It took Jay a good while longer, be he's probably more trusting than I am.

No, just more thorough. I saw the supposedly missing flap the very first time I saw the video. I wanted to go the second mile and show exactly what the flap was, so I scoured the photo set and examined every Apollo PLSS within a 600-mile radius of where I live.

Notice how the crosshairs bleed against the bright lit lunar surface.

Absolutely. Michael Light's Full Moon is full of high quality prints in which the fiducials are partly obscured.

White objects tend to obscure the fiducials. The lunar surface will too, if overexposed. Highlights on silver objects almost always obscure the fiducials. Since silver reflects light more directly than white, it's clearly a function of how much light strikes the film.

Not only that, fiducials near the edge tend to bleed out more than center fiducials. That means film base halation is also an issue. For a while Kodak was even interested in what I had learned about this, but they've satisfied their curiosity. (Apparently it was a known problem with the Estar base as manufactured then.)

So what are we supposed to do with Percy? He cuts a dashing figure on television. He smiles pleasantly and tells the world that gosh he'd really like to believe in the Apollo moon landings, but he just can't anymore. What an act!

I would really like to believe David Percy, but I can't. His photographic "evidence" is simply wrong. And if he says he is a professional photographer, I think he's making up faulty arguments on purpose.

_________________
"The contemplation of celestial things will make man both speak and think more sublimely and magnificently when he descends to human affairs." -Marcus Cicero

<font size=-1>[ This Message was edited by: AstroMike on 2002-02-06 19:05 ]</font>

Can you explain that in more detail please? I'm curious.

Photographic film is an emulsion of light sensitive chemicals spread over a transparent base of celluloid or plastic. The Estar base is a Kodak base commonly used in aerial photography because it is very thin and can be rolled up into spools to save space in photo pods.

Halation is the phenomenon whereby the optical properties of the base -- chiefly scattering, refraction, and internal reflection -- intrudes upon the imaging by the emulsion. The base acts like a rectangular prism. If the light strikes the film perpendicular to its surface, only scattering is an issue. If it strikes it at a more oblique angle -- as it would near the edges of the film plane -- the light rays refract and reflect off the back of the base, striking the back of the emulsion and "bleeding" a bright image.

Film formulations have historically employed antihalation coatings, but these have adverse effects on the image quality. It has been considered better to devise bases with physical properties that reduce halation. I do not believe the Estar base uses a separate antihalation layer. Since the Ektachrome emulsion is a reversal emulsion, it does not darken when light strikes it. The opacity of negative emulsions when exposed helps reduce halation in the entire film system -- once the emulsion is fully dark (i.e., saturated) no more light passes through it.

I believe Kodak does not habitually use the Ektachrome emulsion and the Estar base and so did not anticipate the halation problems. And it must be stressed that the halation is very minimal. The image, in general, is not affected. But the fiducials are only 0.02 mm thick and are very easily obscured.

The issue of halation is important in the hoax theory because it supports the already well-established contention that the obscuration of fiducials is caused by photographic exposure.

His photographic "evidence" is simply wrong. And if he says he is a professional photographer, I think he's making up faulty arguments on purpose.

Clearly. David Percy claims to be a photographer, and I have no real reason to doubt him. But I haven't seen any photos he's taken -- and I've looked -- except those he has presented to support moon hoax arguments. He claims to be an award-winning filmmaker, but the only award I've been able to confirm is a yearly award given by an organization of makers of industrial films. He seems to make most, if not all, his living on the moon hoax stuff.

He might be a photographer, but so far he seems to know very little about field of view, perspective, lighting, shadow, geometry, or exposure. In the field of photography, what's left?

I've shown his evidence to people who I know are good photographers and lighting designers. I know what their skills and qualifications are. They think Percy is a loon.

So what am I to conclude? I suppose someone can be an "instinctive" photographer with no real knowledge of the technical aspects. But that's not what Percy claims to be. He discusses photos from a technical perspective. If he wants to be a shoot-from-the-hip photographer, he can't pretend to be a photo analyst.

