[chaos83]

Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here.

---

i recently got the vivitar pka version, and i tried using it with a k200d and an FA 50mm 1.4. after putting it all together, the aperture doesnt show on the camera. i should be able to control the aperture on the camera on A setting right?

left the lens on A mode and i cant seem to change the aperture via the dial.

strangely enough, when i took several pics in A mode, the exif shows the aperture as 1.4 open wide. i know it meters since the camera still stays in multi segment metering instead of switching to spot metering.

could i have a defective example where the aperture contacts dont work and yet the metering works?

[Egg Salad]

Is there a way to remove the lenses from the converter without destroying them?
It doesn't look like it's just screwed in but I didn't want to break it so I didn't try.

Unsurprisingly the results I get when using lenses reversed are better than with this converter. But because of its extension feature it would probably make a great variable extension tube.


To answer the question before: I sometimes get the same error but with my self-made A-lenses. It doesn't sisplay the aperture but still in the EXIFs there is aperture information. I don't think your converter is broken but not all contacts seem to make contact with the lens or camera.

[jerrymouse]

i recently got the vivitar pka version, and i tried using it with a k200d and an FA 50mm 1.4. after putting it all together, the aperture doesnt show on the camera. i should be able to control the aperture on the camera on A setting right?

left the lens on A mode and i cant seem to change the aperture via the dial.

strangely enough, when i took several pics in A mode, the exif shows the aperture as 1.4 open wide. i know it meters since the camera still stays in multi segment metering instead of switching to spot metering.

could i have a defective example where the aperture contacts dont work and yet the metering works?

Try this:
https://www.pentaxforums.com/forums/493608-post21.html

[avsroy]

Thanks very much! I have a Vivitar 2x Macro (PK/A version) that now works perfectly - thanks to the detailed repair guide here. Greatly appreciate!

[solar1]

For those in the know, does this compare quality wise to the Vivitar? This is not listed as Macro though, too bad!

http://cracklecdn-zoovy-2.simplecdn.net/v1/img/goshotcamera/W423-H320-Bfffff...elecon_mc7.jpg

2x Teleconverter Lens for Pentax Digital SLR K200D KX - eBay (item 120541336802 end time May-08-10 21:35:18 PDT)

[bobmaxja]

I am a lucky one today.
Somebody was selling school equipment
They were selling a Pentax K1000 including a Pentax SMC A 50mm f2 + 3 teleconverter
I dont care too much about the K1000 and lens but for the TC
2 Vivitar 2x Macro focusing P/K-A R-P/K made in japnin evry good condition and a Tamron F AF 2xPz-AF BBAR MC7
This Tamron is the same as the Kenko in the database. AF is perfect
This is the best buy I never made.
I also do have a Vivitar 2x -22 Made in Japan

Now I have too much of them and need to decideIf I will keep the Vivitar's

[elliott]

I just picked one of these up at a thrift store, I'm quite happy with it so far. I was wondering if anyone has experimented with adding extension tubes to this teleconverter. Would it be better to place one between the teleconverter and body or between the teleconverter and lens?

[Not a Number]

I would think optically it would be better to put the tubes between the lens and the TC. For physical reasons (see below) it might be better to put the tubes between the body and the TC. The optics in the TC will have their own flaws and putting the tubes after the TC would (I'm guessing) magnify those flaws.

A scan of the user manual for this TC can be found here:

Page 75

Please note that the helicoid isn't very sturdy so the cautions on usage with heavier/longer lenses should be heeded.

[elliott]

Please note that the helicoid isn't very sturdy so the cautions on usage with heavier/longer lenses should be heeded.

Yeah, I realized that when I put my Vivitar Series 1 70-210mm on it, unless you're supporting the lens it is very hard to turn.

[jpzk]

Has anyone tried either of the two "TC's"** with a lele lens such as the DA*300/4 and would post some results?

** Kenko 2x 1:1 Macro Teleplus MC7 converter
** Vivitar 2X Macro Focusing Teleconverter (the P/K-A R-P/K type)

JP

[pacerr]

. . . adding extension tubes to this teleconverter.

The short answer:

** If we place the extension device ahead of the optical elements in the TC, the optics must deal with a "broader" (fuzzier?) distribution of the color characteristics in each light ray. If we place the optics first in the path, the extension device will effectively enlarge the area of any chromatic aberrations present at the sensor.

