maintained by Klaus Schroiff
This small FAQ is based on the lens test guide, canon publications, summaries from the EOS mailing list and some personal experiences. Therefore it contains subjective interpretations and third-party data which may not be accurate and/or reliable. If you want to contribute an article on a certain subject or simply correct some wrong information just email me.
1. What's the meaning of "Canon EOS" ?
2. What quality classes of Canon EF lenses are available ?
3. What is Micro-USM, Ring-USM, AFD ?
4. What is FT-M ?
5. Are there compatibility restrictions between Canon components ?
6. Are there compatibility issues with third-party products ?
7. What about Canon teleconverters ?
8. How's the performance of Canon tele converters on affordable L lenses ?
9. Teleconverter and low-speed lenses ?
10. What's so special about Canon "L" lenses ?
11. What's the difference between CaF2, SUD & UD elements ?
12. How's the quality of Canon's lens coating SSC (Super-spectra-coating) ?
13. Is there any cheap way to use normal lenses for macro photography ?
14. Third-party lenses - a good alternative in the EOS universe ?
15. Which Canon lenses feature "floating elements" ?
16. Which Canon lenses feature "Flare-Guard" - a "flare-cutting diaphragm" ?
17. Which Canon lenses feature "tropicalization" (sealing against dust and huminity) ?
18. Which Canon zoom lenses are parfocal ?
19. Which Canon lenses provide distance information for E-TTL II ?
20. The current line-up of EF-S lenses.
21. Image Stabalization:
o What is it ? What does it ? Does it work ? Where are the limits ?
o What about IS and tripods ?
o Tell me more about the Canon EF 28-135/3.5-5.6 USM IS !?
o Tell me more about the Canon EF 75-300/4-5.6 USM IS !?
o Tell me more about the Canon EF 300/4 L USM IS !?
o Tell me more about the Canon EF 100-400/4.5-5.6 L USM IS !?
o Give me an overview of the current IS lenses
22. Some VERY frequently asked Lens Comparisons:
o Canon EF 24-85/3.5-4.5 USM vs EF 28-105/3.5-4.5 USM
o Canon EF 50/1.4 USM vs EF 50/1.8 mk I vs mk II
o Canon EF 75-300/4-5.6 USM vs EF 100-300/4.5-5.6 USM vs EF 100-300/5.6L
o Searching on the long road ... the 400mm variety pack
23. Old vs New L class Lenses or ... are old L lenses a bargain ?
o Canon EF 16-35/2.8L USM vs EF 17-35/2.8L USM vs EF 20-35/2.8L vs EF 17-40mm f/4 USM L
o Canon EF 70-200/2.8L USM (IS) vs EF 80-200/2.8L vs EF 70-200/4L USM
o Canon EF 28-70/2.8L USM vs EF 28-80/2.8-4L USM vs EF 24-70/2.8L USM
o Canon EF 200/2.8L USM II vs EF 200/2.8L (mk I)
24. List of Sources
Q: What's the meaning of "Canon EOS" ?
A: Originally (1934) Canon started under the brand name "Kwanon" which is the name of the Buddhistic Goddess of Mercy.
Later it was changed to "Canon" - the reason for that remains a bit fuzzy. "Canon" also relates to a greek term meaning something like "an accepted principle or rule" or "criterion or standard of judgment" or so. After all it may also be just a simple name based on marketing research. Anyway ...
EOS means Electro-Optical System which describes the electronic coupling of camera body and lens.
Q: What classes of Canon EF lenses are available ?
"Silver ring" consumer lenses like e.g. the EF 28-90/4-5.6 or the EF 28-200/3.5-5.6 represent the bottom end of the Canon lens line-up. They're very cheap, the mechanical construction is simple (usually featuring a plastic mount) and the optics... well, let's say they all produce pictures. The AF motor is either a standard micro motor (usually DC type) or a micro-USM. The lenses have a silver colored ring next to the focus ring and are usually sold in kits. The silver ring "design" is new so there're a couple of older bottom-end lenses in the current line-up without silver ring such as the EF 80-200/4.5-5.6 II.
"Standard" type lenses represent the classic consumer segment. With the exception of the EF 50/1.8 these lenses have a metal mount and better build though there's still much plastic involved. The optical quality of these lenses is usually decent - some of the fix-focals such as the EF 100/2.8 USM macro perform stellar and are optically comparable to L class lenses.
TS-E "Tilt-Shift" is not exactly a quality class - these lenses are a very special breed though. They are the only lenses in the EF line-up without AF - this is indicated by the "E" (as opposed to "EF" - Electronic Focus). "TS" means "Tilt-Shift" which is a feature that allows a selective modification of focus plane (shift) and perspective (tilt). These lenses are especially interesting for architecture. The TS-E 24/3.5 is actually also an L lens.
L "Luxury" lenses represent the professionl segment - both regarding optical and mechanical construction as well as regarding the price. L class lenses feature either UD, SUD, CaF2 and/or ground aspherical glass elements (see below). L class lenses have a red ring next to the filter thread. Against urban legends L lenses aren't always white colored - this is limited to long tele lenses - probably for thermal protection because these lenses are often exposed to the sun for several hours e.g. during sport events.