Either David Percy isn't the kind of photographer who has the skills necessary for photo analysis, or he has the skills and uses the cloak of expertise to deliberately mislead and deceive his readers for his own profit.

Lately I've cruised around the web and read some stuff on Percy, but I am wondering if any of you have ever spoken with him? I'd just really like to get a sense of this guy, who is so obviously wrong and most likely an outright scam-artist.

I am wondering if any of you have ever spoken with him?

I had a brief e-mail conversation with him. I asked him some detailed questions about his arguments, how he had examined certain photos, what his science background was. After I revealed that I was a professional engineer and disagreed with his findings, he stopped responding to my e-mails.

His web site can be found at http://www.aulis.com. It used to feature an unmoderated interactive forum. After several of Percy's main arguments had been thoroughly refuted on the forum, the forum was abruptly removed and all traces of refutory arguments were erased. There is a sort of guestbook where you can leave messages, but it is very difficult to get anything refutory or even argumentative posted there. It is heavily moderated. Apparently it's intended more as a shrine to ignorance than as a serious discussion forum.

To get back to discussing the original site listed at the start of the thread, I had a quick look at it as well.

I note with interest the theory that the missions took place but all the photography was messed up, so they had to fake it back here on Earth. We then read that such a theory would upset everyone, cos the HBs would have their proof the photos were faked, while the rest of us would have our proof the missions really occurred.

Speaking as someone who's had some experience in industrial relations, the concept of a solution which pleases no one is very attractive (it my experience, if everyone was unhappy with the resolution of a problem, we figured we were close to an ideal solution).

Of course, what blows the theory out the window is the idea that for 7 missions (Apollos 11 to 17) NASA kept fouling up the photography. It's believeable that there might be some effect on or near the Moon which affects photography, and which wasn't thought of at first. After all, it took until Apollo 12 for people to realise that a Saturn 5 could act as a lightning rod.

But the point is that whatever problems arose on any mission were sorted out by the next one. So even if there were problems with photography on the Moon for Apollo 11, you can be sure they would've been sorted out for Apollo 12. They certainly wouldn't have continued for the remaining missions.

I understand parallax, a 3 year old would basically understand parallax, and you know it. And I sure ain't no expert at anything. What I don't understand is why every time Dave Scott took a photo of Jim Irwin with Mt. Hadley in the background, the top of Hadley is basically straight.
near the end of EVA2:
http://www.hq.nasa.gov/office/pao/Hi...5/20135257.jpg

in 11866, he was using Irwin's camera and didn't put it in his RCU bracket in this real video. Notice his right lean.
http://www.hq.nasa.gov/office/pao/Hi...5v.1635901.ram

and here in this real video the camera is in his RCU, we can't tell if he took it out or not. Did he usually take his camera out of his RCU bracket? If so, oops on my part. http://www.hq.nasa.gov/office/pao/Hi...5v.1485317.ram

but the mountain top is still basically straight. A 10-15 degree difference in mountain angles, that are 3 miles away and about 2.5 miles from a camera that (may be) in his RCU bracket. The only thing I can figure is that Dave Scott was mis-cropped on both pics.

thanks,
CraigZ

I understand parallax, a 3 year old would basically understand parallax, and you know it.

No, most hoax believers don't understand parallax, or else they conveniently forget about it when "analyzing" Apollo photos. You talk about crater patterns and wonder about it being "explained away easily." It is explained away easily, and if you had known anything about parallax to start with you wouldn't have drawn the circles and arrows into your proof photos and talked about it at all. People who understand parallax generally don't need to call attention to it as something that's putatively fishy.

And I sure ain't no expert at anything.

This much is clear. There are several principles of photography of which you seem to be almost completely ignorant. 95% of your evidence can be summarily shot down on that basis.

This particular argument is quite easily dealt with. The fixed elements of the photos remain in almost perfect alignment. The mountain background, the LM, and the flagpole line up in every photo.

