Snkrboii
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 Posted: Mon Aug 17, 2009 6:14 pm Post subject: [***Everything To Do With Cameras 3.0***] |
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FLASH PHOTOGRAPHY – BEGINNER’S GUIDE
| PoTN wrote: | FLASH PHOTOGRAPHY CAN BE COMPLICATED
If you find using flash to be a frustrating experience, don’t despair. Flash photography is at least three times more complicated than ambient light photography. But when you come to understand all that happens during those few milliseconds after you press the shutter button, you’re well on your way to taking consistent flash photographs with predictable results.
THE BASICS
Before you venture into the world of flash shooting, you need to first understand the basics of exposure. This guide assumes that you understand how shutter speed affects exposure and motion blur, how aperture affects exposure and depth-of-field, and how the ISO setting affects exposure and digital noise. If you don’t yet have at least a theoretical grasp of these concepts, then it’s best to learn about them before venturing into the flash world.
LESSON 1: FACTS THAT EVERY FLASH SHOOTER MUST UNDERSTAND
The first four facts are universal, whether you’re using the camera’s built-in flash, a hotshoe-mounted flash unit, or studio strobes.
Flash fact #1: Every flash photograph is two exposures in one – an ambient light exposure and a flash exposure. This is a critical fact to remember. The shutter opens, the flash fires, the shutter closes. During this time, both ambient light and flash will contribute to the recorded image. Flash photography requires managing both exposures.
Flash fact #2: Flash exposure is not affected by shutter speed. The entire burst of light from the flash begins and ends while the shutter is open, so keeping the shutter open longer won’t help with flash illumination. The flash exposure and the effective range of your flash unit will be affected by aperture and ISO settings, but not the shutter. Of course, the ambient light component in a flash photograph is affected by shutter speed. So changing the shutter speed is one way to manage the amount of ambient light that contributes to a flash photograph.
Flash fact #3: Flash illumination is dramatically affected by distance. This is known as the inverse square law. Think of it this way: Suppose you’re using a lens that gives you a 4 x 6 ft. field of view at a distance of 10 feet. That same lens will give an 8 x 12 ft. field of view at a distance of 20 feet. So when you double the distance, the same light is covering an area four times larger (96 square feet vs. 24 square feet)! So you need four times as much light to get the same illumination. This phenomenon, sometimes referred to as “flash falloff”, will affect any image with more than one subject at different distances. Whenever your subject distance increases by a factor of roughly 1.4 (the square root of 2), the flash illumination will be cut in half. Suppose you’re taking a large group portrait. The people in the first row are 10 feet away, and the people in the back row are 14 feet away. With on-camera flash as the primary light source, the front row will be a full stop brighter than the back row!
In the image below, each cup is one stop brighter than the one behind it, and one stop darker than the one in front of it. It would take 16 times as much light to properly expose the cup at 11 feet verses the cup at 2.8 feet. Do those distance numbers look familar? They're the same as standard f/ stops for aperture settings, and the relationship is identical. This thread from PhotosGuy gives an example of how to use this relationship in the field.
Flash fact #4: Your camera measures ambient light and flash illumination separately. In Av, Tv or P modes, it will attempt to expose properly for the ambient light by adjusting either the shutter speed, aperture, or both. The fact that you have your flash turned on has no effect on this** ( one exception is that in P mode it will not use a shutter speed slower than 1/60 with flash). The camera’s metering system cannot predict how much illumination will be gained by the flash, so it doesn’t try. In manual mode, the meter in the viewfinder measures only ambient light, because that’s all it has to measure.
Fact 5 refers to any form of automatic flash metering, including older “auto thyristor” flash units, TTL film cameras, and E-TTL or E-TTL II digital cameras.
Flash fact #5: With automatic flash metering, the flash illumination is measured after the shutter button is pressed, and the flash output is adjusted accordingly. There are technical differences between the various types of flash metering, but all of them operate independently from the camera’s metering of ambient light, and all of them work by adjusting the output of the flash, not by changing the camera’s exposure settings.
Facts 6 and 7 apply to any camera with a focal plane shutter (all SLR cameras with a mechanical shutter).
