http://www_photo_net/bboard/q-and-a-fetch-msg?msg_id=000mda

80-200/2.8L = 300/4L = 200 f2.8L = 200 f2.8L II
=/=
70-200/2.8L = 300/4L IS = 100-400 IS.

http://www_photographyreview_com/reviews/35mm_zoom_lenses/product_5804.asp
200mm f/2.8 L =  EF 70-200mm f4L USM

To:AirForceOne
那个网页的内容帖在下面，可能有些表格格式不好，将就着看吧。
另：你可找个※※※※※进去
Lens mini-FAQ
maintained by Klaus Schroiff
(Last Update)

--------------------------------------------------------------------------------

Spanish translation of this FAQ by Ricardo López

--------------------------------------------------------------------------------

This small FAQ is based on the lens test archive, 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.

--------------------------------------------------------------------------------

FAQs:
What s the meaning of "Canon EOS" ?
What is Micro-USM, Ring-USM, AFD ?
What is FT-M ?
Are there compatibility restrictions between Canon components ?
Are there compatibility issues with third-party products ?
What about Canon Teleconverters ?
How s the performance of Canon TCs on affordable L lenses ?
Teleconverter and low-speed lenses ?
What s so special about Canon "L" lenses ?
What s the difference between CaF2, SUD & UD elements ?
How s the quality of Canon s lens coating SSC (Super-spectra-coating) ?
Is there any cheap way to use normal lenses for macro photography ?
Third-party lenses - a good alternative in the EOS universe ?
Which lenses feature "floating elements" ?
Which lenses have a "flare-cutting diaphragm" ?
Image Stabalization:
What is it ? What does it ? Does it work ? Where are the limits ?
What about IS and tripods ?
Tell me more about the Canon EF 28-135/3.5-5.6 USM IS !?
Tell me more about the Canon EF 75-300/4-5.6 USM IS !?
Tell me more about the Canon EF 300/4 L USM IS !?
Tell me more about the Canon EF 100-400/4.5-5.6 L USM IS !?
Give me an overview of the current IS lenses
Some VERY frequently asked Lens Comparisons:
Canon EF 24-85/3.5-4.5 USM vs Canon EF 28-105/3.5-4.5 USM
Canon EF 50/1.4 USM vs Canon EF 50/1.8 mk I vs mk II
Canon EF 75-300/4-5.6 USM vs Canon EF 100-300/4.5-5.6 USM
Searching on the long road ... the 400mm variety pack
Old vs New L class Lenses or ... are old L lenses a bargain ?
Canon EF 17-35/2.8L USM vs Canon EF 20-35/2.8L
Canon EF 70-200/2.8L USM vs Canon EF 80-200/2.8L vs Canon EF 70-200/4L USM
Canon EF 28-70/2.8L USM vs Canon EF 28-70/2.8-4L USM
Canon EF 200/2.8L USM II vs Canon EF 200/2.8L (mk I)
List of Sources

--------------------------------------------------------------------------------

General Questions
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. Previously I mentioned that it is "Latin and means Precision". However, one user informed me that it is actually a Greek term meaning either a) an accepted principle or rule, b) a criterion or standard of
judgment or c) a body of principles, rules, standards, or norms. 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 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:
Ring-USM is the fastest USM. Usually it comes with FTM (full-time-manual AF)
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:
silent! The only thing you ll heard are some movements caused by the focus group(s).
Ring-USM is extremely fast compared to conventinal systems
Micro-USM is a bit slower than Ring-USM but still pretty fast compared to AFD/MM
low energy consumption
no problems in extreme temperature conditions
You name of the lens does NOT specify the type of USM!
AFD/MM. It has the following characteristics:
loud
pretty slow except with IF lenses. AFD is a bit faster than MM.
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.

--------------------------------------------------------------------------------

Are there compatibility restrictions between Canon components ?

A: There re no compatibility problems within the 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.
The only "restriction" concerns the combination of the 300/f4L IS lens plus 2x teleconverter (= 600/f8) where older EOS cameras will shut down the IS (only). However, this 600/f8 combo doesn t make much sense in terms of optical quality anyway so it s really a very theoretical problem.

--------------------------------------------------------------------------------

Are there compatibility issues with third-party products ?

A: It is known that older Sigma and Tokina lenses (~  93 or older) will cause software malfunctions on recent EOS cameras (EOS 5/A2(E), EOS 50/Elan II(E), EOS 500n/RebelG) which can temporarily shut down the camera (mirror remains in upward positon and the battery symbol starts to blink). 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. However, it is known that Sigma is not able to upgrade all types of lenses so better stay away from some great 2nd hand Sigma offers at your dealer. Tamron seems to be the only third-party manufacturer with no problems with EOS camera - so far.
Today all these compatibility problems are -temporarily- solved but there s not guarantee that it ll stay that way because Canon does NOT provide any information about the camera - lens communication! E.g. just recently it was discovered that there re now problems with third-party lenses on the new Nikon F5. If it can happen there it could happen on the next generation of EOS cameras as well. So make sure you can life with that outlook if you buy a third-party product ...

--------------------------------------------------------------------------------

Q: What about Canon Teleconverters ?

