[kaseki]

Two 1.4 Teleconverters do fit together.
...

I only measured at the edge to avoid risk of scratching. If the rear lens rear surface is sufficiently concave, the units would mate without metal meeting glass. It is hard to see such concavity. A cockpit error on my part is also possible. In any case, using a cotton swab as a probe against a straight edge on each side, it seems that there is sufficient clearance to allow mating. Thanks for the correction.

[RICHARD L.]

Not knocking the 2x yet.

We're all "suckers" when the time comes to evaluate a Pentax product positively ... lol !

Best Regards, Doug

[TDvN57]

Surprised to learn two converters fit together. Would be interesting to compare two 1.4 vs the 2x. Suspect the 2x should win vs twice as many optical elements.

Funny you mention shooting the 2x lens combo wide open. I bought a 2x at an incredible price from Japan. Slapped it on the FA 400 and was underwhelmed. To be fair the tripod needed to be bigger and there was some wind. But still, pretty soft

A couple of days ago I put the 2x on the 645 A 120 macro to get greater working distance and magnification. Bug moved on and spoiled the shot. The corn field was nicely lit and I took a non macro shot. Amazed how sharp the 120 macro and 2x looked. Didn't shoot wide open. It was F6.7. This 2x requires more investigation. Think you may be correct. Perhaps diffraction plays a big roll. Not knocking the 2x yet.

Thanks,
barondla

Before I discovered the open aperture benefit with the TC's I compared two 1.4 TC's with a single 2.0 TC. The result was similar and underwhelming. I never tried it again at wide open, which may shift the goalposts. It might be worth a re-test.

Thinking about it, it may be not be too practical to carry around two 1.4's. A better solution would be one 1.4 and one 2.0, and perhaps even combine them to get a 2.8 at the expense of 3 f stops.

Just for fun I'll add it to my list... Not promising quick results anytime soon. First need to select the most appropriate lens. Suggestions welcome.

[kaseki]

... First need to select the most appropriate lens. Suggestions welcome.

Well, since going 2X on a 35 to get 70 might be absurd, given the existence of the 75, I would suggest using a long lens known to be sharp. However, to avoid atmospheric scintillation interfering with sharpness interpretation, the target distance should be well within 100m. Ideally, the 1.4X 400 could be compared to the 600. Then the 2X 400 could be compared to the 1.4X 600.

Waiting with bated breath.

[TDvN57]

645 Teleconverter test results:

I selected the P645 FA* 300mm f4 lens because we know it plays well with the teleconverters and it gives the best starting point. I want to clarify at the outset that I was not looking for a "most ideal" setup, but rather a stress test to see where the weaknesses are and then each person can decide how and where they see an application. I hope you guys are OK with such an approach.

As a target I selected a TV Booster box from a neighbor's roof which according to Google is +/- 30m (100ft) away from our backyard deck. My camera (645z) is mounted on a heavy Leofoto tripod with a Manfrotto video balancing head. (If someone really wants to know model numbers then I'll look it up).

(The camera is mounted on the tripod and the lens with TC's are causing a tension on the whole setup, which in my experience reduces any shake/vibration. For the blessed souls that are more talented in physics, I think the theory is that the vibration force will induce a torsion force (?) that has to be greater than the inertia of the unbalanced rig. Any forces less than that will be mostly attenuated. But I stand to be corrected on this, I just know that it works for smaller lenses like the 300mm.)

I set the camera on a high shutter speed, aperture on f4, mirror up and wired remote. Focus was done manually with enlarged live view, and shutter was triggered with live view off with the wired remote. If someone wants the DNG files to play with it, let me know I'll share it.

In each picture I post here you will see the uncropped picture as a background with an inset of 500% of the booster box label. This is an unfair enlargement but I wanted to see the extreme ends. Thus what you may see as a fairly un-sharp inset picture may be sharp when viewed at a normal size. I also added an aperture chart that shows the actual aperture with the TC's. Pse note on this point that the camera EXIF registered a very different number. For example at f4 with the 1.4TC the aperture registered f5.6 (correct), with a second TC the aperture would stay on f5.6 (not correct). When closing down the aperture it would give a number as if there was only one 1.4TC mounted. Hence I calculated the actual aperture for comparison. (Hope the calcs are correct -- pse correct me if I am wrong).

