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01-05-2020, 11:17 PM   #1
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645 lens on K mount with 1.4 TC

When using a 645 lens on K mount (say the 600mm ED IF f5.6) using the Pentax 645->K adapter, which would work better on an apsc camera (K3 or K5):

a) the 645 version 1.4 teleconverter mounted to the lens, before the K adapter?
Or
b) the well regarded, (almost magical... ) 35mm (K mount) 1.4x-l converter mounted after the K adapter?

Anyone tried (b)? I can’t think why it wouldn’t work...

I suppose if mechanics are a consideration, perhaps the mechanical connection between 645 lens and 645 converter might be stronger(?)


Last edited by MalcS; 01-06-2020 at 08:51 AM.
01-06-2020, 03:16 AM   #2
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Following this thred as I am interested in adapting a 645 120mm macro on K mount
01-06-2020, 07:47 AM   #3
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the newest converter has better glass. outside of saving a few bucks or playing around, there's no reason to use the 645 120 macro on k-mount bodies.... plenty of better macro lenses to choose from. either way you lose af and auto aperture.
01-12-2020, 10:02 AM - 2 Likes   #4
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QuoteOriginally posted by MalcS Quote
When using a 645 lens on K mount (say the 600mm ED IF f5.6) using the Pentax 645->K adapter, which would work better on an apsc camera (K3 or K5):

a) the 645 version 1.4 teleconverter mounted to the lens, before the K adapter?
Or
b) the well regarded, (almost magical... ) 35mm (K mount) 1.4x-l converter mounted after the K adapter?

Anyone tried (b)? I canít think why it wouldnít work...

I suppose if mechanics are a consideration, perhaps the mechanical connection between 645 lens and 645 converter might be stronger(?)

I have used the 645 1.4 and 2x adapter with my 645 *600. The 1.4 is very good on the small sensor K5. The 2x is not too bad either. It was not quite up to the image quality of the A*1200 I had, but it did the job when I needed the extra focal length. I have yet to put it on my K1ii. Perhaps i will give both a shot today and report back to you. That is if I can find the 645 to K adapter I have misplaced 😂.

Sorry, I donít have the current K 1.4 so I canít help you there.

Stephen

---------- Post added 01-12-2020 at 10:04 AM ----------

QuoteOriginally posted by sculptor666 Quote
the newest converter has better glass. outside of saving a few bucks or playing around, there's no reason to use the 645 120 macro on k-mount bodies.... plenty of better macro lenses to choose from. either way you lose af and auto aperture.
Iíll second your comments. Very accurately stated.

01-15-2020, 02:11 PM - 1 Like   #5
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I finally found the 645 to K adapter.

Here are some quick shots, nothing scientific, utilizing the Pentax 645 *600mm lens on a K-5 with a 645 1.4X, 2X and a Sigma 35mm APO 1.4X extender. Image exposures varied due to dynamic changes in outdoor lighting. But hopefully, you will get the jist of the images.

First images is of a box face using the lens without a converter.

Second images is the Sigma APO 1.4X converter. (Looks quite nice in my opinion)

Third is with the 645 1.4X. Different lighting and subject top possible focus issue

Fourth is with the 645 2X. Subject to the same conditions as the 1.4X.

All shots on K-5 at iso 1600 at f8, mounted on a Gitzo GT5540LS and Wimberley Gimbal.
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Last edited by SCGushue; 01-15-2020 at 02:22 PM. Reason: data
01-15-2020, 04:58 PM   #6
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QuoteOriginally posted by SCGushue Quote
I finally found the 645 to K adapter.

Here are some quick shots, nothing scientific, utilizing the Pentax 645 *600mm lens on a K-5 with a 645 1.4X, 2X and a Sigma 35mm APO 1.4X extender. Image exposures varied due to dynamic changes in outdoor lighting. But hopefully, you will get the jist of the images.

First images is of a box face using the lens without a converter.

Second images is the Sigma APO 1.4X converter. (Looks quite nice in my opinion)

Third is with the 645 1.4X. Different lighting and subject top possible focus issue

Fourth is with the 645 2X. Subject to the same conditions as the 1.4X.

All shots on K-5 at iso 1600 at f8, mounted on a Gitzo GT5540LS and Wimberley Gimbal.
Thanks for going to the trouble and posting those.

I just picked up a good 645 1.4x for $50 from Japan and will probably get a 645 2x if only to ‘have the set’ Both seem dirt cheap on eBay considering the size of the glass elements and the bomb proof construction. Mechanically speaking the coupling between 645 components seems stronger than the K mount coupling.

