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11-24-2009, 11:24 AM   #1
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medium format lens on as-c camera

What's the crop factor from a 6x6 Lens on aps-c ?

11-24-2009, 11:30 AM   #2
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i have found the answer


Fotopunto.com: Crop factor and focal length equivalence calculator
11-24-2009, 12:07 PM   #3
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You found a utility that can give answers to this sort of question, but the way you worded it suggests you won't be using the utility correctly to get the right answer. The right answer is this: all lenses lens of a given focal length has *exactly* the same field of view when used on APS-C, regardless of whether the lens was designed for 35mm film, for APS-C, or for 6x6. So for example, a 50mm lens is a 50mm lens whether it's designed for APS-C or 6x6. Crop factor is only relevant if you are comparing how one given lens perform one APSC versus 6x6 - it is true that if you are already accustomed to what a 50mm looks like on 6x6, you'll have to multiply that figure by a crop factor to find out what it will look like on APS-C. But if you're just wondering what a 50mm lens for 6x6 will look like on APS-C, you don't need to know about crop factors - that 50mm lens will look exactly like all other 50mm lenses on APS-C.
11-24-2009, 03:55 PM   #4
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Marc speaks the truth.

I recently got a "wide angle" 6x6 lens to mount on my K20D, and sure enough - what is a "wide" 50mm lens on medium format is the same FOV as my FA50mm (but 4x larger and heavier). But, the image circle is comparatively gigantic! This huge image circle allows me to use a tilt or shift-adapter on a 35mm or APS-C frame, and move the lens all over without any vignetting:




And another thing to look out for is distortion. A 30mm "fisheye" from medium-format-land would be a "normal" perspective lens on APS-C, but with some serious barrel distortion for that crop factor, and even crazier effects if you tilt or shift it around the image circle! But then, that could be the fun part...

-Mark


Last edited by panoguy; 11-24-2009 at 04:04 PM.
11-25-2009, 02:55 AM   #5
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QuoteOriginally posted by Marc Sabatella Quote
You found a utility that can give answers to this sort of question, but the way you worded it suggests you won't be using the utility correctly to get the right answer. The right answer is this: all lenses lens of a given focal length has *exactly* the same field of view when used on APS-C, regardless of whether the lens was designed for 35mm film, for APS-C, or for 6x6. So for example, a 50mm lens is a 50mm lens whether it's designed for APS-C or 6x6. Crop factor is only relevant if you are comparing how one given lens perform one APSC versus 6x6 - it is true that if you are already accustomed to what a 50mm looks like on 6x6, you'll have to multiply that figure by a crop factor to find out what it will look like on APS-C. But if you're just wondering what a 50mm lens for 6x6 will look like on APS-C, you don't need to know about crop factors - that 50mm lens will look exactly like all other 50mm lenses on APS-C.


i know, a 50mm is always a 50mm lens, but i dont have the same angle of field (view) on a aps-c / 6x6 camera whit the same 6x6 lens.


QuoteOriginally posted by panoguy Quote
Marc speaks the truth.

I recently got a "wide angle" 6x6 lens to mount on my K20D, and sure enough - what is a "wide" 50mm lens on medium format is the same FOV as my FA50mm (but 4x larger and heavier). But, the image circle is comparatively gigantic! This huge image circle allows me to use a tilt or shift-adapter on a 35mm or APS-C frame, and move the lens all over without any vignetting:




And another thing to look out for is distortion. A 30mm "fisheye" from medium-format-land would be a "normal" perspective lens on APS-C, but with some serious barrel distortion for that crop factor, and even crazier effects if you tilt or shift it around the image circle! But then, that could be the fun part...

-Mark
nice
i plan to buy a MC VOLNA-3 B 80mm F2.8 with tilt adapter
11-25-2009, 03:06 PM   #6
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QuoteOriginally posted by eigelb Quote
What's the crop factor from a 6x6 Lens on aps-c ?
I have a range of Mamiya 6x7 mf lens. Is there an adapter out there that lets me fit them to a K mount camera??

