Lenses

1. Lenses • Lenses define 2 important things: • Angle of view (focal length) • Aperture

3. Focusing A look at the overall camera system Film/Sensor Where the light is recorded Lens Bends the light Subject Source of light Trajectory of light

4. Result: Light converges at sensor ‘In focus’ Light converges past sensor ‘Out of focus’ Light converges before sensor ‘Out of focus’

5. Result: ‘In focus’ Circle of confusion Image doesn’t have to perfectly converge. If it converges within a “circle of confusion”, it is still ‘in focus’ ‘In focus’ ‘Out of focus’

6. In focus Out of focus Out of focus

7. Things at a certain distance are “in focus” (perfectly sharp) • The further from this distance, the blurrier things are • There is a range of distance where things are ‘sharp enough’ to be considered ‘in focus’. This range is known as the “depth of field” Depth of field Amount of Blur

8. Depth of field Range that is ‘in focus’ Film/Sensor Where the light is recorded Circle of confusion Maximum non-convergance allowed to be ‘in focus’ Far limit of focus Near limit of focus Focus point

9. Depth of field Circle of confusion When using a bigger lens (larger aperture), the depth of field shrinks

10. Depth of field Circle of confusion Longer subject distances mean larger depth of field range

11. Depth of field Circle of confusion Longer focal lengths mean smaller depth of field range

12. A = aperture f-number (e.g. f5.6) f = focal length (e.g. 50mm) d = distance to subject (e.g. 3000mm) c = circle of confusion (e.g. .02mm) Factors to note: Smaller apertures (larger f-number) gives larger depth of field Shorter focal length gives larger depth of field Longer distance to subject gives larger depth of field Larger circle of confusion gives larger depth of field

13. As aperture increases, depth of field increases

14. As focal length increases, depth of field decreases. At very wide focal lengths (ultrawide), depth of field increases rapidly

15. Translating focal length into angle of view 35mm equivalent focal length Actual focal length

17. As subject distance increases, depth of field increases At very long subject distances, depth of field increases rapidly (hyperfocal distance)

18. For a constant magnification, depth of field is roughly the same across all distance/focal length combinations

19. 40mm, f/2.8 Landscape/scenery 280mm, f/2.8 Bokeh

20. Landscape/scenery Macro Architecture Small depth of field Uses of large depth of field

21. Portraits Isolation Sports Flowers Uses of small depth of field

22. Focal length ranges Two types of lenses: Zooms (variable focal length) and Primes (fixed focal length) Different focal lengths are useful for different things Canon 70-200 f2.8 $1139 • Large aperture zooms • As large as f/2.8 aperture • Expensive! Canon 17-55 f2.8 $999

23. Focal length ranges Two types of lenses: Zooms (variable focal length) and Primes (fixed focal length) Different focal lengths are useful for different things • Large aperture primes • Very large apertures (f2, f1.8, f1.4, f1.2) • (Mostly) Cheaper than large aperture zooms • Fixed focal length (angle of view) Nikon 85mm f1.8 $419 Canon 50mm f1.4 $316 Canon 50mm f1.8 $83

24. Portrait Assignment • Focus on the following elements: • Lighting (direction, intensity) • Vantage point (camera direction, setting, background) • Perspective (subject distance vs. focal length) • Depth of field • Directing the subject (poses, props, expression) • Before shooting: Login to the gallery, choose 2 photos and evaluate each of these elements • What was done, how it worked out, and how you would do it