A: Currently there re two Canon teleconverters avaliable:

Extender EF 1.4x (costs 1 f-stop)
Extender EF 2.0x (costs 2 f-stops)
These are among the best on the market but can only be used with fix-focal Canon "L-class" lenses with a focal length of min. 135mm & up plus the Canon 70-200/2.8L & 100-400/4.5-5.6L IS
On the third-party front there re a couple of cheaper alternatives that are not all that bad:

Sigma AF 1.4x APO EX
Sigma AF 2.0x APO EX
Kenko AF Pro 300 1.4x
Kenko AF Pro 300 2.0x
The Sigmas can only be used with dedicated Sigma EX lenses plus fix-focal Canon "L-class" lenses with a focal length of min. 135mm & up plus the Canon 70-200/2.8L & (probably) 100-400/4.5-5.6L IS. The Kenko can be used with all lenses because they do not have a protruding front element. Nonetheless the Kenko Pro series is optimized for > 200mm tele so the usage with std. zooms is pointless.
As a general rule AF remains functional as long as the combination has a max. aperture equal of bigger than f/5.6 (or f/8 in case of the Canon EOS 3). Some lens + third-party converter combination do not work regardless of this rule (compatibility problems ?).
Don t expect wonders with the 2x TCs - these are usually too much for many lenses regardless whether it is the Canon EF 2.0x or the Kenko AF PRO 2x. Only ultra-high performance lenses like the 300/2.8 (IS) or 400/2.8 II (IS) manage to produce a very good performance here.

--------------------------------------------------------------------------------

How s the performance of Canon TCs on affordable L lenses ?

A: You cannot pinpoint the performance of a tele converter because it is also heavy dependent on the design of the target lens (besides the principal quality of the converter). However, there re some general rules that apply here:

the larger the max. aperture of the lens the better is the potential quality with converter. The resulting aperture of a combination should not exceed f/5.6 - beyond that the performance is usually less than desirable though some very high performance fix-focals may produces "usable" results in such a scenario.
in general a Canon EF 1.4x will eat "one school mark" (a very good lens becomes a good 1.4x combo) whereas the EF 2x eats two school marks (a very good lens becomes an average 2.0x combo). A 2x converter is usually too demanding for most lens designs. It has no sense to add a converter, even a 1.4x,  to a sub-average lens like e.g. a 75-300 USM (nor is it mechanically possible with Canon converters).
Till recently third-party teleconverter offered a very poor performance. However, Sigma (APO converters) and Kenko (AF 300 "pro") both introduced some serious alternatives that can almost match the orginal Canons so if you re on a budget you may have a more serious look at these. It should be noted that future compatibility problems may also apply to these converters - you should keep that in mind.
The following table is based on the MTF-charts from the Canon "Lens Work" book. I ve no idea whether this data is reliable - some charts look a bit strange - but it s better than nothing, I guess ... The colors indicate combinations of same focal length (approx.).
(max. *****, A/B means A = reading at wide-open aperture, B= reading @ f/8, details at bottom of this page)
  

Lens Contrast  
no TC  Sharpness  
no TC Contrast w/1.4xTC Sharpness w/1.4xTC Contrast w/2xTC Sharpness w/2xTC Info  
Canon EF 2.0 135mm L USM  ***/*****  ***/*****  *****/****  ****/***  ***/*  ****/*  Bad edge performance w/2xTC.  
Canon EF 3.5 180mm L USM  *****/***** *****/*****  *****/*****  *****/****  ****/****  ***/****  Outstanding performance!  
Canon EF 2.8 200mm L USM  ***/*****  ***/****  ***/****  ***/****  **/**  */**  -  
Canon EF 2.8 70-200mm L USM @ 200mm  ****/*****  ****/*****  ****/**** ****/****  ***/****  ***/****  Canon recommends to use the central AF sensor. Amazing performance for a zoom.  
Canon EF 5.6 100-300mm L @ 300mm  ****/****  ****/****  Cannot take EF extenders!  The "cheap" alternative till 300mm!  
Canon EF 4.0 300mm L USM  ***/****  ***/****  **/***  ***/***  f/16:  
*/***  f/16:  
**/*** somewhat below expectations
Canon EF 5.6 400mm L USM  ****/****  ****/****  ***/***  ***/***  f/22:  
**/**  f/22:  
***/***  Still good w/1.4xTC!  
Canon EF 4.5-5.6 100-400mm L USM IS @ 400mm  ****/****  ****/*****  ***/****  ***/****  f/22:  
***/****  f/22:  
***/***  unbelievable performance with the TCs. (probably unlikely in the real world).

--------------------------------------------------------------------------------

Q: Teleconverter and low-speed lenses ?

A: All EOS cameras except the EOS 3 will shut down AF with a lens-TC combo which is slower than f/5.6. However, this is not entirely true. Third-party TCs do not transmit the correct aperture - e.g. a f/4 lens + generic 2x converter looks still like a f/4 lens for the camera while the Canon 2xTC will calculate and transmit the correct f/8. So what happens ? You ll indeed have a "sort of AF" till f/8 or so but don t expect arrucate and stable focusing. On a sunny day you ll probably get a reasonable performance up to f/6.7.

BTW, there is a possibility to make AF working with a slow combination of lens and Canon TCs. Canon TCs have 3 additional contacts (I think) so simply use a piece of thin plastic tape to block them. With this trick it should be possible to get AF on combos like 500/4.5+1.4xTC or 180/3.5+2xTC.

Do not try not use a TC on "low-performance" lenses like slow 75-300mm zooms. The resulting image quality is horrible! I did some tests with my Canon 100-300/5.6L + Kenko 2xTC but results are still far from being acceptable (at least for slides & posters).

