Fujifilm GFX 50S With Pentax MF Lenses 6x7 or 645

Nick0 · 04-11-2017, 08:18 PM

Hi folks, I am new here and wondering if anyone can help me with my query.
I am looking to move up to the new Fujifilm GFX. I wanted to ask if anyone knows of - or has experience with using Pentax 6x7 lenses with this camera? (Or 645 lenses)
I shoot almost entirely landscape - so almost everything is shot in fully manual, with manual focus on a tripod etc.
The reason for considering the Pentax lenses is the cost would be considerably lower than the new GFX lenses as well as the amount of lenses available at the moment.
I've had conflicting information from the two companies I have contacted, with Fujifilm pro support telling me the crop would be 0.79 and the adaptor manufacturer stating 1.6 crop.
Anyway, I wondered if I would be losing out on the sensor capabilities by putting these lenses on them, whether the colour accuracy would be retained and whether the resolution of these lenses would be high enough.
I'm looking at the 45mm 6x7. The two zooms Pentax has too.
Any help would be welcome. Cheers!

Fcsnt54 · 04-11-2017, 09:17 PM

I think what the fuji company was referring to is if you want an equivalence to full frame the factor is .79. In terms of using the 645 lenses on the gfx there is no crop factor and are a direct crossover, so if you were to use the 645 A75 mm 2.8 it would be the same on the fuji gfx. Not really sure where the 1.6 comes from. As far as losing capabilities, i think the only part you would be losing would be the AF, saying that a good number of lenses perform well on the 44x33 sensor.

Adam · 04-11-2017, 09:24 PM

Yup, there would be no crop and no limitations in terms of infinity focus. Just more tedious to set the exposure & you'll have to focus manually.

Nick0 · 04-12-2017, 07:16 AM

Originally posted by Fcsnt54

I think what the fuji company was referring to is if you want an equivalence to full frame the factor is .79. In terms of using the 645 lenses on the gfx there is no crop factor and are a direct crossover, so if you were to use the 645 A75 mm 2.8 it would be the same on the fuji gfx. Not really sure where the 1.6 comes from. As far as losing capabilities, i think the only part you would be losing would be the AF, saying that a good number of lenses perform well on the 44x33 sensor.

That's great to hear thank you!

Nick0 · 04-12-2017, 07:17 AM

Originally posted by Adam

Yup, there would be no crop and no limitations in terms of infinity focus. Just more tedious to set the exposure & you'll have to focus manually.

Thanks Adam! The manual focus is fine with me, however the loss of metering could be pretty cumbersome at times. Thanks for your reply, I appreciate it!

tuco · 04-18-2017, 01:25 PM

What modern digital landscape photographer that doesn't focus stack and/or exposure blend these days? I think with the Sunny 16 rule and and a few test exposures you'd hone in on a good exposure in no time for a subject that doesn't move around.

04-11-2017, 08:18 PM	#1
Nick0 New Member Join Date: Apr 2017 Posts: 3	Fujifilm GFX 50S With Pentax MF Lenses 6x7 or 645 Hi folks, I am new here and wondering if anyone can help me with my query. I am looking to move up to the new Fujifilm GFX. I wanted to ask if anyone knows of - or has experience with using Pentax 6x7 lenses with this camera? (Or 645 lenses) I shoot almost entirely landscape - so almost everything is shot in fully manual, with manual focus on a tripod etc. The reason for considering the Pentax lenses is the cost would be considerably lower than the new GFX lenses as well as the amount of lenses available at the moment. I've had conflicting information from the two companies I have contacted, with Fujifilm pro support telling me the crop would be 0.79 and the adaptor manufacturer stating 1.6 crop. Anyway, I wondered if I would be losing out on the sensor capabilities by putting these lenses on them, whether the colour accuracy would be retained and whether the resolution of these lenses would be high enough. I'm looking at the 45mm 6x7. The two zooms Pentax has too. Any help would be welcome. Cheers!

04-11-2017, 09:24 PM	#3
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,608	Yup, there would be no crop and no limitations in terms of infinity focus. Just more tedious to set the exposure & you'll have to focus manually. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

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04-11-2017, 09:17 PM	#2
Fcsnt54 Veteran Member Join Date: Nov 2015 Location: California Posts: 621	I think what the fuji company was referring to is if you want an equivalence to full frame the factor is .79. In terms of using the 645 lenses on the gfx there is no crop factor and are a direct crossover, so if you were to use the 645 A75 mm 2.8 it would be the same on the fuji gfx. Not really sure where the 1.6 comes from. As far as losing capabilities, i think the only part you would be losing would be the AF, saying that a good number of lenses perform well on the 44x33 sensor.

04-12-2017, 07:16 AM	#4
Nick0 New Member Join Date: Apr 2017 Posts: 3 Original Poster	Originally posted by Fcsnt54 I think what the fuji company was referring to is if you want an equivalence to full frame the factor is .79. In terms of using the 645 lenses on the gfx there is no crop factor and are a direct crossover, so if you were to use the 645 A75 mm 2.8 it would be the same on the fuji gfx. Not really sure where the 1.6 comes from. As far as losing capabilities, i think the only part you would be losing would be the AF, saying that a good number of lenses perform well on the 44x33 sensor. That's great to hear thank you!

04-12-2017, 07:17 AM	#5
Nick0 New Member Join Date: Apr 2017 Posts: 3 Original Poster	Originally posted by Adam Yup, there would be no crop and no limitations in terms of infinity focus. Just more tedious to set the exposure & you'll have to focus manually. Thanks Adam! The manual focus is fine with me, however the loss of metering could be pretty cumbersome at times. Thanks for your reply, I appreciate it!

04-18-2017, 01:25 PM	#6
tuco Pentaxian Join Date: Jul 2009 Location: Pugetopolis Posts: 11,031	What modern digital landscape photographer that doesn't focus stack and/or exposure blend these days? I think with the Sunny 16 rule and and a few test exposures you'd hone in on a good exposure in no time for a subject that doesn't move around.