Further, the variable elements of the photos (i.e., the astronaut) actually become more coherent when the image boundaries are ignored and the photos are rectified using the background and foreground elements as alignment guides.

What I don't understand is why every time Dave Scott took a photo of Jim Irwin with Mt. Hadley in the background, the top of Hadley is basically straight.

What's not to understand? The camera was canted at different angles for the various shots. Some of the cant angles resemble others, some are unique. This explains all the visible effects. Wild speculations about cut-and-paste astronauts or falling drops raise far more questions that they answer.

Did he usually take his camera out of his RCU bracket?

If an astronaut is being handed a camera to take one photo and then he will likely hand it back to his crewmate, it's unnecessary and a waste of time to put it in the RCU mount.

I'll try and keep this as short as possible (within reason), I don't want to try your patience.

On the not-sound-earth pic, if I found an AS15-XX-XXXXX number on it then it wouldn't be Mr. Teague's 'fault' (for lack of a better word)?

Pic. 8, It's either too late in the night to be typing this and I'm not seeing things correctly but did you just say pic 8 was not a visible spectrum pic and then in the next paragraph say it was?

pic, 12 Am I understanding you correctly, lunar dust? Is lunar dust why this sun seems so huge in this Apollo 12 pic?
http://www.hq.nasa.gov/office/pao/Hi...-46-6806HR.jpg

And would it be ignorant of me not understanding why it seems this earth (from Apollo 17)
http://www.hq.nasa.gov/office/pao/Hi...87-cropped.jpg
could not eclipse the afore mentioned Apollo 12 sun? If I'm not allowed to jump missions (for some reason) why does it appear it wouldn't eclipse an Apollo 17 up sun shot?

Pic, 13. I knew you thought that to be a sunstrike pic, I've been to your website. I was trying to get someone to say it was a lens flare, then I was going to point them to your sunstrike page, but no one claimed it was. As for the anomalies at top, going perpindicular to the sunstrike. Could these anomalies appear without a sunstrike?

This is a numbered link pic, it's ID is AS15-82-11216. I don't think this a sunstike, but what is it?

http://www.hq.nasa.gov/office/pao/Hi...5/20147789.jpg


pic 13b, I don't see that, there's no reflected light on anything in the LM. No silhouette or reflection of the photographer or anything else. Must be my naivety showing.

pic 14, http://www.hq.nasa.gov/office/pao/Hi...5-92-12424.jpg

pic 15,
http://www.hq.nasa.gov/office/pao/Hi...5-85-11514.jpg

Again, I don't see it. Someone posted in newsgroup SSH that it was the astronauts white suit reflecting in. I can see that given the high spot of where the light is stiking.

Could I put your explanations on my website?

thanks for responding,
CraigZ

I looked at this picture. It looks like there is reflected light off the top of the astronauts helmet. That splotch near the top of the frame is of the same general size and shape of the bright spot on the helmet and a straight line can be drawn from the flash on the helmet through the splotch on the film and the diffuse stuff at the very top of the picture.

__________________
Valiant Dancer

I don't want to try your patience.

You'll find I have an enormous amount of patience if people merely ask for explanations or argue their cases well. You'll find I have very low patience for arguments based on ignorance or ad nauseam insistences. Ignorance itself isn't a problem. Understanding the picky details of Apollo or any space enterprise often requires very specialized skills that not everyone has or is expected to have.

On the not-sound-earth pic, if I found an AS15-XX-XXXXX number on it then it wouldn't be Mr. Teague's 'fault' (for lack of a better word)?

Not necessarily. Anyone can change a file name without changing the picture. The JSC scans from the 1980s are known to have color distortion, value distortion, and vertical space distortion. If you found a digital photo that you could reasonably assure yourself was not from the JSC scans, you could indeed argue that the problems with the JSC scans do not apply. However, other problems may apply.

