Pentax 645n 150mm/2.8 and 1.4X Teleconverter quality

[keirst]

I just got a nice used Pentax 645n and 55mm/2.8 SMC-A lens to compliment my Bronica RF645 and its

excellent 45mm and 65mm lenses. I love having an f/2.8 close-focusing moderate wideangle, but am

thinking about the telephoto end now. I am thinking of getting the SMC-FA 150mm/2.8 IF tele whch

seems to have a great reputation, and was wondering if it performs well with the Pentax 1.4X

teleconverter? I think I would mostly use the 150mm alone, but occasionally would like to go longer. I'd

rather not buy a 200mm/4 that would be used only rarely.

 

I couldn't find a post about this 150mm/2.8 + 1.4X combination, though I ran across someone who said

they were disappointed with the 150mm/3.5 manual focus lens and the 2X teleconverter. Is the

150mm/2.8 better on teleconverters than the 150mm/3.5? Any opinions would be appreciated.

[xato]

I own the 150/2.8 and the 1.4x but have never used them together--probably because I also have the excellent 200/4. I use the 1.4x strictly with the 300/4. I don't use the 2x very much (used in this instance with the 300/4) because it was sort of soft or my tripod was too shaky or bad technique or something. You may as well get a used 200/4 as it costs the same as the 1.4x. The B&H site doesn't list the 1.4x and the 150/3.5.

[philipp1]

Pentax does not recommend any converter to the 150 mm lens. Download the Pentax FA lens manual at www.onpact-canada.ca/645 and read on page 23.

[peter_weimann1]

With the extender you will no more have autofocus. Both the extenders were made for the 300 and 600 manual focus lenses. Why not take the excellent Zoom 150-300? It is outstanding. If you do not need the 2,8 aperture go with that lens.

[keirst]

Thanks for the replies. I think I will go for the 150mm/2.8 on its own, then later if I need it

get a 200mm or 300mm ED lens. I think I would like f/2.8 for shallow depth of field and low

light use.

[thomas_janik]

Steven:

 

I use the 55, 150 and 200mm; I sold my teleconverter. Based on my experience and other comments, I think you are making the right choice.

[keirst]

Well, I've discovered Philipp v. Roeder was wrong about the compatibility of the Pentax

645 1.4X Teleconverter (Rear Converter) and the smc Pentax-FA 645 150mm f/2.8 (IF)

lens. The converter is now listed as compatible with the 150mm/2.8 (but not the

older150mm/3.5 A) lens in the current Pentax instruction manual for the 1.4X and 2X

converters. However, it does have a bug in its behavior that Pentax acknowledges, the

1.4X TC does not report the correct effective aperture of the 150mm/2.8 to the camera,

and wrongly indicates the 150mm/2.8 having two stops of light loss instead of one. Thus

if the lens is set to f/5.6 the camera is told it is effectively f/11 instead of the correct value

of f/8. So you have to compensate your exposures by ?1 EV to avoid a one stop over

exposure indication of the internal light metering. This behavior was discussed in a thread

on Pnet in 2002: <a href="http://www.photo.net/bboard/q-and-a-fetch-msg?

msg_id=001yE0"> http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=001yE0

</a>.<br><br>

 

This is the official list of compatible lenses for the Pentax 645 A Rear Converter:<br>

smc PENTAX-FA 645 MACRO 120mm f/4<br>

smc PENTAX-A 645 MACRO 120mm f/4<br>

smc PENTAX-FA 645 150-300mm f/5.6 ED(IF)<br>

smc PENTAX-FA 645 150mm f/2.8 (IF)<br>

smc PENTAX-FA 645 200mm f/4 (IF)<br>

smc PENTAX-A 645 200mm f/4<br>

smc PENTAX-FA 645 300mm f/4 ED(IF)<br>

smc PENTAX-A 645 300mm f/4 ED(IF)<br>

smc PENTAX-FA 645 400mm f/5.6 ED(IF)<br>

smc PENTAX-A 645 600mm f/5.6 ED(IF)<br><br>

 

All others are listed as incompatible, though the 300mm/5.6 Pentax-FA 645 ED(IF) lens is

omitted from the brochure, so it may have been made after the manual was last printed. It

might be usable too.<br><br>

 

The manual indicates that the TC 1.4X reports the uncompensated aperture for the FA

150-300/5.6 ED(IF), FA 400/5.6 ED(IF) and FA 600mm/5.6ED(IF) lenses.<br><br>

 

I changed my mind about the 1.4X TC and bought one from B&H since I?d rather not have

a zoom or a big 200mm to cart around on walks and hikes with the camera. A converter is

a much lighter addition. I?ll let people know what results look like after a while. Thanks for

your help.<br><br>

[anders_perstr_mer]

<p>I have just bought the 1,4x converter and tried it on FA150/2,8 and FA200/4. Both these lenses can be mounted on the converter however not be focused to infinity. They work OK on the "clean" 645N body though (yes, I know I have to focus manually with the converter!).<br>

I can see no possibility to adjust the converter as the the glass elements seems to be fixed and non-adjustable.<br>

So I have to claim this 1,4x converter can not be used for these lenses. Anyone disagree??</p>

[keirst]

<p>Something is wrong with your teleconverter I think. My 150/2.8 does focus to infinity on my 1.4x teleconverter. I suggest you return it as defective.</p>

[keirst]

<p>I just double checked and looking through the Pentax-FA 150mm/2.8, I see it focuses perfectly to infinity on the Pentax Rear Converter-A 1.4X. In fact it focuses slightly beyond infinity at full twist, as I think it should, no doubt to compensate for temperature effects on the 150mm. Many telephotos need to focus differently at hot vs cold temperatures. Is it possible you have over-focused yours Anders, passing the point of sharpest focus?</p>

[anders_perstr_mer]

<p>Strange! Both 150 and 200 mm lenses can be focused beyond infinity (very little on the 150) on the body itself, but not with the 1,4 conv. mounted. I can focus close, but not to, infinity. I agree it seems as there is something wrong with the converter, but how is that possible? No moving parts. It looks like new all over and the optical elements cannot be adjusted. At least not forward as it will hit the front cap. Can it be that BOTH my lenses cannot be focused <em>enough</em> beyond infinity on the body? I shall try to borrow another 1,4 conv. to see if the same thing happens.<br>

In the FA lens manual p. 23 the 1,4 conv. is recommended for FA200. It is named "converter-A 646" however!! At least in my downloaded version, printed 1997. Misprint, or are there TWO 1,4 converters??</p>