Flash fact #6: Every SLR camera with a mechanical shutter has a maximum flash sync shutter speed. This has to do with the way focal plane shutters work. At slower shutter speeds, the first curtain opens, the flash fires, and after the specified time duration, the second curtain closes behind it. At shutter speeds faster than flash sync, the second curtain begins to close before the first curtain is completely open. The second curtain follows the first across the frame, exposing only a slice of the image at any given moment. Firing a flash during this process would illuminate only part of the image.
Flash fact #7: (Applicable to modern electronic cameras only) If you set your shutter speed faster than flash sync, or use Av mode with an aperture setting that requires a shutter speed faster than flash sync for proper exposure, the camera will automatically revert to flash sync speed when the shot is taken if a built-in or hotshoe-mounted flash is turned on. Usually this results in overexposure (unless you have a “safety shift” custom function enabled). If you’re getting overexposed images when using flash outdoors, this is probably the reason. The image is not overexposed because of light from the flash. It’s overexposed from ambient light because the shutter speed was too slow. If you’re using flash for fill in bright situations, it’s necessary to stop down the aperture or lower the ISO setting to get the shutter speed below flash sync.
More on Flash -
Chapter 2 - (Why) Should I Get A Flash Unit For My Camera?
Chapter 3 - A Systematic Approach To Bounced Flash
Chapter 4 - Guide Numbers and High Speed Sync
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CIRCULAR POLARIZER
| WP wrote: | A polarizing filter, used both in color and black and white photography, filters out light polarized perpendicularly to the axis of the filter. This has two applications in photography: it reduces reflections from non-metallic surfaces, and can darken the sky.
Light reflected from a non-metallic surface becomes polarized; this effect is maximum at Brewster's angle, about 56° from the vertical (light reflected from metal is not polarized, due to the electromagnetic nature of light). A polarizer rotated to pass only light polarized in the direction perpendicular to the reflected light will absorb much of it. This absorption allows glare reflected from, for example, a body of water or a road to be much reduced. Reflections from shiny surfaces of vegetation are also reduced. Reflections from a window into a dark interior can be much reduced, allowing it to be seen through. (The same effects are available for vision by using polarizing sunglasses.)
Much of the light from the sky is polarized (bees use this phenomenon for navigation). Use of a polarizing filter will filter out the polarized component of skylight, darkening the sky; the landscape below it, and clouds, will be less affected, giving a photograph with a darker and more dramatic sky, and emphasizing the clouds.
The benefits of polarizing filters are largely unaffected by the move to digital photography: while software post-processing can simulate many other types of filter, a photograph does not record the degree of polarization, so the optical effects of controlling polarization at the time of exposure cannot be replicated in software.
A polarizer filters out the polarized component of light from the sky in a color photograph, increasing contrast with the clouds (right).
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SHUTTER SPEED
| Shot Addict wrote: | Shutter speed is perhaps the most creative adjustment available to the digital photographer. It allows us to freeze action or use motion blur to create a variety of effects. The term shutter speed refers to how long the shutter stays open and is expressed in seconds or fractions of seconds depending on the length of exposure.
A high shutter speed (1/1000 of a second or higher) can freeze even very fast moving objects dead in their tracks. For this to work you are going to need a brightly lit subject, as shutter speeds this high don’t allow your camera much time to gather light for exposure. You can get around this to a degree by using a higher ISO setting, but don’t go to high, or noise will creep into your shot.
This shot was taken using a 1/1000 of a second shutter speed.
Medium shutter speeds (1/20 of a second to 1/80 of a second) can be used to create motion blur when photographing moving objects. This gives the photo a sense of life and motion.
This shot was taken using a 1/20 of a second shutter speed.
Low shutter speeds (1/8 of a second up to 30 seconds and beyond) can be used to create a variety of effects: Moving water looks smooth and silky; car lights turn into long colourful trails; city lights seem to twinkle, and the list goes on. For these long exposures a tripod or some other means of keeping the camera perfectly still is necessary to avoid creating unintended blur.
This shot was taken using a 4 second shutter speed.
This shot was taken using a 4 second shutter speed.
This shot was taken using a 15 second shutter speed.
