Pentax 645 lens to FF

sunshine7913 · 10-20-2015, 07:42 PM

Well, Im really exciting to use 645 lens to FF if Pentax make an AF adaptor for 645 lenses. (I don't have any adaptor yet)

I have 645 macro 120mm lens.

If I use this lens on FF, what's the focal length?

**pepperberry farm** · 10-20-2015, 07:48 PM - **1 Like**

120mm

**UncleVanya** · 10-20-2015, 08:07 PM

https://www.pentaxforums.com/forums/48-pentax-medium-format/133518-crop-factor-645d-2.html

An old topic that covers this in great detail. Essentials to remember. Focal length does not change. Equivalent focal length is just mental shorthand to give a comparison frame of reference. Crop factor is hard to compare in 645d vs ff of apsc since the ratio of height vs width isn't the same but a rough estimate is that your lenses would act as though they were 1.27x longer than they are in your current frame of reference. In other words the 120mm on FF gives the same field of view as a 152mm lens on the 645d.

Another way of looking at this is that a 95mm lens on FF gives the same field of view as a 120mm on a 645d/z.

**clackers** · 10-20-2015, 08:22 PM

Pepperberry Farm is quite right, Sunshine.

The focal length will still be 120mm, the FoV will be about that of a 150mm lens.

There is a 645 to K-mount adaptor already, no?

**jatrax** · 10-20-2015, 08:22 PM

And here is the adapter: Pentax-K Adapter for 645 Reviews - Pentax K-mount Teleconverters and Adapters - Pentax Lens Reviews & Lens Database
Pentax 645 Lens to Pentax 35mm K-Mount Body Adapter 38455 B&H

sunshine7913 · 10-20-2015, 08:30 PM

Originally posted by jatrax

And here is the adapter: Pentax-K Adapter for 645 Reviews - Pentax K-mount Teleconverters and Adapters - Pentax Lens Reviews & Lens Database
Pentax 645 Lens to Pentax 35mm K-Mount Body Adapter 38455 B&H

I mean the adaptor with AF function.

**jatrax** · 10-20-2015, 08:36 PM

Originally posted by sunshine7913

I mean the adaptor with AF function.

And which one is that?

Adam · 10-20-2015, 08:51 PM

Originally posted by sunshine7913

I mean the adaptor with AF function.

There aren't any.

**ivanvernon** · 10-21-2015, 12:37 AM

Is the quality of 645 lens good enough to justify adapting to K-3? I have A55mm, A200mm, and A80-160mm.

**pepperberry farm** · 10-21-2015, 03:09 AM

I asked a similar question a while back:

https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/301113-m42-vs-645-a.html

there are adapters for 645 to K; all make the 645 lenses fully manual.... I am still debating the question I posed in the topic...

**UncleVanya** · 10-21-2015, 06:16 AM

Originally posted by sunshine7913

Well, Im really exciting to use 645 lens to FF if Pentax make an AF adaptor for 645 lenses. (I don't have any adaptor yet)

Originally posted by clackers

There is a 645 to K-mount adaptor already, no?

Originally posted by sunshine7913

I mean the adaptor with AF function.

Originally posted by jatrax

And which one is that?

Originally posted by Adam

There aren't any.

Originally posted by pepperberry farm

there are adapters for 645 to K; all make the 645 lenses fully manual....

The way I read this was that OP posed the question with the hope that Ricoh would create a 645 AF adapter. I don't think the first post was meant to be a question as to the existence of an adapter with AF capabilities.

I'm not sure what such an item might cost but I suspect it would be cost prohibitive for most people and only really appeal to those with a stable of lenses for their 645.

**jatrax** · 10-21-2015, 08:01 AM

Originally posted by UncleVanya

posed the question with the hope that Ricoh would create a 645 AF adapter.

Missed that. Agree it would be cool but also cost prohibitive.

Over in this thread there is a rumor showing a slide that mentions a 645 adapter. Looks quite fake to me & most others but who knows.

**Pål Jensen** · 10-21-2015, 09:18 AM

Originally posted by ivanvernon

Is the quality of 645 lens good enough to justify adapting to K-3? I have A55mm, A200mm, and A80-160mm.

I don't have any of those lenses but among my lenses (33-55, 75, 120Macro, 150-300) only the 120mm is worth using on 35mm.

**RuiC** · 10-21-2015, 09:32 AM

Originally posted by clackers

Pepperberry Farm is quite right, Sunshine.

The focal length will still be 120mm, the FoV will be about that of a 150mm lens.

There is a 645 to K-mount adaptor already, no?

120 times 1.5 = 180 !!!

**UncleVanya** · 10-21-2015, 11:04 AM

Originally posted by RuiC

120 times 1.5 = 180 !!!

But the crop factor in question depends on frame of reference. From a 645d or z the crop factor is only 1.27x.

This chart and article helps.
The Crop Factor Unmasked - Articles and Tips | PentaxForums.com

10-20-2015, 07:42 PM	#1
sunshine7913 Guest	Pentax 645 lens to FF Well, Im really exciting to use 645 lens to FF if Pentax make an AF adaptor for 645 lenses. (I don't have any adaptor yet) I have 645 macro 120mm lens. If I use this lens on FF, what's the focal length?

