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Another question - How to convert medium format lens to equivalency of a 50mm normal lens (35mm camera) in APS-C digital cameras



 
 
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  #1  
Old May 31st 09, 10:13 AM posted to rec.photo.digital,uk.rec.photo.misc
Woody[_3_]
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Posts: 7
Default Another question - How to convert medium format lens to equivalency of a 50mm normal lens (35mm camera) in APS-C digital cameras

What needs explaining here is what at 'standard lens is - and
that is simple.

It is the lens which has a focal length equivalent to the longest
measurement of the format in use, i.e. the diagonal. It this
follows that a 'standard' lens for 35mm will, by Pythagorus, be
about 42mm, and for 645 will be 75mm.

AP-C cell sizes vary, but assuming 23x15mm this would make a
'standard' lens about 27mm. The ratio of 35mm to AP-C is thus
about 42/27 or 1.5 which is what is generally accepted as 'about'
the magnification factor. Due to fanufacturing processes and the
way the brain 'sees' a picture, 50mm (with a magnification factor
or 50/42 or 1.2) is usually accepted as 'standard' for 35mm.

By the same token a 645 'standard' lens on an AP-C camera will be
75/27 or about 2.8, which in 35mm lens terms would be the
equivalent of about 140mm.

HTH


--
Woody

harrogate three at ntlworld dot com


  #2  
Old May 31st 09, 06:09 PM posted to rec.photo.digital,uk.rec.photo.misc
Rob Morley
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Posts: 126
Default Another question - How to convert medium format lens toequivalency of a 50mm normal lens (35mm camera) in APS-C digital cameras

On Sun, 31 May 2009 10:13:23 +0100
"Woody" wrote:

What needs explaining here is what at 'standard lens is - and
that is simple.

It is the lens which has a focal length equivalent to the longest
measurement of the format in use, i.e. the diagonal. It this
follows that a 'standard' lens for 35mm will, by Pythagorus, be
about 42mm, and for 645 will be 75mm.

44.4mm 70.6mm

Just in case anyone thought Pythagoras was playing up. :-)

  #3  
Old May 31st 09, 06:59 PM posted to rec.photo.digital,uk.rec.photo.misc
Woody[_3_]
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Posts: 7
Default Another question - How to convert medium format lens to equivalency of a 50mm normal lens (35mm camera) in APS-C digital cameras

"Rob Morley" wrote in message
news:20090531180949.58a0297b@bluemoon...
On Sun, 31 May 2009 10:13:23 +0100
"Woody" wrote:

What needs explaining here is what at 'standard lens is - and
that is simple.

It is the lens which has a focal length equivalent to the
longest
measurement of the format in use, i.e. the diagonal. It this
follows that a 'standard' lens for 35mm will, by Pythagorus,
be
about 42mm, and for 645 will be 75mm.

44.4mm 70.6mm

Just in case anyone thought Pythagoras was playing up. :-)




Sorry - fogot the spel-chequer!


--
Woody

harrogate three at ntlworld dot com


  #4  
Old May 31st 09, 07:04 PM posted to rec.photo.digital,uk.rec.photo.misc
Woody[_3_]
external usenet poster
 
Posts: 7
Default Another question - How to convert medium format lens to equivalency of a 50mm normal lens (35mm camera) in APS-C digital cameras

"Woody" wrote in message
...
"Rob Morley" wrote in message
news:20090531180949.58a0297b@bluemoon...
On Sun, 31 May 2009 10:13:23 +0100
"Woody" wrote:

What needs explaining here is what at 'standard lens is - and
that is simple.

It is the lens which has a focal length equivalent to the
longest
measurement of the format in use, i.e. the diagonal. It this
follows that a 'standard' lens for 35mm will, by Pythagorus,
be
about 42mm, and for 645 will be 75mm.

44.4mm 70.6mm

Just in case anyone thought Pythagoras was playing up. :-)






Let's split the difference shall we? (36^2+24^2)^0.5 = 43.2.
(60^2+45^2)^0.5=75 as I said. (This using Windows Calculator.)

Try your Pythagoras again maybe?


--
Woody

harrogate three at ntlworld dot com


  #5  
Old May 31st 09, 08:12 PM posted to rec.photo.digital,uk.rec.photo.misc
Rob Morley
external usenet poster
 
Posts: 126
Default Another question - How to convert medium format lens toequivalency of a 50mm normal lens (35mm camera) in APS-C digital cameras

On Sun, 31 May 2009 19:04:40 +0100
"Woody" wrote:

Let's split the difference shall we? (36^2+24^2)^0.5 = 43.2.


It seems I succumbed to one of the fundamental laws of Usenet.

(60^2+45^2)^0.5=75 as I said. (This using Windows Calculator.)


The neg size of 645 is more like 56×41.5mm, because 120 film is based
on 2 1/4", not 60mm.

Try your Pythagoras again maybe?

Next time I'll double check before posting. Or just try to abstain
from nitpicking. :-)

 




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