Blue glow

[gwiz]

...after all, it was French...

..and thus Systeme Evolue Contre les Americains.

[Laurel]

Those two were useless.  First, they destroy the television camera.  Then they smudge the camera lens on one of the Hasselblads.  Then they leave a magazine on the surface.

I think all the astronauts should be fined for littering...

Make them go back to the Moon and pick everything up. I'm sure they'd agree to this "punishment."

[dwight]

No, no NO! I have been very bad. I litter all the time. Send me to the moon as punishment.

[JayUtah]

In this case, I'm referring to an artifact due to the film's emulsion, not the optics.

Yes, film halation is the property of a film's base (and, to a lesser extent, its emultion) that mimics a prism in the sense that light reflects internally.  That is, light passing through the emulsion into the base reflects internally from the rear-facing base boundary and back up into the emulsion.  Since light strikes the film at an angle on the edges, it will reflect back from the rear of the base to hit a different place on the emulsion, causing artifacts.

The blue glow in the Apollo photograph is not likely to be film halation.  Halation rarely extends so far away from boundaries between high contrast.

Most modern films have anti-halation coatings on the rear of the film base.  Film halation was not a problem for Apollo owing mainly to the extremely thin film base and the application of this coating to the Estar base.

Another form of halation occurs in the optics, but it is merely chromatic aberration at small f-stops manifesting itself in the final image as an effect similar to film halation.  Its physical cause and properties have nothing to do with film halation.

[JayUtah]

Also with green chromakey you can get a bluish glow.

Hogwash.  With green chromakey you get green spill and halation, not blue.

I hate having to clean up chromakey spill in my photographs, so I use lumakeying whenever possible.  That is, I photograph the subject against matte velvet black.  If I use chromakeying, I use blue.  Green is too close to flesh tone to get a proper separation.

Key halation occurs when the thresholding mechanism (either the algorithm for doing it digitally, or the saturation for doing it optically) fails to find a clean edge, leading to a misregistration or poor fit between the holdout matte and the separation matte.  This can sometimes let a small fringe of the key color leak out around the foreground.

Key spill occurs when colored light reflects from the key screen onto the foreground.  Typically the screen must be brightly and uniformly lit, which interferes in small studios such as mine with the more subtle artistic lighting on the subject.  So the subject will often have an undesired color cast relating to the key color.  After extraction, manual localized hue corrections have to be applied.

Of course none of that explains the massive blue aura around the astronaut.  It's not characteristic of any sort of keying error.  Sheesh.

[JayUtah]

I have a big 500mm Sigma lens, get some blue glow with that at times.

I think it's cute how you don't know that long lenses are far less susceptible to optical halation than short lenses.  Next time you try to create a sock puppet who supposedly has photography experience, do more homework.

[nomuse]

I find it easy to visualize how you could get blue "within the lines" of the figure you were trying to separate from background. 

How would you get a blue halo outside of the subject?  I can't seem to think of a scenario that would make this likely.  Perhaps someone with more experience could explain.

(Only thing I can think of is bleed, optical interference, etc. causing sufficient discoloration of areas outside the figure proper sufficient to throw off the keying. But I can't see how this would extend for very far!  Now, throw hair or angora sweaters into the mix, and yeah, all sorts of horrible things happen.  But beta cloth?)

[Sus_pilot]

In this case, I'm referring to an artifact due to the film's emulsion, not the optics.

Yes, film halation is the property of a film's base (and, to a lesser extent, its emultion) that mimics a prism in the sense that light reflects internally.  That is, light passing through the emulsion into the base reflects internally from the rear-facing base boundary and back up into the emulsion.  Since light strikes the film at an angle on the edges, it will reflect back from the rear of the base to hit a different place on the emulsion, causing artifacts.

The blue glow in the Apollo photograph is not likely to be film halation.  Halation rarely extends so far away from boundaries between high contrast.

Most modern films have anti-halation coatings on the rear of the film base.  Film halation was not a problem for Apollo owing mainly to the extremely thin film base and the application of this coating to the Estar base.

Another form of halation occurs in the optics, but it is merely chromatic aberration at small f-stops manifesting itself in the final image as an effect similar to film halation.  Its physical cause and properties have nothing to do with film halation.

Honestly, I didn't bother to look at the image to which he was referring.  I though it was something off a hot spot (corner reflection of the sun) in the image.

Good point about long lenses, BTW.  Some of my favorite images in my 35mm days were up-sun shots using a 28mm lens.

[JayUtah]

Honestly, I didn't bother to look at the image to which he was referring.

http://www.lpi.usra.edu/resources/apollo/frame/?AS12-46-6826

Certainly not film or optical halation.  My best hypothesis is still contamination on the lens, probably very fine dust.

[raven]

I have seen early Chromakey, Monty Python's flying circus uses it a few times, and that is *not* Chromakey edge screw ups. For one, the glow is somewhat visible over the whole of the astronaut.

[Mag40]

Honestly, I didn't bother to look at the image to which he was referring.

http://www.lpi.usra.edu/resources/apollo/frame/?AS12-46-6826

Certainly not film or optical halation.  My best hypothesis is still contamination on the lens, probably very fine dust.

