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12-31-2012, 10:15 PM   #1
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green light in photo?

Hi I am posting a photo I shot tonight. Practicing night shots with my new/old lens. A Pentax smc-A 28mm f/2.8 on my K100D. I used a tripod,turned off SR and shot in bulb mode. Here is the exif: exposure: 1 sec.
aperture: 3.5
ISO: 400 auto white balance.
I noticed what appear to be green dots/lights in the photo that start from the chair on the porch down to the middle of the image.I also noticed some just to the left of the bush. Can anyone tell me what this is, and what caused this? Of the 20 or so shots I took, I think about 5 did not have this going on. Thanks , Joe

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12-31-2012, 10:24 PM   #2
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QuoteOriginally posted by jjbacoomba Quote
Hi I am posting a photo I shot tonight. Practicing night shots with my new/old lens. A Pentax smc-A 28mm f/2.8 on my K100D. I used a tripod,turned off SR and shot in bulb mode. Here is the exif: exposure: 1 sec.
aperture: 3.5
ISO: 400 auto white balance.
I noticed what appear to be green dots/lights in the photo that start from the chair on the porch down to the middle of the image.I also noticed some just to the left of the bush. Can anyone tell me what this is, and what caused this? Of the 20 or so shots I took, I think about 5 did not have this going on. Thanks , Joe
Do you have a filter on your lens? If so that is probably where the reflection is coming from. Remove it and try again.
12-31-2012, 10:25 PM   #3
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It looks like reflection caused by lens filter.
12-31-2012, 10:26 PM   #4
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I think they are reflections from the lights to the right of the chair. The dots seem to match.

12-31-2012, 10:53 PM   #5
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Wow, thanks guys. yes I do have a filter on the lens. Its a skylight filter. Never occured to me to take it off. Was on the lens when I got it. I guess it was on a as protection kind of filter. I will have another go soon. Thanks again and Happy New Year.
12-31-2012, 11:05 PM   #6
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QuoteOriginally posted by jjbacoomba Quote
Wow, thanks guys. yes I do have a filter on the lens. Its a skylight filter. Never occured to me to take it off. Was on the lens when I got it. I guess it was on a as protection kind of filter. I will have another go soon. Thanks again and Happy New Year.
Glad to help. I myself have quit using filters except for the occasional CP filter. I would like to try a ND filter sometime for the appropriate situation.
01-01-2013, 05:46 AM - 1 Like   #7
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These reflections are common with cheaper or older filters, but only are obvious in such lighting conditions. After buying a lot of used lenses and cameras I've learned that the ones that have filters on them are nearly always in the best shape (optically), just like the camera bodies that have been in a "never-ready" case tend to be more pristine. When you have good lenses it is a dilemma: do you protect the lens as much as possible, or live with reflections? Besides Pentax I also use Leica, and even the 50mm f2.0 "normal" lens is over $2K, so you do want to protect it!
However, the best multicoated filters reduce reflections to where you won't notice them even in lighting like this. I find the Hoya and B&W top-end multicoated filters are worth it, on expensive lenses. (Lens hoods can also offer good protection from fingerprints and such.)
Filter reflections occur symmetrically opposite the center of the image, due to the curvature of the front element (on most lenses), so I set up a test shot to demonstrate. These are center crops, just to illustrate the effect of coating and filters on such reflections. First is a 50mm f2.0 lens with a good (B&W) UVa filter, but not multi-coated:
Name:  2012Sum_BWProF.jpg
Views: 310
Size:  193.2 KB
Next is the same setup, but with the MRC (multi-coated) version of the same filter:
Name:  2012Sum_BWProF-MRC.jpg
Views: 307
Size:  201.9 KB
And finally the bare lens without filter:
Name:  2012Sum_Bare.jpg
Views: 306
Size:  212.0 KB

Last edited by TomB_tx; 01-01-2013 at 08:08 AM.
01-01-2013, 08:24 AM   #8
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I use my lens hood to protect the lens and only use a CPOL when it is needed.

01-08-2013, 06:26 AM   #9
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QuoteOriginally posted by jjbacoomba Quote
Hi I am posting a photo I shot tonight. Practicing night shots with my new/old lens. A Pentax smc-A 28mm f/2.8 on my K100D. I used a tripod,turned off SR and shot in bulb mode. Here is the exif: exposure: 1 sec.
aperture: 3.5
ISO: 400 auto white balance.
I noticed what appear to be green dots/lights in the photo that start from the chair on the porch down to the middle of the image.I also noticed some just to the left of the bush. Can anyone tell me what this is, and what caused this? Of the 20 or so shots I took, I think about 5 did not have this going on. Thanks , Joe
Believe it or not a bluetooth in your ear can do it. I once had blue dots in some pics I was taking at night. I was like what the heck! I finally figured out it was the blue light from my blue tooth going into the OVF and finding a way down to the mirror chamber. This is what the cover for the OVF is for. To get accurate readings in bright light and just to help keep light out. Technically the mirror should seal it, but its not 100% sealed from light that comes from the OVF.
01-08-2013, 10:54 PM   #10
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Thanks for the test shots Tom, they were very helpful.
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