Canon EOS-1 Tips And Techniques

Also see for EOS-1: Instruction manual Instructions Brochure Settings guide Instructions

Contents

Canon EOS-1 Tips And Techniques Manual pdf 23 page image

II. LENS ISSUES 23AF Speed According toEF Lens VintageEF Extender IssuesJust as EOS cameras have improved over time in terms of AF calculation speed, EFlenses have improved in terms of lens drive speed. Although most if not all EF lensesregardless of vintage autofocus quickly enough to satisfy the needs of photographerswho specialize in stationary subjects, there is a significant improvement in lens drivespeed for fast-moving applications such as sports photography when the newer lensesare used with newer cameras like the EOS-1 class digital SLRs.Generally speaking, all USM lenses introduced since 1999, starting with the first 4models in the IS (Image Stabilizer) super-telephoto series (300mm f/2.8L IS, 400mmf/2.8L IS, 500mm f/4L IS and 600mm f/4L IS), autofocus noticeably faster than thenon-IS versions they replaced when used with an EOS-1 class digital SLR. Therefore, ifyou want to experience the maximum performance of your EOS-1 class digital SLR interms of AF speed, you must use a recent lens.The technical reason behind the improved performance lies in new programming on thecircuit board in the lens that supplies an initial burst of electrical power to the USMmotor that’s twice as high compared to the older lenses. The USM motor takesadvantage of this extra power to focus the lens faster.All single focal length L-series lenses from 135mm to 1200mm plus several L-seriestelephoto zooms are compatible with Canon’s 1.4x and 2x EF Extenders. Theseaccessories are understandably popular among professional and advanced amateurphotographers because of the extra value they offer in terms of increased focal lengthwithout forcing the photographer to invest in longer prime lenses.Of course, there are trade-offs for this convenience. The 1.4x and 2x Extenders cost 1 or 2f/stops respectively. This means, for example, that a 300mm f/2.8 lens when used with a2x extender becomes a 600mm f/5.6. Additionally, EF Extenders reduce lens drive speed.As noted in the instruction sheets supplied with the Extenders, the EF 1.4x or 1.4x IIreduces lens drive speed by approximately 50~67% depending on the lens in use. The EF2x or 2x II reduces lens drive speed by up to approximately 75%. This speed reductiongives the AF system more time to detect focus. This is helpful since the depth of focus isreduced with the longer effective focal length and the chance of defocus increases.However, the reduced tracking speed and smaller maximum apertures (that sometimesresult in the loss of cross-type sensor focus detection as mentioned in the description ofthe 45-point Area AF Sensor at the beginning of this document) caused by the use ofExtenders can be a disadvantage with fast moving subjects, particularly in low light.II. LENS ISSUES