Most digital cameras have a shutter speed priority setting, which allows you to control the shutter speed—try it—it can open up a whole new world, and its loads of fun to boot.
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APERTURE
| Digital Photography School wrote: | Your aperture, or your F-stop, controls (along with the shutter speed which we’ll discuss in the next post so just throw that out of your brain for now before you get confused) how much light hits your sensor.
A lens’s aperture (fstop) is basically a hole (and we’re getting as basic here as is humanly possible) that opens to let in more light and closes to let in less light. Similarly to the iris in your eye, but if that analogy doesn’t work for you feel free to throw it on out. The larger the “HOLE” or aperture (fstop), the more light will hit your sensor, the smaller the “HOLE” or aperture (fstop) the less light will hit your sensor, capiche?
Seriously, try not to over complicate it.
NOW: I’m going to sucker punch you here and I’ll just apologize in advance. A HIGH aperture number (fstop) = LESS light being recorded on your digital sensor (or film) while a LOW aperture number = MORE light being recorded on your digital sensor (or film). Yay to the genius who decided upon that little gem of a system! Seriously, I’d be game for toilet papering his house . . . you just let me know the time and place and I’m there.
The TRUE apertures are as follows (called fstops):
There are third “stops” in between (just think of it as where the “hole”, aperture, STOPS to let in a set amount of light), your camera may or may not have these.
The best way to find out will be to crack your manual or flip through the aperture dial on your camera and see which apertures show up. If you get numbers like: 2.8, 3.2, 3.5, 4.0, 4.5, 5.0, 5.6 then you’ve got third stops to work with. If on the other hand you’ve got 4.0, 5.6, 8, 11, 16. . . then you’ve got the true apertures and no option for 3rd stops.
NOTE: your lens may not have numbers as low as 2.8 or it may have an aperture number as low as 1.2. Your lens isn’t broken, it’s just got more or less capacity to let in more or less light. . . The general range of most lenses are highlighted in blue above.
Last word about aperture: it is your aperture (fstop) that controls the depth of field in a photo.
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DEPTH OF FIELD
| Digital Photography School wrote: | Depth of field is basically the amount of an image that is in focus. An image with a very deep depth of field would be an image where everything is in focus, while an image with a very shallow depth of field would have a lot of “fall off” or BLUR with only one segment of the image in focus.
**QUIZ: Does the image above have a deep or a shallow depth of field??
ANSWER: Shallow, because only the boy is in focus and everything else is thrown out of focus.
STOP! Before we go any further, I want you to have a steady grasp of the way your aperture (fstop) functions. So I have a couple of assignments below for those who are desperate to learn about manual settings. . . or simply want a refresher.
FIRST: Memorize the full fstops. Just commit them to memory. The end. You can do it! Here they are again.
SECOND: For this assignment you will need 2 objects placed on a flat surface 1-3 feet apart outside or in a well lit room. Pop your camera over to Aperture Priority and experiment.
Aperture Priority (AP or AV) will allow you to play around with Aperture and how it affects depth of field without having to worry about shutter speed, because in AP/AV the camera automatically selects your shutter speed for you depending on the amount of light available.
Once you’re in AP/AV, set your lens on the LOWEST POSSIBLE APERTURE (fstop) probably somewhere between 2.8-4.0. Focus on the object closest to you and take a picture. NOW, “stop up” to the next FULL fstop. . . you just memorized them, so it should be easy. Skip over the third stops. . . or don’t. It’s up to you. So let’s pretend that I have a lens that has a maximum aperture of 4.0. I’d start by taking an image at 4.0. Then I’d take the same shot at 5.6, then at 8.0 then at 11 then at 16. . . see how this goes? You’ll notice a difference in the depth of field. That’s the goal of the assignment: to learn how aperture affects depth of field.
Don’t be dismayed if your images are slightly dark. I’ve noticed that for the most part when you shoot in AP/AV images tend to be slightly underexposed. . . . surely to protect from the digital photographer’s nemesis of over exposure! Muhahahaha! Watch out for him. He’s a real beast.
