FLASH BLOCKED BY LENS. Ugly shadow created. WORK-AROUNDS?

SelfEmployedDebtFree · 08-30-2011, 08:03 PM

Great replies! Thanks!
OK, it seems I screwed up. I got the lens via UPS yesterday and rushed out to snap pictures of everything on my property! (Has anyone else ever done that??? haha.) It seems that after more careful testing the flash shadow goes away after 35mm or more. At 18mm the shadow is very bad. At 20 still bad. 25 not as bad. 30 barely noticeable, and 35 its gone completely. After 35 nothing wrong. So I think I can work with this. Im totally confused now though. I originally noticed this at 18mm. I assumed that the length of the lens was the issue. (I ran into this same issue with one of those cheap ebay super wide angle adapters.... but thats another thread.. be watching for it.) I would have assumed that the length of the lens was the issue. But it's not. That seems backwards to me. It gets worse at super wide angle. Can anyone explain why that is?
Thanks!

yeatzee · 08-30-2011, 09:35 PM

the onboard flash itself does not have a wideangle "add-on" like a decent speed light does to reach those wider angles. Alone it cannot even get close to doing 18mm worth of coverage

newarts · 08-31-2011, 09:38 AM - **1 Like**

Originally posted by SelfEmployedDebtFree

Great replies! Thanks!.....ts gone completely. After 35 nothing wrong. So I think I can work with this. Im totally confused now though. I originally noticed this at 18mm. I assumed that the length of the lens was the issue. (I ran into this same issue with one of those cheap ebay super wide angle adapters.... but thats another thread.. be watching for it.) I would have assumed that the length of the lens was the issue. But it's not. That seems backwards to me. It gets worse at super wide angle. Can anyone explain why that is?
Thanks!

Both lens physical size and focal length are issues; Here's an illustration of what's going on...

If the lens is bigger (either longer or fatter) the shadow will be bigger.
If the flash is moved up the shadow will be smaller.
If the focal length is long the shadow won't be seen.
if the focal length is short the shadow may be seen - the wider the lens angle, the greater the potential problem

It gets worse when the ground is considered. I added a ground plane to the above illustration showing how the flash shadow can easily show on the ground in front of you. It gets even worse if the camera is tilted down, so if you need to take a short focal length flash photo of a child, kneel or squat to avoid getting the ground in the photo.

Hope this helps...

SelfEmployedDebtFree · 09-01-2011, 09:17 AM

Yes. That really explains it perfectly. Common sense actually now that you see the diagram.

GerryL · 09-06-2011, 05:27 PM

Just get one of those third party off-camera flash cords.
Costs less than $20 and it should take care of the shadow problem.

08-31-2011, 09:38 AM - 1 Like	#18
newarts Inactive Account Join Date: Dec 2008 Location: Ames, Iowa, USA Photos: Albums Posts: 2,965	Originally posted by SelfEmployedDebtFree Great replies! Thanks!.....ts gone completely. After 35 nothing wrong. So I think I can work with this. Im totally confused now though. I originally noticed this at 18mm. I assumed that the length of the lens was the issue. (I ran into this same issue with one of those cheap ebay super wide angle adapters.... but thats another thread.. be watching for it.) I would have assumed that the length of the lens was the issue. But it's not. That seems backwards to me. It gets worse at super wide angle. Can anyone explain why that is? Thanks! Both lens physical size and focal length are issues; Here's an illustration of what's going on... If the lens is bigger (either longer or fatter) the shadow will be bigger. If the flash is moved up the shadow will be smaller. If the focal length is long the shadow won't be seen. if the focal length is short the shadow may be seen - the wider the lens angle, the greater the potential problem It gets worse when the ground is considered. I added a ground plane to the above illustration showing how the flash shadow can easily show on the ground in front of you. It gets even worse if the camera is tilted down, so if you need to take a short focal length flash photo of a child, kneel or squat to avoid getting the ground in the photo. Hope this helps... Last edited by newarts; 09-01-2011 at 01:21 PM.

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08-30-2011, 08:03 PM	#16
SelfEmployedDebtFree Junior Member Join Date: Jun 2010 Location: NC Posts: 41 Original Poster	Great replies! Thanks! OK, it seems I screwed up. I got the lens via UPS yesterday and rushed out to snap pictures of everything on my property! (Has anyone else ever done that??? haha.) It seems that after more careful testing the flash shadow goes away after 35mm or more. At 18mm the shadow is very bad. At 20 still bad. 25 not as bad. 30 barely noticeable, and 35 its gone completely. After 35 nothing wrong. So I think I can work with this. Im totally confused now though. I originally noticed this at 18mm. I assumed that the length of the lens was the issue. (I ran into this same issue with one of those cheap ebay super wide angle adapters.... but thats another thread.. be watching for it.) I would have assumed that the length of the lens was the issue. But it's not. That seems backwards to me. It gets worse at super wide angle. Can anyone explain why that is? Thanks!

08-30-2011, 09:35 PM	#17
yeatzee Veteran Member Join Date: Feb 2009 Location: Temecula Photos: Gallery \| Albums Posts: 3,675	the onboard flash itself does not have a wideangle "add-on" like a decent speed light does to reach those wider angles. Alone it cannot even get close to doing 18mm worth of coverage

09-01-2011, 09:17 AM	#19
SelfEmployedDebtFree Junior Member Join Date: Jun 2010 Location: NC Posts: 41 Original Poster	Yes. That really explains it perfectly. Common sense actually now that you see the diagram.

09-06-2011, 05:27 PM	#20
GerryL Veteran Member Join Date: Jan 2009 Location: CA Posts: 2,731	Just get one of those third party off-camera flash cords. Costs less than $20 and it should take care of the shadow problem.

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