISO 200. The possibilities go on and on. :D



Hi Deva, Glad I could help. :D :D :D
Now, just figure out which ranges will work best for you, make some cheat sheets with all your variables, and go shoot. As I've said before, I LOVE all the options you have with the 550EX. :wink:
.........Bruce

[tvnuts]

This is great reading .I own a 550 too but I still confuse if I am using multiple flash.
How to calculate those power ?