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ACHIEVING SHALLOW DoF
| Filipinoise wrote: | With UWA lens, you naturally have a huge amount of DoF to play with, which is the main reason UWA's are used for. You need a large DoF for landscape shots, etc. The 10mm of the Sigma is so wide that even using f/4 (which is somewhat good for OOF backgrounds on more telephoto lenses) will not give you great OOF results unless the background is miles away from the subject. Getting closer minimizes your DoF which is good for better OOF backgrounds but 10mm is so wide that the hyperfocal distance is so great, meaning it you're getting DoF as if you're shooting f/13 or something like that with a 50mm lens, when you shoot at f/4 with the Sigma @ 10mm. It's just how wide angles work. If you want nice OOF backgrounds;
1) get closer to the subject (minimizes DoF so you have a better chance at getting better OOF rendition)
2) buy a lens with a fast maximum aperture (50mm f/1.8 is good and inexpensive)
3) buy a telephoto lens for headshots and stuff like that
The closer you get the better OOF rendition (eve a 55-200 should be somewhat good at 200mm f/5.6 in daylight), but stopping down will help you achieve greater sharpness - try 200mm f/7.1 or f/8 and see how the OOF rendition is and if it's satisfying). |
FILTERS
| Filipinoise wrote: | Filters all serve different purposes.
To give a very brief explanation:
UV/NC - Protect from UV rays, protect front element.
CPL - Adding contrast & saturation, prevents blown out highlights when exposing properly.
ND - Used to obtain long exposures in daylight, for subjects such as waterfalls. You can get an ND filter that can cut back 1, 2, or 3 stops of light.
Graduated ND - Square filters for use with square Cokin/LEE/etc. filter holders, used primarily for landscape photography to expose the foreground and background of a photo perfectly. One half of the square filter is dark, other half is clear.
Warming - Various types, used to add color casts in a photo to chance white balance.
Moose - Combination of a warming filter and a CPL, better than buying the two types of filters and stacking the CPL on top of the warming filter.
Best filter brands - Heliopan, B+W, Hoya
Best Graduated ND filter brands - LEE, Singh-Ray, Cokin |
WHAT IS ISO?
| Filipinoise wrote: | ISO is something that many beginner photographers leave alone and end up not worrying about, and thus learning about and finding about later, only to say something like "Damn! I wish I knew about this earlier!"
ASA [ISO] speed is originally the film speed of the 35mm film in the film days.
ISO speed on Digital serves the same purpose.
LOW ISO
The lower the ISO (100, 200, 400, etc.), the less grain you get, the more contrasty your images come out, and more quality is preserved. But likewise, low ISO's have their cons. Using a low ISO means that if you're shooting indoors where lighting is somewhat dim, you'll either be forced to shoot at maximum aperture in order to get a sufficient shutter speed, or shoot a slow-ish shutter speed and risk motion blur, camera shake, etc. to screw up your photos. Tripods are very useful as well, as they make sure no camera shake gets in your way. Low ISO's are recommended for shooting in daylight/model photography (with strobes, etc.), in which you have lots of light so you won't have to bump up your ISO to compensate for it. Low ISO's are great for landscapes, models, and daylight photography. The more megapixels your camera has, as well as the bigger the sensor your camera has (i.e. full frame as opposed to APS-C) will give you better results at low-ISO's, and thus better image quality especially when blowing up images.
http://www.flickr.com/photos/patrick-smith-photography/3103966854/
This was taken with a Canon 5D + 17-40L @ 30mm, f/20, ISO 50, and 25sec. Tripod mounted.
As you can see, there is virtually NO GRAIN WHATSOEVER, and the low ISO benefited this picture because since the ISO was so low, the aperture was f/20, and the photographer used ND filters, he was able to achieve a slow, 25 second exposure which allowed for silky smooth waters and a nice blur in the clouds which I suspect were moving pretty quickly.
