Intro to Cameras

Greenbook Please organize lab materials in the following fashion and please put in a binder: Please organize lab materials in the following fashion and please put in a binder: Green Front Cover Green Front Cover Schedule then Syllabus Schedule then Syllabus Telescope and Camera instructions Telescope and Camera instructions Labs (in order) then Notes (in order) Labs (in order) then Notes (in order) Star Charts Star Charts Observing Session Handouts Observing Session Handouts Quizzes and Tests Quizzes and Tests Photographic logs (if any) Photographic logs (if any) H sections (lab questions often answered here) H sections (lab questions often answered here) Green Back cover Green Back cover

Cameras Single-Lens-Reflex (SLR) Cameras Single-Lens-Reflex (SLR) Cameras This is a camera in which viewing, focusing and picture taking is done with the same lens. This is a camera in which viewing, focusing and picture taking is done with the same lens. Depending on the camera, lenses have a universal screw mount or use a “bayonet” (push-and-twist) mount. Depending on the camera, lenses have a universal screw mount or use a “bayonet” (push-and-twist) mount. The ones that are most useful to astronomy are the ones that have a setting which allows the shutter to be open indefinitely. The ones that are most useful to astronomy are the ones that have a manual (M) or bulb (B) setting which allows the shutter to be open indefinitely. A cable release is also handy which allows one to open to the shutter without touching the camera A cable release is also handy which allows one to open to the shutter without touching the camera

Cameras Lenses Lenses A typical normal lens is one that has a focal length which is similar to the size of the film A typical normal lens is one that has a focal length which is similar to the size of the film For 35-mm cameras the film is 43 mm from corner to corner, so normal lenses have focal lengths which typically range from 40 to 55-mm. Digital sensor are typical smaller than this, though some DSLRs are this large. For 35-mm cameras the film is 43 mm from corner to corner, so normal lenses have focal lengths which typically range from 40 to 55-mm. Digital sensor are typical smaller than this, though some DSLRs are this large. These lenses have focal ratios (focal length/diameter = F/D) which typically range from 1.8 to 2.8, but can be “stopped down” to various higher ratios. These number are often called f/stops. These lenses have focal ratios (focal length/diameter = F/D) which typically range from 1.8 to 2.8, but can be “stopped down” to various higher ratios. These number are often called f/stops. Typically, you want the lens wide open (i.e. the lowest or “fastest” f/stop) to get as much light as you can. Higher or “slower” f/stops will let in less light (good for moon and sun pictures). They also give better “depth of focus”, but that’s not important in astrophotography.

Depth of Field f/22 f/4

Cameras More Lenses More Lenses A telephoto lens allows one to magnify on an object while showing a narrower field of view. A telephoto lens allows one to magnify on an object while showing a narrower field of view. A wide-angle lens is just the opposite: it shows a much wider field of view. A wide-angle lens is just the opposite: it shows a much wider field of view. A teleconverter can be placed behind a normal lens and change it into a telephoto lens A teleconverter can be placed behind a normal lens and change it into a telephoto lens A zoom lens allows the focal length of the lens to be changed without (hopefully) the image going out of focus A zoom lens allows the focal length of the lens to be changed without (hopefully) the image going out of focus

Terms derived from old-style Film Film speed Film speed Film speed is indicated by a ISO number which can range (typically) from 50 to 3200 Film speed is indicated by a ISO number which can range (typically) from 50 to 3200 The higher the number the more sensitive the film is to light and shorter the exposure is needed. The higher number film is also more grainy looking. For digital cameras a higher ISO will make the picture fuzzier. The higher the number the more sensitive the film is to light and shorter the exposure is needed. The higher number film is also more grainy looking. For digital cameras a higher ISO will make the picture fuzzier. Film or sensor sensitivity Film or sensor sensitivity Typically twice the exposure gives you twice the light, except at super short and super long exposures (Reciprocity failure – not an issue with digital cameras). Typically twice the exposure gives you twice the light, except at super short and super long exposures (Reciprocity failure – not an issue with digital cameras).

Digital Cameras Most of these compact digital cameras used by everyday people have modes which allow short exposures and do not have interchangeable lenses. Most of these compact digital cameras used by everyday people have modes which allow short exposures and do not have interchangeable lenses. However, some of the mid-range compact digital cameras have a manual mode which allows the user to control the f/stop, exposure time, focus and sensitivity. However, some of the mid-range compact digital cameras have a manual mode which allows the user to control the f/stop, exposure time, focus and sensitivity. Digital SLRs with interchangeable lenses are getting more common and more affordable. Digital SLRs with interchangeable lenses are getting more common and more affordable. These images are digital, they can be added up and processed to get a better image ( More on this later ) These images are digital, they can be added up and processed to get a better image ( More on this later )

Point and shoot star trails Point towards Polaris and take a picture! Point towards Polaris and take a picture! How many degrees does the Sky turn in one day (24 hours)? How many degrees does the Sky turn in one day (24 hours)? So how far (in degrees) does it turn in one hour? One minute? So how far (in degrees) does it turn in one hour? One minute?

