Category: Photography

The Magic of Lighting in Photography

On By Christopher LansdownIn Interesting Finds, PhotographyLeave a comment

This video, which is apparently a trailer for a music video rather than a documentary about the power of lighting in photography, is absolutely fascinating:

If you take pictures, or even just look at pictures, it is worth watching this video in full because it shows you just how powerful the effect of lighting is.

Part of where lighting gains its power, by the way, is that our brain does an enormous amount of processing on the images it gets from the eyes. Not only does it remove the blood vessels and the blind spot in front of our optic nerve from what we perceive based on its knowledge of what it is that it’s looking at (the origin of many optical illusions), it also does color correction.

We’re used to thinking of an object as having a color based on what light it reflects but this is only partially true. A red ball does, in fact, absorb green and blue (etc) and only reflect red, but the light which reaches our eyes is dependent on what light hits the ball. In white light, the standard description of color more-or-less applies. But in, for example, blue light, no light comes back from the ball and it looks black. In red light, the same amount of red light comes back from a red ball as comes back from a white ball, so the white ball looks red. Or, depending on how our brain decides to interpret it, the red ball looks white. That’s the basis of those secret messages which were printed in blue against a red squiggly background. In white light the squiggles dominate our ability to see images, but in red light (usually achieved by using red cellophane as a filter) the red squiggles look no different than the white paper and so disappear, while the blue text which was the same brightness (in white light) as the red squiggles now show up as black.

There’s all sorts of interesting tricks which can be pulled off with light, too, because the red, green, and blue photo-receptors in our eyes are not equally sensitive. Green seems the brightest to us, so you can make the colors of, for example, tropical fish pop more by illuminating them with lights that have a lot of red and blue but not much green; thus the amount of red and blue which reflects off the fish compared to the overall brightness is higher and they look more colorful (this is why they always look better in the pet store unless you invest in the special lights for your home aquarium—on the plus side those lights are better for aquarium pants, too).

There are similar considerations when lighting people with little pigment in their skin. Light which has too much red in it can easily make their skin look very reddish.

There’s another curious effect which is that the overall quantity of light will change things because every photo-receptor (whether in a camera or an eye) has a maximum amount of stimulation. If you can use so much light that you can exceed the maximum amount of stimulation, you can “wash” the colors out as everything tends towards white since the relative balance of colors changes. You can use tricks like this to lighten or darken someone’s skin in a photo shoot, for example.

Cameras don’t like by commission, but they lie by omission all the time.

God’s Blessing on January 21, 2017

On By Christopher LansdownIn Photography, UncategorizedLeave a comment

God’s blessing to you on this the twenty first day of January in the year of our Lord’s incarnation 2017.

Previously I talked about my new mirror lens. In that post I said I’d put up some pictures taken with it. I did manage to take a few. I’m still learning how to use lens, and I think that my manual focusing is rusty, so the pictures didn’t look very good at full size, but since I think that they shrink down to decent photos, I’ve decided to put the four best up here.

The first is macro-photography of the trunk of my ficus. The minimal focal distance is about 1.5 meters, so at 500mm, it’s hardly the lens to take picture’s of a fly’s eye, but it gets closer than many lenses do. Incredibly short focal depth at that distance, though. (That’s a problem with most macro photography, though.)

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The next is the roof of a shed my neighbor has. It’s been up for a long time, and has accumulated some interesting lichens. (I should note that it was a grey, overcast day.)

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The clouds were looking interesting, so I decided to try some cloud photos. I figured that since they were so far away at the very least I should have a decent depth of field. On the other hand, my not being very skilled at manual focusing didn’t help.

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And finally while I was out shooting, a red-tailed hawk landed on my neighbor’s roof to look for mice in the yards around it. Unfortunately I didn’t get any great photos, but this wasn’t bad:

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I was shooting at 1600 iso to get a 1/400th shutter speed, which is still sub-optimal for a 500mm lens. I suspect that when taking photos of living subjects, I really need a bright sunny day to get enough light to shoot at a fast shutter speed and low ISO (the higher the ISO, the more noise you get). If I get a chance to take pictures on a bright sunny day, I’ll post some of those for comparison. And I suspect that I need to practice at manual focusing, too.

Glory to God in the highest.

God’s Blessings on January 7, 2016

On By Christopher LansdownIn Photography, Uncategorized1 Comment

God’s blessings to you on this the seventh day of January in the year of our Lord’s incarnation, 2017.

