Aperture spots

[Unnamed21]

When I set my G3 to Av priority and choose an aperture > F2, I see some aperture spots on the pictures when I flash with my 380EX. Choosing a aperture of F2, the spots are gone. In P-mode they are also gone.
It looks like how darker the room is, how more spots there are.

Any thoughts how to avoid this? I like the Av-mode because of the smaller lens opening.

Evert

 

[Unnamed21]

see sample
http://www.pbase.com/image/11280872

When I set my G3 to Av priority and choose an aperture > F2, I see
some aperture spots on the pictures when I flash with my 380EX.
Choosing a aperture of F2, the spots are gone. In P-mode they are
also gone.
It looks like how darker the room is, how more spots there are.

Any thoughts how to avoid this? I like the Av-mode because of the
smaller lens opening.

Evert

 

[Gowan]

Are you using a diffuser on the 380EX? I get similar spots when using a diffuser on my 420EX, aiming the flash straight forward.

--
Gowan

 

[Andrus Suitsu]

I believe that this is flare. I guess that this happens probably because you are too close to the subject so too much light is reflected back. The camera cannot use a fast enough shutter speed to keep exposure to meaningful levels. You could either use a flash diffuser, use bounce flash techniques or use the built in ND filter to cut down ligth levels.

Andrus

When I set my G3 to Av priority and choose an aperture > F2, I see
some aperture spots on the pictures when I flash with my 380EX.
Choosing a aperture of F2, the spots are gone. In P-mode they are
also gone.
It looks like how darker the room is, how more spots there are.

Any thoughts how to avoid this? I like the Av-mode because of the
smaller lens opening.

Evert

 

[Unnamed21]

Yes, I use a diffuser. To cut down the light levels I think I can also use a higher f-number. But I tried that also, and it is even worse.

Evert

Andrus

When I set my G3 to Av priority and choose an aperture > F2, I see
some aperture spots on the pictures when I flash with my 380EX.
Choosing a aperture of F2, the spots are gone. In P-mode they are
also gone.
It looks like how darker the room is, how more spots there are.

Any thoughts how to avoid this? I like the Av-mode because of the
smaller lens opening.

Evert

 

[Tom Rokicki]

If you're using a diffuser, make sure the front of the flash is behind the plane of the lens, or you will get precisely this sort of flare. It's light bouncing off the most minute particles on your lens.

With the 420ex, just point the diffuser up; you are diffusing, after all; the light will not be directional.

Evert

Andrus

When I set my G3 to Av priority and choose an aperture > F2, I see
some aperture spots on the pictures when I flash with my 380EX.
Choosing a aperture of F2, the spots are gone. In P-mode they are
also gone.
It looks like how darker the room is, how more spots there are.

Any thoughts how to avoid this? I like the Av-mode because of the
smaller lens opening.

Evert

 

[Unnamed21]

Thanks for your answer Tom.

But why is this only with a diffuser? Besides this, isn't a diffuser just to flash directly to the subject? And how do I make the front of the flash behind the plane of the camera? It is a G3 with a 380EX.

Also, with the lens full open, this flare is gone!

Evert

With the 420ex, just point the diffuser up; you are diffusing,
after all; the light will not be directional.

Evert

Andrus

When I set my G3 to Av priority and choose an aperture > F2, I see
some aperture spots on the pictures when I flash with my 380EX.
Choosing a aperture of F2, the spots are gone. In P-mode they are
also gone.
It looks like how darker the room is, how more spots there are.

Any thoughts how to avoid this? I like the Av-mode because of the
smaller lens opening.

Evert

 

[Tom Rokicki]

Howdy!

The reason this typically shows with a diffuser is that the diffuser takes what is originally a directional beam of light from the flash and diffuses it all over. If the diffuser body is in front of the lens, some of the flash hits the lens surface and bounces off any contaminants on the lens directly into the camera.

This also happens without a diffuser if you are in a dusty area or are taking pictures of snow; the flash lights up dust or snow particles very close to the camera very effectively; since they are not in focus they appear as circles or hexagons.

If you are using a diffuser, point the flash up. It really doesn't make much difference where the flash points when you are using a diffuser, since light is going everywhere, but by pointing it up you get it out from in front of the lens.

I'm not sure what you mean by "isn't a diffuser just to flash directly to the subject"; maybe ask with more words?

And if opening the lens aperature fully (I presume that's what you mean) makes the problem go away, I'm really not sure. Perhaps opening up the aperature makes more light come from different portions of the lens that do not have a dust speck on them?

Note that the same thing might be caused by some nearby large reflective surface that is bouncing significant flash light towards the lens.

But if tilting the flash up while using a diffuser makes the problem go away, I'd just do that. If you can reproduce it with the flash tilted up, or with no diffuser on, then let's chat some more.

But why is this only with a diffuser? Besides this, isn't a
diffuser just to flash directly to the subject? And how do I make
the front of the flash behind the plane of the camera? It is a G3
with a 380EX.

Also, with the lens full open, this flare is gone!