Teleconverter comparison II

Following up on a previous thread, I again compare the Kenko Pro line. Admittedly, there is some residual chromatic aberration on brighter backlit objects, but if you need the extra range, I still think the Kenko KUT 300 Hi is a good value. Other's disagree, but hey, this is America

The Kenko KVC200 (2x) and the Olympus B300 (2x) are odd couples designwise. The former weighs 285 gm, 52mm long, 4 elements in 4 groups, objective is 66mm dia. The B300 weighs 265gm, 77mm long, 5 elements in 3 groups, objective is 70mm. Optically they are virtually identical IMO (air space is also considered an element in optic design), with the each consuming considerable real estate in the view finder obstruction department. Comparitively the KUT300 is light at 210gm. For a camera like the C2100, the extra length and weight of the B300 is more stressful on the camera IMO. The KUT300 has 3 elements in 3 groups. So you pays your money and takes your choice. The following is a C2000 photo of each, ISO 100, at f/5.6, halogen lighting; yes, the OLD Girl still has life:



Ciao...Barry

Barry,

I always feel like I've gained some understanding from your posts.

Could you expand a little on your observation the B300 and KVC200 are "odd couples"? Are they unusual in optical terms?

Also, I believe I remember a comment you might have made in a previous post to the extent that by putting a teleconverter in front of your lens, you have actually replaced your objective with that of the teleconverter. Might that be used to advantage by putting a B-300 in front of another teleconverter on my 2100? My reasoning would be that, even if another teleconverter has a smaller diameter lens, the large diameter of the B300 as objective is what governs, hence I might reduce the vignetting, compared to a single 3X device which would in all likelihood have a smaller objective than the B300? In other words, might two tandem 1.7X converters, with the front one being the B300, be better than a single 3X lens of lesser quality (I'm not sure if that means smaller diameter, less precise optics, or both) ? I apologize if this is a silly optical question. My background is not optical design.

Thank you for your comments.

Regards,

DG

Barry Carter said:

Following up on a previous thread, I again compare the Kenko Pro
line. Admittedly, there is some residual chromatic aberration on
brighter backlit objects, but if you need the extra range, I still
think the Kenko KUT 300 Hi is a good value. Other's disagree, but
hey, this is America

The Kenko KVC200 (2x) and the Olympus B300 (2x) are odd couples
designwise. The former weighs 285 gm, 52mm long, 4 elements in 4
groups, objective is 66mm dia. The B300 weighs 265gm, 77mm long, 5
elements in 3 groups, objective is 70mm. Optically they are
virtually identical IMO (air space is also considered an element in
optic design), with the each consuming considerable real estate in
the view finder obstruction department. Comparitively the KUT300
is light at 210gm. For a camera like the C2100, the extra length
and weight of the B300 is more stressful on the camera IMO. The
KUT300 has 3 elements in 3 groups. So you pays your money and
takes your choice. The following is a C2000 photo of each, ISO
100, at f/5.6, halogen lighting; yes, the OLD Girl still has
life:



Ciao...Barry

Click to expand...

My background is not optical design either, but optics and telescope making is a life long hobby. Using the classic wavefront theory of light, anything thing thing you put in front of your camera will degrade the image if not null optically. Even a hot day or cool evening can create unsteady air which can degrade an image. Filters have to be of good flat plane parallel glass and be multi-coated, otherwise the will create flare, ghost images, and loss of light throughput. When you use a teleconverter (which is really a small low power telescope) in front of the digital camera, the teleconverter becomes the principle lens. If you just understand this you're OK. Ideally, if you want to hook up a camera afocally, the less zoom a camera has the better. No zoom lens is as good as a lens designed for a fixed focal length. The power would come strictly from the teleconverter.

The following shot (not mine) was taken with an Olympus D490 attached to a 3.5" Questar. I don't know how he did it, because I don't have anything that looks this good, and it is a straight vanilla shot. So technique in this business counts more than tossing big bucks at it IMO



The problem with stacking lenses is the image degradation multiples quickly. The C2100 has too many optical elements to be adding more. Once you get beyond photographic infinity, you don't need all that glass! That's why a good spotting scope will outperform a C2100 on birds anyday IMO when attached to a lowly D490 say. Long focal lengths are designed for long distance shooting (> 40 ft say) IMO. Hope this helps.

Ciao...Barry

David Grove said:

I always feel like I've gained some understanding from your posts.

Could you expand a little on your observation the B300 and KVC200
are "odd couples"? Are they unusual in optical terms?

