Weird double set of lights... help?

[panda-R]

Hi guys, i'm new!

I recently took a trip to HK with my new Rebel XSi (my first DSLR) and I took some pics from the peak. However there was a very weird thing that showed up and I'm not sure what it is, maybe you guys can help and tell me what I did wrong.

If you take a look at the picture, there is a building on the right hand side that has zig-zag lights (Bank of China), there seems to be an extra set of lights that has shown up. Is there a reason why only tha building is affected? I ruled out camera shake because all the other buildings seem to look good. The only thing I can remember is we used a cheapie Hoya CPL that night, maybe somehow the CPL did something?

http://farm4.static.flickr.com/3234/2825881773_2e12bebe5d_o.jpg

Thxxx!

[Mark_Cohran]

A cheapie filter with no anti-reflective coatings can cause all kinds on image degradation. What I can't understand is why you would be using a CPL at night?

[Jamie Holladay]

I am with Mark on the CP at night.
I looked at your image but can't seem to find what you are talking about.

[Jamie Holladay]

Welcome to POTN BTW. Pull up a keyboard and stay a while. there is a wealth of knowledge here, I am sure you will enjoy it as much as the rest of us.

[DerekRob]

Even though there is double lights I still like this shot though.

[manutd101]

I don't see double lights :(

[20droger]

I see thrm, but they hardly ruin the shot.

Two things.

First, the reason that such double lights occur in the first place is planar reflections. Flat surfaces in the optical pat can cause a back reflection, producing a double image. I used to have a diagram showing how this worked, but I cant seem to find it right now, so I'll try text (hopefully less than a thousand words for the missing picture).

As light enters the camera through the lens, it eventually reaches the sensor. The sensor is shiny and flat, so it reflects a portion of this light back into and out of the lens in a reverse direction. If the light leaving the lens encounters a flat reflecting surface, like the surface of a filter, some of it re-reflects back into the camera again, and reached the sensor a second time. This produces the ghost image.


As the light bounces back and forth, most of it gets absorbed by the sensor and the coated surfaces of the lens elements. This is why the ghost image is so faint relative to the first ("original") image. In theory, the light can bounce back and forth forever, but in practice, this absorption quickly lowers its intensity to the point where it is too dim to affect the sensor. The most I have ever seen was an original and three ghosts, but this was a staged shot taken specifically to maximize the ghosts.

High-quality filters with good, multi-layer anti-reflective coatings do much to reduce the ghost effect. Cheap filters with missing or poor coatings aggravate the problem.

Second, the appearance of a ghost is as much an issue of contrast as it is of the intensity of the light. Ghosting is visible in your sample photo for all the buildings with very bright lights (look just to the right of the top of the tallest building left of center, or the top of the buildings at the lower right with pyramidal roofs). The Bank of China building's ghosts are a little more evident because there is a very dark area immediately to the right of the building, and the building itself is very dark except for the very bright lines of light. These conditions make it perfect for exhibiting ghosts.

Hope this answers your questions.

Roger

[manutd101]

See it!

[PhotosGuy]

I don't see it mentioned here, so...
"Weird double set of lights" is called flare, if you care to google it.

Paranormal photography. (http://photography-on-the.net/forum/showthread.php?t=553696)

This thread shows some nice ectoplasm shot with a chipped lens.
http://photography-on-the.net/forum/showthread.php?t=558457

[Microcosm]

I see thrm, but they hardly ruin the shot.

Two things.

First, the reason that such double lights occur in the first place is planar reflections. Flat surfaces in the optical pat can cause a back reflection, producing a double image. I used to have a diagram showing how this worked, but I cant seem to find it right now, so I'll try text (hopefully less than a thousand words for the missing picture).

As light enters the camera through the lens, it eventually reaches the sensor. The sensor is shiny and flat, so it reflects a portion of this light back into and out of the lens in a reverse direction. If the light leaving the lens encounters a flat reflecting surface, like the surface of a filter, some of it re-reflects back into the camera again, and reached the sensor a second time. This produces the ghost image.


As the light bounces back and forth, most of it gets absorbed by the sensor and the coated surfaces of the lens elements. This is why the ghost image is so faint relative to the first ("original") image. In theory, the light can bounce back and forth forever, but in practice, this absorption quickly lowers its intensity to the point where it is too dim to affect the sensor. The most I have ever seen was an original and three ghosts, but this was a staged shot taken specifically to maximize the ghosts.

High-quality filters with good, multi-layer anti-reflective coatings do much to reduce the ghost effect. Cheap filters with missing or poor coatings aggravate the problem.

Second, the appearance of a ghost is as much an issue of contrast as it is of the intensity of the light. Ghosting is visible in your sample photo for all the buildings with very bright lights (look just to the right of the top of the tallest building left of center, or the top of the buildings at the lower right with pyramidal roofs). The Bank of China building's ghosts are a little more evident because there is a very dark area immediately to the right of the building, and the building itself is very dark except for the very bright lines of light. These conditions make it perfect for exhibiting ghosts.