--------------------------------------------------------------------------------

Q: What s so special about Canon "L" lenses ?

A: "L" means "Luxury" and defines pro-quality lenses. In contrast to consumer lenses they feature ground aspherical, UD, SUD or CaF2 elements which are an important basis for potentially outstanding optical performance. Usually the build quality is far superior as well.

--------------------------------------------------------------------------------

What s the difference between CaF2, SUD & UD elements ?

A: These are special elements to reduce the amount of chromatic aberations (color defects) which is a common problem with tele lenses. CaF2 (a synthetic calcium flourite crystal) elements provide an excellent correction potential and are about two times more effective than standard UD glass (Ultra-low Dispersion) but it s also far more expensive and only used in few lenses. UD elements are commonly used in L class tele lenses. SUD (Super-UD) is better than UD but still worse than CaF2. So far it s only used in the 400/5.6L lens. Based on magazine tests is pretty save to say that even "normal" UD glass outperforms third-party APO elements by far.

--------------------------------------------------------------------------------

How s the quality of Canon s lens coating SSC (Super-spectra-coating) ?

A: Canon uses "multiple layers of vapor deposited film reducing the reflection rate to 0.2~0.3%". Uncoated glass reflects 4~10% of the incoming light. So the coating seems to be pretty effective. However, the other major competitors (M*, N*, P*) seem to perform a bit better regard here - this is also confirmed by some magazine tests. There were some user reports stating that e.g. Pentax lenses (with SMC coating) are much less prone to flare compared to Canon lenses. Canon seems to be aware of this "problem" because many new lenses with a bigger number of elements feature a flare-cutting diaphragm now. E.g. it is known that e.g. the new 17-35L is much less prone to flare compared to its predeccessor - probably due to a floating flare-cutting diaphragm (called "Flare-guard").
The comments above are a bit speculative because of missing hard data though!

--------------------------------------------------------------------------------

Q: Is there any cheap way to use normal lenses for macro photography ?

A: There re various possiblilities to achieve higher magnification. Close-up lenses or Extension tubes are simple and cheap solutions. The table below shows some useful combos:
  

Table of  
max. magnification Close-up lenses Extension Tubes
Device Canon 250D Canon 500/500D Canon EF 12 Canon EF 25
EF50mm f/1.4 USM  not useful  0.39  0.68  
EF50mm f/1.8 II  0.39  0.68  
EF50mm f/2.5 Macro  0.74  1.04  
EF100mm f/2.8 Macro  1.41  1.21  1.17  1.38  
EF200mm f/2.8L USM  n/a  0.57  not useful  
EF300mm f/4L USM  n/a  0.70
EF400mm f/5.6L USM  n/a  0.91  
EF35-350/3.5-5.6L USM  n/a  @ 350mm: 0.70
EF70-200/2.8L USM  n/a  @ 200mm: 0.55  
EF70-210/3.5-4.5 USM  @ 210mm: 0.85  @ 210mm: 0.51  
EF75-300/4.0-5.6 II USM  @ 300mm: 1.54  @ 300mm: 0.89  
EF80-200/4.5-5.6 II  @ 200mm: 0.99  @ 200mm: 0.57  
EF100-300/5.6L  @ 300mm: 1.59  @ 300mm: 0.92  
EF100-300/4.5-5.6 USM  @ 300mm: 1.22  @ 300mm: 0.70

You can also combine several extension tubes for higher magnifications but sooner or later you ll loose AF or it ll get pretty difficult to focus manually due to the dark viewfinder. A relatively cheap alternative could be the Vivitar AF 100/3.5macro lens (see Lens Test Archive).

--------------------------------------------------------------------------------

Third-party lenses - a good alternative in the EOS universe ?

A: Third-party lenses are often cheap in comparison to original Canon lenses. Many times the lower price is bought at the expense of lower optical and especially mechanical quality. Here and there we can find some very attractive lenses though - like e.g. the Tokina 28-70/2.6-2.8 ATX Pro II which make it worth to think about divorcing from Canon. However, regardless of the offered quality there s another important issue in the world of Canon - compatibility. It may well be that a current third party lens works just fine on current EOS cameras but it fails on a next generation model. THIS HAS HAPPENED SEVERAL TIMES! The reason behind this is that none of the third party manufacturers has actually licensed the lens mount nor the camera-lens communication protocol - they reverse-engineered this critical component by analysing signal behaviour of the camera and original lenses. Obviously this method cannot be perfect. The mess with this workaround started with the EOS 5/A2E where Sigmas produced stange noises due to frequent aperture operations. After an update of the firmware everything worked fine ... till the EOS 50/Elan II was released causing both Sigma and Tokina lenses to lock up the whole camera. Again the firmware was updated within months - often at customer costs and some older lenses were excluded from the procedure. For about 3 years the world of Sigma & Co. was shiny again ... till the PhotoKina  98 where the new EOS 3 was released. And guess what ... ?! Well, yes - the majority of third party lenses, even the newest models (like several Sigma EX lenses), didn t work properly again on the new camera - sometimes as severe as a malfunctioning aperture or as "minor" as an unusable AF behaviour. By today the problem is fixed again but these continuing problems can melt off the inital price advantage rather quickly and a not updatable lens is scheduled for the trash bin ...
Sure, we can blame Canon for the whole mess but on the other hand ... all Canon lenses, even the old ones, continue to work just fine on the newest camera model so they just make use of some firmware features.
We ll probably see more compatibility problems till the third-party manufacturers bite the bullet and spend the big bucks for the mount license.

