[el baroda]

Hi. I hope I am in the right forum.

Would somebody please advise how the above converter would perform with the Pentax M 135mm f/3.5 lens? I have a dedicated Vivitar 100mm macro lens but I would like to have a longer working distance since I like taking macros of active insects. With the Pentax 135mm lens plus converter, what would be the magnification and working distance?

Thank you very much.

[Rampage2k5]

I have one and it feels like i loose 2 stops in brightness and a bit of sharpness if your taking stills or if its really bright outside/flash then i would not see issues but
to be honest the Pentax 1.4x and pentax 1.7x are much superior material.

[Not a Number]

I couldn't say what the working distances would be like in macro mode. As a straight TC the close focus distance of the lens would be unchanged.

This TC is optimized to be used with 50mm lenses so I would imagine the more you stray from this focal length the more negative impact on image quality will be.

[el baroda]

I have one and it feels like i loose 2 stops in brightness and a bit of sharpness if your taking stills or if its really bright outside/flash then i would not see issues but
to be honest the Pentax 1.4x and pentax 1.7x are much superior material.

Hi. I intend to use it mainly as a macro and not as a tele converter. Does that make sense?

---------- Post added 11-22-2014 at 01:33 PM ----------

I couldn't say what the working distances would be like in macro mode. As a straight TC the close focus distance of the lens would be unchanged.

This TC is optimized to be used with 50mm lenses so I would imagine the more you stray from this focal length the more negative impact on image quality will be.

I guess I'll have to do more research. Thanks.

[Dewman]

If you're attempting what I think you are, you would be better off buying a set of extension tubes. I recently bought an inexpensive set (some may cringe when they read this!) and I've had great success with them. If memory serves me, they were less than $10.00. The are not the aperture-coupler type, so you would have to set the aperture manually, but here's a sample photo using them. Also, another inexpensive avenue is to buy a reversing ring. I've never tried using it on a 135mm lens, only a 50mm, but it worked splendidly, far beyond my expectations.


Dewman
SW Idaho, USA

[pacerr]

It's not necessarily "optimized" for 50mm but it does have engraved magnification scales for use of a 50mm on the barrel since that was considered a 'normal' lens when it was designed. I've seen printed charts for use with 35 and 100mm lenses and you can calculate custom charts if you wish to make the effort.

The variable device can be stacked with other extension tubes/bellows and converters but the results have diminishing returns for IQ and lose of light.

Most experienced users agree that it performs best when used as a macro/close-up device. It's performance as a 2X tele-converter is typical of and comparable to others of its era - not especially impressive.

IME, the value of continuously variable magnification is negligible in most uses and one or two simple extension rings or close-up filters are much lighter and more convenient in the field. In the lab/studio when dealing with exacting macro enlargement on slide film where PP cropping isn't possible is where I found it most useful. It's lost much of it's unique macro value in the digital PP era but is a fun device to play with.

[el baroda]

If you're attempting what I think you are, you would be better off buying a set of extension tubes. I recently bought an inexpensive set (some may cringe when they read this!) and I've had great success with them. If memory serves me, they were less than $10.00. The are not the aperture-coupler type, so you would have to set the aperture manually, but here's a sample photo using them. Also, another inexpensive avenue is to buy a reversing ring. I've never tried using it on a 135mm lens, only a 50mm, but it worked splendidly, far beyond my expectations.


Dewman
SW Idaho, USA

Excellent image. What I really want is a longer working distance for working with active insects, which I believe is not feasible when using extension tubes. Please correct me if I am wrong here. As I mentioned earlier, I have a dedicated 100mm macro lens but would like to have a working distance greater than what it allows. That's why I asked how the macro focusing teleconverter would perform with a Pentax 135mm which I also have. I hope I am making sense. Thanks.

---------- Post added 11-22-2014 at 03:08 PM ----------

Most experienced users agree that it performs best when used as a macro/close-up device.

This is exactly how I intend to use it. Thanks.

[old4570]

Hi. I hope I am in the right forum.