BTW, if you don’t mind, what is the length of the tripod foot on the 645 600, and what is the size of the tripod threads (lens not here yet...need to get a plate for it), in pics it looks like 3/8 with a 1/4 insert reducer, or maybe it’s straight 1/4?

Thanks!

Last edited by MalcS; 01-15-2020 at 05:21 PM.
01-15-2020, 07:20 PM   #7
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QuoteOriginally posted by MalcS Quote
Thanks for going to the trouble and posting those.

I just picked up a good 645 1.4x for $50 from Japan and will probably get a 645 2x if only to Ďhave the setí Both seem dirt cheap on eBay considering the size of the glass elements and the bomb proof construction. Mechanically speaking the coupling between 645 components seems stronger than the K mount coupling.

BTW, if you donít mind, what is the length of the tripod foot on the 645 600, and what is the size of the tripod threads (lens not here yet...need to get a plate for it), in pics it looks like 3/8 with a 1/4 insert reducer, or maybe itís straight 1/4?

Thanks!
I think the hole is a straight 3/8 ..... but please donít hold me to that.

The plate that I am using for the 645 A*600 is 6.5 inches.. I find that it gives me the stability I need to move the lens into balance on my Markins Q10 or the Wimberley gimbal..

Glad to post the images even though they are not scientific. My commitment to posting made me try to locate the 645 to K adapter that I hadnít been able to locate for the past six months. It was frustrating me. Finally found it attached to the Sigma 1.4X. Go figure.

You will find that focusing with a TE on this lens is a challenge as it goes dark. And the increased focal length makes stability an issue.....which I think is an issue on some of my images.

Please post your findings. I look forward to seeing some images.

Stephen
01-16-2020, 03:12 AM - 1 Like   #8
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QuoteOriginally posted by sculptor666 Quote
the newest converter has better glass. outside of saving a few bucks or playing around, there's no reason to use the 645 120 macro on k-mount bodies.... plenty of better macro lenses to choose from. either way you lose af and auto aperture.
I already own 35 105 and 200mm macro on k mount.
I have read great comments about this 645 120mm lens and wanted to compare

01-16-2020, 05:11 AM - 1 Like   #9
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QuoteOriginally posted by fsge Quote
I already own 35 105 and 200mm macro on k mount.
I have read great comments about this 645 120mm lens and wanted to compare
The 645 120, in both A and FA are fantastic lenses. I perhaps, favor the 120 A for my style of work. That said, although it does produce beautiful images on the K mount, it is quite cumbersome to use due to the lack of an automatic diaphragm. Itís just too dark to view and focus when stopped down. Both lenses do still function and produce outstanding images on all iterations of the 645ís.

I too have a number of macros, 35, 50, 100, 180 and find them much easier to use on a K mount. Since purchasing the 645z, however, I find that I am very comfortable using the Z with the 120 A for nearly all my macro work.
01-17-2020, 05:19 AM   #10
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QuoteOriginally posted by SCGushue Quote
I think the hole is a straight 3/8 ..... but please don’t hold me to that.

The plate that I am using for the 645 A*600 is 6.5 inches.. I find that it gives me the stability I need to move the lens into balance on my Markins Q10 or the Wimberley gimbal..

Glad to post the images even though they are not scientific. My commitment to posting made me try to locate the 645 to K adapter that I hadn’t been able to locate for the past six months. It was frustrating me. Finally found it attached to the Sigma 1.4X. Go figure.

You will find that focusing with a TE on this lens is a challenge as it goes dark. And the increased focal length makes stability an issue.....which I think is an issue on some of my images.

Please post your findings. I look forward to seeing some images.

Stephen
Thanks for the info. I’m hoping to use this lens mostly for rocket launches, both here in VA (yes, we have rockets to the ISS!) and FL, where distance to rocket is on the order of 2-10 miles depending. Focusing shouldn’t really be an issue at that distance hopefully, and auto exposure, (which is not available with this lens of course using a K body) may not be that helpful anyway as when the rocket lights the exposure changes dramatically, so probably best to pre-guess exposure. Hours of waiting followed by 30 secs of frantic panic kinda sums it all up!

Lens coming from Japan, looks to be about as mint as can be, doesn’t even have scratches on the bottom of the tripod foot(!) and has both regular and polarizer filter holders, plus filters, caps, case, etc.

Meantime, here’s a few of the Antares Cygnus 12 leaving VA for the ISS from November, 300mm DA*: I’m sure they could be processed better... Distance about 2 miles, which is as close as you can be. Mirage was a problem, even though it was pretty cold.
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Last edited by MalcS; 01-17-2020 at 11:59 AM.
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