The ALSJ -

"Pete took this partial pan from the southeast rim of Middle Crescent just before he and Al headed back for the LM. The frames are AS12-46- 6836 to 6844. Note the strong colors at the center of the righthand frames. Examination of successive frames indicate that this related to the camera lens, very likely a dust smudge. Kipp Teague notes "The lens aberration begins at as12-46-6813. It's a blue glow around the astronaut in 6818, again in 6826, a discoloration in other frames, affecting clarity in most, and it's not gone again until 6853 (back in the LM). Whatever the phenomenon is, it has a varying impact on color based on the brightness of the central object in the image. On bright subjects, the aberration adds a blue cast, and on darker subjects, the aberration adds a reddish cast." I note that it also seems to vary with sun angle."

I also recall some tiny blue blobs on some exposures caused by very fine particles getting onto the film.....not sure how....but the explanation pointed towards the emulsion on the film itself, having the top layer eroded.

[JayUtah]

I also recall some tiny blue blobs on some exposures caused by very fine particles getting onto the film.....not sure how...

The magazines were not standard Hasselblad mags, nor were they installed in the customary way.  They were "longroll" magazines designed by a third-party company in Hollywood -- not specifically for Apollo, but modified for use on Apollo by the company.  The longroll magazine could hold up to 180 frames, depending on film thickness.  The standard Hasselblad magazine for this format, using commercial film, holds 12-20 frames.

Normally the magazine is fitted with a darkslide to prevent exposing the film during magazine changes.  The magazine is attached to the back of the body and then the darkslide is removed, opening the gate to the light path.  Subsequently the magazine cannot be removed until the darkslide is once again inserted.

However for Apollo the cameras and magazines were modified to allow interchanging the magazines without the darkslide in place.  The magazine was removed from storage, the darkslide was removed and discarded, and the magazine attached to the back.  At the end of the roll, the film trailer was simply wound into the magazine and the magazine detached and stored.  Several initial and final frames of each roll were often sunstruck.

All of that has been to point out that the possibility of dust contamination and subsequent scratching was very real and even likely.  After the darkslide was removed, nothing prevented lunar dust from adhering to the film surface and then being pressed subsequently against the reseau plate.  Conversely, with the magazine removed, nothing prevented dust from adhering to the exposed reseau plate.  Either mechanism, or both, would subject the film to possible particulate erosion.

but the explanation pointed towards the emulsion on the film itself, having the top layer eroded.

Yes, I confirmed this possibility with my own scratch tests on E-3 and E-6 emulsions.  Lightly abraded, the resulting transparency biases toward blue in the abrasion spots.

[Mag40]

I also recall some tiny blue blobs on some exposures caused by very fine particles getting onto the film.....not sure how...

The magazines were not standard Hasselblad mags, nor were they installed in the customary way.  They were "longroll" magazines designed by a third-party company in Hollywood -- not specifically for Apollo, but modified for use on Apollo by the company.  The longroll magazine could hold up to 180 frames, depending on film thickness.  The standard Hasselblad magazine for this format, using commercial film, holds 12-20 frames.

Normally the magazine is fitted with a darkslide to prevent exposing the film during magazine changes.  The magazine is attached to the back of the body and then the darkslide is removed, opening the gate to the light path.  Subsequently the magazine cannot be removed until the darkslide is once again inserted.

However for Apollo the cameras and magazines were modified to allow interchanging the magazines without the darkslide in place.  The magazine was removed from storage, the darkslide was removed and discarded, and the magazine attached to the back.  At the end of the roll, the film trailer was simply wound into the magazine and the magazine detached and stored.  Several initial and final frames of each roll were often sunstruck.

All of that has been to point out that the possibility of dust contamination and subsequent scratching was very real and even likely.  After the darkslide was removed, nothing prevented lunar dust from adhering to the film surface and then being pressed subsequently against the reseau plate.  Conversely, with the magazine removed, nothing prevented dust from adhering to the exposed reseau plate.  Either mechanism, or both, would subject the film to possible particulate erosion.

but the explanation pointed towards the emulsion on the film itself, having the top layer eroded.

Yes, I confirmed this possibility with my own scratch tests on E-3 and E-6 emulsions.  Lightly abraded, the resulting transparency biases toward blue in the abrasion spots.

Thanks for the explanation. I can hardly envisage a counter explanation....relevant to this being faked on Earth..... as to why or how this was even done. It's just another incidental example of stunning consistency of the Apollo record.

[ka9q]

Yes, I confirmed this possibility with my own scratch tests on E-3 and E-6 emulsions.  Lightly abraded, the resulting transparency biases toward blue in the abrasion spots.

And the top layer of the emulsion is the blue sensitive layer, so if you damage only that layer the result is a blue scratch.

Below the blue-sensitive layer is a yellow filter, i.e., it stops blue.

Next is a green-blue sensitive layer. Because of the filter, it responds only to green light in the scene.

And at the bottom is a red-blue sensitive layer. It similarly responds only to red in the scene.

So the color of the scratch depends on how deeply you scratch the emulsion. Scratch just the blue-sensitive layer and you get blue scratches.  Scratch the blue and green layers but not red and you'll get cyan. Scratch them all and you'll get white.

[JayUtah]

So the color of the scratch depends on how deeply you scratch the emulsion.

Exactly the results I got.  I scratched progressively harder to reveal the different manifestations of abrasion damage, down to the base.  Now if I can only find where I put the images of the results...