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07-11-2008, 05:37 PM   #1
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Tips on pictures of rainbows?

Seem to be getting a lot of evening showers resulting in rainbows. Thought they would make a nice background for pictures of the kids. Any advice on the best aperture etc for capturing rainbows?
thx in advance...

07-11-2008, 06:28 PM   #2
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As far as I know, there's no special setting to get rainbows, as they're pretty static.

Personally I'd pick whatever aperature gives your lens the best sharpness, set the camera up on a tripod with 2-sec timer and take the sharpest photo you can. You should be able to focus on a distant object (maybe even the bow?) or manually set the lens to infinity focus and fire away.
07-11-2008, 11:16 PM   #3
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Does the K100d/k200d have a rainbow setting?

Ok, lame joke.
07-12-2008, 12:57 AM   #4
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f/8 and be there.

07-12-2008, 11:07 PM   #5
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You might try using a polarizing filter too. Since the rainbow is a result of diffracted light, it is polarized. By filtering out the rays of light that are of a different polarity than those of the rainbow, you should get a brighter, more vibrant result.
07-13-2008, 02:00 PM   #6
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Polarizing filter for rainbows

As noted above, use a polarizing filter. As you adjust the filter, in some positions the rainbow's colors will stand out.
07-13-2008, 03:37 PM   #7
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I supose the focus should be at the rain drops from which the sun light is reflected, but how do you focus on rain? You might not even see it, though you see the rain bow. Pretty far away in any case, so if you want dof enough to get the foreground sharp as well you need to step down, how much depends on the lens and how close your foreground (kids) are, 5.6 may be enough for some wide angles, more needed for other lenses.

Note that there is a possibility of two rainbows, the secondary inside the primary. Both are centered (the center if you would be able to see the full circle of the rainbow, and yes you can see the full circle, a round rainbow, from airplanes) around the "anti-sun", that is 180 degrees from the sun. I may get the numbers wrong (I hold a Ph.D. in meteorology, but it is some time since I took the course converting rainbows, and I have not worked with them in my research since 1994 or so), but I think the primary (the normal) rainbow is 45 degrees from the anti-sun and the secondary 22 degrees. The primary is caused by light reflected twice inside raindrops, and the secondary three times (again my memory may cheat me). Keep an eye open for the secondary rainbow on you photos because it is often easier to spot on pictures than on the real sky and a polarized filter may help to enhance it since it is almost always more faint than the primary.
The color separation happens much the same way as it does in a not so good camera lens. Would be interesting to know if any one have used infrared photographing on rainbows since there should be a for humans invisible infrared line outside the normal color-fields, as well as an ultra violet on the other side.
If there is not real rain but drizzle the smaller size of the droplets makes the colors overlap creating the arctic white fog bow. You don't need to be in the Arctic Ocean to see it, but it is relatively common there and puzzled the early polar travelers.

But this was more than you asked for, right? Not hoping for rain in the summer vacation...?
07-13-2008, 09:35 PM   #8
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Man, what a great forum! Thanks for all the feedback. More than I expected! I'll post anything that might be impressive...

07-14-2008, 01:51 PM   #9
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Picked up a polarizing filter today. Any ISO suggestions?
07-14-2008, 03:11 PM   #10
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Use the lowest ISO you can set.

I'd just like to add to the comments re polarized light form the rainbow. The direction is tangential to the bow, in other words, by rotating the polarizer to pass the rainbow colours at say the10 o'clock position, you will completely block the 2 o'clock position. So use it to great effect on small sections of rainbow, leave it off to capture full horizon-2-horizon ones.
After playing with it in front of a rainbow you'll see what I mean.

One last thing - you can get them at night too, created by the moon.
APOD: 2001 July 4 - Moonbow with Sailboats although they are obviously very faint and need extra long exposures.

dbh - and post your results here.
07-15-2008, 03:29 PM   #11
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I'm not sure his kids will stay still for 30 seconds

Seriously, great shot on the moon-bow!
07-15-2008, 05:52 PM   #12
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QuoteOriginally posted by beaumont Quote
Any advice on the best aperture etc for capturing rainbows?
If anyone would know, it'd be a leprechaun, but they're not likely to tell.

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