Would somebody please advise how the above converter would perform with the Pentax M 135mm f/3.5 lens? I have a dedicated Vivitar 100mm macro lens but I would like to have a longer working distance since I like taking macros of active insects. With the Pentax 135mm lens plus converter, what would be the magnification and working distance?

Thank you very much.

With so many converters out there : ?


Double your magnification , 135mm lens becomes 270mm F3.5 becomes F7 ..
I can barely hold 200mm of macro lens steady , @ 250mm there is so much movement I lose about 50% of shots to blur ... The rest are soft , and maybe 10% can be considered good .
Focus distance could increase as well , this is not a bad thing with so much magnification ...
I run a Tamron 90mm BBAR on a 2x Tele converter ( 180mm + Crop factor ) And I consider that the outer limits for magnification and hand held photography .


Now what sort of converter is it ? Fixed or adjustable ? Matched or for a fixed size ( mm )
Do you have a picture of the converter to share ?


And don't let anyone dissuade you from trying a converter , I use them all the time .. ( Truly wonderful little accessories )
A 50mm lens and 2x Tele Macro converter can be had for $100 or less and will compare to some seriously expensive Macro glass when components are carefully chosen .

[Not a Number]

Yes, you can get pleasing results from this TC. I used it until I could afford to pickup some MF macro lenses. The Super-Multi-Coated Takumar f/4 Macro (screw-mount) or Pentax-A 50mm f/1.7 on bellows out-performs this TC with the f/1.7 at roughly the same magnification. Not only do you lose 2 stops of speed from the TC you will also lose f-stops from the extension factor when you use the macro extension. When comparing the results vs the same lens on bellows the chromatic aberration, loss of sharpness and mainly loss of contrast is quite noticeable. Much of this can be reduced in Post-Processing.

The working distance between the lens and subject is impossible to calculate without knowing the optical formula of the lens - you need to know the principal points/planes. The instruction manual says as much. You can download the manual from here:

Page 75

[LensBeginner]

One of the weak points of TC is that they kinda emphasize the distinctive traits of the lenses you use them on.
If a lens is at its sharpest at f/5.6, like a good 50mm prime, then you'll get an optimal image at that aperture, meaning at 100mm f/11(.2) with a 2x TC.
If a lens is slow, and get reasonably sharp at, let's say, f/11, you'll get the most out of it only at f/22, that is, a lot past the limit of diffraction for a modern (16MP, even worse for 24MP) sensor.

[el baroda]

Yes, you can get pleasing results from this TC. I used it until I could afford to pickup some MF macro lenses. The Super-Multi-Coated Takumar f/4 Macro (screw-mount) or Pentax-A 50mm f/1.7 on bellows out-performs this TC with the f/1.7 at roughly the same magnification. Not only do you lose 2 stops of speed from the TC you will also lose f-stops from the extension factor when you use the macro extension. When comparing the results vs the same lens on bellows the chromatic aberration, loss of sharpness and mainly loss of contrast is quite noticeable. Much of this can be reduced in Post-Processing.

The working distance between the lens and subject is impossible to calculate without knowing the optical formula of the lens - you need to know the principal points/planes. The instruction manual says as much. You can download the manual from here:

Page 75

Thank you very much. Your input is very much appreciated. Regards.

---------- Post added 11-23-2014 at 07:03 AM ----------

One of the weak points of TC is that they kinda emphasize the distinctive traits of the lenses you use them on.
If a lens is at its sharpest at f/5.6, like a good 50mm prime, then you'll get an optimal image at that aperture, meaning at 100mm f/11(.2) with a 2x TC.
If a lens is slow, and get reasonably sharp at, let's say, f/11, you'll get the most out of it only at f/22, that is, a lot past the limit of diffraction for a modern (16MP, even worse for 24MP) sensor.

Thanks and regards.

[edri]

I would like to buy such a macro teleconverter in KA mount. But most of those who are KA are KAX actually with the infamous RIcoh pine. AFAIK that Ricoh pin can lead to stuck in the Pentax DSLR body. It would be wise to buy a teleconverter with this Ricoh pin, or I to give up the KA mount and to buy a K mount teleconverter without that dangerous pin. ???