Camera Optics – the single lens reflex (SLR)

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Figure 1 - Cross-section of a modern SLR camera. Image from the Wikipedia and created by CBurnett, in the public domain under creative commons attribution license.

Figure 1 – Cross-section view of SLR system: 1: Front-mount lens (four-element Tessar design) 2: Reflex mirror at 45-degree angle 3: Focal plane shutter 4: Film or sensor 5: Focusing screen 6: Condenser lens 7: Optical glass pentaprism (or pentamirror) 8: Eyepiece (can have diopter correction ability). From the Wikipedia and created by CBurnett, in the public domain under creative commons attribution license.

I’d like to return today to our technical discussion of camera optics.  We have looked at what mirrors do to light and at what lens do to light.  Based on what we learned so far take a look at Figure 1 which shows the innards of a single lens reflex or SLR camera.  The first object that we see is the lens.  The lens is actually a composite of multiple lenses.  However, we know that the lens is going to invert the object on the sensor or film.  Up and down is flipped, and so is right and left.  Look at Figure 2.  If the object was the letter F (Today’s blog is brought to you by the letter F) then what appears on the sensor or film is the “lens inverted image.” This is what you see in a large format camera on the ground glass.

Figure 2 - Image inversions in a modern SLR camera. Image may be used under Creative Commons Attribution license.

Figure 2 – Image inversions in a modern SLR camera. Image may be used under Creative Commons Attribution license.

It is also all that you need to make a camera if it is to be purely digital. This is because in a digital camera you can make all the corrections that you need computationally.  You display and store the file with all the corrections made.

The In the next generation of camera, makers decided that this inversion needed to be fixed.  By putting a mirror into the camera at a right angle they could create a “righted mirror image”  where up and down were fixed but right and left were still flipped.  You can do this with a single lens, in which case the lens needed to be flipped out of the way when the picture was taken.  A second approach was the twin lens reflex, which had two identical lens: one for the picture and one for the viewfinder.  This is, of course, a bit costly and also introduces what are called parallax effects as the object gets closer and closer to the image.

To create the right side up image of the modern SLR viewfinder, makers use a pentaprism, which is actually a set of reflective (like a mirror) surfaces that multiply flip the image until it is corrected and do this in a fairly confined space.  For illustrative purposes you can follow the multiple reflections of the blue and red rays in Figure 3 to convince yourself that geometric points wind up where they need to be.  This is shown in Figure 1 and in more detail in Figure 3.  Again with the modern SLR it is necessary to flip the mirror out of the way during the exposure.  This can be done either automatically or manually before exposure if you are afraid of vibrations affecting your image.

Figure 3 - Schematic showing operation of a pentaprism in a modern SLR camera. Image from the Wikipedia created by Paul1513 and in put in the public domain under creative commons attribution license.

Figure 3 – Schematic showing operation of a pentaprism in a modern SLR camera. Image from the Wikipedia created by Paul1513 and put in the public domain under creative commons attribution license.

 

Abstract bubbles and hidden light at the mall

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Figure 1 - Bubbles, (c) DE Wolf 2014

Figure 1 – Bubbles, (c) DE Wolf 2014

Well as I have bemoaned repeatedly, it has been a bad winter here in Massachusetts.  So I have often been driven back to the mall to walk.  That’s not so bad and I always have my cell phone with me to serve as a pseudo large format IPhone camera for photographing abstractions.  So today I have two offerings from a visit last Sunday.  The first is a wall beside  “Marbles, The Brain Store” tiled with bubbles.  I love it.  The second is of two overlapping white tiled walls, and there is a glow of light from behind.  For some reason this picture reminds me of one of those 1950’s low-budget B science fiction movies.  “Don’t go near the nuclear glow behind the wall!  Alright winter has taken my wits from me.

The glow image is an example of where the IPhone fails.  It is eight bit and cannot really handle the high dynamic range of the image.  There is just too much graininess when you get rid of the useless bits.  I retried it with the HDR setting, but that wasn’t much better.