David
12-16-2009, 07:52 PM   #7
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QuoteOriginally posted by David Quote
I have a range of Mamiya 6x7 mf lens. Is there an adapter out there that lets me fit them to a K mount camera??

David
I would like to know this, too.
12-16-2009, 08:58 PM - 1 Like   #8
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QuoteOriginally posted by eigelb Quote
What's the crop factor from a 6x6 Lens on aps-c ?
To help in deciding which lens to pick, the lens descriptions in our lens review database include the field of view of medium format lenses when used on an APS-C camera as in this example:

Pentax Lens Review and Specification Database - 35mm F3.5

A while back I developed this table which might be useful as well:

Attached Images
 

Last edited by Ole; 12-16-2009 at 09:06 PM.
12-20-2009, 09:52 AM   #9
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Hi Ole, I'm based in AZ too, and shoot for AZ HWYS, and have shot the 67II for years around the Southwest. My question for you is what my 300/4.5 67 ED optic will compare to on my K7, as I do have the 67-K mount adaptor. This lens would be longer or shorter in effective focal length than it's nominal 300 design?
Kerrick James
12-20-2009, 10:17 AM   #10
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QuoteOriginally posted by David Quote
I have a range of Mamiya 6x7 mf lens. Is there an adapter out there that lets me fit them to a K mount camera??

David
here is an adapter

Mamiya 645 lens adapter to pentax K PK K20D K200D K10D - eBay (item 160288424554 end time Dec-23-09 23:39:24 PST)
12-20-2009, 01:06 PM   #11
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QuoteOriginally posted by kjames5 Quote
Hi Ole, I'm based in AZ too, and shoot for AZ HWYS, and have shot the 67II for years around the Southwest. My question for you is what my 300/4.5 67 ED optic will compare to on my K7, as I do have the 67-K mount adaptor. This lens would be longer or shorter in effective focal length than it's nominal 300 design?
Kerrick James
question well put!

if crop factor of K7 is 1.5 compared to ff, angle of view of 300mm lens on crop camera will be equivalent to angle of view of 450mm lens on ff.

crop factor of FF is (approximately) 2x compared to 67, so angle of view of 300mm 67 lens on K7 is equivalent to angle of view of 2 x 1.5 x 300mm = 900mm lens on 67.
12-21-2009, 12:50 PM - 1 Like   #12
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QuoteOriginally posted by kjames5 Quote
Hi Ole, I'm based in AZ too, and shoot for AZ HWYS, and have shot the 67II for years around the Southwest. My question for you is what my 300/4.5 67 ED optic will compare to on my K7, as I do have the 67-K mount adaptor. This lens would be longer or shorter in effective focal length than it's nominal 300 design?
You need to put aside the notion that a 300mm lens has an inherent field of view that is "correct" when used on your camera but somehow "incorrect" when used on another camera. The fields of view are just different, but it's not the case that one is correct and the other not. Which is to say, words like "effective focal length" and "nominal" are not appropriate here. The 300mm lens remains a 300mm lens no matter what camera it is mounted to - it isn't a "nominal" focal length, it is is the true focal length, always. It *is* true that the field of view when used on the K-7 will be very different than what it was on the 67 - it will be similar to what you would have needed a much longer lens for. Say I told you it is similar to what a 900mm lens would do on the 67 (I think that's what the chart above suggests - a "crop factor" of 2.9, which I conveniently rounded to 3). That doesn't mean the "effective" focal length is 900mm; it just means a 900mm lens on your 67 and a 300mm lens on a K-7 would have the same field field of view.

It's a subtle distinction, but as long as one persists in the misconception that the field of view one has become accustomed to associating with given focal lengths is the "correct" or "effective" focal length, the lnger one will cotninue to be confused by the whole comparison.
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