Getting consistent flash exposures? 580EX + Lightsphere

[matt_k1]

I'm shooting with Canon 580EX and find that I am often getting inconsistent exposures with ETTL II. The

body is a 5D. I usually have the camera set to manual exposure mode, flash in ETTL. I am waiting for the

flash to recycle.

<p>

I normally use a Lighsphere or an Omnibounce. Looking back on the images, it seems that in general (but

not always) there's almost "sweet spot" where if you're around a certain distance from your subject (about

10 -15 feet) it's great. But closer and I get harsh, uneven lighting. Further and I get underexposures. I'm

mostly talking about indoors and bouncing off ceiling in these cases.

<p>

Also, the "inverted dome" diffuser for the Lightsphere gives me problems. When I use it outdoors with the

flash pointed straight ahead at the subject, I always get underexposures. Either it's cutting the power too

much or fooling the ETTL mechanism some how. So I no longer use it much at all. Anybody have any

recommendations for the diffuser? And yes, I've watched the Lightsphere DVD / Gary Fong advertisement.

<p>

Any suggestions?

[jeffc1]

Matt

 

I am glad that you have posted this topic because I was going to say something simalar. I have always used the Omnibounce and I have gotten very good results with it. I saw the Gary Fong thing on the Lightsphere and decided to go with it, so I purchased both the clear and the frosted version this summer and used them on 2 weddings that I had done. They worked fine when bouncing with lid off, but I never had good results by having lids on. The lids on, and the flash pointed upward as if I were going to bounce just gave me lighting that I didn't like on my subjects. And by pointing the lid directly at my subjects didn't give me what I wanted either. I just did a wedding last night in a new church that I had never been in before. The church was very big, and very nice, but it was one of those steel buildings and it had black ceilings, so guess what I wasn't going to be able to do? Yep, no bouncing off ceiling for me. And the walls, which were white, were angled so that I could go off them either. So it was my Omnibouce to the rescue. What it all comes down to is this: know the look you want, know how your equipment works, and determine which you should go with since not all shooting situations will be the same. There are pro's and con's to both. I was going to put my Lightsphere's on Ebay, but I figured I would hang on to the bulky things because I will probably continue to use them from time to time. Good luck.

[jeffc1]

By the way. The reason you are getting varying exposures may have to do with your camera settings (tecnique & white balance). Are you shooting manual, AV, TV, P, modes etc and are you shooting with AWB or another setting? Then there are the things that your sensors pick up within the composition to determine the exposure, which will determine the flash output. Then there's the lens, are you zooming in out, back to sensors as mentioned previously. Then batteries within the flash, are you just using "AA" alone, or are you using a battery pack to speed up the flash cycle? So you see, there's a lot of factors there that will determine how the images (exposure) comes out, especially with ETTL. Shoot RAW, try to do things the same as much as possible, use a battery pack for flash, and take 2-3 images of a single pose. Then work it out when processing on computer.

[matt_k1]

As I mentioned, I'm shooting in manual exposure mode. I shoot everything Raw. White

balance is set to auto (though it doesn't really matter with Raw).<p>

I know zooming and distance are big variables, as well as whatever it is that I happen to be

bouncing off of (distance, color, reflectivity, etc.). Probably distance to subject and bounce

surface/distance are the biggest factors. I know for that stuff I just need to know where I

am and to make the adjustments based on what I know.

<p>

But sometimes even with the same subject, and same distance, same zoom setting, I'll get

different exposures when I'm just changing the composition. Nearest I can tell is that the

TTL is picking up different parts of the scene and using that to set the exposure. I think

there's a setting to tie the TTL with autofocus points or not or something lke that which I

need to look at see what's happening.

<p>

[cjogo]

No problem--simply place your flash on manual, also.

 

http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00IPG8&tag=

[picturesque]

The recycling issue is separate from exposure problems. The diffuser causes the flash to put out more power, and many times, you are shooting every frame during a reception at max or almost max output. So to keep recycling as fast as possible, get an external battery.