If you're dealing with digital photos exclusively, you must also deal with the fact that no scanner is perfect. Granted, most desktop scanners today would do a much better job that the transparency scanner JSC used in the 1980s, but you must account for aberration in any photos you deal with -- even high-quality prints. For example, many prints of Aldrin descending the LM ladder have been overexposed during printing to compensate for the dark lighting conditions.

The only foolproof evidence of an egg-shaped earth would come from examining a contact transparency of the master for this photo. That's the only way you can reasonbly eliminate the sources of distortion induced by a duplication process. The only argument against an egg-shaped earth at that point would be shrinkage of the master, which is rather farfetched.

It's not that hard to get research quality photo reproductions from the Apollo sets. NASA has a photo contractor to handle those requests. It's not free, however.

Pic. 8 ... was not a visible spectrum pic

I may have made a typo. Let me try it again without the ambiguity.

The photo taken from lunar orbit showing the LM's shadow is a visible spectrum photograph. It was made by aiming the camera out of the CM window.

The Clementine photo that allegedly shows the Apollo 15 landing site disturbed by the DPS, is not a visible spectrum photograph. It was created digitally by "registering" (i.e., exactly superimposing) various original digital Clementine photos of the same area taken in various spectra -- visible and invisible (e.g., ultraviolet) -- and algorithmically computing the final image on a pixel-by-pixel basis.

Clementine was intended to gather information about mineral deposits and the chemical composition of the lunar surface. This can be done remotely by multispectral imaging. The Clementine photo so clearly shows the DPS disturbance because the algebraic process of combination used for this photo is one which is known to be able to detect recent disturbances in the lunar regolith.

pic, 12 Am I understanding you correctly, lunar dust?

Not clouds of it, of course, but a fine layer on the camera lens.

Is lunar dust why this sun seems so huge in this Apollo 12 pic?

Possibly, but certainly not necessarily.

Do you understand film saturation? Remember that film is exposed over time. The shutter opens and light starts striking the film. It continues to do so until the shutter closes. What the film records is an accumulation of all the light that has fallen onto it during that length of time. That's why in night shots of city streets you see long streaks instead of tail lights. The light moved, but the film recorded it at all the points along the way. The image didn't "disappear" from the film when the light moved away from its initial position.

Saturation occurs when the film is simply unable to respond any further to light. So much light has fallen on the film that it's as dark or light (depending on what kind of film it is) as it's going to get. The little silver salt crystals in the emulsion have all done their thing.

Scattering is a particular interaction that occurs between light rays and a lens. When light strikes a lens, basic optics describes the process of refraction which produces a focused image. That's the theory. In the real world, when light strikes the lens it doesn't refract perfectly. Irregularities in the lens surface (microscopic or even molecular) mean that some of the light rays are bent more than others. So a perfectly parallel "bundle" of light rays may enter the lens, but when they come out the other side they're a sort of cone of slightly diverging rays. This means some of the rays will strike the film a short distance away from where they were intended to.

Dust or other contaminants on the lens greatly increase the scattering. This is why some Apollo pictures are foggy or have bluish halos around the brighter areas. (The shorter the wavelength, the more susceptible a light ray is to scattering.) But it can happen with the most expensive lens that has been scrupulously cleaned.

Normally the divergent light rays are not photographically significant. That is, a good lens will not scatter enough light to drastically affect the picture. But when you shoot straight at the sun, an enormous amount of light enters the lens. This means the amount of scattered light increases. In fact, the amount of scattered light from the sun is so great that it not only exposes the film, it saturates it. So not only do you have the patch of saturation on the film that would correspond to the image of the sun, but you have the surrounding patch of saturation that resulted from the scattering of the lens.

Reversal film, which is the type of color film used on Apollo, has what photographers call a narrow exposure latitude. Modern amateur film has ridiculously wide exposure latitudes. That means you don't have to precisely adjust the camera. The film will "forgive" you for sloppy exposure settings and give you a good picture.
Kodak Ektachrome is merciless. Professional photographers who use it usually "bracket" the metered exposure. That means they set the camera according to the light meter and take a photo, then they take one that's underexposed relative to that, and other that's relatively overexposed. One of them will usually turn out.

