One of the wonderful things that the Internet has brought to us is the vast amount of images available on every topic. For meteorites many different issues can create challenges for getting images done well. Even as I write this I realize that I will not be able to show the images in this article at their hi resolution. We are forced by bandwidth and speed to compress our images and reduce their size. Still it is possible to capture and offer nice meteorite images.
I thought for this month’s article I would do it on one of the areas of imaging that we use frequently with meteorites. Close up, macro and ultra close up, are terms often seen. They are different in slight ways but they are an area that has many similarities and can be discussed as a single topic. For the sake of simplicity lets just call it macro photography. No microscope will be involved.
I went digital years ago and had a point and shoot digital camera that did acceptable macro as one of its dedicated functions. By today’s standards it did not give me much control of exposure or lighting. And when the camera was so close to the object at .7 inches it was difficult to light the subject. With most point and shoot cameras there was no way to take the picture except by pushing the actual shutter button. I could put it on timed delay and that helped with vibration some if I used a tripod. But the camera was not very macro friendly.
I got a Canon DSLR a while back to be my general photography camera. I use it for astrohotography and much of my meteorite imaging. I have normal and telephoto lenses for outdoor pictures to use with it. I was considering what to do for my macro and ultra close up work. Did I want to get a dedicated macro lens, extension tubes, bellows and all the rest? I should mention that I have a very nice 5 megapixel digital microscope for when I need to get in really close, but I enjoy using a regular camera more. How deeply did I want to get invested in new macro equipment?
I had kept all my lenses from film days and had a full line of equipment for macro and closer work to fit my Minolta SRT 201. A little exploring on the net and I found that conversion rings were available for my old Minolta lenses to let them fit on my Canon T4i. If I wanted to use my Minolta normal and telephoto lenses I needed a conversion mounting ring that had a corrector lens in it. Otherwise it would not be able to reach infinity. You don’t have to reach infinity with macro photography. The lens-less converting mount was perfect. So suddenly I had all my old equipment back to use with the Canon DSLR.
My biggest problem with that Nikon point and shoot digital which did macro was it had a small diameter lens and only went to f8. That is not going to ever be very good for advanced macro work. You need a little larger lens that you can really stop down to at least f22 or f32. And it will go to even slower settings when you start putting on extension tubes or bellows. So I needed the wide aperture control of a DSLR with a manual mode. My Minolta stuff mounted on the Canon gave me that. I was back in business for only a few dollars investment in the conversion mounting ring.
In close up photography there are two topics that are just more important than anything else. Focus and depth of field. And they work hand in hand. In outdoor photography there might be times when the background is of no interest or even something you do not like. Well you can crank open the lens and focus on the foreground and like magic the background is blurry and not a problem. Other times you may want the background and the foreground to both be in great focus. So you squeeze that aperture down and the camera will take a longer exposure or you run up the ISO and there you are; the whole shot front to back is in focus.
In close up photography you have the issues of the last paragraph to deal with. But the distances from foreground to background are compressed to usually a fraction of an inch or at most one or two inches. If your close up subject is a 3D object that you want well focused in all parts you have a real challenge. Even if you learn to control the depth of field. Briefly this is how it works. When the lens is wide open you have rays of light coming into the lens at all different angles which are bent to strike the film or sensor. The rays hitting the center of the picture will be focused at one setting but those hitting the edges of the film or sensor will not be focused at that same setting. When the aperture is stopped down so that only the very center of the lens is used the rays of light enter the camera nearly parallel without having to be bent by the system of lens elements very much. The light is much decreased in strength but it focuses across the whole piece of film or the digital sensor very close to the same focal point.
This is an image taken at f8 and 1/160th of a second exposure. The camera was focused on the front part of the bright metal mounting ring. Note the words “Minolta” and “Japan” are also quite sharp. The internal parts down in the extension tube are so blurred that you can barely make them out.
This is the same framing and the lens is set for f36 and the exposure has moved to 1/8th of a second. It is quite easy to see the difference. The whole item is now focused and the internal working parts are actually quite sharp. This was taken a few inches from the subject making the possible depth of field rather broad. This will not be the case when the subject is only 1-2 inches from the lens.
With macro photography you are never going to get very huge amounts of focal depth range. You are dealing with factions of lifesize or lifesize, or even larger than lifesize images being put on the film or sensor. Features such as the rolling away edges of meteorites will quickly move from focused to blurred.
You need to stop down the lens and get the best focus on the most interesting part and basically accept the amount of blur on the other parts. While it is true that there are programs that do “focus stacking” which will stack slices of an object at different focus points and make a very nice fully focused image of a deep three dimensional subject. For day to day work we are shooting a single aspect or in fact a flat slice or polished face of meteorite. You still want to use the tight small lens aperture (high f number) so that the edges of the image are as sharp as the center of the image.
I don’t think there is a feature that I love for both astrophotography and macrophotography as much as the magnified live view of focus on the LCD screen of the camera. I use it all the time. Focus is such an important thing for making it a great image or having it be a poor image. And being able to view the focus and the framing as you adjust the camera in and out from the subject is just wonderful. Many DSLR cameras also have a button to let you do an aperture preview. You can see the effect of the f-stop settings on the depth of field. The image will darken on some models when you push the button but look to see the focus sharpen. Unfortunately this feature is not available to me when using Minolta equipment on my Canon camera. But it is available to me when I use Canon lenses of course. The first time you see the way that the background and deeper parts snap into focus when you push the aperture preview you will be sold on using a high f-stop number. Now we have to figure out the lighting to make it work.