HIGH ISO
The higher the ISO (800, 1600, 3200, etc.), the more grain you get in your images, the less contrasty, and not as much quality is preserved. These are all cons, but high ISO's serve one very important purpose. They allow you to achieve faster shutter speeds which can be crucial for things such as event photography, sports photography, or pretty much any type of photojournalism work. Especially for sports, though, where you need a fast shutter speed to freeze action. The grain can be fixed in post, but motion blur can't be fixed. Any sports picture with (non-purpose) motion blur is pretty much a dud and must be discarded. The bigger the sensor your camera has (i.e. full frame as opposed to APS-C), the better your results will be at high-ISO's, and thus better image quality since, with the bigger sensor, there is more space for the extremely light-sensitive pixels (so they're not all stuffed and crammed into a small sensor, like APS-C) so you will get cleaner high ISO images.
http://www.flickr.com/photos/felipedana/3688463695/
This was taken with a Nikon D3 + 300mm f/2.8 @ 300mm, f/2.8, ISO 2000, and 1/500sec. Monopod used.
This is an excellent example of what kind of results High ISO's can give you. The photographer had to use maximum aperture (f/2.8) AND use ISO 2000 just to achieve 1/500sec, but the result is clearly amazing. |
CROP FACTOR
| airbutchie and Filipinoise wrote: | It's called "crop factor" or "sensor size" fellas...
For Canon, there are three different crop factors/sensor size formats; full frame (1.0x), APS-H (1.3x), and APS-C (1.6x)
For Nikon, there are two; full frame (FX format) and 1.5x (DX format)
Canon:
Full Frame (1.0x) - 1Ds Mark 3, 1Ds Mark 2, 1Ds Mark 1, 5D, and 5D Mark 2
APS-H (1.3x) - 1D Mark 3, 1D Mark 2, 1D Mark 2N, 1D Mark 1
APS-C (1.6x) - All xxD Series (10D, 20D, 30D, 40D, 50D) and Rebel Series (XT, XTi, XS, XSi, Ti1)
Nikon:
Full Frame (1.0x) - D3/x, D700
APS-C (1.5x) - All Dxx, D300/s, D200, D100, D1/H/X, D2H/s, D2X/s
You basically multiply the focal length (mm) times the crop factor/sensor size your camera has... For example... 18mm on a full frame body will be 18mm (1.0 x 18mm)... However, on a APS-C cropped body the 18mm is equivalent to 28.8mm (1.6 x 18mm)... Simple math, but a big difference in focal length... |
LENS TYPES
| Filipinoise wrote: | Canon:
EF= Electronic Focus; Lenses that fit all Canon EOS cameras.
EF-S= Electronic Focus - Short back focus; Lenses that only fit onto APS-C (1.6x) Canon EOS cameras.
UD= Ultra Low Dispersion glass - expensive glass elements that are used to fight off chromatic aberrations and thus give sharper images; same concept as Nikon's ED.
L= "Luxury"; Pro series lenses - Can be identified with a red band near the end of the lens' barrel.
USM= Ultrasonic Motor - fast & silent autofocusing; same concept as Nikon's AF-S.
II, III, etc. = Mark, version, model & production series number. Used to designate newer models from older.
IS = Image Stabilization - System inside of the lens to reduce camera shake; same concept as Nikon's VR.
DO = Diffractive Optics - Special optical formula and design which minimizes length and weight to make the lens more compact and easier to handle.
Nikon:
DX= A lens with a smaller image circle, exclusively for APS-C Nikon DSLR's; same concept as Canon's EF-S.
AF-S= Autofocus-Silent Wave Motor - fast & Silent autofocusing; same concept as Canon's USM.
AF-D= Autofocus-Distance Information supported.
AF-G= Autofocus-"Gelded" (according to kenrockwell) - aperture ring is was removed (done electronically) to make the lens lighter and with a newer design; unable to work on old, manual focus film SLR's.
ED= Extra Low Dispersion glass - expensive glass elements that are used to fight off chromatic aberrations and thus give sharper images; same concept as Canon's UD.
VR= Vibration Reduction - System inside of the lens to reduce camera shake; same concept as Canon's IS.
II, III, etc.= Mark, version, model & production series number. Used to designate newer models from older.
N= Nano-Crystal Coating - A nano crystal element inside of the lens used to combat flare, increasing contrast in pictures.
IF= Internal Focusing - Lens front element does not move at all in the front, used for faster and quieter AF'ing.
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Please PM me with more information to be added.
Link To Old Thread - http://www.solecollector.com/forums/topic-t658925.html
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Last edited by Snkrboii on Mon Aug 17, 2009 7:21 pm; edited 4 times in total |
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