Where did this rainbow come from???

ntenny · Dec 19, 2010

I've just scanned the attached photo. There's nothing especially remarkable about how it was created; I braced the camera against the column, pointing at the capital, set the exposure (1/2 second or so at f/2, I believe), and went click. Bessa-R with a 50/2 Nikkor, Provia 100F; the roll was developed commercially and the other frames show nothing unusual.

The rainbow, I am pretty certain, was not visible at the time of exposure! Can anyone suggest what happened here? (Yes, it's on the slide, not just a scan artifact.)

-NT

Brian Legge · Dec 19, 2010

Flare from a light that is just out of the frame?

ath · Dec 19, 2010

Brian Legge said:
Flare from a light that is just out of the frame?

+1

bdial · Dec 19, 2010

Brian Legge said:
Flare from a light that is just out of the frame?

+2

jp80874 · Dec 19, 2010

If you had an older uncoated lens without a lens hood it would be even more dramatic and/or harder to avoid. This is either very exciting and interesting or one of the common mistakes when shooting up into the sky. It is all about what spin you put on your story.

John Powers

RalphLambrecht · Dec 19, 2010

The shadows on the foot of the column suggest that the main light is coming from a direction towards the center of the 'rainbow' circle. Consequently, +3.

ntenny · Dec 19, 2010

Wow. I had no idea that flare could so easily produce a really crisp prismatic effect. I guess the intruding light source would have to be very close to the plane of the lens, right?

I think it's a pretty interesting effect, but I'm glad it didn't happen to a better photo. The rainbow is clearly the best thing about this one!

-NT

Hikari · Dec 19, 2010

That is not flare. Flare in non-image forming light and there is an image of a rainbow. Did you take a roll out of a camera and forget you had shot a rainbow frame? It looks like a double exposure.

RalphLambrecht · Dec 19, 2010

Hikari said:
That is not flare. Flare in non-image forming light and there is an image of a rainbow. Did you take a roll out of a camera and forget you had shot a rainbow frame? It looks like a double exposure.

Real rainbows don't look like that. A double exposure would have shown more of the 'other' image too. A rainbow is typically faint and not the brightest part of the image.

Hikari · Dec 19, 2010

RalphLambrecht said:
Real rainbows don't look like that. A double exposure would have shown more of the 'other' image too. A rainbow is typically faint and not the brightest part of the image.

Rainbows are circular with blue being in the inner arch. So it does look like a rainbow. Rainbows can certainly be brighter than the sky behind them--I have seen several. There also appears part on another image inside the rainbow at the top of the frame. So it is very possible that it is a rainbow image.

However, if it is flair, how does it produce a circular refraction pattern with a distinct spectra?

Hikari · Dec 19, 2010

The brightest part of this image is the rainbow. (BTW, I am no rainbow photographer.)

ntenny · Dec 19, 2010

There's pretty much zero chance of a double exposure---the film came out of its packaging, went in the camera, went straight through in a day, and got an identifying label stuck in the canister with it when it came out. (And I saw no rainbows that day; it was uniformly grey from dawn to dusk.)

So while it may be possible for the image of a "real" rainbow to look like that, I'm willing to exclude that possibility from consideration.

-NT

Hikari · Dec 19, 2010

NT, does this "rainbow" continue past the frame and into the sprocket holes and frame number? Has this happened before?

ntenny · Dec 19, 2010

Hikari said:
NT, does this "rainbow" continue past the frame and into the sprocket holes and frame number?

Good question, but I don't know the answer as I got the slides back mounted. I just went and had a close look at the slide but really couldn't tell.

Has this happened before?

No, and as far as I can think, everything about the equipment and processing is identical to things I've done a million times. (The processor is a pro lab with a good reputation; I use the camera all the dang time and lately this lens has lived on it.) Nothing unusual about the rest of the roll either.

I'm inclined to think it almost has to be a flare-like event that happened at exposure, but I still think the optical coincidence that produces a tight little spectrum like that, with no significant flare effects otherwise, is pretty striking.

I mean, normally when you see a rainbow effect from flare, it's hazy at the edges and accompanied by other obvious flare artifacts. Here I see some lightening to the right of the rainbow in the upper part of the image, against the dark ceiling, but it doesn't seem to cause much loss of contrast, which normally is kind of the definition of flare.

I say it's weird!

-NT

Hikari · Dec 19, 2010

If the image extends beyond the frame, then it could have been introduced by the processor. If not, then flare seems to be an explanation. However, I am at a loss to how such a pattern is made.

RalphLambrecht · Dec 19, 2010

Hikari said:
The brightest part of this image is the rainbow. (BTW, I am no rainbow photographer.)

Hikari

You're right, but even in this image there is enough to leave more than just the rainbow in a double exposure. However, your suggestion about a processing error is intriguing.

Brian Legge · Dec 19, 2010

I would expect a processing issue to cross the frame boundaries. If the artifact is constrained to the image frame that seems unlikely...

Poisson Du Jour · Dec 19, 2010

Does the Bessa-R + Nikkor 50/f2 combination have any problems such as internal reflections from rear element? It looks like quite an elegant form of chroma maybe through internal reflection, flare, shifting light... very different to the usual flare spots that are making a vogue comeback amongst landscape photographers.

MattKing · Dec 19, 2010

Was there a filter on the lens?

ntenny · Dec 20, 2010

MattKing said:
Was there a filter on the lens?

No filter, no hood. Essentially all the light is artificial; the room is pretty dim (it was late afternoon on a cloudy day, and there are minimal windows in the upper gallery where this was taken), but off to the right of the frame there are in fact several light sources (the lighting for a photo exhibition).

I do think I see some lightening to the right of the "rainbow", especially at the top of the frame---however, I'm pretty sure that the "map of Africa" shape in that area is actual discolouration on the ceiling, not a light artifact.

Supposing it were a processing issue, is there a plausible mechanism? This frame is in the middle of the roll, for what that's worth. I don't know how Chrome do their E-6 process.

-NT

lxdude · Dec 20, 2010

The color temperature to the right of the rainbow is very different compared to the left of it.

Joe VanCleave · Dec 20, 2010

The Bessa R is a rangefinder; you wouldn't necessarily see the "flare" in the camera's taking lens as viewed through the rangefinder viewfinder.

~Joe

railwayman3 · Dec 20, 2010

The camera appears to have been pointing vertically.

Could there have something fallen or laying on the lens?

It almost looks like the edge of a circular filter which has slipped out of place to one side?

Where did this rainbow come from???

ntenny

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