There're now 2 DO "Diffractive Optics" lenses in the line-up. DO lenses aren't better (but slightly worse) than L grade lenses but their major feature is being SUBSTANTIALLY smaller and more light-weight. Unlike L class lenses they've a green ring next to the filter thread. Thanks to a newly developed optical element ("diffrative") the DO lens is about 30% smaller and lighter than comparable standard lenses in its range. Unfortunately the price didn't shrink by a similar factor but increased by about a factor of 2 compared to similar "classic" design. Optically and mechanically the lenses are on L class level. The DO technology is unique to the Canon EOS system.
EF-S "short back focus“ lenses are the latest class of lenses by Canon. EF-S is no measurement for quality - it's defines that these lenses are specifically designed for the very latest APS-C (1.6x crop) D-SLRs starting with the EOS 300D (Digital Rebel). EF-S lenses are NOT compatible with film SLRs nor older APS-C D-SLRs or D-SLRs with bigger sensors. The rear element is a little protruding so these lenses require a dedicated (retracting) mirror design. The image circle covers the APS-C format only. This design allows extreme wide-angle lenses with a relatively long zoom range and a comparatively decent performance.
Q: What is Micro-USM, Ring-USM, AFD, MM ?
A: The vast majority of current Canon EF lenses feature USM (UltraSonic-Motor) for auto-focusing. A few lenses in the current line-up and many discontinued lenses use an AFD (Arc Form Drive) and MM (Micro-Motor) AF motor system. So what are the differences? Conventinal motors like AFD/MM convert electromagnetic force into rotational force while USM is based on ultrasonic vibrational energy using a traveling wave. See Canon's "Lens Work" book for details or follow this link. On the practical side there're the following effects:
· USM. There're two different types of USMs:
o Ring-USM is the fastest USM. Usually it comes with FTM (full-time-manual AF)
o Micro-USM is used in cheaper Canon lenses like 75-300II, 28-80II-IV, 35-80 etc. The only Micro-USM lens featuring FTM is the Canon 50/1.4USM!
It has the following characteristics:
o silent! The only thing you'll hear are some component movements caused by the focus group(s).
o Ring-USM is extremely fast compared to conventinal systems
o Micro-USM is a bit slower than Ring-USM but still pretty fast compared to AFD/MM
o low energy consumption
o no problems in extreme temperature conditions
Be careful: the USM designation on a lens does NOT specify the type of USM!
· AFD/MM. It has the following characteristics:
o loud
o pretty slow except with IF lenses. AFD is a bit faster than MM.
o high energy consumption
Q: What is FTM ?
A: FTM (=Full-Time Manual) allows you to focus manually despite activated AF! This allows you to do some fine-tuning or to change the focus plane completely. Obviously this does only make sense when shooting in "One-Shot" AF-mode (camera stops AF once a focus is achieved)..
Q: Are there compatibility restrictions between Canon components ?
A: The nice thing about the Canon EF system is that there're no compatibility problems within the (genuine brand) EOS system! Every Canon EF lens will work properly on every EOS body without any loss of function, performance or whatsoever. You'll not loose any programs or AF just because you want to use an older lens on a new body or the other way round - like it is a common problem in the world of Nikon. Brand new E-TTL flash units can still be used in TTL mode on the very oldest bodies. Even IS ("Image Stabilization") is functional on all bodies - the only "restriction" concerns the lens-converter combinations with an effective aperture slower than f/5.6 (e.g. 300mm f/4L IS + 2x converter) where older EOS bodies shut down the IS feature (the lens itself remains functional naturally).
Q: Are there compatibility issues with third-party products ?
A: It is known that several older Sigma and Tokina lenses can cause software malfunctions on recent EOS cameras which can temporarily shut down the camera. This will not harm the camera but you'll not be able to use such a lens unless it gets a software upgrade from the manufacturer - if possible because there's no gurantee that this is acutally possible. Therefore we extra-careful when buying used equipment.
Tthese compatibility problems are -at least temporarily- solved at the moment but there's not guarantee that it'll stay that way because none of the third-party manufacturers seems to have bothered to obtain a license from Canon. So make sure you can live with that outlook if you buy a third-party product.
Starting from about mid 2001 (the production date of the lenses that is) there were no reported compatibility problems.
The Hall of Fame (NO GUARANTEES FOR COMPLETENESS WHATSOEVER):
History
Sigma
Tokina
Tamron
till EOS 100 / Elan
no problems
few problems The 100/2.8 can lock the EOS Elan/100.
EOS 5 / A2(e)
many lenses: wildly working aperture when half-pressing the shutter release button
EOS 50(e) / Elan II(e) (same with EOS 500n / Rebel G)
most lenses: camera stops working after releasing the shutter leaving mirror in upward position with battery symbol blinking
EOS 3 (same with EOS 1v)
many lenses except HSM versions: camera stops working after releasing the shutter leaving mirror in upward position with battery symbol blinking
There seems to be a batch of 28-70/2.6-2.8 and 28-80/2.8 which "sometimes" "crashes" the camera software and leaves mirror in upward position.
EOS 30/33/Elan 7(e)
some problems with many lenses
There seems to be a batch of 28-70/2.6-2.8 and 28-80/2.8 which focuses fine with the central AF sensor _only_!
reported April 22th, 2001 EOS 30/33/Elan 7, EOS 1v, EOS 1n, EOS 1 and EOS D30
aperture control problems:
· 20mm f/1.8 EX
· 24mm f/1.8 EX
· 28mm f/1.8 EX
· 180mm f/3.5 EX APO macro HSM
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