View Full Version : Why No EF-S Compatible Tele Extender?
Does anyone know why this wouldn't be technically possible? Seems like a slam dunk idea. I'm surprised a third party like Kenko hasn't stepped up...
Does anyone know why this wouldn't be technically possible? Seems like a slam dunk idea. I'm surprised a third party like Kenko hasn't stepped up...With IS! (As someone here suggested previously)
With IS! (As someone here suggested previously)I'd settle for no-frills 1.5x...;)
Canon will probably come out with some very slight mounting change to its stable of EF-S lenses to enable using extenders. Then you can buy all new lenses. :)
cwphoto
06-19-2006, 04:22 PM
Does anyone know why this wouldn't be technically possible? Seems like a slam dunk idea. I'm surprised a third party like Kenko hasn't stepped up...
Which EF-S lens would you like to extend? I don't really see much of a market.
Any lens worth extending is going to be EF IMO.
cdifoto
06-19-2006, 04:38 PM
Which EF-S lens would you like to extend? I don't really see much of a market.
Any lens worth extending is going to be EF IMO.
I agree. Unless Canon came out with an EF-S 400mm f/2.8 IS that I haven't heard about...
...which, btw, probably wouldn't come with a hood. :)
coldrain
06-20-2006, 01:59 AM
Only Canon makes EF-S lenses. All other reduced image circle lenses, like from Sigma, Tamron and Tokina, are EF lenses... although with a reduced "APS-C" image circle.
What EF-S lenses are there? 18-55, 17-85, 10-22, 17-55 and a 60mm macro.
Not really a target group of lenses that will make one want an extender, is it?
You can extend your Sigma 18-200 (which is not an EF-S lens) with for instance a Soligor 1.7x tele convertor. But, due to the not so big max. aperture of your lens, you will probably not be able to auto focus very reliably or at all.
What makes a Canon EF-S mount lens different from a APS-C lens from Sigma, I hear you ask? EF-S lenses have a back element that protrudes more into the mirror box than EF lenses. This is also why they can not be mounted on cameras that are full frame or 1.3x, and why they can not be mounted on for instance the EOS 10D (the back element of the lens would collide with the mirror).
as previously pointed out there really aren't any EF-S lenses to extend. the canon TC's only work with a handful of L's as it is (not even regular non-L EF lenses) so them making an EF-S extender would be asking a bit much.
What makes a Canon EF-S mount lens different from a APS-C lens from Sigma, I hear you ask? EF-S lenses have a back element that protrudes more into the mirror box than EF lenses. Thank you Coldrain!
I ask a technical question and you're the only one who bothered to give a technical answer instead just slamming my question (like most did), so thanks again.
So, I want to follow up on something you said...let's take the Sigma and Tamron APS-C only lenses (DC and Di II only)....like the 18-200 or the 18-125. Are you saying that these lenses are designed differently than the EF-S lenses, and that they do not protrude into the mirror box in the same way?
Thanks!
from my point of view i don't see anyone slamming your post
from my point of view i don't see anyone slamming your postHey, I felt slammed...most answers amounted to "what's the point?"...instead of trying to give a technical explanation...but it's no biggy...
coldrain
06-20-2006, 07:53 AM
Thank you Coldrain!
I ask a technical question and you're the only one who bothered to give a technical answer instead just slamming my question (like most did), so thanks again.
So, I want to follow up on something you said...let's take the Sigma and Tamron APS-C only lenses (DC and Di II only)....like the 18-200 or the 18-125. Are you saying that these lenses are designed differently than the EF-S lenses, and that they do not protrude into the mirror box in the same way?
Thanks!
Yes, they are designed differently. 35mm SLRs have a big mirror box in front of the film/sensor, and this limits lens design. Canon chose to take advantage of the fact that their APS-C cameras do not need as big a mirrorbox, to design lenses where the back element can get closer, in theory enabling more freedom when designing lenses (probably true with the EF-S 10-22 USM and EF 60mm macro).
To prohibit these lenses to damage mirrors in other cameras, they introduced a slightly altered mount, the EF-S. All other manufactures for Canon compatible lenses use EF mount, and design the lenses so that they can be used also on Nikon, Pentax, KM/Sony etc. (and older EOS D 1.6x crop factor cameras like D30, D60, 10D).
My APS-C lenses (Tokina 12-24 f4, Sigma 18-50 f2.8) work fine on full frame, although the Sigma will vignet very very badly on its entire focal range, and the Tokina vignets between 12-16mm.
The reason you only can use the Canon extenders on a limitted raneg of lenses has to do with the design of its lens system. The front element protudes a lot, and only lenses taht have a back element that is quite recessed can fit on the Canon extenders.
Teleconvertors from Soligor, Tamron and Kenko are less limitting in that respect, although AF will depend on the lens used.