The biggest real problem for most people with macro or even other types of imaging is illuminating the subject. To some extent it is an artistic thing that is true, but if you can not see areas of the subject because of surrounding shadows or the whole image is dark then it stops being so artistic and becomes something to explore. Once you start to really stop down the lens to get the depth of field you are cutting off the amount of light in a mathematical relationship. Each f-stop move is half or twice the light entering the camera depending on if you are opening one stop or closing one stop. So if your outdoor snap shot of the kids is fine at f8. When you change it to f22 to get the distant snow covered mountains also focused you have moved the aperture through f11, f16 to f22. You had half the light at f11 a quarter at f16 and so on down the line. Sometimes you can find yourself at f32 or even f64 in macrophotography. How do you make up for that loss of light. Well the simple answer is longer exposure time. There are subtle caveats to this that make it not exactly right but for the sake of this article twice the time or half the time is equal to one f-stop of aperture. Again it depends of if you are opening or closing the lens aperture.
Outdoors for that snapshot of the kids it is not going to be a problem if it is 1/1000 of a second or 1/500 of a second or for most people with a digital who have steady hands even 1/250 of a second exposure time. The automatic aperture control will pull closed the lens to the correct setting automatically to make a well exposed unblurred image.
But, at a sporting event at night with poor light and fast action you want to use that 1/1000 or even 1/2000 of a second to stop the action and there is not enough light. The images are under exposed or the camera keeps trying to use a flash. Which is a joke and nuisance since you are far from the sports action and you are using a telephoto lens. The solution is always more light. A bigger lens or a telescope, or higher ISO setting that makes the sensor seem more sensitive and let you use a shorter exposure to get that blur free stop action well lit image. Thus you have the huge diameter lens that you see at such events. For macrophotography the issues are similar to the last paragraph. You stop down the aperture to a tiny opening so you can get great focus. Now you need a tremendous light source or a long exposure. Remember that relationship between the length of the time the light is going in the lens, to the amount of actual light allowed through the lens opening. You are constantly trying to balance these two factors to get the correct exposure in all types of photography. But for macro the lens opening has been made tiny to get depth of field forcing longer exposure time and brighter lights.
Again nothing beats seeing what the camera will do before you take the shot. The LCD screen will show you what you are going to get. You put the camera on Manual Mode set a high f-stop number and see what is on the screen. Frame the picture and focus (usually) on center of field. Use the aperture preview button if you have one. You will see the depth of field focus but maybe not see the way the exposure will be. The image may be dark since it is stopped down in preview. If you want a nice clean non grainy shot you need to keep the ISO down a little. Newer digital cameras are much better as far as high ISO noise than they used to be. But generally speaking I would stay as low as I could on the ISO setting. It is always better to work with higher photon quantities than to increase the amplifier gain and work with fewer photons. We are going to make that possible by using a vibration free sturdy tripod, and a remote shutter cable or the delay timer for the shots. Now you can make the exposure time longer to get back to a well exposed image. We are going to eliminate vibration during the long exposure by being hands free. Now that 1/2 second or 1/4 second exposure if you have to use it is fine. With really bright studio type lights I am often around a 1/20 second exposure. But it is not unheard of to be at an exposure time of as long as 1 second.
As far as artistic possibilities for macrophotography they are still there. The framing of the meteorite is going to be in the eye of the person on the shutter button. The choice of what feature you think is cool and want to shoot is still all yours. The background you place under your specimen is an area you can have fun with. The arrangement of extra lights to accentuate some features are yours to decide about. For example, I often hand hold a pure white LED flashlight to use as a fill light to lessen shadows on one side or to illuminate and reflect the brightness of metal grains into the camera. Lighting placement is going to be something to learn and even if you choose a light box for smooth even illumination it is not going to do everything you want. You will likely find yourself wishing that you could shoot at an angle to get some reflection or want to backlight through a thin slice of pallasite or tektite. You will need several options for lighting.
Sometimes there are meteorites where going in closer just does not really get you that return for the trouble. This slice of NWA 6488 a polymict eucrite is a variety of grays and has a very porous texture that when shot close up become quite distracting. This meteorite slice looks much better when shot at a distance and with less magnification factor. This was shot to get the entire slice in the frame at f22 and 1/20 of a second but at a lens to subject distance that makes it no longer a macrophoto. In general though the definitions are not universal, for it to be macrophotography the object has to be smaller than 2 inches or 5 cm. There are a great many “bug” photographers doing macro work with lens that let them be two or three meters from the insect. In a more studio type setting like for meteorites the equipment can be very different and the work done much closer to the subject.
All the images in this article were taken with a Canon T4i using macro photography equipment. All were taken with a remote cable release switch. The camera was on a tripod pointing down at the specimens. Nothing fancy for these images they were done deliberately without much fluff. Some were taken using a lifesize extension ring, others were taken with macro lenses alone. No microscopic images are in this article. Someday I may take on that topic. Much of the discussion is similar though the problems are just even more intense with a microscope. This is by no means the last word. Hundreds of whole books have been written on this. For the creative there is a big DIY area available. Stages and stands to hold specimens, or magnet holders that will lift specimens and diminish or eliminate shadows are all fun projects for handy imagers. Hope you go and have fun.