What's caused this?

Dman · 21 Nov 2009

I did a shoot for a brother and sister today and got some sort of blue glare in the middle of some of the shots. Tried shooting outside without problem, it just appeared in some of the lighting ones.

Any ideas? The lens was clean and the camera is pretty much brand new. This shot is pretty much as shot in RAW.

Davec223 · 21 Nov 2009

Have you got a filter on your lens? Looks possible that it could be flare.

Dman · 21 Nov 2009

Davec223 said:
Have you got a filter on your lens? Looks possible that it could be flare.

No, I took it off prior to the shoot.

Davec223 · 21 Nov 2009

I still think it is flare, possibly caused by light spill from the background lights if you gad no filter on the lens

Garry Edwards · 21 Nov 2009

It's definately flare, due to overlighting the background. Making sure the lens is spotlessly clean may help - or may not.

Eddie1 · 21 Nov 2009

looks like flare as the backgrounds too bright, if you look closely at the edge of his arms you can see the materials burning out as backgrounds too bright,

HoppyUK · 21 Nov 2009

It's flare from an overlit background, especially over the lad's right shoulder.

Background light should be even all over, and ideally no more than half a stop brighter than the main foreground subject light. It's almost impossible to achieve that in a home studio set up, but aim for it. I'm guessing that parts of that background are more than two stops over exposed, and that is just too much.

If you can screen off any background that is out of shot, and shield the lens from the light, it will make a big difference to contrast and really pump up the colours. Again this isn't easy in a small studio and I find a really good lens hood helps a lot. I have used one with a rectangle cut out of black card, just exactly big enough, and not a fraction bigger. That works well. But now I just use the hood from my 100-400L lens on my EF-S 17-55 2.8. It does not vignette at all from about 45mm, believe it or not.

rotherad · 21 Nov 2009

I used to get this a lot when using my 50mm 1.8 on a pure white background and found that the back lights were just spilling a bit too much, once they were turned down it sorted the issue.

Dman · 21 Nov 2009

HoppyUK said:
It's flare from an overlit background, especially over the lad's right shoulder.

Background light should be even all over, and ideally no more than half a stop brighter than the main foreground subject light. It's almost impossible to achieve that in a home studio set up, but aim for it. I'm guessing that parts of that background are more than two stops over exposed, and that is just too much.

If you can screen off any background that is out of shot, and shield the lens from the light, it will make a big difference to contrast and really pump up the colours. Again this isn't easy in a small studio and I find a really good lens hood helps a lot. I have used one with a rectangle cut out of black card, just exactly big enough, and not a fraction bigger. That works well. But now I just use the hood from my 100-400L lens on my EF-S 17-55 2.8. It does not vignette at all from about 45mm, believe it or not.

Cheers. The background was lit at f/22 with the subject f/11 according to the light meter, but maybe there was another half a stop or so in the background to cause this. I'm at a bit of a disadvantage as I've still only got the two heads, so getting the background even at half a stop brighter than the subject is pretty much impossible. It was only in a handful of shots though, but I'll try and get a lens hood as I haven't got one for this lens.

rotherad said:
I used to get this a lot when using my 50mm 1.8 on a pure white background and found that the back lights were just spilling a bit too much, once they were turned down it sorted the issue.

Exactly the lens I was using. Funnily enough, the 18-135mm that I have on my other body for some reason causes an uneven and underexposed background, whereas when I get a nice bright white background, but as in this example I even get overspill.

HoppyUK · 21 Nov 2009

Dman said:
Cheers. The background was lit at f/22 with the subject f/11 according to the light meter, but maybe there was another half a stop or so in the background to cause this. I'm at a bit of a disadvantage as I've still only got the two heads, so getting the background even at half a stop brighter than the subject is pretty much impossible. It was only in a handful of shots though, but I'll try and get a lens hood as I haven't got one for this lens.

In a situation like this, a lens hood has to be really accurate and very close to the image frame to make a real difference. Most lens hoods are just not that accurate, for example, any lens hood made for a full frame lens like the 50 1.8 will not be close enough to the cropped format of your camera. You need to cut one specifically out of black card. Likewise, the petal-shaped lens hoods for zooms are only ever optimum at the widest focal length.

Exactly the lens I was using. Funnily enough, the 18-135mm that I have on my other body for some reason causes an uneven and underexposed background, whereas when I get a nice bright white background, but as in this example I even get overspill.

I wonder if the uneveness of the background with the zoom is vignetting? If the corners are darkened evenly that's what it is. It is usually less marked at longer focal lengths and at higher f/numbers. You don't even notice it unless it unless you have a plain background to show it up.