Fiddling With Your Camera Fiddling With Your Camera or How I learned to stop worrying and just press the darn shutter release ... Technical Parameters Focal length Aperture Exposure time Sensitivity Technical Parameters Focal length (determines field of view) Aperture (determines depth of field) Exposure time (affects motion in your image) Sensitivity (affects film/sensor response level) Which parameters matter most? Which parameters matter most? Focal length: 50 mm Exposure time: 1 s Aperture: f/8 Sensitivity: ISO 200 Which parameters matter most? Which parameters matter most? Focal length: 100 mm Exposure time: 1/125 s Aperture: f/16 Sensitivity: ISO 200 Focal Length Focal Length Two types of lenses: prime (one focal length) zoom (many focal lengths) Focal Length Directly determines field of view Indirectly determines perspective 50 mm 135 mm Your position, not the lens, determines perspective! Wide Angle Lenses Roughly 35 mm and shorter Short focal length large field of view Wide Angle Lenses Wide Angle Lenses Focal length: 18 mm Wide Angle Lenses Challenge: organize the chaos! How does one image element relate to another? Hard to use effectively Wide Angle Lenses Creative possibilities: Get close! (exaggerates perspective) Drop your viewpoint Find a strong foreground element Focal length: 17 mm Focal length: 24 mm Focal length: 17 mm Telephoto Lenses Roughly 85 mm and longer Long focal length narrow field of view What are telephoto lenses good for? Focal length: 420 mm Pick Out Details Narrow field of view pick out distant details Focal length: 135 mm Focal length: 100 mm Compressed Perspective Telephoto lenses don’t compress However, distant objects appear closer together Compressed Perspective Compressed Perspective Focal length: 200 mm Focal length: 77 mm Focal length: 135 mm Control of Backgrounds Narrow field of view: Find a pleasing background for your subject Avoid distractions Focal length: 420 mm Focal length: 260 mm Focal length: 160 mm Focal length: 200 mm Avoid Distractions Two examples: Avoid undesirable patches of sky Keep verticals straight Focal length: 70 mm Focal length: 110 mm Aperture Aperture Refers to size of opening of the lens Expressed relative to the focal length of the lens f-number = focal length / lens diameter Aperture Denoted using f-numbers (f-stops): f/1.4 f/2 f/2.8 f/4 f/5.6 f/8 f/11 f/16 f/22 large small Why the strange number sequence? Why The Strange Numbers? Denoted using f-numbers (f-stops): f/1.4 f/2 f/2.8 f/4 f/5.6 f/8 f/11 f/16 f/22 Each number is bigger than previous one by sqrt(2) Example: let’s change aperture from f/2.8 to f/4 lens diameter shrinks by sqrt(2) lens area decreases by factor of 2 Therefore, f/4 admits half the light of f/2.8 F-Stops f/1.4 f/2 f/2.8 f/4 f/5.6 f/8 f/11 f/16 f/22 F-stop: refers to the doubling or halving of light Common language: stopping down (higher f-numbers) opening up (smaller f-numbers) wide open (maximum aperture) Example: stop down two f-stops from f/4 to f/8 Identifying Lenses Lenses are identified by: focal length (or range of focal lengths) maximum aperture Examples: 135 f/2 17-40 f/4 17-85 f/4-5.6 How To Change Aperture? Traditional mechanical aperture ring set aperture by touching lens Current: electronically-controlled diaphragm set aperture on camera Electronic Diaphragm Common usage: focus and compose at maximum aperture camera tells lens to stop down at shutter release can also stop down using depth of field preview Some nice benefits: bright viewfinder during composition helps autofocus Depth Of Field Main creative application of aperture Bigger aperture less depth of field 50 mm f/1.4 135 mm f/2 Why Shallow Depth of Field? Better subject-background separation Make the subject stand out 135 mm f/2 420 mm f/4 200 mm f/4 Why Shallow Depth of Field? Incorporate out-of-focus areas into the image Really big apertures lead to a dreamy background 85 mm f/1.2 85 mm f/1.2 300 mm f/2.8 Another Way To Lose Depth Of Field Closer focusing less depth of field 200 mm (+diopter) f/13 Stopping Down How far to stop down? Just enough to get the depth of field you need! 100 mm f/16 135 mm (+diopter) f/22 135 mm (+diopter) f/22 Exploiting Diffraction Light bends as it passes through small slits or holes 24 mm f/22 17 mm f/22 Aperture Summary Expressed in f-stops (e.g. f/2.8, f/4, f/5.6, ...) F-stop: a doubling or halving of light Stop down smaller aperture, more depth of field Open up bigger aperture, less depth of field Controlled electronically in modern lenses Lenses denoted by focal length and maximum aperture Exposure Time Exposure Time Controls amount of time the shutter is open More time more light Exposure Time Measured in seconds or fractions of a second Convenient to think in stops, too: 1/15 is one stop slower (longer) than 1/30 1/100 is one stop faster (shorter) than 1/50 1/2000 1/20 1/2000 1/20 same exposure f/4 f/32 Freeze Or Blur? More time more blur Affects the sense of motion in the image 300 mm f/3.5 1/640 300 mm f/3.2 1/400 145 mm f/5.6 1/2500 50 mm f/8 1/2 115 mm f/22 1 s 50 mm f/8 1/2 17 mm f/8 1/250 100 mm f/8 1/50 35 mm f/4 1 s 24 mm f/22 30 s Sensitivity Sensitivity Determines response of film/sensor to light More sensitivity more response Measured in ISO values: ISO 100, 200, 400, 800, 1600, 3200, ... ISO 200 provides 2x response of ISO 100 Sensitivity Tradeoff Higher ISO value: shorter exposure time (for same exposure level) more noise Current digital SLRs have excellent noise control use the necessary ISO to get the shot you want! ideal: 50 mm f/8 ISO 100 1/5 s 50 mm f/5.6 1/80 ISO 800 300 mm f/3.5 1/640 ISO 800 Which Parameter Values? 1. Find correct exposure 2. Figure out which parameters matter the most 3. This determines the rest of the parameters 100 mm f/16 1/125 ISO 200 85 mm f/1.2 1/100 ISO 1600 280 mm f/5 1/1000 ISO 400 130 mm f/22 1/8 50 mm f/16 1/2 75 mm f/5.6 1/1250 1/200 s 1/4 s 300 mm f/2.8 .