10-20-2015, 08:51 PM	#8
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,609	Originally posted by sunshine7913 I mean the adaptor with AF function. There aren't any. 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:

10-21-2015, 12:37 AM	#9
ivanvernon Loyal Site Supporter Join Date: Oct 2012 Location: Medina, OH Photos: Albums Posts: 7,224	Worth the effort? Is the quality of 645 lens good enough to justify adapting to K-3? I have A55mm, A200mm, and A80-160mm.

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10-20-2015, 07:48 PM - 1 Like	#2
pepperberry farm amateur dirt farmer Join Date: Dec 2014 Location: probably out in a field somewhere... Photos: Gallery \| Albums Posts: 41,781	120mm

10-20-2015, 08:07 PM	#3
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,472	https://www.pentaxforums.com/forums/48-pentax-medium-format/133518-crop-factor-645d-2.html An old topic that covers this in great detail. Essentials to remember. Focal length does not change. Equivalent focal length is just mental shorthand to give a comparison frame of reference. Crop factor is hard to compare in 645d vs ff of apsc since the ratio of height vs width isn't the same but a rough estimate is that your lenses would act as though they were 1.27x longer than they are in your current frame of reference. In other words the 120mm on FF gives the same field of view as a 152mm lens on the 645d. Another way of looking at this is that a 95mm lens on FF gives the same field of view as a 120mm on a 645d/z.

10-20-2015, 08:22 PM	#4
clackers Otis Memorial Pentaxian Join Date: Jul 2013 Location: Melbourne Photos: Albums Posts: 16,397	Pepperberry Farm is quite right, Sunshine. The focal length will still be 120mm, the FoV will be about that of a 150mm lens. There is a 645 to K-mount adaptor already, no?

10-20-2015, 08:22 PM	#5
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,992	And here is the adapter: Pentax-K Adapter for 645 Reviews - Pentax K-mount Teleconverters and Adapters - Pentax Lens Reviews & Lens Database Pentax 645 Lens to Pentax 35mm K-Mount Body Adapter 38455 B&H

10-20-2015, 08:30 PM	#6
sunshine7913 Guest	Originally posted by jatrax And here is the adapter: Pentax-K Adapter for 645 Reviews - Pentax K-mount Teleconverters and Adapters - Pentax Lens Reviews & Lens Database Pentax 645 Lens to Pentax 35mm K-Mount Body Adapter 38455 B&H I mean the adaptor with AF function.

10-20-2015, 08:36 PM	#7
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,992	Originally posted by sunshine7913 I mean the adaptor with AF function. And which one is that?

10-21-2015, 03:09 AM	#10
pepperberry farm amateur dirt farmer Join Date: Dec 2014 Location: probably out in a field somewhere... Photos: Gallery \| Albums Posts: 41,781	I asked a similar question a while back: https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/301113-m42-vs-645-a.html there are adapters for 645 to K; all make the 645 lenses fully manual.... I am still debating the question I posed in the topic...

10-21-2015, 06:16 AM	#11
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,472	Originally posted by sunshine7913 Well, Im really exciting to use 645 lens to FF if Pentax make an AF adaptor for 645 lenses. (I don't have any adaptor yet) Originally posted by clackers There is a 645 to K-mount adaptor already, no? Originally posted by sunshine7913 I mean the adaptor with AF function. Originally posted by jatrax And which one is that? Originally posted by Adam There aren't any. Originally posted by pepperberry farm there are adapters for 645 to K; all make the 645 lenses fully manual.... The way I read this was that OP posed the question with the hope that Ricoh would create a 645 AF adapter. I don't think the first post was meant to be a question as to the existence of an adapter with AF capabilities. I'm not sure what such an item might cost but I suspect it would be cost prohibitive for most people and only really appeal to those with a stable of lenses for their 645.

10-21-2015, 08:01 AM	#12
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,992	Originally posted by UncleVanya posed the question with the hope that Ricoh would create a 645 AF adapter. Missed that. Agree it would be cool but also cost prohibitive. Over in this thread there is a rumor showing a slide that mentions a 645 adapter. Looks quite fake to me & most others but who knows.

10-21-2015, 09:18 AM	#13
Pål Jensen Site Supporter Join Date: Dec 2007 Location: Norway Photos: Albums Posts: 4,371	Originally posted by ivanvernon Is the quality of 645 lens good enough to justify adapting to K-3? I have A55mm, A200mm, and A80-160mm. I don't have any of those lenses but among my lenses (33-55, 75, 120Macro, 150-300) only the 120mm is worth using on 35mm.

10-21-2015, 09:32 AM	#14
RuiC Site Supporter Join Date: Jan 2009 Location: Lisboa - The best destination in Europe Posts: 633	Originally posted by clackers Pepperberry Farm is quite right, Sunshine. The focal length will still be 120mm, the FoV will be about that of a 150mm lens. There is a 645 to K-mount adaptor already, no? 120 times 1.5 = 180 !!!

10-21-2015, 11:04 AM	#15
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,472	Originally posted by RuiC 120 times 1.5 = 180 !!! But the crop factor in question depends on frame of reference. From a 645d or z the crop factor is only 1.27x. This chart and article helps. The Crop Factor Unmasked - Articles and Tips \| PentaxForums.com