Exposure time estimation where: t = exposure time in seconds f/ratio = focal ratio s = film speed expressed in ISO (ASA) units B = a constant indicating the brightness of the object being photograph

Taking pictures – outdoors, part I Choose one target illuminated by the sun – set focus at near-infinity Set the camera for f-stop to f/3.5 and ISO at 100 – focal length of 18 mm Set the camera for f-stop to f/3.5 and ISO at 100 – focal length of 18 mm Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Change f-stop to f/10.0 Change f-stop to f/10.0 Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Change f-stop to f/22.0 Change f-stop to f/22.0 Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds Change ISO to 800, return f-stop to f/3.5 Change ISO to 800, return f-stop to f/3.5 Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Change f-stop to f/10.0 Change f-stop to f/10.0 Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Change f-stop to f/22.0 Change f-stop to f/22.0 Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds.

Taking pictures – outdoors, part II Now we zoom in by changing the focal length to 55 mm. Choose another target illuminated by the sun – set focus at near-infinity Set the camera for f-stop to f/5.6 and ISO at 100 – focal length of 55 mm Set the camera for f-stop to f/5.6 and ISO at 100 – focal length of 55 mm Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Change f-stop to f/10.0 Change f-stop to f/10.0 Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Change f-stop to f/22.0 Change f-stop to f/22.0 Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds Change ISO to 800, return f-stop to f/5.6 Change ISO to 800, return f-stop to f/5.6 Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Change f-stop to f/10.0 Change f-stop to f/10.0 Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Change f-stop to f/22.0 Change f-stop to f/22.0 Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds. Now run through exposure times 1/2000, 1/1000, 1/500, 1/250, 1/125 seconds.

Taking pictures – “outdoors” -alt Choose one target illuminated by the room lights set focal length to 18 mm. Set the camera for f-stop to f/3.5 and ISO at 100. Now run through exposure times 1/250, 1/125, 1/60, 1/30, 1/15 seconds. Change f-stop to f/10 Now run through exposure times 1/250, 1/125, 1/60, 1/30, 1/15 seconds. Change ISO to 800, return f-stop to f/3.5 Now run through exposure times 1/250, 1/125, 1/60, 1/30, 1/15 seconds. Change f-stop to f/10 Now run through exposure times 1/250, 1/125, 1/60, 1/30, 1/15 seconds. Change f-stop to f/22 Now run through exposure times 1/250, 1/125, 1/60, 1/30, 1/15 seconds. Now change focal length to 55 mm, change target and repeat steps above (note lowest f-stop will be f/5.6)

Taking pictures – indoors, dark Choose one target in the dark of the room, use red flashlight carefully. Use the remote shutter control, put the camera on self-timer mode. For each of the settings below do one 30-second exposure. Set the camera for f-stop to f/8.0 and ISO at 200 (400). Set the camera for f-stop to f/8.0 and ISO at 200 (400). Change f-stop to f/5.0 Change f-stop to f/5.0 Change f-stop to f/3.5 Change f-stop to f/ Change ISO to 800, return f-stop to f/8.0 Change ISO to 800, return f-stop to f/8.0 Change f-stop to f/5.0 Change f-stop to f/5.0 Change f-stop to f/3.5 Change f-stop to f/3.5 Now with f-stop of 3.5 and the ISO at 800 take 10 consecutive 15- second exposures by using the multiple picture shooting mode (and use the remote shutter control). Return the camera to single picture mode and change the camera to the B (bulb) setting. Use the remote shutter to take a 2-minute picture of the dark room use sensible f-stop and ISO settings.

Questions – Put in H section Using the Table on page 8 of your textbook (or the slide on the next page), how long can you expose the stars without tracking Using the Table on page 8 of your textbook (or the slide on the next page), how long can you expose the stars without tracking With a 28 mm lens? With a 28 mm lens? With a 100 mm lens ? With a 55 mm lens? With a 18 mm lens? With a 100 mm lens ? With a 55 mm lens? With a 18 mm lens? Suppose to record stars down to 6 th magnitude with a 30-second exposure, required the f-stop to be set at f/8.0 and the ISO to be set at 400. If I change the ISO to 800, how long would be exposure be to get the same number of stars? What if instead you set the f-stop to f/3.5 (but kept the ISO at 400)? Suppose to record stars down to 6 th magnitude with a 30-second exposure, required the f-stop to be set at f/8.0 and the ISO to be set at 400. If I change the ISO to 800, how long would be exposure be to get the same number of stars? What if instead you set the f-stop to f/3.5 (but kept the ISO at 400)? [ B= ]

Table on page 8 of text Maximum exposure Times without Tracking (Region, Celestial Equator) Maximum exposure Times without Tracking (Region, Celestial Equator) Focal LengthExposure Time 28 mm35 seconds 50 mm20 seconds 135 mm7.5 seconds 300 mm3.3 seconds

Other slides

Film All photographic films of today contain crystals of silver halide (silver chloride, bromide or iodide) All photographic films of today contain crystals of silver halide (silver chloride, bromide or iodide) When treated with a developer, these crystals precipitate an amount of dark silver proportional to the amount of light to which they have been exposed. When treated with a developer, these crystals precipitate an amount of dark silver proportional to the amount of light to which they have been exposed. With dye couplers and multilayered film, color photos are possible. With dye couplers and multilayered film, color photos are possible.