photographing red lights

[supertackyman]

I have a question for all the photographers out there:
I am trying to take night panoramas specifically, real wide ones of las vegas, and although I can get my camera focused fine for most buildings, I am having trouble with anything that is lit with a red light. blue lights are ok and focus well, as do green. yellow is a but hazy and red is next to impossible to get into focus.
is there a filter out there that i should know about?

I also realize that a bunch can be done post, in photoshop.
please keep those suggestions limited to features available on ps-7 though, as even if cs2 has a one click interface to solve my problem, its not worth the expense. (yet)

any thoughts?

[tamlin]

I'm not quite sure what you're asking here. Is it that your camera's auto-focus won't work properly if the scene is lit predominantly with red light, or is it that the red-lit areas appear out of focus (while other areas are fine)?

If it's the former, how about trying manual focus? Auto-focus tends to be a bit unreliable in low-light situations anyway.

[supertackyman]

I believe its the latter.
It seems to me that the red light is just scattering.
other areas are fine, focus well (for what im doing) its almost like the red is waayyy oversaturated. I could probably adjust my apeture and shutter speed, but then the other colors and buildings are too dark. I cant really change my settings for each shot too much because this is a panorama.

[tamlin]

Any chance you could post an example?

[supertackyman]

ok, soits a bit grainy and I made the file small so there is pots of compression.
but.... see how the blue and green are a bit sharper than the red?
its like the red light is too bright.

also I realize that this is also probably due to the fact that im 13 miles away. and there is lots of atmosphereic s*it between me and it.
I know that this may just be the best that i can get it. given what i want to accomplish.
I'm probably just asking for more than my equipment and the situation is able to give.
but since im here to learn i figure I will let myself be taught

[synthetic]

I see... the red lights due tend to "flare" out a bit more... could be the intensity maybe?

[tamlin]

Well, I'm no physicist but I wonder if it could be the effect of differing light wavelengths over a distance? Red light is at the long-wavelength end of the spectrum, while blue and violet are at the short end. That's the only explanation I can think of (and it's probably not a very good one).

[supertackyman]

that was my theory. blue light carries far. red does tend to scatter. I believe thats why the sky is blue.

which brings me back to filters?
if it truly is a wavelegnth thing, then would the proper polarizer allow less of the red light thru, while still allowing the other colors on a narrower wavelength to pass unobstructed?
sorta like the screen on a microwave door.

[tamlin]

Well you could certainly try a polarizing filter, but the problem then is that a polarizer also acts as a neutral density filter, requiring exposure compensation to the tune of about 1.5 to 2 stops. If you're using TTL metering and autofocus, you'll probably find that they're unreliable in low-light situations anyway. Adding a polarizing filter might tip them over the edge completely, in which case you'd need to rely on manual metering and focussing.

[supertackyman]

from what ive found on google, if you use a red filter in color photography, it will block the yellows and blues. and a blue filter will block the reds and yellows.

link to below: Filters
WHAT DO COLORED FILTERS DO?

Colored filters absorb light and transmit the light they don’t absorb. A filter is yellow because it absorbs blue light (its complementary color) and allows yellow light to pass through it.

We say an object - a banana, for instance - is yellow because it reflects yellow light. So, if we use a yellow filter when photographing a banana, the filter will allow all the yellow light to pass through it and reach the film.

But, what if we use a green filter when photographing a yellow banana? Will the green filter allow the banana’s yellow light to reach the film? The answer is no, it won’t. The yellow light is blocked. Well, if that’s so, you may ask, how can a yellow banana be photographed through a green filter? Good question. The answer lies in remembering that yellow light is a combination of green and red light. (See Light and its color.) So a green filter blocks the red portion but allows the green portion of the banana’s reflected light to reach the film.

On color film, the banana would therefore register as being green because the red portion of its reflected light is absorbed and only its green light strikes the film.



so. according to this, if I used green filter? perhaps that will alleviate the problem.

[supertackyman]

that reminds me tamlin, are your filters still up for grabs? or have you got a taker?

[tamlin]

The only problem is that coloured filters like red, green and blue are usually only used in black & white photography. For example, a red or yellow filter is generally used to make the blue of a sky dark and thereby accentuate any clouds (in other words, the red/yellow filter blocks the blue light, causing blue areas to be underexposed and therefore appear darker on monochrome film). Green filters lighten foliage, since they allow through more of the green light reflecting off leaves and grass, resulting in a relative overexposure (and therefore lighter tone) in the green areas.

Unfortunately, this doesn't translate directly to colour photography. The sorts of colour filters used in colour photography (such as the 81 warming range and the 82 cooling range) are much less aggressive that B&W coloured filters, and are generally used for light balancing or colour compensation.

So yes, if you take a colour photograph of a yellow banana with a green filter, the banana will turn out green. Unfortunately, so will everything else in the picture.

Oh, and yes, those Cokin filters are still available if you're interested.

[supertackyman]

Yes I am intrested. pm with terms please.

[supertackyman]

I found this webarticle quite usefull

Shutterbug: Photo Filters