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Why the aversion of front mounted TCs? They are better.

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My take on the debate is purely a practical one. It's much the same as the debate between using prime lenses vs using zooms. A rear-mounted TC is much more versatile because you can use it with most (if not all) available lenses for the mount. If properly mated to a certain lens, a front-mounted TC would probably offer better quality, but it would perform best for that one lens.

Bill
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ljfinger said:
Darrell Spreen said:
This is not correct and you can prove it to yourself without even
taking a picture. As long as the sensor (any size) is in the focal
plane, it uses all of the lens diameter.
Click to expand...
Theoretically, that's true. What we're talking about is the
lower-left image in figure 2.

http://www.vanwalree.com/optics/vignetting.html
Click to expand...
I'm not sure what you think that image proves--there's no way tell from the picture alone what portion of the image plane the white seen through the lens represents. Plus a fast lens with a grossly undersized front element is a best-case for your theory anyway. It may well use all of its too-small front element even for the very center. Doesn't prove that that occurs in all cases. Try the same thing with a quality slow wide.
 
Daniella said:
that's a web size image, post a 100% crop wide open maybe? and of
a subject with possible CA problem. then you will see what I am
talking about.
Click to expand...
....but what you're talking about doesn't seem to be a problem with the Raynox. Since you were describing your problems wth the Oly TCON17, however, you would have to do the sample -- and I guess you sold the TCON, so it's hard to evaluate the problems you had.

Darrell
http://members.aol.com/pixbydg/still/life.html
 
FF (35mm format) gives a wider field of view than an APS sized sensor, so to go from that to the narrower field of view (of APS) you would need a teleconverter which would result in less light reaching the sensor. But I bet you don't even read these replies. Prove me wrong. If you need more convincing look up the focal length multiplier (note multiplier, not divisor) which is stated for all DSLR cameras reviewed on this website.
 
Darrell Spreen said:
Daniella said:
that's a web size image, post a 100% crop wide open maybe? and of
a subject with possible CA problem. then you will see what I am
talking about.
Click to expand...
....but what you're talking about doesn't seem to be a problem with
the Raynox. Since you were describing your problems wth the Oly
TCON17, however, you would have to do the sample -- and I guess you
sold the TCON, so it's hard to evaluate the problems you had.
Click to expand...
well, I don't really care for front mounted TC. I have a good rear TC that works much better, so I have no intention of returning to front mounted.

I did try the Raynox at some point but it was even worse than the Tcon17.
Member said:
Darrell
http://members.aol.com/pixbydg/still/life.html
Click to expand...
--



http://www.pbase.com/zylen

'Never argue with an idiot, they drag you down to their level and beat you with experience'
 
mdg said:
FF (35mm format) gives a wider field of view than an APS sized
sensor, so to go from that to the narrower field of view (of APS)
you would need a teleconverter which would result in less light
reaching the sensor. But I bet you don't even read these replies.
Prove me wrong. If you need more convincing look up the focal
length multiplier (note multiplier, not divisor) which is stated
for all DSLR cameras reviewed on this website.
Click to expand...
 
For reasons outlined in other messages on this topic. But you clearly aren't interested in learning why, only trolling.
 
Darrell Spreen said:
Daniella said:
I did try the Raynox at some point but it was even worse than the
Tcon17.
Click to expand...
I think it's clear you just couldn't get a match to your basic
lens. Raynox has made many tele attachments -- the 1540 is a brand
new formulation. It's interesting that I stopped using rear TC's
after trying two different brands because of very poor edge
performance. To each his own.
Click to expand...
if you have one you are welcome to post 100% crop of it, center and corner.
Member said:
Darrell
http://members.aol.com/pixbydg/still/life.html
Click to expand...
--



http://www.pbase.com/zylen

'Never argue with an idiot, they drag you down to their level and beat you with experience'
 
mdg said:
For reasons outlined in other messages on this topic. But you
clearly aren't interested in learning why, only trolling.
Click to expand...
It's not remotely impossible, it's been done! As mentioned in other messages in this topic. But you're clearly not interested in learning, only trolling.

There's nothing terribly special optically about making a 0.5x rear converter vs. making a 2x.

There are huge, probably insurmountable, physical problems with making it work as an add-on to an existing system, especially an SLR system. Let's see, you've got elements that just clear the mirror, now you've got to shoehorn another 5-7 elements in there AND move the existing elements closer to the sensor. Bzzzzzzt.