Also, I believe I remember a comment you might have made in a
previous post to the extent that by putting a teleconverter in
front of your lens, you have actually replaced your objective with
that of the teleconverter. Might that be used to advantage by
putting a B-300 in front of another teleconverter on my 2100? My
reasoning would be that, even if another teleconverter has a
smaller diameter lens, the large diameter of the B300 as objective
is what governs, hence I might reduce the vignetting, compared to a
single 3X device which would in all likelihood have a smaller
objective than the B300? In other words, might two tandem 1.7X
converters, with the front one being the B300, be better than a
single 3X lens of lesser quality (I'm not sure if that means
smaller diameter, less precise optics, or both) ? I apologize if
this is a silly optical question. My background is not optical
design.

Thank you for your comments.

Regards,

DG

Barry Carter said:

Following up on a previous thread, I again compare the Kenko Pro
line. Admittedly, there is some residual chromatic aberration on
brighter backlit objects, but if you need the extra range, I still
think the Kenko KUT 300 Hi is a good value. Other's disagree, but
hey, this is America

The Kenko KVC200 (2x) and the Olympus B300 (2x) are odd couples
designwise. The former weighs 285 gm, 52mm long, 4 elements in 4
groups, objective is 66mm dia. The B300 weighs 265gm, 77mm long, 5
elements in 3 groups, objective is 70mm. Optically they are
virtually identical IMO (air space is also considered an element in
optic design), with the each consuming considerable real estate in
the view finder obstruction department. Comparitively the KUT300
is light at 210gm. For a camera like the C2100, the extra length
and weight of the B300 is more stressful on the camera IMO. The
KUT300 has 3 elements in 3 groups. So you pays your money and
takes your choice. The following is a C2000 photo of each, ISO
100, at f/5.6, halogen lighting; yes, the OLD Girl still has
life:



Ciao...Barry

Click to expand...

Click to expand...

If you look at the designs of the two, you'll notice how much longer the B300 is. I suspect the B300 adds another negative lens element to expand the focal length of the "weak" front objective. The Kenko has the classic Galilean design with the 2-element front and the negative 2-element rear. The design of the Kenko front element is a longer focal length and hence no need for another element. However the longer throw of the negative element in the B300, provides a narrower light cone, which will tend to mask the CA present. Besides the B300 is designed for a 24x36mm film, which is 28x more area than a 1/2 CCD. It works suprising well, given that the IS-series sucks as far as performance is concerned IMO. It is big, off-balance, and optically slow. Olympus designed the B300 to be used at max of 170mm with the IS-series. Hence when you extract over 600mm from it on a C2100, it seems to hold up well. OTOH, the Kenko VC200 is designed for video, which is basically low-res (if you are not convinced, drag out that old 35mm slide projector and see what REAL quality and resolution we're missing). If you pour too much magnification on the VC200, the CA will be evident. That is why the Kenko's work better with the C2000-C3040 series camera, where the zoom max is 3x. As I said before, one usually buys a zoom lens to AVOID using add-ons I'd think. I believe in the KISS principle of design. Keep it simple and use a tripod if you want great pictures with long lenses.....

David Grove said:

Barry,

I always feel like I've gained some understanding from your posts.

Could you expand a little on your observation the B300 and KVC200
are "odd couples"? Are they unusual in optical terms?

Click to expand...

Thanks Barry for the enlightement. I use a B300 on my 2100 and find it big and bulky but it does produce very good pics. I haven't had the chance to compare it to another tele yet. I shoot a lot of wildlife and reaching out there really helps, even though I know I sacrifice a bit of sharpness.

Any thoughts on strapping a EagleEye Optizoom 5x or CrystalVue Optics
SharpShooter 8x32 tele on a 2100?

I eventually want to mate up the 2100 camera to a good spotting scope like a Kowa.

Jesse

Barry Carter said:

David Grove said:

Barry,

I always feel like I've gained some understanding from your posts.

Could you expand a little on your observation the B300 and KVC200
are "odd couples"? Are they unusual in optical terms?

Click to expand...

Click to expand...

Thank you for both your replies, Barry.

Well, maybe I need to buy another (simpler lens) camera to use for looong lenses, and then hang an EE (or other stuff) on it.

Regarding my earlier comment about "back to back" teleconverters, what I had in mind was something like this:

http://members3.clubphoto.com/larry255900/b300_Nikon_TC-E2_B-300_Combo_Info/

Do you have any thoughts on the concept? I'm wondering what the principles might be that would guide the selection of components. For instance, does the order make a difference? Is the B300 a particularly good choice for a front component of a pair? (Maybe it depends on what the "back end" lens might be.) What principles might apply to choosing among one of the Kenkos or the Nikon TCE2, or even some other candidate, for the back end? (Previous question assumes B300 for front, but maybe there's something better?)

