420EX flash BAD hotspot

I have used subject flash with a 10 D body and "OK" with results. Put it on a full frame 5D

body this

Christmas (guess what I got for Christmas!) and YIKES! really poor illumination, even with

a

50mm 1.4 normal. When I used it with the 24-85 zoom, although the flash head indicated

it

was zooming with focal length, there is a severe hot spotting in the center and pretty rapid

and drastic fall off about 1/4 of the frame width on either side. Top/bottom illumination

is

better, maybe because of ceiling bounce - although the head is aimed coaxially with the

lens

and NOT in a bounce mode.

Anyone else have this problem? Any solution? Defective Unit I would think? Help Please!

 

Thanks

Harvey<div></div>

The 'hot spot' may be the clue to your answer here. It isn't so much a hot spot as a reflection. Since the flash cuts out when it 'thinks' it has illuminated enough of the frame, any bright reflections would 'confuse' the flash. Try using your camera and flash in manual mode and I am sure you will find you get enough illumination. Do let me know.

This reason for this effect is obvious. The light from the flash is reflecting off the glass in the picture frame. This will happen with whatever flash you use, unless you move the flash away from the camera.

Well. . .yes. . the reflection is causing general underexposure. But the lighting is very uneven.

 

I would try a diffuser. It will improve all shots with the flash.

Harvey,

 

I'd be curious to know why you chose not to use the flash in bounce mode. As others have pointed out, you had reflective surfaces directly in front of you (which is a good argument for not pointing the flash directly at those surfaces). And you had a convenient white ceiling available above you to bounce the light off. I think bounce mode would have fixed this problem.

Bounce mode, that is, in conjunction with manual mode on the camera (as David pointed out). I would put the camera in manual mode, set it to (say) 1/125 at f/4 or f/5.6, and point the flash so that it bounces off the ceiling. If necessary (if the shot is underexposed), you could also set the ISO of the camera to 400. Please let us all know if this fixes it for you!

The problem here is reflection of the light cone off the ceiling (and to a lesser extent the walls). This reflects lots of extra light onto the far wall but no extra light reflects into the corners. The general underexposure is a caused by the white walls (you should have dialed in positive flash exposure compensation (FEC)). The specular highlight in the picture frame is irrelevant to the uneven exposure.

 

In general I have a low opinion of the Stofen Omnibounce but this is exactly the situation in which it is useful. You still may have a problem since the situation is very problematic. If the 420EX has a wide angle panel then deploying this should also reduce the problem.

Um...hot spot looks like flash bouncing off of glass picture.

 

Don't use direct unless you must. Bounce bounce bounce!

 

CE

Conrad,

 

He is not worried about the reflection off the picture, he is worried about the very dark corners.

One reason I don't use camera-mounted flash in a dark-ish room like that, is because of the rather uneven lighting problems. There's quite a lot of space there to cover in this particular shot.

 

Considering the low noise performance of the more recent Canon bodies at high ISO, and the lack of any moving subjects in this scene, I'd simply turn off the flash, move the ISO to 400 or higher, and take the shot.

 

The 24-85 lens will hobble him somewhat, in that it isn't very fast for that kind of application, but using a tripod or similar fixed object to hold the camera against should work.

 

Myself, I have a triplet of fast primes for indoor photography like this: 28, 50, and 85 f/1.8's. They not only let me dispense with the flash in a lot of situations, but when I do have to use the flash, they extend the depth of coverage for me such that I don't tend to get brightly lit foregrounds in 'dark tunnel' syndrome like the example above.

 

Unless you are doing portrait photography, and using multiple diffused flash sources, the general rule is 'flash is for outdoors, not indoors'. Use flash to lessen harsh outdoor shadows, as fill light, rather than blasting away with it indoors.

 

For some indoor situations, on-camera flash is an absolute disaster. I was shooting some painted wall murals recently, as part of a preservation project, for a panaromic stitch, and no matter how I bounced the flash, with or without a diffuser, I got glare off of the glossy mural paint on the walls. I finally turned off the flash, and used the ghastly overhead diffused fluorescents in the room and took the shots on the tripod. There is a definite light fall-off near the floor, but I've resigned myself to dealing with that using gradient masks in Photoshop.

 

You do what ya gotta' do, to make the shot. I'm certainly glad that I can review what I'm getting in the LCD, before leaving a location. In the old days of film, you could end up with crap and no way to fix it after the fact.