--------------------------------------------------------------------------------

Which lenses feature "floating elements" ?

A: Floating elements are a relatively reliable indication for a good performance towards closer focus distances. Magazine tests often measure the performance at the infinity setting only though the performance at real-life distances may deteriorate significantly (higher curvature of field) - especially with wide-angle & large aperture lenses. The following lenses in EOS mount feature floating elements (excluding true macro lenses which usually have FEs anyway):

Canon EF 2.8 14mm L USM
Canon EF 2.8 20mm USM
Canon EF 2.8 24mm
Canon EF 1.0 50mm L USM
Canon EF 1.2 85mm L USM
Canon TS-E 3.5 24mm L
Canon TS-E 2.8 45mm
Canon EF 2.8 17-35mm L
Canon EF 4.5-5.6 100-400mm L USM IS
Tokina AF 3.5 17mm AT-X Pro
Tokina AF 2.8 20-35mm AT-X Pro
Tokina AF 2.8 80-200mm AT-X Pro
Sigma AF 2.8 24mm macro

--------------------------------------------------------------------------------

Which lenses have a "flare-cutting diaphragm" (FCD) ?

A: Flare is a major problem in contra-light situations. There re 3 methods to reduce ghostings & flare:

anti-reflection lens coating
electrostatic flocking techniques
anti-reflection construction techniques
The first two methods are commonly used but the third is not always standard. The following list shows some lenses that feature a "flare-cutting diaphragm". It is not an evidence for potentially low flare but maybe a hint that a manufacturer had put some effords in reducing it.
Canon EF 2.8 20mm USM
Canon EF 1.8 28mm USM
Canon EF 2.8 28mm
Canon EF 2.0 35mm
Canon EF 1.0 50mm L USM
Canon EF 2.0 135mm L USM
Canon EF 3.5 180mm L USM macro
Canon EF 2.8 300mm L USM
(*) = moving FCD according to zoom position Canon EF 2.8 17-35mm L USM (*)
Canon EF 3.5-4.5 20-35mm USM
Canon EF 3.5-4.5 24-85mm USM (*)
Canon EF 2.8 28-70mm L USM (*)
Canon EF 3.5-5.6 28-80mm (USM) IV (*)
Canon EF 2.8 70-200mm L USM
Canon EF 4-5.6 75-300mm (USM) II
Canon EF 4.5-5.6 80-200mm (USM) II
Canon EF 4.5-5.6 100-300mm USM
Tokina AF 4.5-5.6 80-400mm AT-X
Tokina AF 4.5-6.7 35-300mm
Tokina AF 2.8 80-200mm AT-X Pro (not sure)


--------------------------------------------------------------------------------

Image Stabalization:
Q: What is it ? Does it work ? Where are the limits ?
A: In short: Camera shake is a major cause for blurred images. This is especially true for long tele-lenses in low-light conditions. The only classical ways to solve this problem is to use a fast (and expensive) lens or a fast (and less sharp and more grainy) film. Canon s new approach solves the same problem by stabalizing the image itself. The camera motion is detected by 2 gyro sensors which measure the angle and speed of the shake. This information is used to shift a certain lens group off the optical axis to counteract this motion. The result is a significant improvement of handholdability under extreme conditions. E.g. it is possible to shoot at 1/60s at 300mm instead of 1/250-1/350s - an equivalent of 2 f-stops! Compared to conventional handheld shots the results are equally sharp and contrasty. There s no deterioration of quality due to IS side effects (tripod shots are always sharper though)! Obviously there are also certain limits of the technology! The gain of 2 f-stops is only "simulated". This means:

a f/5.6 IS lens is still a f/5.6 lens. You may use it like a f/2.8 lens but you ll never be able to achieve the shallow depth-of-field which is possible with large-aperture lenses only!
you gain these f-stops by shooting at slower speeds. E.g. you may shoot at -say- 1/90s at 300/f5.6 while a true 300/f2.8 lens can be used at 1/350s! This is Ok for static objects but you ll run into difficulties when the subject is moving.
On the other hand - most mortals can afford an IS lens but not a 300/2.8L ...

--------------------------------------------------------------------------------

What about IS and tripods ?
A: There are some rumors about there that state that the IS gets damaged when activated on a tripod. This is obviously just - nonsense. This is what you can read in the manual: "Do not set the image stabilizer switch to  I  when using the camera on a tripod. Doing so may cause the image stabilizer to act erratically. Turn the image stabilizer off before using the camera on a tripod.".  Further more this is only true for the following lenses:

EF 28-135mm f/3.5-5.6 USM IS
EF 75-300mm f/4-5.6 USM IS
EF 300mm f/4 USM L IS
EF 100-400mm f/4.5-5.6 USM L IS
Here the explanation for Chuck Westphal (Canon USA):
"The IS mechanism operates by correcting shake. When there is no shake, or when the level of shake is below the threshold of the system s detection capability, use of the IS feature may actually *add* unwanted blur to the photograph, therefore you should shut it off in this situation. Remember that the IS lens group is normally locked into place. When the IS function is active, the IS lens group is unlocked so it can be moved by the electromagnetic coil surrounding the elements. When there s not enough motion for the IS system to detect, the result can sometimes be a sort of electronic "feedback loop," somewhat analogous to the ringing noise of an audio feedback loop we re all familiar with. As a result, the IS lens group might move while the lens is on a tripod, unless the IS function is switched off and the IS lens group is locked into place."
Canon just released the next generation IS professional lenses. These lenses feature a "tripod-detection" mode which means that it is no problem to use IS on a tripod. Even more than that - IS will correct vibrations caused by the mirror operations of the camera. So far the feature is available on the following lenses.

