550EX and 16-35mm - Omni or not?

[alex_tudor]

If I want to shoot wider than 24mm, which is the better way to go:

 

1. Leave the OmniBounce on and let that diffuse while leaving my

550EX zoom at 24mm.

 

2. Take the OmniBounce off and use the 550EX's built in extendable

diffuser which will automatically set the zoom to 17mm.

 

For speeds's sake, and possibly consistency, I'd say #1, but I have

not taken enough flash shots to say.

 

Also would one ever do both (i.e. use the extentable built in

diffuse AND put the Omnibounce on as well)? Any point to that?

 

Thanks,

 

Alex

[bill_goldman]

The OmniBounce will provide wide coverage regardless of the zoom setting on your 550EX. Using the built-in wide panel at the same time as the OmniBounce will only serve to reduce the flash output power.

[alex_tudor]

Thanks Bill. Since the Omni diffuses does it even MATTER what the zoom setting is on my 550EX at ANY time with ANY lens? I mean even when using my 70-200mm lens for instance? Do I need to bother with the zoom on the 550EX or should I just ignore it completely when the Omni is on? I would still think to zoom but I don't know.

 

If I ignore it, should I at least set it to the widest setting - 24mm anyway then?

 

So far I've only used the 550EX on E-TTL auto which zooms by itself since I only use the Omni when shooting in direct mode, and in direct mode the 550EX's zoom is automatic. When I tilt, I take the Omni off. I have never tilted with the Omni - only used it for direct flash.

 

I know Omni recommends tilting 45 degrees (but that shouldn't be necessary with E-TTL), and if what you say about ignoring the zoom is OK for ALL situations, then maybe I will tilt with the Omni and see if that's better. The reason I don't is because when I tilt the zoom goes out of auto mode and I forget to set it manually.

 

In my limited experience with flash, I've used the 550EX in E-TTL auto w/ Omni for 99% of direct shots, w/o Omni and tilt for bounce, and w/o Omni and direct when I need to light a LOT - outdoors. I also used the 550EX in Av mode with H-Sync outside for fill flash.

 

Any recommendations or criticisms of what I may be doing wrong?

 

Thanks,

 

Alex

[Greg M]

I was faced with the same question, but with the 420EX flash. With the OMNI bounce attached all the time you really do cut down on the range your flash will reach- at least that's what I have found with the 420EX. When confronted with a wide angle shot I zoom to 24mm & check to see if that will cover what I want to do. If it doesn't I fit the OMNI bounce, which I have become tired of doing. It fits so snug on the flash head it's sometimes a testy process to fit when mounted to the camera and I find myself taking too long to get it all the way on, so I've just ordered a 550EX flash to, among other things, completely eliminate the need for the omni bounce with my 17-40 zoom.

[preston_merchant]

Alex, you're thinking way too hard!

 

If you tilt the 550 EX up, the zooming issue disappears. A diffuser's purpose is to scatter the light. Zooming just narrows the angle of coverage, so any indirect use of flash will not be "zoomed." With any attached diffuser, you have to aim the flash up slightly--so don't worry about zooming. Remember that the diffuser only works with the flash tilted; otherwise, you are just using hard flash.

 

My suggestion is just that you take the Omnibounce off until you figure out why you need it. The 550 EX in ETTL mode is virtually foolproof. You can tilt the flash up for bounce, and the raise that little built-in diffuser just slightly (or rubber band a white index card to the back of the flash) to throw some light forward.

 

You can also try various zoom settings in direct mode for different effects. Zoom the thing to 105 mm, and shoot with a 50 mm lens or wider, and you will have a narrow circle of flash coverage in your photo. Try that in black and white and the results can be pretty cool.

[bill_goldman]

Alex, you should always use the OmniBounce with your flash head tilted up approximately 45 degrees. With the zoom head in auto mode, it will default to 50mm, which is fine, as the zoom position is irrelevant. And never use it with the built-in panel flipped down as it only reduces the maximum power of the flash.

 

The OmniBounce simulates a bare bulb flash head, throwing light in every direction and bouncing it off of ceilings and walls. It will induce some color casts to your pictures if the walls are not white or at least a light color.

 

The easiest way to use it is just pop it on when you think it will benefit the situation and forget about adjusting anything. That way you won't have to make any unnecessary adjustments when you take it off.

[alex_tudor]

Preston, I guess I don't understand why I have to tilt with a diffusor? Like I said, I shoot direct (0 tilt) w/ the Omni. It's not hard flash to me. I've taken comparison shots of the 550 direct w/ and w/o the Omni and there's a HUGE difference. w/o the Omni it's HARSHHH!!

 

I don't see any reason to NOT use the Omni unless I need a lot of direct light outdoors where I can't bounce, or I have an ideal ceiling where I can bounce indoors. Otherwise why NOT keep the Omni on all the time?

 

So I'm *trying* to keep it simple.

 

The only thing puzzling is why I must tilt when using the Omni. I just don't get it. Omni recommends it for A-TTL where it will interfere with the sensor, but that's not the case witht the 550 it seems. They also talk about the wraparound effect, and I can see that, but not as a necessity - and it also reduces light output.

 

Thank you both for clearing up the zoom issue!

 

If only I could understand why the necessary 45 tilt w/ the Omni I'd be all set :) The only place that it makes sense is on vertical shots - tilt up 45 to reduce some shadows.