Figure 2 - Hidden light, (c) DE Wolf 2014

Figure 2 – Hidden light, (c) DE Wolf 2014

John Dillwyn Llewelyn, the photographer of Penllergare

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Figure 1 - John Dillwyn Llewelyn, Theresa, John, and Willie at Caswell, 1853, from the Wikimedia Copmmons and in the public domain.

Figure 1 – John Dillwyn Llewelyn, Theresa, John, and Willie at Caswell, 1853, from the Wikimedia Copmmons and in the public domain.

Last week I was reading about a man in Wales, who was cleaning out his garage in 1973 and came upon a box of old daguerreotypes. His brother-in-law sought the advice of Noel Chanan, a photographer and filmmaker.  The rest, as they say, is history.  The box contained upwards of forty family images by the great-great grandfather of the man, John Dillwyn Llewelyn (1810-1882).  Llewelyn was a British amateur scientist and photographer.  He was married to a cousin of Henry Fox Talbot.

Llewelyn’s earliest attempts at photography were not, in his opinion, all that successful.  He experimented both with Talbot’s process and with daugerreotypes.  After a few years he abandoned photography, but picked it up again in the 1850′ s by which time the processes had advanced considerably.  He invented what he called the “oxymel process,” which combined honey and vinegar to produce a dry plate.  This was important because the wet colloidal process, then in use, was cumbersome in that it required the photographer to immediately develop his/her negatives.  With the “oxymel process” the glass negative could be held for a few days before developing.  He is also credited with the invention of an instantaneous shutter – enabling for instance the photgraphs of breaking waves and moving water.

Many of Llewellyn’s photographs can be seen on Noel Chanan’s website.  He has also recently released a biography of John Dillwyn Llewelyn, “The Photographer of Penllergare,” which is available through the website.

Figure 1 is an excellent example of Llewellyn’s work. It shows his family (Theresa, John, and Willie at Caswell in 1853).  This is precisely the kind of intimate glimpse of nineteenth century life that we have been talking about.  There is a sharp freshness to the scene, and we almost imagine that we are there with them.  They do not stare back at us, but rather appear to be involved with each other.  They seem however, as I have suggested before, not oblivious to us, but rather seem to know that we are out there (here).

Both the book and Mr. Chanan’s website are filled with this kind of familial image. But there are other outstanding gems as well.  I particularly like “The Stag, 1856,” which appeals to a sense of English mythology and was taken using a taxidermy specimen because a real stag could not be counted upon to stand still long enough for proper composition and exposure.  I also think that “St. Catherine’s Island, Tenby, 1854″  is as fine a piece of landscape photography as I have ever seen.  As is always the case we can learn a lot from these early photographic pioneers.  Their compositions a classical sense of what a picture should be.

 

Images of the first winter Olympics

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Figure 1 - Gold medal figure skater Gillis Grafström at the 1924 winter games in Chamonix, FR. Image from the Wikimedia Commons uploaded by Scanpix, photographer unknown, in the public domain.

Figure 1 – Gold medal figure skater Gillis Grafström at the 1924 winter games in Chamonix, FR. Image from the Wikimedia Commons uploaded by Scanpix, photographer unknown, in the public domain.

A link containing some wonderful photographs from the first winter Olympics in Chamonix, France was brought to my attention by reader and friend, Wendy.  I just couldn’t resisted reposting them along with Figure 1, which shows three time gold medalist in men’s figure skating, Gillis Grafström, of Sweden, in Chamonix in 1924.

About 250 athletes participated in the 1924 winter Olympics and there were 16 events including: alpine and cross-country skiing, figure skating, ice hockey, Nordic combined, ski jumping, and speed skating. The winter games were held regularly every four years until 1936.  The 1940 games were awarded to Saporo, Japan but this was cancelled with the Japanese invasion of China.  The Winter Olympics resumed in 1948.  They held every four years.  In 1992 it was decided to stagger the winter and summer games by two years.  So the winter games were held in 1992 and then again in 1994, when the four year cycle resumed.

