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A Rant re Focal Length Multipliers

 
 
C Wright
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      01-24-2005
Is anyone else bothered by the frequent use of "focal length multipliers" or
"crop factors" when describing digital cameras and their lenses?
Why don't the manufacturers just tell us what a "normal" lens is for a
particular camera. If, for example, the manufacturers would tell us that a
35mm lens is a normal lens for a particular digital camera we would know
that we would need shorter lenses than that if we expected to get
wide-angle. You would also know, of course, that anything longer than that
would be moving toward telephoto.
After all a 50mm lens is a 50mm lens is a 50mm lens (a rose is a rose is a
rose)! It does not magically change to a 75mm lens on a digital camera with
a focal length multiplier of 1.5.
No one publishes the 35mm camera equivalent for an 80mm lens on a
Hasselblad; no one publishes the 35mm camera equivalent for a 150mm lens on
a 4x5 view camera!
All of this I think adds to the confusion of new comers to the digital world
who may go around thinking, for example, that the 200mm lens that they want
to buy is really a 320mm lens on their 1.6 focal length multiplier camera.
No it's not, it's a 200mm lens! The fact is that if you put that lens on a
'full frame' 35mm camera and cropped a picture to the same size as a camera
with a 1.6 focal length multiplier you would have exactly the same picture.
There, I feel better!
Chuck


 
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Chris Brown
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      01-24-2005
In article <BE1A6FB2.16B59%wright9_nojunk@nojunk_mac.com>,
C Wright <wright9_nojunk@nojunk_mac.com> wrote:
>Is anyone else bothered by the frequent use of "focal length multipliers" or
>"crop factors" when describing digital cameras and their lenses?
>Why don't the manufacturers just tell us what a "normal" lens is for a
>particular camera.


Some people can't get their head out of the 35mm mindset. Those of us who
shoot multiple formats (digital "APS-C", 35mm, 6*6, 6*7 and 6*9 in my case)
have no problem with the concept that a normal lens scales with capture
diagonal, but the concept seems utterly alien to some.

Witness the occasional person who thinks you can't use a 50mm lens as a
portrait lens on a 24*16mm DSLR because "it will still have the perspective
of a standard lens", or some such nonsense. Some of these people seem quite
unshakable in their strange beliefs about the magical properties of various
focal lengths.

>No one publishes the 35mm camera equivalent for an 80mm lens on a
>Hasselblad; no one publishes the 35mm camera equivalent for a 150mm lens on
>a 4x5 view camera!


Quite, but there seems to be an assumption amongst the camera manufacturers
that those buying medium and large format equipment are generally not
ignorant when it comes to this sort of thing (almost certainly justified),
and that those who buy DSLRs might be (maybe justified, maybe not).

Call it more evidence of "dumbing down" if you like, but I agree with you.
If someone really can't understand the concept of focal length and how it
relates to field of view, given varying format sizes, or just wants a camera
for casual use and isn't interested in photography as an art form or
occupation, you have to wonder if a sophisticated interchangable lens camera
is really the right choice for them. Having said that, the manufacturers
seem to think so, as many of them continue to put those point and shoot
modes with the strange little icons of skiers and what-have-you on really
quite high-end camera equipment.
 
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bob
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      01-24-2005
C Wright <wright9_nojunk@nojunk_mac.com> wrote in
news:BE1A6FB2.16B59%wright9_nojunk@nojunk_mac.com:

> Is anyone else bothered by the frequent use of "focal length
> multipliers" or "crop factors" when describing digital cameras and
> their lenses?
>


I think it's an easy to understand shorthand. So many people have so much
experience with 35mm that understanding how the field of view will be
different is a pretty useful thing.

If you stipulate that 50mm is "normal" for 35mm film, then a Nikon D70
would have a 33mm "normal" lens. If you already own a Nikon 24mm lens,
and you want to know what kind of pictures to expect from a D70, what
system would you suggest that would allow a person to know, other than a
1.5 factor of some sort?

Bob
 
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Jim
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      01-24-2005

"C Wright" <wright9_nojunk@nojunk_mac.com> wrote in message
news:BE1A6FB2.16B59%wright9_nojunk@nojunk_mac.com. ..
> Is anyone else bothered by the frequent use of "focal length multipliers"

or
> "crop factors" when describing digital cameras and their lenses?

Not particularly.
> Why don't the manufacturers just tell us what a "normal" lens is for a
> particular camera.