The world of photography is an interesting one. I’m very much an amateur, but owing to my mother’s much greater interest and budget for pursuing her passion, together with the progress in DSLRs (Digital Single-Lens Reflex cameras) I have a hand-me-down Nikon D300S. It’s an 8 year old camera which has been superseded by a subsequent model, but it was a great camera when it came out and it still takes better pictures that I’m capable of taking. Also, it takes the same lenses that all other Nikons do, and as a very rough rule-of-thumb, the lens is more important than the camera body. Some day I’ll probably invest in a newer body, but especially given the amount of time I have to devote to photography, it will undoubtedly be years before I’ve developed my skill to the point where the camera body is holding me back.

As a Christmas present, I was given a 500mm mirror lens. Whereas normal lenses focus light be refraction inside of glass, mirror lenses work like telescopes and focus light by reflection off of the surface of a pair of concave and convex mirrors. (The larger, concave mirror concentrates light onto the smaller, convex mirror, which then straightens it out and directs it at the camera’s sensor.) Oh, and a 500mm lens is a zoom lens roughly equivalent to 10x magnification from like a telescope or binocular. The curious thing about mirror lenses is that they are wildly cheaper than glass lenses. The cheapest glass-based 500mm lens that Nikon makes is over 12x more expensive than the lens I was given, and why this is the case is, I think, quite interesting.

Refracting light through glass has the problem that different wavelengths of light refract different amounts. This varies with the material, but the problem is that, to oversimplify, red, green, and blue light will actually have different focal points, which results in what is called “chromatic aberration”, or to be less technical, weird, slightly blurry colors. So to combat this, telephoto glass lenses have to be made out of very carefully engineered glasses. I use the plural, because in order to correct the light, telephoto lenses will actually have somewhere between 7 and 14 “elements” (i.e. a telephoto lens is really a system of a bunch of lenses), many of them made of different materials to correct imperfections in what the previous lenses did. As you can imagine, this is expensive, both because of the careful engineering, the precision of assembling that many lenses together, and just making and grinding that many pieces of optically clear glass.  It’s sort of a miracle that lenses are as cheap as they are. And the good ones run into the tens of thousands of dollars!

In comparison, reflection works the same for all wavelengths of light, so a mirror lens can be made of just two mirrors as I described above. And mirrors are cheaper to make than polished optically clear glass with no internal distortions. So when you put it all together, mirror lenses are wildly cheaper than glass lenses. (Incidentally, you can also probably see why “mirror lens” is a contradiction in terms, and why the technical term for them is catadioptric  optical systems.)

At this point you’re probably wondering why, if mirror lenses are so much cheaper to make at the same quality, they aren’t the standard. To some degree I wonder the same thing, but possibly one of the bigger reasons is that people generally don’t like the bokeh of a mirror lens. (Bokeh is basically how the things which are out of focus blur; glass lenses blur things into circles, which mirror lenses blur them into donuts.) There are shots where bokeh isn’t relevant, but it’s relevant in an awful lot of photography, hence the dominance of glass lenses. There’s also the fact that glass lenses come with auto-focus, and diaphragms to change the amount of light allowed onto the sensor (narrower openings give you greater depth-of-field, but require slower shutter speeds, while bigger openings give you a narrower depth of field; which is better depends on what sort of shot you’re going for). I’m not sure that’s inherent to glass lenses, though; I suspect that mirror lenses have basically found the niche of cheap, and as long as they’re going for that, they’ll sell best if they’re very cheap. At 12x cheaper than a glass lens, a 500mm mirror lens makes sense to play around with; if it was only half the cost of a glass lens, I suspect most people would just pay the extra money for the glass lens. Which brings up, once again, the curious topic that all sorts of things are technologically possible and would even make a lot of sense but aren’t done simply because there’s no market for them. Anyway, as I figure out how to get good results from my mirror lens, I’ll post some pictures on the blog.

(At 500mm, even slight shake in the camera makes the images blurry, so a tripod and a shutter-release remote are necessities, but it turns out that the camera shake caused by mirror-slap is a problem too. If you don’t know, an SLR uses a mirror in front of the sensor to allow you to look through the lens in the viewfinder. This mirror must get out of the way during photographs, and so it does, but you can’t move mass around quickly without it applying force to the body of the camera, and the sensor is mounted to the body of the camera, so it shakes. Normally this doesn’t matter, but for telephoto shots, and especially since a mirror lens is very light and thus doesn’t have enough mass to damp down the vibration, this is a real problem. Fortunately, there’s a mode my camera has where you can press the shutter button once to move the SLR mirror out of the way, and a second time to actually take the shot. Unfortunately, there’s nothing you can do about the shake from the shutter moving, at least unless you have a really top-of-the-line DSLR. Come to think of it, this is another reason to prefer glass telephoto lenses. The fact that they weight anywhere from 5-15 pounds (for the really huge ones) damps vibrations, which will give a clearer shot.)

Glory to God in the highest.