EF 300mm f/2.8 USM L IS
EF 400mm f/2.8 USM L IS
EF 500mm f/4 USM L IS
EF 600mm f/4 USM L IS

--------------------------------------------------------------------------------

Tell me more about the Canon EF 28-135/3.5-5.6 USM IS !?

A: This is the only member of the IS gang that includes wide focal lengths. Optically it is quite comparable to the popular 24-85/3.5-4.5 and the 28-105/3.5-4.5. The performance is said to be equal, maybe slightly better than these non-IS std. zooms but worse than the 28-70/2.8L (no surprise here). Magazine tests indicate that it is a bit soft wide-open (especially towards the corners) but the performance gets desent when stopping down a bit. With activated IS Canon states a "gain" of 1.5 stops at 28mm (-> min. 1/10s) and 2 stops at the long end (-> min. 1/30s). The lens features a Ring-type USM with FTM. Like with the 75-300 IS there s just one IS mode.
Overall this lens is probably the very best one-lens-travel-solution from Canon.

--------------------------------------------------------------------------------

Tell me more about the Canon EF 75-300/4-5.6USM IS !?

A: The optical performance is virtually the same compared as with the conventional 75-300mm zoom. This is a bit sad because results get very soft towards 300mm. The optical quality is acceptable between 75mm and 200mm . It s quite fascinating to get sharp shots at 75mm with 1/15s. 1/60s are no problem at 300mm. Dependent on your personal "shake rate" you may shoot at much slower speeds but 1/15s @ 300mm should be the limit for non-robots.
The mechanical quality is slightly superior compared the the non-IS version but it still features micro-USM without FTM. It has a rotating front-element and the AF performs is relatively slow compared to -say- the 100-300/4.5-5.6 USMl. Overall this should be a very nice lens if you shoot primarily for smaller prints.

--------------------------------------------------------------------------------

Tell me more about the Canon EF 300/4L USM IS !?

A: Compared to the consumer grade 75-300IS this is a very different baby! Image quality and mechanical construction are on "L" class level. Tests indicate no deterioration compared to the conventional 300/4L. The IS lens is probably at little bit more prone to flare due to the bigger number of elements (13 vs 8). Additional to the standard IS mode there s also a new "panning" mode where the IS corrects vertical shakes only. This is useful for action/sports photography where you have to track your subject horizontally. Potentially the IS mechanism works with both Canon teleconverter. This is true for camera bodies starting with the EOS 50 and newer. Older camera (incl. EOS 5 (A2E), 1N) are restricted to the 1.4xTC when you want to use the IS feature!

--------------------------------------------------------------------------------

Tell me more about the Canon EF 100-400/4.5-5.6 L USM IS !?

A: Users of the first samples of this lens mentioned a rather mixed performance with less-than-optimal results at 400mm. However, this "early production bug" has been fixed in the meanwhile. The first serious tests indicate that this is indeed an excellent zoom. "Chasseur d Images", usually a very reliable resource, mention that this is the very best zoom in this range they have ever tested - no wonder in regard to the crap which is offered here though. The performance charts indicate a very even high quality throughout the whole range even at wide-open aperture. The same goes for the MTF charts in the Canon Lens Work book show an excellent performance especially at 400mm. The performance with the 1.4xTC seems to be quite impressive as well though a 560mm f/8 lens isn t very appealing. It also takes the 2xTC transforming it into a 800mm f/11.2 monster which is probably not very desirable.
Just like the 300/4L IS the lens has 2 IS modes - a normal one which corrects image blurr in two dimensions and a "panning" mode which just corrects vertical movements. As usual the IS "gains" 2 f-stops enabling the user to shot with 1/125s (or less) at 400mm.
On the down side the lens is a push/pull construction. You can change the focal length very fast but finding an exact setting is more difficult than with conventional zoom controls. The chosen focal length can be locked in order to prevent "zoom creeping". In terms of mechanical quality it is build up to the commonl L standards.

--------------------------------------------------------------------------------

Give me an overview of the current IS lens line-up
  
Lens IS - mode 1  
(standard) IS - mode 2  
(panning) Tripod  
detection
Canon EF 28-135mm f/3.5-5.6 USM IS x - -
Canon EF 75-300mm f/4-5.6 USM IS x - -
Canon EF 100-400mm f/4.5-5.6 USM L IS x x -
Canon EF 300mm f/4 USM L IS x x -
Canon EF 300mm f/2.8 USM L IS x x x
Canon EF 400mm f/2.8 USM L IS x x x
Canon EF 500mm f/4 USM L IS x x x
Canon EF 600mm f/4 USM L IS x x x

Explanation:
IS - mode 1 = std. mode for static objects
IS - mode 2 = panning mode for moving objects (horizontally)
Tripod detection = lens can be used on a tripod with activated IS

--------------------------------------------------------------------------------

Some VERY frequently asked questions
Canon EF 24-85/3.5-4.5 USM vs Canon EF 28-105/3.5-4.5 USM vs Canon EF 28-135/3.5-5.6 USM IS
A: Apart from focal range these lenses perform roughly identical in all major aspects. They show a good optical performance outperforming most comparable third-party offerings. Nonetheless the results are not outstanding as with the EF 28-70/2.8L which cannot be expected in regard to the price anyway. In general the distortions are pretty hefty at the wide end and the long end tends to be a bit soft. These lenses feature a fast Ring-USM with FTM. The filter size is quite different (58mm (28-105) vs 67mm (24-85) vs 72mm (28-135)).  Overall the 28-105 & 28-135 IS seem to be a good choice if you prefer the portrait photography while the 24-85 seems to be a good option for landscape photography. Obviously the 28-135 IS is a bit more versatile due to its IS but that was already explained above.
  

