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05-02-2010, 04:11 PM   #1
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Bright spot on macro's

Today with my K7, I was playing with macro / extension tubes. As you can see from the picture, I am getting bright spots in the center of the photo. It is not being caused by the flash, as I tried a couple without flash. Also tried a couple different lenses, but it's there. It doesn't appear (that I can see) under normal situations, only when playing with macro. I've used this exact combo on my *istD, and never seen this. Is there something in the settings on this camera that I need to adjust? It's also there in Live View.



05-02-2010, 04:16 PM   #2
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looks like you have something infront/inside the lens.... atleast thats what it looks like.
05-02-2010, 04:46 PM   #3
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QuoteOriginally posted by yeatzee Quote
looks like you have something infront/inside the lens.... atleast thats what it looks like.
Except that it was there on 2 different lenses.
05-02-2010, 04:47 PM   #4
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Right, im just saying what it looks like. i had a similar effect when a dog slobbered on the inside element of one of my lenses. I thought I cleaned it all but there was a thin film like layer left which caused the same effect.

05-02-2010, 04:52 PM   #5
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Most likely, that is a reflection off the sensor to the rear lens element and then back to the sensor as image forming light.
If this is the case, the cure, such as there is one, is to use a less bright background for your macro shots.
05-02-2010, 05:17 PM   #6
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Just tried again, and background was not a light color, but it's still there. It almost seems like there is some sort of light bouncing around in there. If I move my hands about between the lens & the object, I can somewhat change it. It's also more noticeable when closed all the way. When I open the aperture , it does go away at some point. Just seems strange that I never noticed it with my other camera.
05-02-2010, 07:59 PM   #7
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How about light entering through the viewfinder? You say it isn't caused by flash, what is your actual setup?

05-02-2010, 08:19 PM   #8
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QuoteOriginally posted by Wheatfield Quote
Most likely, that is a reflection off the sensor to the rear lens element and then back to the sensor as image forming light.
If this is the case, the cure, such as there is one, is to use a less bright background for your macro shots.
I agree with this explanation. I see this when I try to turn the FA 35/2 into a DA 35/2.8 by using a 25mm extension tube. It doesn't show in the viewfinder at all. I tried a lot of shading and hood techniques without affecting the problem.

05-03-2010, 12:16 AM   #9
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Could be a light leak from that extension tube or some form of internal reflection.
05-03-2010, 02:28 AM   #10
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QuoteOriginally posted by Just1MoreDave Quote
I agree with this explanation. I see this when I try to turn the FA 35/2 into a DA 35/2.8 by using a 25mm extension tube. It doesn't show in the viewfinder at all. I tried a lot of shading and hood techniques without affecting the problem.
I concur with this explanation too, when you're shooting macro there is a lot of light which doesn't hit the sensor due to the large mag factor, this can get reflected off the wall of the mirror box and of the surfaces of the lens and sensor.
05-03-2010, 04:14 AM   #11
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QuoteOriginally posted by JeffJS Quote
How about light entering through the viewfinder? You say it isn't caused by flash, what is your actual setup?

I thought about light entering the viewfinder, and covered that up, but that didn't make a difference. I know it wasn't cause by the flash, as the last batch I tried, I didn't use the flash at all, just to make sure that wasn't causing the issue.
05-03-2010, 04:17 AM   #12
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QuoteOriginally posted by creampuff Quote
Could be a light leak from that extension tube or some form of internal reflection.
Don't think it's an extension tube leak. I made sure everything was tight. Internal reflection may make more sense. It's almost like the camera is shining a light down the middle. Does it use some sort of light to confirm the focus? Not sure how that works, but being as the bright spot is right in the middle, makes me wonder if it's something to do with that or not.
05-03-2010, 05:06 AM   #13
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QuoteOriginally posted by eccs19 Quote
I thought about light entering the viewfinder, and covered that up, but that didn't make a difference. I know it wasn't cause by the flash, as the last batch I tried, I didn't use the flash at all, just to make sure that wasn't causing the issue.
The mirror totally obscures light entering through the finder when it's up and resting below the focus screen. And focus determination is all passive, cap the lens and the spot will go away ;-)
05-03-2010, 09:33 AM   #14
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QuoteOriginally posted by distudio Quote
The mirror totally obscures light entering through the finder when it's up and resting below the focus screen.
Then why does Pentax tell us to cover the viewfinder for long exposures?

05-03-2010, 10:06 AM   #15
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QuoteOriginally posted by Wheatfield Quote
Most likely, that is a reflection off the sensor to the rear lens element and then back to the sensor as image forming light.
If this is the case, the cure, such as there is one, is to use a less bright background for your macro shots.
QuoteOriginally posted by Just1MoreDave Quote
I agree with this explanation. I see this when I try to turn the FA 35/2 into a DA 35/2.8 by using a 25mm extension tube. It doesn't show in the viewfinder at all. I tried a lot of shading and hood techniques without affecting the problem.
QuoteOriginally posted by distudio Quote
I concur with this explanation too, when you're shooting macro there is a lot of light which doesn't hit the sensor due to the large mag factor, this can get reflected off the wall of the mirror box and of the surfaces of the lens and sensor.
I'll add my 2 cent's worth, and agree with you three.

I have an old Rikenon 135 F2.8 screw mount that has the same issue. It is the only lens I have that exhibits it out of 30 lenses in total.
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