Pictures such as these evoke two feelings, to me at least.  One is a sense of nostalgia and the lost innocence of simplicity.  The games have become multimedia events and very glitzy.  The other sense, and maybe it’s because of what’s going on outside my window right now, is one of how cold everything looks.  But several points are universal, the spirit of youth and the concept of bridging borders through sports.

Icicle

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Figure 1 - Icicle, (c) DE Wolf 2014.

Figure 1 – Icicle, (c) DE Wolf 2014.

Winter here in the Northeast is snow and ice.  I have been focusing a lot on photographing the snow.  But ice can also offer some magical possibilities.  And the most magical ice of all are icicles.  They grow on your house and are really beautiful until you realize that they are harbingers of ice dams and roof leaks – not so good.  When I was in graduate school in Ithaca, NY we had icicles behind the physics building that were feet around and five to ten feet long.  They hung from the eaves of the third floor and if you parked beneath them – well let’s just say “Excalibur!” Really not good at all.

In a sense icicles are a record of winter. Successive bulges spell out, like tree rings, the diurnal melting and refreezing. And they are truly magical house ornaments.  I love the way they catch light, refracting it like imperfect lenses, and scattering it off encased air bubbles.

This afternoon I was particularly intrigued by the shining icicles hanging outside our bedroom windows. And since my wife was downstairs, she could not protest as I flung open the window and removed the screen to take some pictures.  The lone icicle of Figure 1 I particularly liked.  It has that specimen quality of something at the same time scientific and beautiful.  After removing the cold blue natural colors and converting to black and white, I found myself toning blue.  Go figure!

Impressionism

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Figure 1 - Impressionism, (c) DE Wolf 2014.

Figure 1 – Impressionism, (c) DE Wolf 2014.

I find that there is real value in having your camera with you at all times.  You never know when a trick of light, color, or shadows is going grab you and demand to be photographed.  Today was a relatively warm day between the endless string of snowstorms.  I had been taking photographs and was putting away my camera at home, when I noticed the golden light of sunset bathing an oil painting and casting the shadows pattern of the window frame.  It was a high contrast light, and I was particularly taken by the flaky texture of the paint.  So I came in really close so as to capture the colors and the texture and I carefully lined up the horizontal shadow of the mullion in such a way as to emphasize the and give three dimensionality to a roof line in the painting.  Figure 1 is my own impressionist interpretation of what was already an impressionist scene.  The colors allow me a short escape from winter’s cold blue tones to a warmer world.

A man-made underground river in Brazil

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On Wednesday we spoke about droughts in the American West, Floods in the United Kingdom, and about the whole issue of global warming.  Today we are hunkering down in front of the fire as New England is once again walloped with a snow storm.  It’s really getting pretty repetitive and boring.  While weather is forefront in my mind, I promised myself that I would not post yet another snow picture.

OK so how about this.  The picture is from January 28 by Ueslei Marcelino of Reuters and takes us inside the Cuncas II tunnel near the Brazillian city of Mauriti in the
Ceara state, Brazil.  The $6.8 billion  tunnel, if it is ever finished, is meant to link canals that will  divert water from the Sao Francisco river to agricultural land in four
drought-plagued states.  The project is, like all such projects three years behind schedule and already at double cost.

The picture to me is amazing.  The man gives size perspective – man and what man creates. And of course, we are haunted by the knowledge that a lot of such projects have unforeseen ecological consequences.  The reflections create an other worldliness.  Tunnel imagery in mythology and its ultimate connection with birth we have already discussed.  Hey, I’m not making this stuff up.  There’s a reason that tunnels are so haunting. Here what seems most important are the allusions to classical mythology that describe journeys in tunnels (where the protagonist swallows a hard gulp of innate claustrophobia and ventures forth, Yes, to be reborn!): to Dante, to Beowulf, to Alice in Wonderland, and even to the Hobbit.

