Photography Prep. Basics for Evidence Tech. School

Transcription

1 Photography Prep Basics for Evidence Tech. School

2 CAMERA BASICS How a digital camera works: Film has been replaced by a sensor (CCD or CMOS) and some type of memory (internal or some type of card) A digital image is data represented by Pixels (picture elements) Three elements control the amount of light hitting the sensor. Shutter Speed, Aperture and ISO setting Shutter Speed The length of time the shutter is open. This affects blur and stopping action. Aperture - how wide the lens is open. This affects depth of field. ISO- Controls the sensitivity of the sensor to light. The higher the number the shorter the exposure, but can introduce noise into captured image. COMMON CAMERA MODES Do you Have Icons Like one of these examples? Common Auto Icons Green Auto- Easiest to use, but doesn t always render best image possible. Face - portraits, shallow depth of field for out of focus backgrounds. Tulip/close ups - sets for maximum depth of field. Runner/skier/action shots - sets a fast shutter speed. Mountains/long shots - not concerned about depth of field due to the distance. LEARN TO TAKE A PHOTOGRAPHS IN THE MODES LISTED BELOW M - Manual, you set everything. P - Program Mode, camera sets everything. These vary, read your manual. A or AV- Aperture priority: you choose the aperture it sets the shutter speed. S or TV - Shutter priority: you choose the shutter, it sets the aperture.

3 FINDING THE RIGHT EXPOSURE It s easy to throw your camera into the Auto mode and go. However you will notice an improvement in your photography skills once you understand how to control the camera manually. This is not to say that there is not a time and place for the Auto mode but you will have many more options available to you once you ve mastered manual photography. USING YOUR CAMERAS METERING SYSTEM: When in an Auto mode your camera meters for you by guessing what it is you want as far as exposure using the overall image in the viewfinder. There will be situations where you ll need to meter manully. The camera meter tells you how much ambient light you have to work with. Make decisions based on this to take a properly exposed photo. Do you need depth of field, or to stop action, or both? The shutter speed and your aperture directly affect one another. If you cut out light with one, you have to let in light with the other. FIND YOUR METER AND UNDERSTAND HOW IT WORKS. The Manual Approach Decide if your shutter speed or your depth of field is more important. Adjust camera setting to fit the situation. Experiment with Aperture Priority Mode and Shutter Priority Mode if available. Press the shutter halfway to activate the meter, change the aperture or shutter speed until the meter indicates proper exposure. Example of common meter located in bottom of viewfinder: Types of Meters Needles that move up and down or right and left. Middle position is correct. Bars that move to the right or left of the middle. Middle is on. You set one function and the meter lights up the other number to set. No Meter. Totally automatic. Some additional metering options Spot - meters a tiny area in the center of the viewfinder or wherever you select. Center Weighted - meters the whole scene emphasizing the center. Multi-patterned - divides the scene of into regions and interprets. TIPS: If you don t have enough light, consider a tripod, flood lights, or a flash. Learn to focus manually as well and become comfortable using the focusing ring on the lens.

4 Automatic Cameras This works on the same principles as manual settings, but is controlled by sensors and a computer chip. The camera makes the decisions for you based on overall content in viewfinder. Special situations like close ups and timed exposures will require you to override these. Be careful where you focus with auto focus lenses. The active square(s) in the viewfinder must be on your subject.

5 SHUTTER SPEED : The length of time the shutter remains open in fractions of a second. Look for numbers like the following. You will only see the bottom numbers of the fraction on your camera s display. The 30 in this image represents 1/30 th of a second. Not 30 seconds. The f32 is your F-Stop (explained below) Full seconds are often displayed with a " behind the number. You may also have a B or T option in your shutter speed choices as well. B (Bulb) - The shutter stays open as long as you hold the button down. T (Timed) Shutter opens when button is pushed. It will remain open until pushed again. Faster shutter speeds stop motion of moving subjects, but let in light for a shorter time. Slower Shutter Speeds blur motion but allow for more light. Fast Shutter Slow Shutter Movement from the operator can blur action if your shutter speed is too slow. Longer lenses exaggerate the movement. When hand holding your camera your shutter speed should be faster than the size of your lens. Examples: A 50mm lens needs 1/60 th sec., A 200mm lens needs 1/250 th sec. A tripod is your best option whenever possible. FIND YOUR SHUTTER SPEED AND UNDERSTAND ITS FUNCTIONALITY

