Teacher: Kenji Tachibana Digital Photography I. Art 115 – The Lens 25 Slides Copyright © 2003 – 2009 Kenji Tachibana

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens C amera’s Eye: When I first got into taking pictures over 45 years ago, I thought that the camera lens was a single piece of glass. And on my Kodak Brownie Hawkeye, it might have been just that. Although real camera lenses always had multiple lens elements to reduce optical distortion and to achieve corner to corner sharpness.

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens Z oom Lens: Not possible without the computer Modern digital zoom lens could not be possible without CAD, computer aided design. That is because the zoom lens has multiple lens elements set into different groups. And the groups move independently of Each other. The example image shows a simple normal ‘fixed’ focal focal length lens. The image taken from a Nikon Accessories Catalogue

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens A nti-reflection Coating: Light going through glass is diminished due to reflection and refraction. Light going through multiple glass lenses loses even more light and the contrast. Camera and lens makers have developed anti- reflection coatings to minimize light and image quality loss. Each maker uses patented formulas for their coatings. Most modern lens coating works quite well regardless of the brand.

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens ED Glass: Low dispersion lass Special glass have been formulated for low dispersion to maximize image clarity. On the other end, there are high quality plastic lenses for cheap mass market cameras that works well for producing 4x6 prints. You can be pretty sure that the camera for $29 has a plastic lens. They use ED glass on prosumer and DSLR lenses.

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens F ixed Focal Length: Before the zoom, there was the fixed focal length lenses. They are small, light, heaper, sharper, and optically less distorted. Less lens elements means less glass. And that is the major contributor to the previous description. And they still produce them for the DSLR market.

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens P referred 3-Lens Set: Historical fact 1.Wide - 28 mm f/2 (super-wide class) 2.Normal - 50 mm * f/1.2 (human eye equivalent) 3.Telephoto mm f/2.8 (long-focus class) Bonus lens- 200 mm f/3.5 (true telephoto) * f/1.2 is a super fast aperture preferred by nigh club photographers.

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens Z oom Lens Design: Zoom lens design has always been designed to meet the ‘balanced’ needs of the engineering (what’s possible) and the marketing (bottom line) departments. The ideal zoom lens would be optically perfect through the whole zoom range. It would also be fast, small, and light. The 18x compact digital superzoon is close to the desired tool. Rather than the trend of extending to 20x, I would rather have a faster (f/2.0) lens. I would like more work on minimizing optical distortion throughout the whole zoom range.

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens S uccessful Marketing Story: Most DSLR cameras are purchased with a poor optical quality KIT lens or KIT lens set. The cheap kit lens brings down the price of the DSLR camera making it ‘falsely affordable’ for the consumer. Camera and lens makers produce much higher quality zoom lenses but they can double or triple the cost of the DSLR. In fact, they make them but it’s usually a purchase made much later.

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens Z oom Lens: Description Historically, they are most often described by their focal length, measured in millimeters (mm) which is calculated by measuring the distance between the rear nodal point of the lens when the lens is focused on infinity, and the focal plane. Although this description often falls short when describing modern zoom lens which has become much more complicated in lens design.

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens D efinition: Nodal points The front nodal point in a compound lens system is the point where the rays of the light entering the lens appear to converge. The rear nodal point is the point where where the rays appear to have originated, after passing through the lens.

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens D efinition: Standard (Normal) Lens A lens with a focal length approximately equal to the diagonal of the film size format. The 35mm format standard lens is mm. The compact digital, which has a much smaller image size also has a smaller focal length number, mm. The ‘Normal’ lens reproduces a scene similar to what the human eye sees.

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens D escription: Equivalency 35 mm photography has been around for a very along time and it’s numbers represents the gold standard for referring to focal length. Equivalency chart shown below: Terms 35 Ref.DSLRCompact Super wide 28 mm18 mm 5.8 mm Regular ide 35 mm23 mm 7.2 mm Normal 50 mm33 mm10.3 mm Telephoto105 mm70 mm23.0 mm EQUIVALENT NUMBERS ARE CLOSE APPROXIMATTIONS

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens W ays of Seeing: Normal shows the scene as your eyes sees it.Normal shows the scene as your eyes sees it. Wide shows a wider view of the scene than your eye. It has to distort the scene in order to do so.Wide shows a wider view of the scene than your eye. It has to distort the scene in order to do so. Telephoto shows a magnified portion of the scene compared to your normal eye view. Telephoto shows a magnified portion of the scene compared to your normal eye view.