Image post processing: I loaded the DNG files into ACR and changed the profile from Camera Landscape to a calibrated profile I prefer. It is not perfect, but it is a bit less saturated and leans a bit away from the reds and greens. I then pressed "AUTO" and only in some cases added more exposure, because my manual exposure setting skills are not always present when I hold the camera. I did not do any further post processing that I can remember, but worthy to note that my camera is set Fine (EX) to max and auto noise reduction. Thus in ACR in the "Detail" settings these selections are visible. I did not change it.

What to look for: On the bottom right of the TV booster's label is small writing "Made in Japan". From previous tests I estimated that printing to be about 1.0mm to 1.5mm high. In one picture a pigeon came to sit on the antenna and just for fun I also enlarged the pigeon 500% as an inset.

Test 1: I tested combinations of the 300mmm lens with the 1.4TC; two 1.4TC's; one 2.0TC; 1.4TC x 2.0TC x 2.0TC. I decided to go for broke and throw everything at it. I did not test two 1.4TC's plus two 2.0TC's because the rig became too heavy for the camera mount without intermediate support. The 1.4TC x 2.0TC x 2.0TC was as far as I was willing to stress the mount.

Test 2: In test two I kept the 1.4TC x 2.0TC x 2.0TC combo and increased the apertures starting at f4, then f5.6, f8 and f11 (I am referring to the settings on the aperture ring - manual mode). I decided for the full rack to demonstrate how quickly the image deteriorate which I think is a combination of refraction with the small aperture and lack of light which added noise.

Control: In an edit to this post I added a control picture at the end, taken with the P645 A* 600mm lens. At the time when I took this picture the sun has shifted to late afternoon and I exposed for the bright parts on the booster box. Thus some noise may be in the shadows, which wouldn't be there if more care is taken with the exposure.

Observations: In Test 1 I saw some CA creeping in with the additional TC's and in some light conditions some purple fringing. The fringing was easy to remove in ACR, although I did not remove it in the final versions, so that it may be visible in the results. I also noted that the two 2.0TC's were losing detail, however when I added the 1.4TC some detail came back (refering to the ability to read the "Made in Japan" writing).

In Test 2 the IQ starts to drop almost immediately going from f4 to f5.6 although still workable. At f8 it all falls apart. I stopped at f11, because the light is so low, as can be seen in the "Actual Aperture".

The 300mm plus (1.4TC x 1.4TC stack) or a single 2.0TC compares well with the 600mm lens, except for the f stop drops to f8 compared with the 600mm lens' f5.6. So if you don't have the 600mm lens and only a 300mm with a 2.0TC then you are good to go, less two f-stops.

Conclusion: I would happily use the 1.4TC and the 2.0TC separately and in exceptional circumstances combine them to get a long shot. The FA* 300mm lens plays well with the setup and from previous tests I am confident the A* 600mm lens will be OK with that as well. The amount of light available would be the main consideration, together with stability. For example at f4 the 300mm lens with 1.4TC and 2.0TC the actual aperture is already f11. On the 600mm lens it will be f16. As with all long lenses the longer lens the shallower the DoF which makes focusing a difficult effort, and could render the stacking of TC's unpractical.

Here are the pictures:

[ProfessorBuzz]

That's crazy! Thanks for the test shots TDvN, really interesting to see the details.

[barondla]

645 Teleconverter test results:

I selected the P645 FA* 300mm f4 lens because we know it plays well with the teleconverters and it gives the best starting point. I want to clarify at the outset that I was not looking for a "most ideal" setup, but rather a stress test to see where the weaknesses are and then each person can decide how and where they see an application. I hope you guys are OK with such an approach.

As a target I selected a TV Booster box from a neighbor's roof which according to Google is +/- 30m (100ft) away from our backyard deck. My camera (645z) is mounted on a heavy Leofoto tripod with a Manfrotto video balancing head. (If someone really wants to know model numbers then I'll look it up).

(The camera is mounted on the tripod and the lens with TC's are causing a tension on the whole setup, which in my experience reduces any shake/vibration. For the blessed souls that are more talented in physics, I think the theory is that the vibration force will induce a torsion force (?) that has to be greater than the inertia of the unbalanced rig. Any forces less than that will be mostly attenuated. But I stand to be corrected on this, I just know that it works for smaller lenses like the 300mm.)

I set the camera on a high shutter speed, aperture on f4, mirror up and wired remote. Focus was done manually with enlarged live view, and shutter was triggered with live view off with the wired remote. If someone wants the DNG files to play with it, let me know I'll share it.

