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6x7 Rear Converter 2x

Reviews Views Date of last review
4 20,587 Tue January 9, 2018
Recommended By Average Price Average User Rating
100% of reviewers $172.25 9.25
6x7 Rear Converter 2x


A 6x7 system teleconverter with a grey finish. This converter multiplies the focal length by 2. The light loss is two stops. The converter is more recent than the T6 version and is compatible with all 6x7 lenses except for the leaf shutter lenses. Refer the notes in the table below for caveats regarding lens compatibility.

It supports inner bayonet as well as outer bayonet lenses.

6x7 Rear Converter 2X
©, sharable with attribution
Image Format
Lens Mount
Pentax 6x7
Light Loss
2 stops
6 elements, 4 groups
Mount Variant (Rear)
Inner Bayonet
Mount Variant (Front)
Inner/Outer Bayonet
Weather Sealing
Diam x Length
91 x 71.5 mm
560 g
Production Years
Engraved name: REAR CONVERTER 2X
User reviews
Grey finish.
Designed for lenses 35 mm to 400 mm, but is compatible with all 6x7 lenses except for the leaf shutter lenses.
Causes vignetting with the Shift 75 mm lens and lenses 500 mm and longer.
The converter supports lenses with inner as well as outer bayonets.
Medium-Format Support
Price History:

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Site Supporter

Registered: January, 2009
Location: East Bay Area, CA
Posts: 6,234
Lens Review Date: January 9, 2018 I can recommend this lens: Yes | Price: $220.00 | Rating: 9 

Pros: great IQ and low price
Cons: limited compatibility

I use this (and the 1.4x version) on my 67 M*300/4 adapted to the 645D and 645Z. Thus, my review is specific to that rig and results may vary on other mounts.

I am thrilled at the quality of the magnified images I get with this teleconverter. To answer the age old question of whether it is better to use this 2x TC or to crop the image to achieve same field of view, I can definitely say the TC wins every time. In fact, stacking this TC with the 2.0x also slightly wins in the same situation.

It is a straightforward, capable component, and well worth the price.

These are 100%crops (645Z M*300@f9, ISO1000, 1/640th sec)


this one uses two TC's stacked together:
Shangri-La Revealed

Site Supporter

Registered: October, 2008
Location: Vancouver, Canada
Posts: 6,777

2 users found this helpful
Lens Review Date: July 5, 2014 I can recommend this lens: Yes | Price: $84.00 | Rating: 9 

Pros: Inexpensive, doubles FL of most 6x7 lenses.
Cons: A bit big.

The 67 2X Rear Converter is the third one made for the 6x7 system and second one that supports both inner & outer bayonet lenses.

I bought the 67 2X converter to use on my 6x7 Takumar 400/4 & 600/4 lenses. The 2X converter allows me to extend my 400/4 to an 800mm or my 600/4 to an 1200mm telephoto. This “extended” focal length is perfect to occasionally shoot boats/freighters in the water around Vancouver, at a minimal cost.

The 67 2X converter works with most inner or outer bayonet lenses (see the exception list below), with a two stop light loss penalty. The 67 2X converter is almost twice the size of the 67 1.4X, but they are both close to the same weight. I find the 1.4X slightly sharper than the 2X converter.

Unlike the 67 1.4X converter, the 67 2X converter works on almost all Pentax 6x7 system lenses. Here is the “exception” list:

Pentax 75/4.5 Shift
Pentax 500/5.6
Pentax 800/6.7 ED
Takumar 1000/8 Reflex

The 67 2X converter also can’t be used on the 90/2.8 & 165/4 LS lenses in the leaf shutter mode.

CASE: The 67 2X Rear Converter comes with the S90-140 soft case.

The 67 2X Rear Converter is a great Pentax 6x7 lens accessory that allows you to double the distance of most lenses at a very reasonable price, with just a minor deterioration in picture quality.

Price: I found my 67 2X Rear Converter at KEH and it cost $84.00USD. It was EXC+ condition and came with both caps, I purchased the case separately.

Sample shots taken with the 67 1.4 X & 2X Rear Converters are in my review of the SMC 6x7 Takumar 400/4.