What this means for up-sun Apollo shots is that saturation occurs relatively quickly given even a very small amount of excess light. The same photo taken with negative film wouldn't show as bright a disk.

So how do we account for the differing sizes of apparent sun disks in color photos? Exposure.

The photographer is not trying to take a picture of the sun. He's trying to take a picture of whatever else is in the picture. In the large Apollo 12 photo case, he's taking an up-sun picture of the astronaut and the equipment in the background. Basic photo technique says to overexpose when shooting up-sun.

Compare this to taking a photo of the earth from orbit, which also happens to include the sun. The earth is amazingly bright from orbit. You can actually take pictures of the lunar surface lit only by reflected light from earth. So when you're taking a picture of something brightly lit, basic technique says to underexpose (to avoid saturation). You can always "push" it later in the darkroom.

The greater the exposure, the more scattering you will capture on the film and the bigger the apparent size of the sun will be.

I realize these are esoteric subjects, but you simply must be fully aware of the differences in how the camera perceives light and how the eye perceives light. You cannot hope to discuss these things intelligently unless you have an expert knowledge of photography. Unfortunately you seem to have a very basic knowledge -- if that -- so if you'll consent to being educated, there are plenty here who can teach you.

why does it appear it wouldn't eclipse an Apollo 17 up sun shot?

Because the earth is not bright enough to cause scatter-related saturation at this exposure setting. If you could magically eliminate the effects of scattering and saturation in the photos, the sun disk would appear about one sixth the size of the earth disk, accounting for phase.

Could these anomalies appear without a sunstrike?

Absolutely. If you re-read my response you'll find I didn't claim the anomalies at the top were sunstrike, merely that the photo is sunstruck. This, combined with the photo ID number, tells us the frame was in a vulnerable spot toward the end of the roll in the magazine after the magazine was removed. That in turn brings to bear a number of possibilities, including light contamination or possibly physical damage from the winding mechanism or magazine cover.

it's ID is AS15-82-11216. I don't think this a sunstike, but what is it?

This is a very classic case of sunstrike. The shadow one fiducial left of center is a dead giveaway. It's the shadow of a tab on the magazine cover.

pic 13b, I don't see that, there's no reflected light on anything in the LM.

The bright spot to the right of the CM is likely the reflection of sunlight off the window bezel.

No silhouette or reflection of the photographer or anything else. Must be my naivety showing.

Recall that the window is tilted outwards. From the pilot's point of view, the top of the window is farther away from him than the bottom. You can't expect to simultaneously see a reflection of the LM ceiling and of the photographer. Try this in the bathroom with a hand mirror.

The windows do have anti-glare coatings on them. Of course no anti-glare coating would be able to fully eliminated sun glare. But it might explain why the rest of the cabin ceiling might not be visible.

But the real answer is obvious. The lights in the LM cockpit are off for the same reason you don't generally drive your car at night with the dome lights on. If you turn on the dome light your view through the windshield is compromised by the reflection of the interior of the car. The instruments in the LM were backlit with a pretty blue light, so they don't need the cabin lights on in order to fly it.

pic 14

Ah, thank you. You're seeing the side shade partially lowered.

The Apollo LEVA helmet evolved during the program. In the J-missions (Apollos 15-17) the overhelmet included the see-through gold visor, but also a sort of sun shade that could be pulled down over the forehead to cut the glare. This featured a separate panel that could be rotated upward and secured to form something like the bill of a baseball cap. Side shields that slid down along the cheeks were also added.

Peruse the photo sets from the J-missions and you'll see the sun shades in various positions. In this photo the astronaut's "bill" is detached from the center shade, but not fastened in the up position. The side shade is partially lowered. Note the tab along the bottom edge.