 

Shakespeare and St. Valentine’s Day – wolves and Ophellia

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Figure 1 - Hungarian actress Török_Irma in the role of Ophelia in 1901. Image from the Wikimedia Commons and believed to be in the public domain.

Figure 1 – Hungarian actress Török_Irma in the role of Ophelia in 1901. Image from the Wikimedia Commons and believed to be in the public domain.

Happy St. Valentines’ Day everyone!  For me Valentine’s Day is filled with Shakespearean connotations.  For regular readers of this blog, there’s no surprise in that!

First of al,l St. Valentine’s Day was meant to replace the ancient Roman holiday of the Wolf, the Lupercalia. So, of course, Hati and Skoll is going to celebrate it.  The Roman holiday was, in fact, celebrated on February 15, but what’s a day in 2100 years.

Shakespeare’s play Julius Caesar begins during the feast of the Lupercal.  Mark Anthony in his “Friends, Roman, countrymen…” eulogy alludes directly to the point:

“You all did see that on the Lupercal
      I thrice presented him a kingly crown,
Which he did thrice refuse. Was this ambition?
Yet Brutus says he was ambitious,
And, sure, he is an honorable man.”

 

And then there is the fair Ophellia from Shakespeare’s Hamlet, who met her untimely  death by suicide, driven mad by Hamlet, on St. Valentine’s Day.  It is, of course, fitting because in a sense she dies for love, caught up in vortex of ambiguity at being in love with her father’s killer.

 ‘Tomorrow is St.Valentine’s Day
And early in the morning betime,
I’m a girl below your window
Waiting to be your Valentine.”

 

For years I thought of Ophelia as a hopeless twit.  But then in 2009 I saw Sir Patrick Stewart’s made-for-television Hamlet and I was quite blown away by Mariah Gale’s Ophelia.  She is stunning!  For the first time ever, and I have seen a lot of versions of Hamlet, I related to Ophellia and felt sorry for her.  So as an aside, if you love Shakespeare as much as I do and have never seen this version, do so.

There are some really amazing images of Ophelia over the years.  Some of these are paintings: for instance John Everett Millais (c1851), John William Waterhouse (1908), and, of course, Dante Gabriell Rossetti (1884-1888).  Figure 1, shows a photographic postcard of one of the great beauties, who has played Ophelia, Hungarian actress Török Irma c 1901.  It is such a lovely image that I thought that I would share another image of Török Irma from the Hungarian Wikisite as Figure 2.  It shows her in  Herczeg Ferenc’s “The Nabob’s Daughter.”

Figure 2 - Török_Irma in "The Nabob's Daughter" 1893. Image from the Hungarian Wikipedia and believed to be in the public domain/

Figure 2 – Török_Irma in “The Nabob’s Daughter” 1893. Image from the Hungarian Wikipedia and believed to be in the public domain/

 

Sochi from the ISS

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Figure 1 - The Sochi Olympic Village photographed at night from the USS. Zoom in on the stadium and you can see the Olympic Torch. Photograph from NASA and in the public domain.

Figure 1 – The Sochi Olympic Village photographed at night from the USS. Zoom in on the stadium and you can see the Olympic Torch. Photograph from NASA and in the public domain.

I know that I have been posting a lot about space pictures, and I have been trying to cut back despite there appeal both as examples of two favorite themes: robotic eyes and the magic of photographic.  However just as I was on a roll of abstinence, I say this amazing picture taken by an astronaut onboard the ISS and showing a night view of the Sochi Olympic Village.

The image becomes really amazing when you zoom in on the Olympic Stadium and suddenly realize that you can easily make out the Olympic Flame, which you may recall actually visited the USS.  The Russians have really outdone themselves with the Olympic Torch.  This is the largest and most powerful torch ever – burning enough gas, I think, to supply a decent size city with heat this winter.  Well maybe that’s an exaggeration.  But wow you can actually see it from space!