And, if I'm going to piggyback lenses like this, what about using the EagleEye as a back end. It seems like some have reported success with this.

Per your previous posts, I understand that the 2100 is not a good candidate for these combinations.

Regards,

David Grove

I forgot one

What about the concept of "piggyback", in general. Would it be more desirable to achieve a certain multiplication factor, say 3X, by a single teleconverter, rather than tandem (approx.) 1.7X. Probably depends on relative quality of optics, right? I would guess that one could always design a single lens system that would outperform two tandem systems, but that's just my uninformed guess.

Then there is the real world of what is actually available (or affordable!). It is conceivable to me (but I have no knowledge or experience) that I might be able to assemble from available products a tandem 3X system that costs a little more than a single 3X system, but might outperfom it. That would be assuming that the individual 3X in question would be at the same general price point as the two 1.7X components. In other words, I'm saying to that I would compare the tandem unit of, say, two Kenkos or a Kenko and Oly to the 3X Kenko, not a Century Optics 3X.

DG

David Grove said:

Thank you for both your replies, Barry.

Well, maybe I need to buy another (simpler lens) camera to use for
looong lenses, and then hang an EE (or other stuff) on it.

Regarding my earlier comment about "back to back" teleconverters,
what I had in mind was something like this:

http://members3.clubphoto.com/larry255900/b300_Nikon_TC-E2_B-300_Combo_Info/

Do you have any thoughts on the concept? I'm wondering what the
principles might be that would guide the selection of components.
For instance, does the order make a difference? Is the B300 a
particularly good choice for a front component of a pair? (Maybe it
depends on what the "back end" lens might be.) What principles
might apply to choosing among one of the Kenkos or the Nikon TCE2,
or even some other candidate, for the back end? (Previous question
assumes B300 for front, but maybe there's something better?)

And, if I'm going to piggyback lenses like this, what about using
the EagleEye as a back end. It seems like some have reported
success with this.

Per your previous posts, I understand that the 2100 is not a good
candidate for these combinations.

Regards,

David Grove

Click to expand...

I have found that the C2000 to C3040 camera's with the 3x zooms can be mated to ANY lens that you can visually see an image. If you want to stack lenses, be mindful that the image will be only as good as the Point lens. If the lead sucks, the sucking will be bigtime when the final image reaches the CCD The best corrected lens and the one with the largest objective should be first in line. The larger objective will compensate for some of the light loss passing through all that glass. Good corrected lenses are expensive. If the B300 had aspheric and ED (extra dispersion glass), the lens would probably go for $500! You want quality; open your wallet

David Grove said:

What about the concept of "piggyback", in general. Would it be
more desirable to achieve a certain multiplication factor, say 3X,
by a single teleconverter, rather than tandem (approx.) 1.7X.
Probably depends on relative quality of optics, right? I would
guess that one could always design a single lens system that would
outperform two tandem systems, but that's just my uninformed guess.

Then there is the real world of what is actually available (or
affordable!). It is conceivable to me (but I have no knowledge or
experience) that I might be able to assemble from available
products a tandem 3X system that costs a little more than a single
3X system, but might outperfom it. That would be assuming that the
individual 3X in question would be at the same general price point
as the two 1.7X components. In other words, I'm saying to that I
would compare the tandem unit of, say, two Kenkos or a Kenko and
Oly to the 3X Kenko, not a Century Optics 3X.

DG

David Grove said:

Thank you for both your replies, Barry.

Well, maybe I need to buy another (simpler lens) camera to use for
looong lenses, and then hang an EE (or other stuff) on it.

Regarding my earlier comment about "back to back" teleconverters,
what I had in mind was something like this:

http://members3.clubphoto.com/larry255900/b300_Nikon_TC-E2_B-300_Combo_Info/

Do you have any thoughts on the concept? I'm wondering what the
principles might be that would guide the selection of components.
For instance, does the order make a difference? Is the B300 a
particularly good choice for a front component of a pair? (Maybe it
depends on what the "back end" lens might be.) What principles
might apply to choosing among one of the Kenkos or the Nikon TCE2,
or even some other candidate, for the back end? (Previous question
assumes B300 for front, but maybe there's something better?)

And, if I'm going to piggyback lenses like this, what about using
the EagleEye as a back end. It seems like some have reported
success with this.

Per your previous posts, I understand that the 2100 is not a good
candidate for these combinations.

Regards,

David Grove

Click to expand...

Click to expand...