I don't know what exactly you believe in anomalous in this photo, but I've seen more space helmets than I can shake a stick at and what I see in this photo is exactly what I would expect.

pic 15, Again, I don't see it. Someone posted in newsgroup SSH that it was the astronauts white suit reflecting in.

The sun is obviously shining brightly off the front of the OPS, but this has nothing to do with what's happening in his shadow.

Look back at some of your up-sun photographs and note the "ray" effects -- also caused by scattering. You can see that they always radiate outward from the sun. In many photos the lens rays are visible even if the sun itself is out of the frame.

Use the shadow and shading patterns on the suit to get an idea of where the sun is. Now look at the astronaut's shadow and at various other places in the full frame. You can see they're overlaid with these very same rays. There are enough of them to extrapolate back to where the sun would have to be if the frame were larger. You should see that it correlates with the shadows.

Further, there's a sort of halo effect happening. Lens rays tend to intensify a certain distance (in image space) from the image of the light source. This is caused by the light's interaction with the lens surface at the molecular level. Again, when photographing objects the scattering is negligible. Only when something provides an enormous amount of source light does scattering become photographically significant.

You must keep in mind that a photographic image is the accumulation of light that strikes the film plane. Once it has arrived and caused the photochemical changes in the emulsion, it is no longer a matter of whether that ray arrived directly through the lens or circuitously through some unintended optical route, or if the original source of the light goes away.

The film does not see the same things the eye sees.

Could I put your explanations on my website?

Of course. Anything I say in public is fair game for quoting, as long as you do so courteously and fairly.



<font size=-1>[ This Message was edited by: JayUtah on 2002-02-07 11:07 ]</font>

CraigZ, do you drive at night? Do you, like me, drive with a perperually dirty windscreen? What happens when someone coming the other way leaves their lights on high? You can't see where you're going. The lights from the oncoming car look massive, even though they are relatively tiny compared to the whole road you are looking down. and your whole windscreen lights up. This phenomenon explains a few of your anomolies. Go out for a drive in the dark with a dirty windscreen and see how much of your vision in obscurred.

<font size=-1>[ This Message was edited by: johnwitts on 2002-02-07 17:13 ]</font>

Two questions for JayUtah:

Was the center crosshair thicker than the others? I’ve noticed that on a lot of the photos there doesn’t appear to be as much bleed through.

Your description of halation (a term I’d never heard) was excellent. Always good to learn something new. Showing my ignorance, were the consecutive frames close enough together to allow bleeding on adjacent frames? In particular, I wonder about the adjacent frame to:

<font size=-1>[ This Message was edited by: SpacedOut on 2002-02-07 17:27 ]</font>

Was the center crosshair thicker than the others?

No, but the lines were longer. They were uniformly 0.02 millimeter thick. It's actually one of the standard Hasselblad reseau plates. You can get one fitted on the EL/550 Data camera, which is the current version of the model on which the Apollo LEVA camera was based.

I’ve noticed that on a lot of the photos there doesn’t appear to be as much bleed through.

Halation would account for that, but the exposure setting and the material being photographed has the greatest effect on the fiducials.

Showing my ignorance, were the consecutive frames close enough together to allow bleeding on adjacent frames?

No. There is always a small gap between frames.

This sounds like rather unkind advice, akin to "go play in traffic." I'm sure we don't wish that, even of HBers. [img]/phpBB/images/smiles/icon_wink.gif[/img]

_________________
"... to strive, to seek, to find, and not to yield." - Tennyson, Ulysses


<font size=-1>[ This Message was edited by: ToSeek on 2002-02-08 08:29 ]</font>

This sounds like rather unkind advice

A safer experiment might be this. Take a picture of yourself using a flash-equipped camera (film, not digital) and a full-length mirror and note how large the burst of saturation appears in the final photo. You know the flash is only an inch or two square, but the burst as recorded on film will likely obscure your entire head.