 

As for the diffuser, every diffuser has a sweet spot, because most diffusers bounce light as well as spray light outward. Different ones have different patterns. The Lightsphere bounces light mostly straight up or slightly forward, with light also coming out of the vinyl bowl of the diffuser. Some of that light goes out toward the subject. The Demb diffuser has a longer "throw" than the LS or the Omni, because it is redirecting a more concentrated beam forward. Plain bounce can be more effective for subjects farther away, because you can aim the beam about 1/2 way between you and the subject. You can't aim the LS too well because the frontal spill gets in the way. Try playing around with shaping the beam of the flash manually, both with the LS and the Omni. The Omni responds less to beam shaping, but it still does. When you tilt the flash head up, most units will revert to a 50mm flash coverage pattern. Try widening it, so the beam that hits the ceiling isn't as concentrated, and more light comes out of the sides of the LS, for instance. Try putting the wide angle diffuser down on the 580EX with the LS and note the differences. You should do this in both low ceiling-ed and high ceiling-ed rooms to see what it does. Also try experimenting with beam width with white cards and the Demb Diffuser. And aiming the beam on the ceiling.

 

The lid of the LS, as far as I can tell, forces more light out the sides, making it act more like an Omni, but it does cut the concentration of the beam hitting the ceiling, which is why it is recommended for low ceilings, so you don't get that awful racoon eye thing.

 

With the lid on and the flash pointed directly ahead, the light loss is about 3 stops. You're probably not getting enough power out of this configuration if you're getting underexposure. It actually gives a very nice diffused light (if you have enough power), making the smaller flash source into a 5" circle (as if you were using a parabolic flash like a Sunpak 120J). The light loss out of the sides, though, is a lot.

 

As for the inconsistencies, it is just due to the whims of automated flash exposure metering. You have to ride the flash compensation dial all the time and account for lightness/darkness of subject and backlighting, etc. Just a small change in viewpoint (including more or less of the scene) does change the flash metering. That is what matrix metering is all about. With automated flash metering and digital cameras, there is no "set and forget" setting. Do a search on flash metering and the 580EX. There is a lot of material on these forums and elsewhere.

[savagesax]

It's hard to find the perfect setup. Not sure if there is one. The LS is nice is some situations and I've actually glued in a soft silver deflector on the back of the LS. Why throw all of that light behind you, seems so silly to design the LS to throw light backwards when the people are in front of you, so now the light is directed forward by this added reflector. It helped a lot, but it's still not the complete answer to all situations. I also have the Quantum 5D strobe and that works well because you can go bare bulb, use defusers or just the reflector. Bare bulb can cause hot spots so you have to watch for reflection and perhaps use it sparingly.

[emmett_s]

Listen to Nadine.....This is the MOST important thing you'll ever read on the subject....'You have to ride the flash compensation dial all the time...' and '...there is no 'set it and forget it'.

[matt_k1]

Thanks everyone. Riding the flash exposure compensation is pretty much what I am doing...

in addition to adjusting the direction of the flash head, bounce direction, etc.<p>

Just thought there might be an easier way. But I guess auto flash exposure is hit or miss, just

like any other automatic mode on the camera.

[picturesque]

Matt--it isn't hit or miss if you get good at predicting what your flash will do and what compensation you need.

 

Bob--putting something solid, white or silver, on the back of the LS will cause the shadows to be harder edged. I thought the same thing before getting the LS, and realized why after I got it. If it is OK with you for the shadows to be harder edged, then fine.

[savagesax]

Nadine, good point, did you put the reflector on the outside or inside of the LS? Forgot to mention that. I haven't seen any problems with it glued on the outside regarding the shadow issue, but never really did a study to compare it. I don't use the 580 flash though. Not sure if that matters. Probably not. I will play around with it this week and do some shots with the reflector inside v/s outside and completely off. Could be a really interesting test. Now you have me wondering!

[picturesque]

Bob--you can put a 3x4 (or whatever) white adhesive mailing label or something similar on the inside of the bowl. Or, if your flash comes with a small white card, like my 580EX (I think the SB800 does too), you can just raise that inside the LS. You can also use a commercially made white card like the Flip It in addition to the LS, but that gets to be a little heavy, and the flash head will probably flop down a lot.

[picturesque]

P.S...realized you can't raise the white card inside the LS without mangling it or blocking the path of the beam toward the ceiling a little.

[savagesax]

Nadine, with the sb800 you can put the reflector flap up and not get in the way of the LS cover. It does help increase the F-stop range by directing the light forward.

 

Again, I will play around with the reflectors and place some pics on line in a few days. Looking forward to seeing the results. I bet you are right and the shadows will be harsh.

 

Right now I'm swamped with editing last weekends weddings and a post office dedication. In fact it's almost 2AM!