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Leonski · 10-14-2014, 11:20 AM

Pls, eqvivalent lens Mamiya M645, lens Mamiya Sekor C f2,8 55mm on Pentax K-5, APSC.
All the best from Leonski, Macedonia

**boriscleto** · 10-14-2014, 11:22 AM

A 55mm lens on 645 is equivalent to a 35mm lens on 35mm FF. So you would need a 24mm lens on APS-C.

ElJamoquio · 10-14-2014, 11:38 AM

Originally posted by Leonski

Pls, eqvivalent lens Mamiya M645, lens Mamiya Sekor C f2,8 55mm on Pentax K-5, APSC.
All the best from Leonski, Macedonia

is that 645 a film camera?

Leonski · 10-14-2014, 01:34 PM

Yes, Mamiya M645 1000S film camera.

ElJamoquio · 10-14-2014, 02:23 PM

645 = 56x41 = 69.4mm diagonal
APS-C = 28.4mm diagonal

55mm*(28.4/69.4) = 22.5mm
f/2.8*(28.4/69.4) = 1.145

So a 23mm F/1.1 would have roughly the same field of view (on the diagonal) with the same light-gathering ability.

Leonski · 10-14-2014, 02:51 PM

Thank You.

**boriscleto** · 10-14-2014, 03:02 PM

F/2.8 is F/2.8. A 24mm F/2.8 lens would give you the equivalent FoV and the same exposure. DoF and perspective are a different matter.

Sandy Hancock · 10-14-2014, 03:14 PM

Originally posted by boriscleto

DoF and perspective are a different matter.

Yes, but still potentially relevant to the OP's question.

ElJamoquio · 10-14-2014, 03:19 PM

Originally posted by boriscleto

F/2.8 is F/2.8.

Yup.

And and F/2.8 gathers the same amount of light as an F/1.1, when you change formats.

FYI perspective is the same on the 23mm APS-C and the 55mm 645, despite whatever you've seen on the interwebz.

10-14-2014, 11:20 AM	#1
Leonski Guest	Equivalent lens Mamiya - Pentax K-5 Pls, eqvivalent lens Mamiya M645, lens Mamiya Sekor C f2,8 55mm on Pentax K-5, APSC. All the best from Leonski, Macedonia

10-14-2014, 01:34 PM	#4
Leonski Guest	Mamiya M645 1000S film camera Yes, Mamiya M645 1000S film camera.

10-14-2014, 02:51 PM	#6
Leonski Guest	Thanks Thank You.

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10-14-2014, 11:22 AM	#2
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,477	A 55mm lens on 645 is equivalent to a 35mm lens on 35mm FF. So you would need a 24mm lens on APS-C.

10-14-2014, 11:38 AM	#3
ElJamoquio Veteran Member Join Date: Feb 2011 Posts: 4,873	Originally posted by Leonski Pls, eqvivalent lens Mamiya M645, lens Mamiya Sekor C f2,8 55mm on Pentax K-5, APSC. All the best from Leonski, Macedonia is that 645 a film camera?

10-14-2014, 02:23 PM	#5
ElJamoquio Veteran Member Join Date: Feb 2011 Posts: 4,873	645 = 56x41 = 69.4mm diagonal APS-C = 28.4mm diagonal 55mm(28.4/69.4) = 22.5mm f/2.8(28.4/69.4) = 1.145 So a 23mm F/1.1 would have roughly the same field of view (on the diagonal) with the same light-gathering ability.

10-14-2014, 03:02 PM	#7
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,477	F/2.8 is F/2.8. A 24mm F/2.8 lens would give you the equivalent FoV and the same exposure. DoF and perspective are a different matter.

10-14-2014, 03:14 PM	#8
Sandy Hancock Moderator Site Supporter Join Date: Feb 2012 Location: Adelaide Hills, South Australia Photos: Gallery \| Albums Posts: 11,275	Originally posted by boriscleto DoF and perspective are a different matter. Yes, but still potentially relevant to the OP's question.

10-14-2014, 03:19 PM	#9
ElJamoquio Veteran Member Join Date: Feb 2011 Posts: 4,873	Originally posted by boriscleto F/2.8 is F/2.8. Yup. And and F/2.8 gathers the same amount of light as an F/1.1, when you change formats. FYI perspective is the same on the 23mm APS-C and the 55mm 645, despite whatever you've seen on the interwebz.

Equivalent lens Mamiya - Pentax K-5

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