Lens weight length min. focus filter size price
Canon EF 24-85mm f/3.5-4.5 USM 380g 69.5mm 0.50m 67 320 US$/Euro
Canon EF 28-105mm f/3.5-4.5 USM 360g 72mm 0.50m 58 300 US$/Euro
Canon EF 28-135mm f/3.5-5.6 USM IS 540g 69.8mm 0.50m 72 500 US$/Euro

Alternatives:

Within the Canon line-up there s the old EF 28-70/3.5-4.5 mk II which is to be supposed one of the very best lenses in its class. It s a bit hard to find because it s discontinued since  92 or so. However, it s a pain to use this lens with a polarizer - the front element rotates and retracts into the inner tube when zooming or focusing. No USM. In terms of optical performance it easily outperforms both the 24-85mm as well as the 28-105mm.
If you re willing to invest a few bucks more the Tokina AF 28-70/2.6-2.8AT-X Pro II seems to be an excellent choice - very good optical performance and a build-quaility that can rival L class lenses.
The Sigma AF 28-70/2.8 EX seems to be an interesting option as well though it seems to be less desirable compared to the Tokina.
(Please note the compatibility issues involved with third party products)

--------------------------------------------------------------------------------

Canon EF 50/1.4 USM vs Canon EF 50/1.8 mk I vs mk II

A: These 3 lenses show a very good optical performance. Resolution and contrast are superb when stopped-down to f/5.6 but a bit soft wide-open which is normal for large aperture lenses.
The optical constructions of the 50/1.8 mk I and mk II are identical. The only visual difference is the color balance which is neutral for the mk II and a bit warm for the old lens. There s a HUGE difference in build quality though! The old mk I lens features a metal mount and has a solid construction while the build quality of the new mk II lens is pretty sloppy. There were some reports of centering problems (uneven sharpness) for the mk II.
The 50/1.4 is obviously a bit faster and also much more solid than the 50/1.8 mk II. Additionally it features a micro-USM with FTM. Normally this lens should be the best choice but it s cost a small fortune in comparison (approx. 4 times the price of the 50/1.8). The best idea is probably to dig for a 2nd hand 50/1.8 mk I but this lens is really hard to find.

--------------------------------------------------------------------------------

Canon EF 75-300/4-5.6 USM (IS) vs Canon EF 100-300/4.5-5.6 USM

A: Probably one of the most frequent questions in the newsgroups and the EOS mailing list concerns the comparison of these two lenses. Despite a different optical construction both lenses perform virtually the same here which means:

pretty good at the wide end
maybe Ok at 200mm
quite soft at the long end (300mm)
This may sound not so good but the same is also true for the vast majority of other 75/100-300mm zooms. In mechanical terms both lenses are pretty different. The 100-300/4.5-5.6USM features Ring-USM, FTM and a non-rotating front element while the 75-300/4-5.6USM has a slower micro-USM and a rotating front element. Overall the 100-300 seems to be the better choice - unless you re on a tight budget. What Canon thinks about these two lenses (format = wide-open/stopped-down):
  
Lens Contrast @ 75/100mm Sharpness @ 75/100mm Contrast @ 300mm Sharpness @ 300mm  
Canon EF 4-5.6 75-300mm USM (IS)  **/****  **/****  **/**  **/**  
Canon EF 4.5-5.6 100-300mm USM  ****/****  ***/****  */**  **/**  
Alternative: Canon EF 5.6 100-300mm L  ***/*****  ***/****  ****/****  ****/****  

Alternatives:

The only affordable lens in the world of Canon (Canon or third-party manufacturer) with a decent performance throughout the 100-300mm zoom range seems to be the Canon 100-300/5.6L (apart from the expensive 100-400L). Obviously you have to pay a hefty bonus for the difference but you can find it pretty cheap in the 2nd hand market (for a little bit more than for the price of a new 100-300/4.5-5.6USM). It doesn t feature USM and it has a push/pull type zooming mechanism. Unfortunately the front elements rotates when focusing. The build quality isn t better than with the consumer lenses but not worse either. Thanks to a big CaFo- and one UD element the pictures look very sharp and contrasty though.
In regard to third-party products the story is usually a sad one as well. The Tamron 70-300/4-5.6 "LD" seems to be an alternative at the bottom end market. It shares its optical construction with the Nikkor 70-300/4-5.6 ED. The "LD" element improves the results towards the long end making it a somewhat superior option compared to the non-L Canon lenses.
The "Sigma AF 70-300/4.5-5.6 APO macro super" (uugh ... what a name ...) sounds interesting but the few user comments indicate rather mixed emotions.
(Please note the compatibility issues involved with third party products)

--------------------------------------------------------------------------------

Searching on the long road ... the 400mm variety pack

A: The table below is an attempt to average the opinions and test results for some of the common consumer grade 400mm lenses in Canon EF mount.
  