CraigZ,
I must say that I am impressed to finally hear of a HB that can ask a question and listen to the response. Historically, most HB's tout the expression "you need to have an open mind", intended to persuade people to think that Apollo >possibly< did not happen. Yet they do not seem to have an open mind to the possiblity that they might be mistaken on several areas of physics, and refuse to acknowledge any accurate explanations.
I applaud your ability to assimulate new facts and explanations even though they may not be what you want to hear.

Kudos for you.

May you learn as much as I have from the people at BABB.

This sounds like rather unkind advice

This was never meant to be unkind. [img]/phpBB/images/smiles/icon_smile.gif[/img] It's just that I hardly ever wash my car, as it's so crappy (before anyone else jumps in), so I drive with a windscreen that is perpetually dirty where the wipers don't wipe. That's how I know that dirty glass scatters light when lit from behind.

<font size=-1>[ This Message was edited by: johnwitts on 2002-02-08 18:32 ]</font>

When you said "flash", I thought of a weld flash and found this.
http://www.ukpandi.com/lp9812/weld.jpg
If the analogy is accurate enough, a definite eye-opener.

But I thought the f-stop (5.6?) would've prevented the sun from saturating the film with light and/or they used some kind of 'antihalation' film, if such a thing existed then.

CraigZ

When you said "flash", I thought of a weld flash and found this.

Perfect example. A welding arc is only a fraction of an inch in size, but it will provide enough light for scatter and saturation.

But I thought the f-stop (5.6?) would've prevented the sun

No. f/5.6 is a very open lens. Most lenses will only open to f/2.8, which is only one stop from f/5.6. And most lenses will only close to f/16 or f/22. There are mechanical limits at each extreme.

Both shutter speed and f-stop can be used to adjust the exposure, but each has a side effect that may be undesirable.

For example, if you want to take a picture of a fountain, you need a shutter speed of about 1/60. If you use a faster shutter speed it will actually freeze the water droplets in mid-flight and your picture will look artificial. You have to keep the shutter open longer so that the cascade produces streaks on the film. That gives a more realistic photo.

But in that case you would have to adjust the f-stop or else you'll overexpose the shot. If you have ISO 100 film in sunny outdoor conditions, you'll want to set for f/22.

Shutter speed is often used to introduce or eliminate indications of motion as desired.

The aperture has the side effect of changing the depth of field -- the tolerance at which the focus is set. Higher f-stops give you more depth of field. Sometimes a photographer will use optical focus to provide compositional focus. Therefore having the whole frame in focus is undesirable. At the other extreme, a wide open aperture may mean that your subject can't be entirely focused. His nose may be in focus but his ears aren't.

Cinematographers run into this all the time. Shutter speeds on motion picture cameras are limited by the frame rate. In theory, at 24 fps you could have a 1/24 shutter speed, but for practical reasons of shutter design and film travel in the gate, you need susbstantially faster shutter speeds. Yet the cinematographer may want more depth of field so that the subject and background are simultaneously in focus. That means a stopped-down lens. What's the answer? Lots and lots of light. That's why film sets are often brilliantly lit, yet the final film appears natural.

The point is that the purpose for which you are taking the photo may dictate how you use the exposure controls on the camera. For example, the Olympic opening ceremony took place about half a mile from my house last night. (I live just down the hill from the stadium.) Of course I photographed some of the fireworks, and the presidential motorcade as it passed my house. Night shots require a very open lens because you can't use shutter speeds of 1/30 or 1/15 second. The film blurs. So we'll see if there's any depth of field in them. Probably not.

(Sorry for the shameless plug; it was very exciting and I had to find a way to work it into this post.) [img]/phpBB/images/smiles/icon_smile.gif[/img]

The sun is simply too bright. Photo flashes at close range are too bright. Welding arcs are too bright. The exposure controls of the typical camera are meant to vary the exposure across the range appropriate to human vision. They are tuned for light levels normally encountered in everyday life, the amounts of sunlight or artificial light reflected of normal surfaces. These are very small quantities of light compared to what comes directly from the sun.