 

Alex

[preston_merchant]

Alex, the diffuser doesn't have any effect unless some of the light from the flash hits that white plastic--and thus diffuses the light around the room (see Bill's post above). Tilting the flash up allows for that. If you shoot with the flash down, it's firing directly.

 

What do you mean by harsh? With ETTL, the exposure will be the same (diffuse or direct), based on your settings. With diffuse, you are brightening the whole room, so the flash may be less obvious on your subject. With direct, your subject will be illuminated by the flash alone, depending on the ambient light.

 

If you shoot in AV mode, in a not terribly dark room, you would achieve a balance between the flash and the ambient light--while shooting with direct flash.

[alex_tudor]

Preston, thanks for your help. I'm trying to figure all this out and I'm stuck on this point that's driving me crazy now!

 

Let me see if I can understand it - I may sound stupid. Even if I don't tilt and shoot direct with the Omni, the light will still hit the Omni and the Omni will disperse some light no? You're saying that light will only hit the Omni if the flash head is tilted. But how can this be? Perhaps it will have MORE dispersion, but even in direct mode the light will hit the Omni and disperse some.

 

When I did my test shots, I shot direct with and without the Omni. Without the Omni it was more harsh - in your face light, harsher / more pronounced shadows, etc. Like you say - the subject was lighted more in comarison to his surroundings. This I think we agree on. And this is WHY I like the Omni. Because I don't always have enough ambient light to shoot in Av mode (I can only wish!), and I want more disperse light around my subject.

 

Now, is there any reason NOT to use the Omni at all times unless I need a lot of light for large distances?

 

Thanks,

 

Alex

[alex_tudor]

Also found this from the makers:

 

Q: Why must I tilt the flash head to 45 degrees?

 

A: In Non TTL models this is necessary to avoid under exposure caused by light from the Omni hitting the external auto sensor of the flash. In TTL models it gives a better feathering wrap around of the light in the range from close to about 15 feet from the subject. Beyond that point with TTL we find straight on works OK for you.

 

-------------

So it seems that the tilt is beneficial but not necessary in TTL flash and you need to use direct at distances > 15ft. At that point I may not even use Omni.

[bill_goldman]

Alex, you're correct in that the OmniBounce will always cause dispersion of the flash even if pointed straight ahead. However, because angling it up generates more light dispersion, more of light is being bounced from the ceiling as well as providing a larger frontal area to illuminate your subject.

 

When you aim it straight ahead, some of the light is directed down to the floor and less is being bounced from the ceiling. Aiming the flash head up at 45 degrees also minimizes and softens the shadows behind your subject. It is also the most effective position for covering the widest possible area for best coverage of ultrawide angle lenses.

 

Next time you shoot flash pictures, try taking 3 identical shots, one without the OmniBounce, one with the OmniBounce aimed straight ahead, and one angled at 45 degrees. Check out the differences and I think you will like the shot with the flash head angled up the best.

[alex_tudor]

Thanks Bill (and Preston), it's been helpful.

 

I've managed to make a not-so-complicated subject more complicated. I've done the tests you speak of, but in that case direct with Omni looked best for some reason. I was shooting a person too close to a white wall so when tilted I think it made everything too bright/white. So based on that I started shooting direct with the Omni. But what you say makes sense though. I'll do some more tests in a better environment. The biggest difference in on vertical shots where rotating the flash head up 45 degrees with the Omni gets rid of the shadow on the right caused by the light coming from the left side flash.

 

So to make it simple it sounds like I will just tilt/rotate for my shots with the Omni on all the time. If the distance becomes too great I'll shoot direct with the Omni or remove the Omni - it all depends on ambient light. And outdoors of course I'll use the Omni in direct mode for fill flash in Av mode.

 

There!

 

Thanks,

 

Alex

[william_le]

Alex, I'm recently new to Canon EOS's. I also am asking the same questions as you. It was mentioned pointing at 45 is best. How is this so, what happens if their is no ceiling to bounce off, what happens if your using ETTL. Doesn't ETTL need to read the preflash to meter correct exposure, if the flash is pointing up, how does it read the reflected preflash light.

 

What Alex is saying with Direct flash is that it is using the diffuser, isnt the white part right in front of the flash head the diffuser when he sticks it on. I think that's what Alex means.

 

Also does ETTL compensate for the diffuser, I read some places it does and doesn't. Thanks and I hope to hear some more replys in detail to help me.

[gene_austin]

I just got finished taking some indoor test shots with a 420ex comparing the

OmniBounce to the Lumiquest Soft Box I bought to use with my 550ex. Using the

Omni pointed straight ahead actually resulted in a similarly soft but slightly brighter

image. Has anyone else done such a comparison either indoors or outdoors? I'm

considering returning the Softbox and just getting another Omni for the 550ex.

[alex_tudor]

William,

 

ETTL will compensate for the Omni so don't worry about that.

 

Gene,

 

I also did the same tests, but if your subject is close to a wall you'll get more noticeable shadows (especially on vertical shots) when shooting direct with the Omni. This is why I'm going for the tilt method now. As long as I tilt and I get the green confirmation light afterwards on my 550 that the exposure was OK, then I'm OK. If not I'll either move close or tilt down more.

 

Bogdan