6 F-STOPS/APERTURE The size of the lens opening. This also controls Depth of Field. Adjust the dial or menu option to change the F-Stop/Aperture. Find your range of Apertures. Each increment is one stop of light. This is often the part that confuses some of those new to photography. As again these numbers represent fractions and are usually only displayed as the bottom number. So the bigger the number displayed, the smaller your lens opening is. Almost a backwards way of thinking at times. Largest Openings Smallest Openings More Light Less Light Least Depth of Field Greatest Depth of Field depending on your lens you may not have the same range of numbers Depth of Field: how much is in focus from near to far. Shallow DOF Mid-Range Deep DOF You lose Depth of Field the closer you are to an object. There are some exceptions where you don't want depth of field, such as when shooting something on glass and you don't want the background to interfere. FIND YOUR APERTURE/F-STOP SETTINGS. WHATS YOUR MAXIMUM/MINIMUM F-STOP? ----

7 ISO Sensor s sensitivity to light. How fast it gathers light. Faster ISO - the higher numbers - gathers light faster, so you can shoot with less light (or faster shutter speeds / smaller apertures), giving you better options in dim light for stopping action and/or depth of field. The trade off is that the higher ISO s may show more noise than lower ISO s in the image. Avoid having your camera select an ISO for you. Some common ISO's 100, 150, 200, 250, 320, 400, 800, 1600, FLASH Keep in mind that flash isn t only needed when indoors or in low-light situations. Sometimes on the brightest days flash is essential: Here is an example of Fill Flash on a sunny day: FILL FLASH Use Fill Flash when you have areas of bright sunlight and shadow together. Sensors cannot always handle such contrast and all detail will be lost in the shadow. The flash can fill the shadows closer to the level of the sunlight. USING AUTOMATIC FLASH If your lucky enough to have a flash designed to be used with your camera you may find you have many extra options; one of the biggest being: (TTL), THROUGH THE LENS- Dedicated Flash Your camera controls the flash with its meter. It reads by metering through the lens, and is therefore more accurate. Set according to your manual. If you re not so lucky

8 USING MANU AL FLASH Set the flash to the cameras ISO. Ignore your cameras internal meter. Set your cameras shutter to the flash your manual). synchronization speed FLASH SYNC (find in Choose the distance range you are shooting, look at the flash info and set the camera s aperture to the F-stop indicated. Make Exposure and evaluate FLASH TIPS Items nearest may be over exposed and further away underexposed. The light can only travel so far, depending on the power of your flash. flashmay be needed to light objects further away. More REFLECTIONS off shiny surfaces Diffuse the light by pulling it farther away and at a 45 degree angle so the light doesn't bounce back directly into the lens. Get the flash off of the camera using an accessory cord. Flash on Camera Flash off Camera

9 Don t have an accessory cord? Try this: BOUNCE FLASH and DIFFUSION You can bounce the flash off the ceiling or any reflective surface to get even, softer lighting of a large area. Bounce halfway into the photo and open up one stop on the camera to compensate. Vaulted ceilings and outdoors will not work as well. You can also diffuse the flash for a softer more even light with a reflector or by putting a white tissue or handkerchief over the flash. Bounce Flash Bounce off a white card Sometimes you have may have to get creative Or use available light rather than flash so you can see what you're getting. (check your White Balance settings).

10 LENSES Wide Angle: 28mm - 35mm: Use at a distance. Exaggerates distance relationships of items in scene. Things closer appear larger, farther away appear small. Can cause distortion Normal mm: "What the eye normally sees". Telephoto - 70mm - 500mm: Brings things closer. Compresses spatial relationship between items. Note: clean lenses with lens tissue only. Some Digital Considerations: At a minimum, always shoot at the highest quality JPEG s for your overall images. Images requiring close-ups ie: fingerprints, impressions, fine detail, etc. shoot in RAW or RAW+JPEG if your camera has one these options. File sizes, especially RAW files, add up quickly. What is your agencies archiving SOP? CD s? DVD s? Servers? Hard Drives? Are these images going to be available to you in 15 years? Always start with a card freshly formatted in the camera. Never format a card in a computer or different camera. Reset your image sequence for each new case starting at 1 (example DSC_001.JPG) Never delete images on the card. It would be like cutting a negative out of a strip. White Balance- While most cameras have an Auto WB learn where the option to change it is and how to use it. Do you notice color shifts if you have your WB set for daylight and you take a photo in a room illuminated with a household lamp? It s good to experiment with these. Most cameras set in Auto WB don t adjust as well with tungsten lighting as well as the actual tungsten WB setting does. Try it what do you notice?