You can compare it to a postal scale. It's meant to weigh letters on the order of ounces and a few pounds. If you try to weigh a cement truck, the scale won't do it and will likely be destroyed. There are scales suitable for weighing cement trucks, but they won't accurately weigh postal items.

The short answer is that the controls of the camera will indeed affect saturation, but in the case of photographing the sun directly they don't have sufficient range of control to eliminate it.

But the question of whether the camera can be adjusted or how to do it is eclipsed by the question of whether or not you should do it.

Let's take your welder photo. Imagine a hypothetical lens that could be stopped down to f/200 or so, and this was the setting that would correctly expose the welding arc. If you snapped the photo, you'd get a photo only of the welding arc -- a little blue spot in the middle of a completely dark frame.

With various filters and exposure settings I can directly photograph the sun with normal film. With a telephoto lens I can actually photograph sunspots. But if I use the same apparatus to attempt normal photography, I get a long string of completely black photos.

The limitations of photography means the photographer often has to settle with parts of his photos being over- or underexposed in order to correctly expose the part of the scene he's interested in.

The shots of Aldrin descending the ladder correctly expose Aldrin and the LM, but the lunar surface behind him is overexposed. The film is saturated. But although it's enough to saturate the film, it's not so bright that the scatter from the lens has produced a flare and rays like the sun would. The scatter has only eliminated the detail that would otherwise be visible.

The point is that Armstrong didn't care that the background would be overexposed. He was actually an accomplished photographer before becoming an astronaut, so he knew how to take photos in shadow. He was interested in Aldrin, and so he set the camera to correctly expose that part of the frame.

The photographer of your photo wanted to take a picture of the welder, not the welder's arc. And in doing so he accepted that the arc would saturate the film and that lens scatter would produce a big burst of saturation around it. But that's just the tradeoff of photography. It's okay to let parts of the photo go wonky if you get what you want in the other parts.

'antihalation' film, if such a thing existed then.

It did. Various means to control halation have been used since the early glass plate days. But halation isn't necessarily a major contributor to the large sun disk in the photo. If it were, we should be able to look at photographs in which the sun is near the edge of the frame, and it would want to "smear" radially away from the center of the frame. Disks near the center of the frame wouldn't necessarily exhibit any halation effects.

I haven't taken any measurements of these sun disks to confirm whether they are perfectly round or whether they are elliptical in a way that halation would cause. But to the naked eye the sun disks don't appear distorted.

Halation, if you recall, is light interacting inappropriately with the film base. Scattering is light interacting inappropriately with the lens. No adjustment to the film formulation can compensate for it, and it's this which creates the large image of the sun disk. Newer lenses employ different coatings to reduce scatter, but you can never fully eliminate it. It's theoretically impossible if you understand how light interacts with the lens surface at a molecular level.

The film base must be as transparent as possible. Antihalation base coatings used during the early and mid 1900s compromise this. And so they must be removed physically or chemically during development. This adds an extra step to the developing process with the possibility of damaging the emulsion.

So Kodak has concentrated on producing film bases whose optical properties provide both the perfect transparency for accurate reproduction, and the resistance to refraction and interreflection that eliminates halation. The Estar base was thought to be resistant to halation simply because it was so much thinner. And it is. Halation seems only to be a problem when you are concerned with very fine details like fiducials near the edges of the frame. And it doesn't even have that great an effect on the fiducials -- the normal bleed in the emulsion is a more pronounced effect.

To say that halation was a problem in the Apollo film is misleading. The point about halation is intended solely to show that the disappearance of the fiducials correlates to known principles of photography, therefore allegations of falsification are unparsimonious.

This is a very dusty thread. The website which was being discussed no longer exists. Clearly, the webmaster lost interest in it and allowed it to expire. One might suppose that his discussion with you lot in this thread changed his mind. If it is, well done.