In each picture I post here you will see the uncropped picture as a background with an inset of 500% of the booster box label. This is an unfair enlargement but I wanted to see the extreme ends. Thus what you may see as a fairly un-sharp inset picture may be sharp when viewed at a normal size. I also added an aperture chart that shows the actual aperture with the TC's. Pse note on this point that the camera EXIF registered a very different number. For example at f4 with the 1.4TC the aperture registered f5.6 (correct), with a second TC the aperture would stay on f5.6 (not correct). When closing down the aperture it would give a number as if there was only one 1.4TC mounted. Hence I calculated the actual aperture for comparison. (Hope the calcs are correct -- pse correct me if I am wrong).

Image post processing: I loaded the DNG files into ACR and changed the profile from Camera Landscape to a calibrated profile I prefer. It is not perfect, but it is a bit less saturated and leans a bit away from the reds and greens. I then pressed "AUTO" and only in some cases added more exposure, because my manual exposure setting skills are not always present when I hold the camera. I did not do any further post processing that I can remember, but worthy to note that my camera is set Fine (EX) to max and auto noise reduction. Thus in ACR in the "Detail" settings these selections are visible. I did not change it.

What to look for: On the bottom right of the TV booster's label is small writing "Made in Japan". From previous tests I estimated that printing to be about 1.0mm to 1.5mm high. In one picture a pigeon came to sit on the antenna and just for fun I also enlarged the pigeon 500% as an inset.

Test 1: I tested combinations of the 300mmm lens with the 1.4TC; two 1.4TC's; one 2.0TC; 1.4TC x 2.0TC x 2.0TC. I decided to go for broke and throw everything at it. I did not test two 1.4TC's plus two 2.0TC's because the rig became too heavy for the camera mount without intermediate support. The 1.4TC x 2.0TC x 2.0TC was as far as I was willing to stress the mount.

Test 2: In test two I kept the 1.4TC x 2.0TC x 2.0TC combo and increased the apertures starting at f4, then f5.6, f8 and f11 (I am referring to the settings on the aperture ring - manual mode). I decided for the full rack to demonstrate how quickly the image deteriorate which I think is a combination of refraction with the small aperture and lack of light which added noise.

Control: In an edit to this post I added a control picture at the end, taken with the P645 A* 600mm lens. At the time when I took this picture the sun has shifted to late afternoon and I exposed for the bright parts on the booster box. Thus some noise may be in the shadows, which wouldn't be there if more care is taken with the exposure.

Observations: In Test 1 I saw some CA creeping in with the additional TC's and in some light conditions some purple fringing. The fringing was easy to remove in ACR, although I did not remove it in the final versions, so that it may be visible in the results. I also noted that the two 2.0TC's were losing detail, however when I added the 1.4TC some detail came back (refering to the ability to read the "Made in Japan" writing).

In Test 2 the IQ starts to drop almost immediately going from f4 to f5.6 although still workable. At f8 it all falls apart. I stopped at f11, because the light is so low, as can be seen in the "Actual Aperture".

The 300mm plus (1.4TC x 1.4TC stack) or a single 2.0TC compares well with the 600mm lens, except for the f stop drops to f8 compared with the 600mm lens' f5.6. So if you don't have the 600mm lens and only a 300mm with a 2.0TC then you are good to go, less two f-stops.

Conclusion: I would happily use the 1.4TC and the 2.0TC separately and in exceptional circumstances combine them to get a long shot. The FA* 300mm lens plays well with the setup and from previous tests I am confident the A* 600mm lens will be OK with that as well. The amount of light available would be the main consideration, together with stability. For example at f4 the 300mm lens with 1.4TC and 2.0TC the actual aperture is already f11. On the 600mm lens it will be f16. As with all long lenses the longer lens the shallower the DoF which makes focusing a difficult effort, and could render the stacking of TC's unpractical.

Here are the pictures:

Amazing test of Pentax 645 teleconverters! The 2x is very useful, at least on the 300. Surprised using multiple converters holds up this well. You added considerable info to our Pentax 645 system knowledge. Thanks for all the effort you put in to these tests. Please consider posting this in the lens review section under 645 teleconverters. These tests need to be easiily found and seen by others.

Glad I purchased the 2x while a bargain. When word gets out, the price will climb. Can't wait to try 2x some more. So pleased you did this reevaluation.

Thanks for all the work and sharing,
barondla

[kaseki]

@TDvN57. Wow. Thanks! Way beyond the call of duty. I seriously considered creating a virtual doppelganger just to give you another 'like.'

