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Rear Converter-A 1.4x-S

Reviews Views Date of last review
4 26,952 Tue December 4, 2018
Recommended By Average Price Average User Rating
100% of reviewers $133.33 8.50
Rear Converter-A 1.4x-S


Pentax Super Multi Coated 1.4x teleconverter with KA mount lens information contacts.

Features of this teleconverter:

  • Manual Focus
  • Supports Tv or P exposure mode (in addition to M and Av), if the camera and lens allows
  • The converter does not transmit focal length and MTF information from lens to camera
  • Designed for lenses up to and including 300mm, with some exceptions.

The following lenses are NOT supported:

  • FA* 200mm F4 Macro
  • F* and FA* 300mm F4.5
  • F* and FA* 250-600mm F5.6
  • K 135-600mm F6.7
  • All other lenses above 300mm
  • K and A 15mm F3.5
  • K 18mm F3.5
  • M 24-35mm F3.5 zoom

The above lens compatibility information is from 2006 and predates the introduction of D FA, DA, DA L and DA* lenses. Compatibility with these newer lenses is not readily available.


Rear Converter-A 1.4X-S
©, sharable with attribution
Image Format
Full-frame / 35mm film
Lens Mount
Pentax K
Light Loss
1 stop
5 elements, 4 groups
Mount Variant (Rear)
Mount Variant (Front)
Weather Sealing
HB-90B or S70-70
Diam x Length
64.5 x 21.5 mm (2.54 x 0.85 in.)
145 g (5.1 oz.)
Production Years
1984 to 2005
Engraved name: REAR CONVERTER-A 1.4X-S
User reviews
The converter retains all exposure modes supported by the attached lens.
The converter does not relay information about focal length, MTF, or lens name to the camera.
The converter is designed for lenses 300mm and shorter, but it is not compatible with the FA* 200mm F2.8 Macro, the F* and FA* 300mm F4.5 lenses, other lenses and zooms with a reach beyond 300mm, the K and A 15mm F3.5, the K 18mm F3.5, the M 24-35 F3.5 zoom, and various other wide angle lenses due to the protruding rear elements of these lenses.

Initially the converter was supplied with a hard case, later with a soft case.

Automatic ApertureFull-Frame SupportDiscontinued
Price History:

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Sort Reviews by: Date | Author | Rating | Recommendation | Likes (Descending) Showing Reviews 1-4 of 4
New Member

Registered: November, 2018
Posts: 1
Lens Review Date: December 4, 2018 I can recommend this lens: Yes | Price: N/A | Rating: 8 

Cons: somewhat disappointed with the image quality

I had this for about four years but did not use it until I bought a Pentax A* 300mm f4. I am somewhat disappointed with the resulting image quality because it is rather soft. Downsizing from 24 to 12MP with some software sharpening improves the images. Web publishing looks good without any tweaking.

The following were taken with the Pentax A* 300mm f4 + 1.4X-S TC

(100% crop)

(100% crop)
Forum Member

Registered: February, 2016
Location: Moab, Utah
Posts: 90
Lens Review Date: January 31, 2017 I can recommend this lens: Yes | Price: $150.00 | Rating: 10 

Pros: Sharp, maintains clarity
Cons: somewhat rare

A very useable teleconverter. This 1.4x is quite a bit sharper and more practical for maintaining image quality than rear converter-a 2.0x-s or other 2x converters I tried. Feels like an a series lens because of the grip. No m series 1.4x option. Works well with M* 300 f4, which is where I almost exclusively use this. Images are still acceptable in quality for all photo editors so far.
Loyal Site Supportaxian

Registered: September, 2013
Location: Texas
Posts: 483
Lens Review Date: December 3, 2016 I can recommend this lens: Yes | Price: $110.00 | Rating: 8 

Pros: Great performance, Better compatibility with lenses than others.
Cons: None, other than no Data or AF connection.

Unlike its 2x brother, which is a diva that only plays well with certain lenses, this rear converter plays well with most, including many modern lenses.
Sharp and contrasty, small in size. This along with the 1.4x L version are the very best of all the classic Pentax Rear converters, only surpassed by the modern HD DA 1.4 Rear Converter.

I rate this an 8. It's very good, but not outstanding. It is sharper than the 1.7x AFA.
Loyal Site Supporter

Registered: November, 2007
Location: Sparwood, BC, Canada
Posts: 10,586

4 users found this helpful
Lens Review Date: January 26, 2012 I can recommend this lens: Yes | Price: $140.00 | Rating: 8 

Pros: Genuine Pentax coatings, good glass, works will with my lenses
Cons: It is a teleconverter. it was designed for shorter lenses

This adapter works well with any of my lenses, maintaining all exposure functions. It cannot, of course, turn either of my M lenses into an A series lens.

My use for the adapter these days is with the M400/5.6 which becomes a quite nice M560/8 with the adapter on the back. The IQ is not horribly degraded with the adapter. The quality is better than an equivalent crop with the 400 on my K10D, despite the adapter being designed for use with lenses no longer than 300mm.

It would be better if the lens could be fitted with the -L adapter, but they are not physically compatible because the projection on the -L is bigger than the throat of the M 400.
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