Lens Performance at 400mm Remarks  
Tamron AF 200-400/5.6 LD poor nice try ...
Tokina AF 80-400/4.5-5.6 AT-X poor no tripod mount (!), rotating front element, rotating focus ring in AF mode, very solid
Sigma AF 170-500/5-6.3 APO Aspherical RF poor very long at 500mm, very slow and unreliable AF, decent results till 300mm
Sigma AF 135-400/4-5.6 APO Aspherical RF average  very slow AF
Sigma AF 400/5.6 APO average Discontinued lens. Very likely compatibility problems on EOS 50/Elan II, 500n/RebelG, 3!!!
Tokina AF 400/5.6 AT-X average optically good when stopped-down but a bit soft at f/5.6, very solid, compact, rotating focus ring in AF mode
Sigma AF 400/5.6 APO HSM macro good HSM is a similar technology to Canon s USM: Very quiet & fast, FTM. Optically identical to the non-HSM version.
Canon EF 300/4L USM (IS) + Canon EF 1.4xTC (excellent)  
good w/TC a great 300mm and a decent 420mm lens (w/TC), quite expensive in comparison.
Canon EF 100-400/4.5-5.6L USM IS good - very good a nature photographers dream ... a bit on the heavy side
Canon EF 400/5.6L USM very good a sure bet but expensive.

    (Please note the compatibility issues involved with third party products)

--------------------------------------------------------------------------------

Old vs New "L" glass:
Canon EF 17-35/2.8L USM vs Canon EF 20-35/2.8L
A: A comparison between these two lenses is a bit tricky because the new lens starts at 17mm so the following comments are restricted to the 20-35mm range only. The overall performance of both lenses is very good though the old lens is supposed to have a very slight edge in terms of resolution. The contrast performance is amazingly high for both lenses even at wide-open aperture and throughout the whole range. At comparable focal lengths the new lens is a bit better in terms of vignetting, distortions and especially flare. USM is probably not such an important improvement for an ultra-wide lens but the 17-35mm comes with FTM as well which is handy for many situations. A "flaw" of the lens is its performance at 17mm where it suffers from visible barrel distortions, vignetting and an "limited" edge resolution at wide-open aperture. At f/5.6 the vignetting disappeared and sharpness improves quite a bit.

Alternatives:

Canon EF 20-35/3.5-4.5 USM - the lens is no match in terms of build quality but optically it compares pretty well except at wide-open apertures.
Tokina AF 20-35mm f/2.8 AT-X Pro - this one shows very low distortions even at 20mm. Wide-open it s soft - stopping down solves the problem. Mechanically this lens is a tank.
Sigma AF 17-35mm f/2.8-4 EX - the major weakness of this lens is its flare behaviour. In contra-light situation it suffers from severe ghostings and a hefty detioration of contrast - typical for most Sigmas. Other than that it seems to be a very serious option.
Tamron AF 20-40mm f/2.7-3.5 SP - overall an interesting lens except though the performance at wide-open aperture is somewhat limited. Distortions are higher compared to the other lenses.
  
  
  
  
  
  

(Please note the compatibility issues involved with third party products)

--------------------------------------------------------------------------------

Canon EF 28-70/2.8L USM vs Canon EF 28-70/2.8-4L USM

A: There were only a few comments in regard to the old lens in the EOS mailing list so it s a bit difficult to sum it up. There were some reports that the old lens suffered from vignetting and distortions - in the press release Canon mentioned that vignetting problem has been solved with the 28-70/2.8L. Both lenses feature a ring-type USM but the old lens doesn t provide FTM.
The 28-70/2.8L is indeed comparable with fix-focals in terms of performance and therefore considered to be a true marvel in the Canon line-up. The only problem is that it extends when zooming towards the long end - however, that s typical for all lenses in this zoom range.

Alternatives:

Tokina AF 28-70/2.6-2.8 AT-X Pro II - indeed a serious competitor except at wide-open aperture where it performs a bit soft. The build quality is excellent.
Sigma AF 28-70/2.8 EX - overall comparable with the Tokina except in terms of build quality. Severe flare problems in contra light situations.
Tamron AF 28-105/2.8 SP - this lens suffers from quite extreme distortions at the end of the focal range. Other than that it is comparable with the other two third-party offerings.
  
  
  
  
  
  

(Please note the compatibility issues involved with third party products)

--------------------------------------------------------------------------------

Canon EF 70-200/2.8L USM vs Canon EF 80-200/2.8L vs Canon EF 70-200/4L USM

A: In optical terms the differences between these lenses are minor or in short - the performance is excellent. Mechanically all are build up to the high L standards. Nonetheless there re several mechanical differences though. :
  

Lens AF motor
(speed) FTM
(full-time-manual) hood-type tripod-mount takes original Canon EF converters filter size weight approx.
price
Canon EF 70-200/2.8L USM Ring-USM
(very fast) yes flower-shaped yes yes 77mm 1275g 1350 US$/Euro
Canon EF 70-200/4L USM Ring-USM
(very fast) yes round optional
(quite expensive) yes 67mm 705g 850 US$/Euro
Canon EF 80-200/2.8L AFD
(medium) no round yes no 72mm 1430g used: 700 US$/Euro

So there s much to choose from depending on your priorities.  The 70-200/4L makes sense for people looking for a light-weight high-performance lens - certainly nice for the outdoors. The 67mm filter size matches the EF 24-85 which would be a natural companion in this context. Its (relatively) small aperture makes it a not-so-interesting option for the usage with converters though. This is the point where the 70-200/2.8L shines. It still offers a very good performance with the EF 1.4x and relatively decent quality with the EF 2x. The old Canon EF 80-200/2.8 relies on third-party offerings here - the new Kenko AF 300 1.4x pro seems to be the best option.