Hey, I felt slammed...most answers amounted to "what's the point?"...instead of trying to give a technical explanation...but it's no biggy...
i'm not going to say how you felt is invalid, but for me, what i saw were different explainations as to why they have no reason to design one yet, as in no lens to make a TC for. a more detailed addition to my post would be that canon does not seem to think TC's are need for lenses less than 135mm, and currently there are no EF-S lenses in that range. i did type up a more technical explanation saying that canon seems to design their TC's with a protruding element which would totally clash with their rear protrusion EF-S design, but i deleted that before posting because i thought it would be unneccessary. I apologize if you took my post in a way that bothered you - it was not the intent.
The reason you only can use the Canon extenders on a limitted raneg of lenses has to do with the design of its lens system. The front element protudes a lot, and only lenses taht have a back element that is quite recessed can fit on the Canon extenders.
Teleconvertors from Soligor, Tamron and Kenko are less limitting in that respect, although AF will depend on the lens used.
yeah, i heard the old canon 80-200 f2.8 L had a rear element that was placed at the very rear extreme of the lens, and because of that it wasn't compatible with their TC's. the newer 70-200's design pushed the rear element forward a bit to make room for the TC protrusion
cwphoto
06-20-2006, 08:15 AM
Hey, I felt slammed...most answers amounted to "what's the point?"...instead of trying to give a technical explanation...but it's no biggy...
All Coldy did was explain the difference between EF and EF-S - strictly speaking he didn't answer the question of whether an EF-S TC would be possible or not...:rolleyes:
coldrain
06-20-2006, 08:39 AM
All Coldy did was explain the difference between EF and EF-S - strictly speaking he didn't answer the question of whether an EF-S TC would be possible or not...:rolleyes:
It would be possible. There... answered ;)
Teleconvertors from Soligor, Tamron and Kenko are less limitting in that respect, although AF will depend on the lens used.Right...so why couldn't there be a teleconverter from Soliger, Tamron or Kenko that worked with the third party APS-C lenses? I guess that's really a different question and the one that I should have originally asked! :o
EDIT: I see you answered it before I typed this! Thanks...
My original assumption that the Sigma and Tamron APS-C lenses used the Canon EF-S design was incorrect and I understand that now...
All Coldy did was explain the difference between EF and EF-S - strictly speaking he didn't answer the question of whether an EF-S TC would be possible or not...:rolleyes:Hey, at least he made an effort...:rolleyes:
DonSchap
06-20-2006, 09:17 AM
Canon EF-S lenses have a 3/16" more of projection into the lens mounting than EF's or Di II lenses.
Di II do not have this projection and mount identically to the standard EF-style lens.
Also, on Canon EF-S lenses, you will note a "white square" alignment mark on the lens, which aligns differently on the camera body. The APS-C sensor style camera body has a corresponding white square on the lens mounting ring.
EF's and Di IIs use the "red circular" dot, on the lens collar, which aligns with the red circle mark on the lens mounting ring.
Why they use these two different alignments still eludes me, but I'm certain they had a reason. I suspect it was so that you could not mount Canon EF-S lenses on a full sensor style camera. I have never tried this... it's just a guess. :eek:
As far as mating an EF-S lens to a standard T/C... even with a Bowers 2x... it is physically impossible.
In the meantime, you may want to consider an extension tube. It might work... I don't use them, so I cannot say. But, what I will suggest is that you plop down the $225 and get a Canon EF 28~105 f/3.5-4.5 II USM and then you can use that T/C of yours. This lens alone will offer this double range, give you more light in the process and comes at a really great price. A kit lens is still a kit lens... rather useless to grow on.
Bottom line: You can't make a silk purse out of a sow's ear.
Canon EF-S lenses have a 3/16" more of projection into the lens mounting than EF's or Di II lenses.
Di II do not have this projection and mount identically to the standard EF-style lens.
Also, on Canon EF-S lenses, you will note a "white square" alignment mark on the lens, which aligns differently on the camera body. The APS-C sensor style camera body has a corresponding white square on the lens mounting ring.
EF's and Di IIs use the "red circular" dot, on the lens collar, which aligns with the red circle mark on the lens mounting ring.
Why they use these two different alignments still eludes me, but I'm certain they had a reason. I suspect it was so that you could not mount Canon EF-S lenses on a full sensor style camera. I have never tried this... it's just a guess. :eek:
As far as mating an EF-S lens to a standard T/C... even with a Bowers 2x... it is physically impossible.
In the meantime, you may want to consider an extension tube. It might work... I don't use them, so I cannot say.
Don and Coldy:
So wait...am I getting this right? I can just use an existing Kenko (or other third party) EF-mount telecoverter with a Sigma or Tamron APS-C lens? And it will fit? Forget about focusing, vignetting, light fall-off, distortions and all that other stuff for now...it will fit?