But built into the body as an integral part of the system, as in the Nikon E2/E3 cameras, it works. Yeah, performance wasn't great, most likely because even with the advantage of designing the system around it they couldn't find room for as many elements as they needed for decent correction. But "was kinda lame in the one well-known application" is far, far different from "isn't possible"
 
...that Jurgen Larson keeps referring to it as a "TC" that concentrates light. As you said, it's a wide converter, or whatever, but not a TC. You can probably call it a "negative extender", but a TC, I don't think so.
Roger Krueger said:
mdg said:
For reasons outlined in other messages on this topic. But you
clearly aren't interested in learning why, only trolling.
Click to expand...
It's not remotely impossible, it's been done! As mentioned in other
messages in this topic. But you're clearly not interested in
learning, only trolling.

There's nothing terribly special optically about making a 0.5x rear
converter vs. making a 2x.

There are huge, probably insurmountable, physical problems with
making it work as an add-on to an existing system, especially an
SLR system. Let's see, you've got elements that just clear the
mirror, now you've got to shoehorn another 5-7 elements in there
AND move the existing elements closer to the sensor. Bzzzzzzt.

But built into the body as an integral part of the system, as in
the Nikon E2/E3 cameras, it works. Yeah, performance wasn't great,
most likely because even with the advantage of designing the system
around it they couldn't find room for as many elements as they
needed for decent correction. But "was kinda lame in the one
well-known application" is far, far different from "isn't possible"
Click to expand...
 
...who keeps posting one line contradictions without even bothering to read what's being written in response. But you're welcome to form your own opinion.

For the record, my position has always been that TELEconverters which amplify light are physically impossible (a view shared by others on this forum). It has not been done - the Nikon E2/E3 featured a WIDE converter.

Jurgen has driven the discussion round in circles, first he claimed he meant decreasing focal length, when the original post was about teleconverters, then he claimed going from FF -> APS would decrease focal length. Then he just posted the original question (about light amplifying teleconverters) again!
Roger Krueger said:
THANK YOU! Love being right. (nt) NEW Jurgen Larssson 2 days ago
You aren't. NEW ljfinger 2 days ago
ehhrm.. topic was DECREASING fl.. Keep up.
Click to expand...
no... the topic was teleconverters, not wide angle converters
Roger Krueger said:
sure, decreasing fl. in the process (nt)
Click to expand...
teleconverters increase fl
Roger Krueger said:
yes, but FF -> APS would decrease it
Click to expand...
no! FF -> APS would increase it
Roger Krueger said:
I repeat: How about a FF-> APS TC to intensify light? (Nt)
Click to expand...
I repeat: physically impossible

Now I've realised he's re-enacting the argument sketch from Monty Python:

http://www.youtube.com/watch?v=teMlv3ripSM
http://www.mindspring.com/~mfpatton/sketch.htm (text)
 
saynomore said:
Roger Krueger said:
mdg said:
For reasons outlined in other messages on this topic. But you
clearly aren't interested in learning why, only trolling.
Click to expand...
It's not remotely impossible, it's been done! As mentioned in other
messages in this topic. But you're clearly not interested in
learning, only trolling.

There's nothing terribly special optically about making a 0.5x rear
converter vs. making a 2x.

There are huge, probably insurmountable, physical problems with
making it work as an add-on to an existing system, especially an
SLR system. Let's see, you've got elements that just clear the
mirror, now you've got to shoehorn another 5-7 elements in there
AND move the existing elements closer to the sensor. Bzzzzzzt.

But built into the body as an integral part of the system, as in
the Nikon E2/E3 cameras, it works. Yeah, performance wasn't great,
most likely because even with the advantage of designing the system
around it they couldn't find room for as many elements as they
needed for decent correction. But "was kinda lame in the one
well-known application" is far, far different from "isn't possible"
Click to expand...
Click to expand...
 
mdg said:
For the record, my position has always been that TELEconverters
which amplify light are physically impossible (a view shared by
others on this forum). It has not been done - the Nikon E2/E3
featured a WIDE converter.

Jurgen has driven the discussion round in circles, first he claimed
he meant decreasing focal length, when the original post was about
teleconverters, then he claimed going from FF -> APS would decrease
focal length. Then he just posted the original question (about
light amplifying teleconverters) again!
mdg said:
THANK YOU! Love being right. (nt) NEW Jurgen Larssson 2 days ago
You aren't. NEW ljfinger 2 days ago
ehhrm.. topic was DECREASING fl.. Keep up.
Click to expand...
no... the topic was teleconverters, not wide angle converters
mdg said:
sure, decreasing fl. in the process (nt)
Click to expand...
teleconverters increase fl
mdg said:
yes, but FF -> APS would decrease it
Click to expand...
no! FF -> APS would increase it
mdg said:
I repeat: How about a FF-> APS TC to intensify light? (Nt)
Click to expand...
I repeat: physically impossible

Now I've realised he's re-enacting the argument sketch from Monty
Python:

http://www.youtube.com/watch?v=teMlv3ripSM
http://www.mindspring.com/~mfpatton/sketch.htm (text)
Click to expand...
 
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