Alternatives:

Sigma AF 70-200/2.8 EX HSM - this one seems to be a quite serious competitor. All magazine tests indicate a similar performance compared to the Canon lenses above. The major weakness of this lens is its flare behaviour. In contra-light situation it suffers from severe ghostings and a hefty detioration of contrast. Other than that it seems to be a very serious option.
Tokina AF 80-200/2.8 AT-X Pro - the Tokina is build like a tank but optically it is inferior especially at the long end (nonetheless quite decent overall). In Europe this lens is often sold at very low prices making it an interesting budget option when looking for a f/2.8 zoom lens. A used 80-200/2.8L may still be more interesting in this context though.
(Tamron AF 80-200/2.8 SP - not too desirable compared to the other options (e.g. rotating front element, quite high price))
  
  
  
  
  
  

(Please note the compatibility issues involved with third party products)

--------------------------------------------------------------------------------

Canon EF 200/2.8L USM II vs Canon EF 200/2.8L (mk I)

A: This one is easy! The optical and mechanical construction is virtually identical. The only difference seems to be the lens hood which of build-in type in the old lens. The hood of the mk II lens has to be attached externally and is much more effective and bulky.
Both lenses come without tripod mount but it seems to be possible to order one from Canon. E.g. they can take the same tripod mount as the 300/4L or 400/5.6L.

--------------------------------------------------------------------------------

Here s how I judged the MTF-graphs from the Canon Lens Work book:
I took 3 readings for both saggitally and tangentially MTF-curves at center, 10mm and 20mm off the center. The numbers for contrast w/o, sharpness w/o and contrast @ f/8, sharpness @ f/8 were averaged without special weighting factors. So finally there were 4 numbers for one focal length.

Contrast: 94 & up = excellent  (*****)
88-<93 = very-good  (****)
82-<87 = good  (***)
76-<81 = Ok  (**)
0-<75 = poor  (*)
Sharpness: 80 & up = excellent  (*****)
70-<80 = very-good  (****)
60-<70 = good  (***)
50-<60 = Ok  (**)
0-<50 = poor  (*)


Note: The MTF-graphs reflect the performance at the infinity focus setting ONLY! The real world performance may look different because of a certain deterioration towards closer focus distances (normal except w/floating elements). MTF-graphs do not reflect the amount of distortions, vignetting and color balance.They are just a method to show potential sharpness & contrast at various aperture settings.

--------------------------------------------------------------------------------

Sources:
Canon Lens Work II
Canon EOS FAQ 2.4
Canon EOS FAQ 3.0
The discussion archive of the Canon EOS mailing list.
Several magazine tests.
Personal experience.

昨晚上我看过，一个字都没有:-(
我试过用300/4IS的接环放到200/2.8上，不行，太大。
我有200/2.8L和80-200/2.8L，准备上100/2.8 MU，如果三枝头的接环能通用就太好了！

Ejz：印象里EF80-200/2.8L，200/2.8L，300/4L都是一个脚架环，就是那个A型，B型从它的名称看是专为100macroU设计的，不知道直径是否一样，看起来承载力还是不一样的。
http://www_photozone_de/canonFAQ.htm 可能有些关于脚架接环的资料，可惜我进不去，谁能帮忙看看再贴过来？

忆松，有钱的话，俺觉得俺那配置不错:-)，不光为个脚环。

一号，你不会为一角座把那一串都收进吧！

黑店：忠诚相机公司，弥顿道100号东英大厦（26号铺天祥在此）隔壁香槟大厦2号铺。到天祥去问一问，也许有且便宜些。

我买这枝头才花了41000日元，在脚架接环上花这么多真不值！打倒Canon！

实际上，这样的测试是不严谨的，只是同一个胶卷出来后，
一个是GR1s拍的，一个是EF200拍的，我知道28和200的确
没有可比性，但那主观感受是很明显的，尤其是色彩。
To：ejz
俺手持拍了几张肖像，速度都在1/500以上，f/2.8,但还是
有几张虚了，可能真是对错了地方？To：小孩
可能俺对这支头的期望值太高，觉得拍出的片子会毫发毕现。

另外，此头的配置是不带三角架接环的，但俺在实际使用时
觉得不是很稳，有必要配一个接环，尤其在使用增倍镜时。

1。解像力不高不知道你指的是啥，是模糊麽？在大光圈下一定要细调，别相信相机的自动对焦，俺用这只头开大光圈第一卷差不多都拍虚了。

2。色彩不够饱和有可能是曝光的问题，可以欠上半挡试试。

我有此头的第一版，光学结构是一样的。我用下来的感觉是非常好的，没有你提到的这些问题。如果你的镜头不是有故障的话，可能是以下原因：
1）长焦镜头要特别注意防止手振，任何好头加上手振都比不上狗头。
2）如果空气中的灰尘较多的话，用长焦镜头会明显降低片子的反差，影响色彩还原。

没这个道理，上官封有这只头，点名找他！

------------------
海纳百川，有容乃大；壁立千仞，无欲则刚。