DonSchap
06-20-2006, 09:37 AM
YES!
In three words: Yes, it will.
This is a TAmROn 18-200mm f/3.5-6.3 XR Di II LD with a Bower 2x T/C on the end of it.
13096
Please note the red dots... on the Di II lens.
Canon EF-S lenses have a 3/16" more of projection into the lens mounting than EF's or Di II lenses.
Di II do not have this projection and mount identically to the standard EF-style lens.
Also, on Canon EF-S lenses, you will note a "white square" alignment mark on the lens, which aligns differently on the camera body. The APS-C sensor style camera body has a corresponding white square on the lens mounting ring.
EF's and Di IIs use the "red circular" dot, on the lens collar, which aligns with the red circle mark on the lens mounting ring.
Why they use these two different alignments still eludes me, but I'm certain they had a reason. I suspect it was so that you could not mount Canon EF-S lenses on a full sensor style camera. I have never tried this... it's just a guess. :eek:
As far as mating an EF-S lens to a standard T/C... even with a Bowers 2x... it is physically impossible.
In the meantime, you may want to consider an extension tube. It might work... I don't use them, so I cannot say. But, what I will suggest is that you plop down the $225 and get a Canon EF 28~105 f/3.5-4.5 II USM and then you can use that T/C of yours. This lens alone will offer this double range, give you more light in the process and comes at a really great price. A kit lens is still a kit lens... rather useless to grow on.
Bottom line: You can't make a silk purse out of a sow's ear.
So then, the Tamron allows you to attempt to mount a DI II lens onto a non-APC body? I believe the FF bodies only have the red dot. It's a precaution to prevent damage from people who unwittingly try it.
An extension tube severely changes the behaviour of the lens for better macro shots. I have also never used one, but I can imagine it severly alters its behaviour for normal shooting.
YES!
In three words: Yes, it will.
This is a TAmROn 18-200mm f/3.5-6.3 XR Di II LD with a Bower 2x T/C on the end of it.
13096
Please note the red dots... on the Di II lens.
Have you shot with that combo? Are the results usable?
DonSchap
06-20-2006, 10:02 AM
I suppose a person could mount their Di II lens on a full sensor camera. Obviously, there will be vignetting at some settings and perhaps none at others.
Di II lenses are usually well marked for their planned use (APS-C designed) and people owning full-size sensor cameras (in that price range - $3000+) are "usually" aware of the differences. I know that can be a dangerous assumption, but there is supposed to be an educational level expectation that comes with the bigger bucks. :eek:
A Di II lens will not damage a full-sized sensor camera... the opposite cannot be said for an EF-S lens on a full-sized sensor camera. If you could actually hang an EF-S lens on it, I'm pretty sure that mirror would take an awful beatin'. :(
DonSchap
06-20-2006, 10:11 AM
Have you shot with that combo? Are the results usable?
Due to the 2-full stops of light loss through the 2x T/C, you effectively have no AF after 105mm indicated on the lens.
With a 1.4x T/C, you can get to about 150mm indicated, before AF failure, as it only loses one f-stop of light throughout. Once the lens hits f/6.3 aperture, indicated in the metering panel... AF fails with a T/C, because you are effectively at f/8 or more (end of the line for AF on a XT/20D/30D).
So, if you are planning on using this combination, I highly recommend adding a manual focusing screen. (see link below)
http://www.katzeyeoptics.com/item--Katz-Eye-Focusing-Screen-for-the-Canon-20D--prod_20D.html
Thanks Don!
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Also, I want to take this opportunity to apologize to all the other responders who I thought were slamming me. I now realize it was my own ignorance that resulted in the responses I recieved. And because of my ignorance, I didn't ask the question in the right way. Even without realizing that the EF-S lenses had a significant design difference, if I had thought about the red dot vs. white square for a moment, I would have understood that the third party APS-C lenses would work with a standard tele-extender. But that's not what I asked...because I made a STUPID MISTAKE born out my ignorance. Sorry again...
Since I haven't had my Sigma off since March, I forgot that it even had the red dot and was really just an EF mount...DOH!!!
cwphoto
06-20-2006, 04:40 PM
Thanks Don!
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Also, I want to take this opportunity to apologize to all the other responders who I thought were slamming me. I now realize it was my own ignorance that resulted in the responses I recieved. And because of my ignorance, I didn't ask the question in the right way. Even without realizing that the EF-S lenses had a significant design difference, if I had thought about the red dot vs. white square for a moment, I would have understood that the third party APS-C lenses would work with a standard tele-extender. But that's not what I asked...because I made a STUPID MISTAKE born out my ignorance. Sorry again...
Since I haven't had my Sigma off since March, I forgot that it even had the red dot and was really just an EF mount...DOH!!!
Don't let it happen again!:p :D
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