Hope this answers your questions.

Roger
Great explanation. That's interesting, I never thought of that.

[panda-R]

hello everyone!

thanks for the help... i'm a newbie so when we took the shots my friend recommended we use the CPL to cut the reflections off the clouds and water. But it was very difficult to set at night and didn't seem to help a whole lot. Anyhow, it is the green box Hoya CPL with no coating so 20droger said, it could be the reflection back maybe. I know better now to not use any filters and stuff at night, hope my next time in HK the pics will come out better!

thanks again everyone!

[Lowner]

Don't loose too much sleep over this minor issue. That's a great image. If you are concerned about it, then it would be very straightforward to fix using pretty well any of the photo manipulation software available - some are even free!

I'd personally NOT call the repeated/reversed lights flare. Flare to me is light degradation of an image over a larger area than the sharp, well defined problem seen here.

If you get a chance to retake something like this again, try to capture the refections off the clouds, I think you'd find it would have made an even better image.

[20droger]

Flare, in the general sense, is images or effects caused by reflections within the lens. So yes, these ghost images fall under the general classification of flare. As a rule, though, ghosts are generally treated as a separate thing.

Flare is most often seen in a bright light setting, such as when direct sunlight strikes the front of the lens. If the sun is relatively near the optical axis, you will often get multiple iris flares. An iris flare is a light patch exhibiting the shape of your lens' iris (diaphragm), which is usually five, six, or eight sided for lesser lenses, and almost perfectly round for better lenses.

If the sun is far removed from the optical axis, flare is often exhibited as a lessening of contrast, sometimes a very severe lessening. With sharply curved front elements, this decrease in contrast may vary significantly over the image.

Other flare effects may be changes in color, color fringing, and an overall reduction in image quality.

[canonloader]

Doesn't anyone have a magnifying mouse button? That extra set of lights are just white zigzags on the "rest" of the bulding that aren't lit up. Buildings are 3D ya know, not flat 2D. :)

[photocrazy12]

Doesn't anyone have a magnifying mouse button? That extra set of lights are just white zigzags on the "rest" of the bulding that aren't lit up. Buildings are 3D ya know, not flat 2D. :)

I was thinking the same thing and you can see it on the top that the part where the zigzag ghost lines end up , there is light, so that part must've been light on the outside which was not visible from where the OP took the picture.

I love the picture btw.

[canonloader]

Well, the "ghost lines" are obviously outlining the back side of the building, But I see how it could be construed as a double image, although when you see it magnified, it isn't. And to back it up, the two pylons with red lights on top of the building are not doubled. This is just an optical illusion.

On the other hand, while looking at it magnified, I do see those water marks, or stretchmarks from it being resized incorrectly. JPG artifacts. Was this shot in RAW? It seems to be, and it was done in Lightroom. Not familiar with it, but I think CS3 does a better job, with fewer or no artifacts.

[krb]

I have had similar ghosts appear when shooting through the glass used in modern buildings.

[20droger]

Doesn't anyone have a magnifying mouse button? That extra set of lights are just white zigzags on the "rest" of the bulding that aren't lit up. Buildings are 3D ya know, not flat 2D. :)

I was thinking the same thing and you can see it on the top that the part where the zigzag ghost lines end up , there is light, so that part must've been light on the outside which was not visible from where the OP took the picture.

I love the picture btw.

Well, the "ghost lines" are obviously outlining the back side of the building, But I see how it could be construed as a double image, although when you see it magnified, it isn't. And to back it up, the two pylons with red lights on top of the building are not doubled. This is just an optical illusion.

On the other hand, while looking at it magnified, I do see those water marks, or stretchmarks from it being resized incorrectly. JPG artifacts. Was this shot in RAW? It seems to be, and it was done in Lightroom. Not familiar with it, but I think CS3 does a better job, with fewer or no artifacts.
I have better than a cursor magnifier, and I totally disagree. I see ghosts. (And I am NOT psychic!)

I am not, however, going to get into a p*ssing contest. If you guys don't see them, you don't see them.

[panda-R]

On the other hand, while looking at it magnified, I do see those water marks, or stretchmarks from it being resized incorrectly. JPG artifacts. Was this shot in RAW? It seems to be, and it was done in Lightroom. Not familiar with it, but I think CS3 does a better job, with fewer or no artifacts.

The shot was done in RAW and hastily processed in Lightroom. I'm still learning how to PP and use lightroom so I'm sure there is room for improvement. It was resized in lightroom.

If you get a chance to retake something like this again, try to capture the refections off the clouds, I think you'd find it would have made an even better image.

Definately will have a chance to reshoot! It was my first time with a DSLR and all the cool stuff to go along with it so next time will be better! Thanks everyone for th comments despite the ghosting effect. I will make you all proud next time!

[20droger]

Just remember rule 1: HAVE FUN!