Question about pictures

[peter eldergill]

Hey there

What is the purpose of the crosshairs in the photos from what seems like all the pictures?

Also, in a book I'm reading (The New Cosmos, from the editor of Astronomy magazine), there is a picture taken of the the lander by Neil Armstrong that seems to be in colour. I was of the understanding the pictures are in black and white. Have I got this wrong?

Cheers

Peter

[Northern Lurker]

Those little crosses or fiducial markers are used to detect distortions due processing and handling and to help correcting them. Also with fiducials you can measure angular distances in photographs.

Lurky

[peter eldergill]

Was distortion that big of an issue on the old photos? What would cause the distortion? I'm assuming that this is not an issue with modern cameras

Cheers

Peter

[Halcyon Dayz, FCD]

Also, in a book I'm reading (The New Cosmos, from the editor of Astronomy magazine), there is a picture taken of the the lander by Neil Armstrong that seems to be in colour. I was of the understanding the pictures are in black and white. Have I got this wrong?

Yes.

Magazine 40 was colour.
https://www.flickr.com/photos/projectapolloarchive/albums/72157658601662068

Some of the images are pretty much greyscale because that is what the landscape looks like.

[bknight]

Hey there

...

Also, in a book I'm reading (The New Cosmos, from the editor of Astronomy magazine), there is a picture taken of the the lander by Neil Armstrong that seems to be in colour. I was of the understanding the pictures are in black and white. Have I got this wrong?

Cheers

Peter

All the missions carried both black and white film and color.  Go to  https://www.hq.nasa.gov/alsj/frame.html
to see all the images and other associated information concerning the Apollo program.

[Kiwi]

Was distortion that big of an issue on the old photos? What would cause the distortion? I'm assuming that this is not an issue with modern cameras

Nearly all lenses produce some sort of distortion, and it is indeed an issue with all cameras, old and new. Cheap lenses usually, but not always, have more distortion than dear ones of similar focal length. The most obvious distortion is caused by wide-angle lenses, which were used on the lunar surface cameras.

Last weekend I browsed through a few hundred Apollo 16 photos on my hard drive and there was one taken of the rover, looking along it from one end. The pair of wheels nearest the camera looked much fatter and much wider apart than the pair on the other end, but the rover wheels were all the same width and both pairs were the same distance apart.

Not sure if it was this photo, but the effect is there:--
http://www.hq.nasa.gov/alsj/a16/AS16-114-18454HR.jpg

Yesterday I saw a photo in a real estate advertisement which was taken inside a bedroom. The top of the high wooden foot of the bed was nearest the camera and would have been horizontal in real life, but it had a very noticeable lean of about eight degrees to one side. Not that every viewer would have noticed at a casual glance -- I was a professional photographer back in the 70s and 80s and am still an amateur.

If you have the experience and know what to look for, you'll see distortion in many photos, but some of what gets called distortion isn't actually -- it's more a case of our brain making corrections so that we "see" things like converging lines as straight, but in truth they actually curve.

This effect is most noticeable in Moon Illusion No. 2, in daytime when the moon is at first- or last-quarter and both sun and moon are visible. The straight edge of the shadow on the moon is not perpendicular to a straight line drawn to the sun. It has a noticeable lean. But in reality that line would curve to the sun, so everything is, in fact, in order.

Google "moon  illusion" if you want to know what No. 1 is -- it's about our perceptions and assumptions, which can be wrong. Moon Illusion No. 2 is harder to find because far fewer people ever see it and question it, yet it occurs twice as often as No. 1.

[ChrLz]

Nearly all lenses produce some sort of distortion, and it is indeed an issue with all cameras, old and new. Cheap lenses usually, but not always, have more distortion than dear ones of similar focal length. The most obvious distortion is caused by wide-angle lenses, which were used on the lunar surface cameras.

Just to clarify, as this topic is a real bee-in-my-bonnet...(I can see that you understand this, Kiwi, from the rest of your post, so don't take it personally!   I just think it's worth repeating/clarifying as it is a common misperception that it is all the lenses fault....)

While lenses do add some distortions of their own, a large portion of the 'distortion' is actually not distortion at all.  As you say, the majority of it appears when using wide angle lenses, and it becomes worse when you get to fish-eye and panoramics...  and it is nothing more than perspective (search curvilinear- or 5-point- perspective).

Every 'normal' image is a recording of a 3d dimensional scene, as viewed from a single point in space - this is important.  If you think that through, you will realise that only the lines you point the camera directly at, are straight - anything that is above/below/left/right of the image's centre point *must* (in reality) bend...  The ones near the centre will only bend slightly, but those further and further away bend more and more (and I can prove that with some very simple geometry..).  That moon tilt illusion thing is one of the few times when your brain allows you to see the problem - the brain is superb at bending everything straight!  As another example, think about standing in the middle of a long straight railway line.  Look down - the lines are a couple meters apart, yet look to your left - they converge at a point on the horizon.  Look right - same thing.  Think about that - from your viewpoint, there is no way that those lines can do that unless, *from your viewpoint* they really are bent...

So, in a sort of contrary way, most lenses have 'correction' in them (rectilinear correction) that tries to straighten everything up by *distorting* the view!  And as long as the field of view of the lens is not too wide, they do a reasonable job...  When you get to fish eye views and stitching up panoramas, it can become a very big issue....  So that type of perspective bending is really not an illusion - it's quite measurable and quite real.  This topic is very nicely covered here:
http://muddycolors.blogspot.com.au/2011/06/todd-lockwood-curvilinear-perspective.html
..Todd Lockwood there uses the moon tilt 'illusion' to start you thinking about it. 

Added..  at another forum I and a few others tried to explain this in great detail, but some of the forum regs and even moderators (Hi, Grapes..) just kept denying it was real and saying it was an illusion..  I gave up.