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens A ngle of View: Diagram view The upside down triangles show the angle-of-view of the different focal length. angle-of-view A.Super wide – black triangle B.Normal wide view C.Normal standard view D.Telephoto (magnified) view S C E N E LENS VIEW

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens L ens View: Wide angle In showing more of the scene than the human eye, the wide angle lens distort the scene. Many zoom lens set to wide angle tend to show barrel (bloated) distortion. For this reason, many architectural photographers prefer the better distortion corrected fixed focal- length wide angle lenses. Or they purchase the very expensive zoom lenses which are also more distortion free.

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens L ens: Telephoto Using the telephoto lens can ‘bring the subject closer’ or ‘enlarge the subject’ in your frame. It function exactly opposite of the wide angle lens. The image also visually feels flat or compressed rather than deep and angular. Using extreme telephoto usually requires a tripod or a solid brace of some kind.

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens L ens: Zoom range Zoom lenses were once consider specialized lenses but they are ubiquitous on most digital cameras today. Most compact (point & shoot) digitals have zoom lenses with a factor of 2.5x. Higher caliber prosumer models come with 4x or more zoom factoring. factor

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens A ll-in-One: Zoom lens Having the wide, normal, and telephoto capabilities all in a single lens is the power of the zoom lens. In a way, it’s a all-in-one tool. Like them, some zooms are more capable than others. At the minimum, a good zoom should have a 4x range and be sharp from corner to corner.

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens B icycle Analogy: Zoom factor For most snapshot use, a 2.5x is perfectly adequate. For most use, the 3 speed bicycle is more than adequate. If you are more serious or a commuter, you might want a 5 to 10 speed bike. That would be equivalent to 5 to 10x zoom factor. If you are a messenger or reply on your bike for a living, you might want a 24 speed bike. That can translate to 18 to 20x zoom factor.

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens C lose-Up Capability: Zooms are notorious for having poor close-up photography capability. And that is still true for the DSLR zoom lenses. Compact digitals zooms are surprisingly good at taking close up shots. And that is because of the small sensor chip size. Unfortunately, the close-up capability of the compact is mainly in the wide angle range. Close up work is better done at the 105 mm equivalent telephoto range.

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens A perture: Much more limited On a compact, wide open is f/2.8 and it stops down to f/8. That is only a 3 f/stop range. It gets even worse on the telephoto end. The wide open may be f/5.6 which is only 1-stop from f/8. I have seen a few compacts with f/5.6 as the only aperture choice. On the other hand, I have seen a few compacts that was limited to f/5.6 on the wide open but offered a smaller f/11 choice on the stopped down end.

Teacher: Kenji Tachibana Digital Photography I Art 115: The Lens S hutter Speed: Less limited but… The hand held shutter speed requirements: Super wide angle lens (28 mm) is 1/30 th sec.Super wide angle lens (28 mm) is 1/30 th sec. Normal wide angle lens (35 mm) is 1/40 th sec.Normal wide angle lens (35 mm) is 1/40 th sec. Normal lens (50 mm) is 1/60 th secondNormal lens (50 mm) is 1/60 th second Long focus lens (105 mm) is 1/125 th secondLong focus lens (105 mm) is 1/125 th second Real telephoto (200 mm) is 1/200 th secondReal telephoto (200 mm) is 1/200 th second Telephoto (500 mm) is 1/500 th secondTelephoto (500 mm) is 1/500 th second

Teacher: Kenji Tachibana Digital Photography I Cameron and his team: C onclusion: Nothing is simple Talking about the lens leads many other things including: DOFDOF ApertureAperture Shutter Speeds.Shutter Speeds.

Teacher: Kenji Tachibana Digital Photography I Cameron and his team: S ummary: Build good habits Please keep shooting and place as many shots in the bull’s eye as possible. Although stay discriminating in your self judgment. Every time you accept a lack luster image as being good, you will be building bad habits.

Teacher: Kenji Tachibana Digital Photography I x End