If YOU can't tell the difference between the various methods -- it doesn't make much difference which one you choose. Until you count the cost of the tools, that is. In any case, LBA will ultimately demand the most expensive, prime macro lens(es) you can afford so it's a mute point anyway.

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

A longer explanation, and perhaps a little simplistic, but generally applicable.

We're dealing with two primary characteristics of light. Imagine a "normal" light ray as narrow in diameter as you care to imagine -- but for discussion purposes let's use one degree. And we're not talking about a coherent, parallel beam such as usually attributed to a laser, just a plain ol' sunbeam as applied to photography.

** White light is composed of all colors. Colored light "filters out" certain colors/wave lengths. Each color is defined by a certain wave length frequency (or Kelvin temperature). Each discrete wave length is refracted (bent) differently as it passes through a medium such as optical glass or water. Remember the physics lab demonstration of sun light through a prism? A simple spherical lens works much the same way, bending the different "colors" present in unique patterns according to the lens' properties.

A complex, aspherical lens formula composed of complex surface curvature and/or multiple elements with different refractive properties tries to restore all "colors" within a ray to a common point of focus on the sensor surface to minimize color aberrations. (Keep in mind also that the plane of perfect-focus is actually a curved surface and the sensor is flat.)

Lens cost and weight are proportional to the design complexity. All glass in the light path extracts a certain price in the amount of illumination striking the film/sensor. That penalty in "lens speed" can only be corrected by adding ever larger, more expensive and heavier glass elements or wider apertures which present additional refractive problems. Lens coatings normally affect reflection and transmission properties, not refraction.

** Back to our one-degree light ray. The radial arc-width of a one-degree ray is wider at one foot than at one inch. Of course, we can attempt to narrow the beam by placing optical glass in the light path but that presents issues of its own -- e.g., refraction. Narrow the beam too much and we end up with a wide angle converter rather than a tele-converter.

Shine a flash light at an electrical wall switch representing the film/sensor at such a distance the light circle just covers the switch plate. Add a small margin to avoid as much optical edge distortion as economically feasible and you have a good approximation of the design properties of a typical lens with no TC or extension device.

Now back away from the wall until the light circle is twice as big as the wall plate. There's your normal lens with an extension tube or TC effect. There's no more light photons from the flashlight but that energy is spread over a MUCH larger AREA. (Pi x R squared, etc). That accounts for the necessary exposure correction with extension tubes. Same effect occurs if we make the sensor smaller as with the APS-C sensor compared to the 135 film format - we capture less of the available image within the circle of light.

The effect didn't optically change the image, it only filled the film/sensor with a smaller portion of the available image. Again, without expensive optical correction, the "perfect" plane of focus is a curved surface projected upon a flat sensor. A flat-field lens optical formula attempts to correct this but presents other compromises.

Replace the extension with an optical converter. Instead of moving the lens (flashlight) farther away from the sensor to enlarge the circle, it bends the light rays with a proportional effect on circle-size and the optically induced aberrations. An expensive glass formula MAY minimize those effects. We now have to account for not only that Pi x R squared lose of light but the optical penalty as well. Same result, different means, different price.

Acutance and resolution suffer as the radial dispersion of each discrete ray of light exceeds the capture area of each discrete sensor (pixel? film grain?) when the lens moves away from that sensor.

** Since the radial arc expansion of a projected light ray is a fixed physical property, the available variable will be the properties of the optics involved and how well or poorly they play with the combination of the sensor resolution, the lens' inherent optical aberrations and the target distance.

So, assuming you actually have both devices available, why not avoid all the aggravation and just do your own practical test then choose the method with the best result? Practical experimentation using digital photography gear provides the advantage of essentially instantaneous results, it's virtually free, and it produces the best results you can achieve with the tools actually at hand.

If you've yet to acquire close-up/macro accessories, first try the non-optical path with extension rings and lens reversal adapters and see if it suits your needs -- it's a lot cheaper. And dare I suggest that close-up diopter filters may fill the need quite nicely and have many advantages in the field.

H2

A question was asked in another forum whether a TC could ever actually improve a lens' optical performance. Well, perhaps by a serendipitous combination of unique properties -- but I'm still waiting on those millions of typewriter-equipped monkeys to duplicate Shakespeare too.

[Nesster]

Instructions here: The Chens: The User's Review: Vivitar 2X Macro-Focusing Teleconverter, Released in 1981

[edri]

This macro teleconverter from Sigma operates on the same principle as the Vivitar teleconverter? There is no marking scale on the Sigma, as seen on the Vivitar. Optical formula is the same?