The pigeon also dropped an opinion, but it was hard to interpret.

kas

[TDvN57]

I appreciate all the positive comments, thank you. The test results exceeded my expectations. Glad I could tore myself away from my beloved household chores to do the test.

I edited the one picture with the equivalent 1680mm fl (300 x 1.4 x 2.0 x 2.0) @ f4 and the results are way beyond I expected.

With another attempt at measuring the size of the letters of 'made in Japan' I found the height +/- 1.3mm and the ink stroke width +/- 0.2mm.

[RICHARD L.]

Glad I purchased the 2x while a bargain. When word gets out, the price will climb. Can't wait to try 2x some more. So pleased you did this reevaluation.

I guess I'll have to give it a new try too ... like I often say "A man's work is never done" ... lol !

Regards

[kaseki]

P.S. Something I hadn't noticed before this exercise is that the 1.4X engraved name is "PENTAX REAR CONVERTER-A 645 1.4X FOR 1:4 300mm ED(IF)" I don't believe the 2X has that '300mm' tailoring [bespokening?] comment. So the test using the 300mm is surely à propos. I wonder if Pentax, at the time of 1.4X design, thought it would not be needed in other applications.

[kaseki]

OK, since the 645 2X's social credit score has been rehabilitated, I ordered one from Japan that arrived today. I observe the following:

• It fits the 90mm
• It provides 7 contact pins; the 90mm has 10
• It does not have a screw drive focus extension carried to the lens, which, in the case of the 90mm, doesn't have one anyway
• Aperture levers are carried forward
• Auto focus doesn't seem to work on the 645Z, only manual focus works
• There seems to be a problem with F/# information, judging from the display
• Related to this, perhaps, there doesn't seem to be a way to set the aperture. This could be an operator deficiency, but without the 2X, the 90mm works as expected. Note that the 2X and the 90mm have aperture levers. But something is missing in the control.
• Qualitatively, the view of a focused scene through the OVF seems to be just as sharp at the corners as at the center.

Actual photos will have to await time and better weather. The limitations w.r.t. other lenses has not yet been evaluated by me.

If Pentax remanufactured these lens assemblies to carry the full gamut of contact pins, more capability might be available.

[barondla]

OK, since the 645 2X's social credit score has been rehabilitated, I ordered one from Japan that arrived today. I observe the following:

• It fits the 90mm
• It provides 7 contact pins; the 90mm has 10
• It does not have a screw drive focus extension carried to the lens, which, in the case of the 90mm, doesn't have one anyway
• Aperture levers are carried forward
• Auto focus doesn't seem to work on the 645Z, only manual focus works
• There seems to be a problem with F/# information, judging from the display
• Related to this, perhaps, there doesn't seem to be a way to set the aperture. This could be an operator deficiency, but without the 2X, the 90mm works as expected. Note that the 2X and the 90mm have aperture levers. But something is missing in the control.
• Qualitatively, the view of a focused scene through the OVF seems to be just as sharp at the corners as at the center.

Actual photos will have to await time and better weather. The limitations w.r.t. other lenses has not yet been evaluated by me.

If Pentax remanufactured these lens assemblies to carry the full gamut of contact pins, more capability might be available.

Smart move getting a 2X before the inevitable price increase. Does the 90 use a motor to set aperture? If so, those 3 missing contacts are probably for power. If the 90 is mounted directly on camera, set to F8, then removed without turning camera off, does the lens stay at F8? That's how Canon EOS lenses work. The Pentax Q lenses do something similar. If it works with the 2X the 90 should be stellar.

Have fun and thanks for the info,

barondla

[TDvN57]

Smart move getting a 2X before the inevitable price increase. Does the 90 use a motor to set aperture? If so, those 3 missing contacts are probably for power. If the 90 is mounted directly on camera, set to F8, then removed without turning camera off, does the lens stay at F8? That's how Canon EOS lenses work. The Pentax Q lenses do something similar. If it works with the 2X the 90 should be stellar.

Have fun and thanks for the info,

barondla

Or buy the FA 120mm with an aperture ring. :-)

[kaseki]

... If the 90 is mounted directly on camera, set to F8, then removed without turning camera off, does the lens stay at F8? ...

The lens doesn't show its aperture. There is no on-lens readout. Further, the aperture is wide open except when taking an image. So unless putting it back on and seeing that the f/no stays the same in the camera readout (and assuming that it wasn't immediately forced there by the camera) confirms the conjecture, or some inspection of the levers confirms it, I don't think this suggested experiment works with the 90mm.