SMC-Pentax-Takumar-6x7-400mm-F4-Lens Review

Registered: February, 2009
Location: Arizona
Posts: 1,164

3 users found this helpful
Lens Review Date: December 5, 2013 I can recommend this lens: Yes | Price: $110.00 | Rating: 9 

Pros: Solid build, good fit, good performance
Cons: None

This converter is a 6 element type consisting of two cemented achromats in the front and an air spaced negative achromat in the rear. It is afocal in that it will not produce an image by itself. Since it is overall, negative, it changes the angle of the light cone to produce a larger image. It turns a non telephoto lens into a telephoto because it magnifies the image from the front group. Using this converter on a lens that is already a true telephoto (300 Takumar, 400 Takumar, 500mm etc.) can cause image degradation. The 300ED and 400 ED are not true telephotos, so using the 2x makes them a telephoto system. Converters not only magnify the image, they magnify aberrations as well. That is why it is critically important that the converter itself does not add any aberrations in its design. The lens elements of this converter appear to be multi-coated. There are 3 positive and 3 negative elements in this converter, so it looks to be a focal system but it does not form an image, so it cannot be. The 3 negative elements have to be high refractive index, high density glass to be able to make this converter afocal. All positive elements are probably low index glass.
The fit onto the camera body and to the lenses is outstanding. The build quality is super ( solid, nice hand grip, rugged). Surprisingly, this 2X fits on every lens I tried it on. The 1.4X is very limited regarding which lenses will fit. Even the 45mm, the two zooms and the 165LS will fit on the 2X. Of course it fits on the outer bay lenses because it has the outer bay tabs.

Shutter shake becomes a major problem with this converter because not only is the distance between the shutter and tripod increased, the added magnification aggravates the situation. Using the 2X on a 400mm or 600 becomes a problem. The use of fast film (400 or 800 speed) is required to increase the shutter speed to get sharp shots. The 600mm + 2x and 1/125 second shutter speed has worked well, although I had to brace the camera body with my hands. Using a 50 speed film and f/45 and long exposures (1-2 sec.) does not work. Shutter vib still blurs the shot.

Since this converter causes a 2 stop loss of light, that 2 stop difference can be used to increase the DOF of shots that were not possible before. As an example-- Let's say you needed to shoot a 200mm at f/45 to get enough DOF for a shot. This could be done with the 105mm plus 2X converter. It becomes a 210mm with f/45. The focal ratio changes because the diaphragm remains unchanged, yet the focal length is lengthened.

This converter allows wide open metering and also allows the lens to be shot wide open without having to stop down manually. In other words, all auto functions of the lenses are maintained. This is the same as the 1.4X converter.

When using it on the 600mm, image degradation can easily be seen at f/4 but sharpens up by f/13 and beyond. Color correction in this converter is outstanding as evidenced by the use of the 400 and 600mm lenses on it. The 2x seems to actually improve the color fringing problem with the 600mm. After seeing the test in Luminous Landscape on this converter, I was expecting to see softness in my slides. Using Velvia 50 and the 165 LS, I shot a scene with fine detail in the middle ground and background. The slides were surprisingly sharp. As sharp as if it were shot from the 45mm. If one is careful in choosing the lens to put in front of the 2X, it can perform well. Putting the 300 Takumar in front is a mistake. Way too much shutter vib.

It is better than I was expecting. Sharp when used with the best lenses. Cheap to own and good enough for publication purposes.
Senior Member

Registered: July, 2008
Location: montreal
Posts: 136

1 user found this helpful
Lens Review Date: May 1, 2011 I can recommend this lens: Yes | Price: $275.00 | Rating: 10 

Pros: Sharp, built to last.
Cons: no

I bought this TC to use it with my Pentax-67 M*400mm/4, sure it's big and heavy (757 gr. with my K-mount adapter, so it's about 730 gr alone.). But i don't mind it's weight since it goes so well with the M*400mm.

Now, how it performs ?
For a TC-2x i was surprised, sure when you start with a great lens it helps a lot.
I find the photos to be sharp from f/5.6 to f/11 at f/4 it's a tad soft to my taste.
I even tried it with 64mm of Extension tubes to take frog shots and the sharpness is very good, you need a good tripod and head with MLU and a cable release with that set-up.

I also tried it with my SMC Takumar (6x7) 200mm/4, the sharpness is not as good as with my M*400mm/4 for sure because the lens is not as sharp to start with, but very usable if needed.

All in all a very surprysing performance for a TC-2X
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