Because they feel that their customers only understand the effect on the
photo in terms of 35mm focal lengths.
Jim


 
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Bob Williams
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      01-24-2005


C Wright wrote:
> Is anyone else bothered by the frequent use of "focal length multipliers" or
> "crop factors" when describing digital cameras and their lenses?
> Why don't the manufacturers just tell us what a "normal" lens is for a
> particular camera. If, for example, the manufacturers would tell us that a
> 35mm lens is a normal lens for a particular digital camera we would know
> that we would need shorter lenses than that if we expected to get
> wide-angle. You would also know, of course, that anything longer than that
> would be moving toward telephoto.
> After all a 50mm lens is a 50mm lens is a 50mm lens (a rose is a rose is a
> rose)! It does not magically change to a 75mm lens on a digital camera with
> a focal length multiplier of 1.5.
> No one publishes the 35mm camera equivalent for an 80mm lens on a
> Hasselblad; no one publishes the 35mm camera equivalent for a 150mm lens on
> a 4x5 view camera!
> All of this I think adds to the confusion of new comers to the digital world
> who may go around thinking, for example, that the 200mm lens that they want
> to buy is really a 320mm lens on their 1.6 focal length multiplier camera.
> No it's not, it's a 200mm lens! The fact is that if you put that lens on a
> 'full frame' 35mm camera and cropped a picture to the same size as a camera
> with a 1.6 focal length multiplier you would have exactly the same picture.
> There, I feel better!
> Chuck
>
>


On all 35 mm film cameras the sensor size is FIXED at 24 x 36 mm.
So all 35 mm camera users know immediately and instinctively whether a
certain focal length lens is super wide angle, extreme telephoto or
something in between.
With Digicams the sensor size varies all over the place, from 24 x 35 mm
in the Canon D1s to 3.34 x 4.45 mm in the Canon A400.
So just telling you the focal length of your lens without also telling
you the sensor size, doesn't give you a clue whether the lens is wide
angle or tele when used with that particular camera. For instance, a
F.L. of 28 mm on a D1s is a wide angle lens. On a Canon A400 that same
focal length would be a strong telephoto.
Bob Williams

 
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Bob Williams
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      01-24-2005


Bob Williams wrote:
>
>
> C Wright wrote:
>
>> Is anyone else bothered by the frequent use of "focal length
>> multipliers" or
>> "crop factors" when describing digital cameras and their lenses?
>> Why don't the manufacturers just tell us what a "normal" lens is for a
>> particular camera. If, for example, the manufacturers would tell us
>> that a
>> 35mm lens is a normal lens for a particular digital camera we would know
>> that we would need shorter lenses than that if we expected to get
>> wide-angle. You would also know, of course, that anything longer than
>> that
>> would be moving toward telephoto.
>> After all a 50mm lens is a 50mm lens is a 50mm lens (a rose is a rose
>> is a
>> rose)! It does not magically change to a 75mm lens on a digital camera
>> with
>> a focal length multiplier of 1.5.
>> No one publishes the 35mm camera equivalent for an 80mm lens on a
>> Hasselblad; no one publishes the 35mm camera equivalent for a 150mm
>> lens on
>> a 4x5 view camera!
>> All of this I think adds to the confusion of new comers to the digital
>> world
>> who may go around thinking, for example, that the 200mm lens that they
>> want
>> to buy is really a 320mm lens on their 1.6 focal length multiplier
>> camera.
>> No it's not, it's a 200mm lens! The fact is that if you put that lens
>> on a
>> 'full frame' 35mm camera and cropped a picture to the same size as a
>> camera
>> with a 1.6 focal length multiplier you would have exactly the same
>> picture.
>> There, I feel better!
>> Chuck
>>
>>

>
> On all 35 mm film cameras the sensor size is FIXED at 24 x 36 mm.
> So all 35 mm camera users know immediately and instinctively whether a
> certain focal length lens is super wide angle, extreme telephoto or
> something in between.
> With Digicams the sensor size varies all over the place, from 24 x 35 mm
> in the Canon D1s to 3.34 x 4.45 mm in the Canon A400.
> So just telling you the focal length of your lens without also telling
> you the sensor size, doesn't give you a clue whether the lens is wide
> angle or tele when used with that particular camera. For instance, a
> F.L. of 28 mm on a D1s is a wide angle lens. On a Canon A400 that same
> focal length would be a strong telephoto.
> Bob Williams
>


Errata;
The full frame Canon EOS Digital SLR is called the 1Ds not the D1s
Its sensor size is 24x36mm not 24x35mm
Bob

 
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John A. Stovall
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      01-24-2005
On Mon, 24 Jan 2005 11:33:59 -0800, Bob Williams
<(E-Mail Removed)> wrote:

>
>
>C Wright wrote:
>> Is anyone else bothered by the frequent use of "focal length multipliers" or
>> "crop factors" when describing digital cameras and their lenses?
>> Why don't the manufacturers just tell us what a "normal" lens is for a
>> particular camera. If, for example, the manufacturers would tell us that a
>> 35mm lens is a normal lens for a particular digital camera we would know
>> that we would need shorter lenses than that if we expected to get
>> wide-angle. You would also know, of course, that anything longer than that
>> would be moving toward telephoto.
>> After all a 50mm lens is a 50mm lens is a 50mm lens (a rose is a rose is a
>> rose)! It does not magically change to a 75mm lens on a digital camera with
>> a focal length multiplier of 1.5.
>> No one publishes the 35mm camera equivalent for an 80mm lens on a
>> Hasselblad; no one publishes the 35mm camera equivalent for a 150mm lens on
>> a 4x5 view camera!
>> All of this I think adds to the confusion of new comers to the digital world
>> who may go around thinking, for example, that the 200mm lens that they want
>> to buy is really a 320mm lens on their 1.6 focal length multiplier camera.
>> No it's not, it's a 200mm lens! The fact is that if you put that lens on a
>> 'full frame' 35mm camera and cropped a picture to the same size as a camera
>> with a 1.6 focal length multiplier you would have exactly the same picture.
>> There, I feel better!
>> Chuck
>>
>>

>
>On all 35 mm film cameras the sensor size is FIXED at 24 x 36 mm.
>So all 35 mm camera users know immediately and instinctively whether a
>certain focal length lens is super wide angle, extreme telephoto or
>something in between.
>With Digicams the sensor size varies all over the place, from 24 x 35 mm
>in the Canon D1s to 3.34 x 4.45 mm in the Canon A400.
>So just telling you the focal length of your lens without also telling
>you the sensor size, doesn't give you a clue whether the lens is wide
>angle or tele when used with that particular camera. For instance, a
>F.L. of 28 mm on a D1s is a wide angle lens. On a Canon A400 that same
>focal length would be a strong telephoto.


I hate to be pedantic on this point but the focal length of the lens
doesn't change with the size of the sensor. The crop size of the image
changes. There is no change in the focal length.

" the cropped area created by the multiplier factor increases the
perceived (practical) focal length of the lens."

Rest of article here.

http://www.lonestardigital.com/multipler.htm



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much money as possible from one party of the citizens
to give to the other."

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David Dyer-Bennet
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      01-24-2005
C Wright <wright9_nojunk@nojunk_mac.com> writes:

> Is anyone else bothered by the frequent use of "focal length multipliers" or
> "crop factors" when describing digital cameras and their lenses?
> Why don't the manufacturers just tell us what a "normal" lens is for a
> particular camera. If, for example, the manufacturers would tell us that a
> 35mm lens is a normal lens for a particular digital camera we would know
> that we would need shorter lenses than that if we expected to get
> wide-angle. You would also know, of course, that anything longer than that
> would be moving toward telephoto.


I find the way they do it much more useful.

> After all a 50mm lens is a 50mm lens is a 50mm lens (a rose is a rose is a
> rose)! It does not magically change to a 75mm lens on a digital camera with
> a focal length multiplier of 1.5.


And the lens is labeled right on the front as a 50mm lens, so no
problem there. And since I know my crop factor is 1.5 (Fuji S2), I
can very quickly find that I get the angle of view I'd normally expect
from a 75mm lens on a 35mm camera.

> No one publishes the 35mm camera equivalent for an 80mm lens on a
> Hasselblad; no one publishes the 35mm camera equivalent for a 150mm lens on
> a 4x5 view camera!


I've been photographing with cameras I could swap lenses on since
1969. I currently own one 4x5 and two medium format, in addition to
my 35mm equipment (5 film bodies plus the S2). I've previously owned
several other medium format cameras. But you know what? I've never
actually had a second lens for *any* of them except the 35mm cameras.
Like the vast majority of photographers, my experience with focal
lengths (as a decision) is 100% tied to 35mm work. I've got those
numbers burned into my brain. Giving me the 35mm-equivalent numbers
is the easiest way to give me that information.

> All of this I think adds to the confusion of new comers to the
> digital world who may go around thinking, for example, that the
> 200mm lens that they want to buy is really a 320mm lens on their 1.6
> focal length multiplier camera. No it's not, it's a 200mm lens! The
> fact is that if you put that lens on a 'full frame' 35mm camera and
> cropped a picture to the same size as a camera with a 1.6 focal
> length multiplier you would have exactly the same picture. There, I
> feel better! Chuck


Glad you feel better. And of course anybody who really gets confused
about focal lengths as opposed to angle of view has been badly served
by their education and by the system. Which is why I prefer "crop
factor" rather than "focal length multiplier".

Meanwhile, I really enjoy my 450mm f2.8 lens and my 87.5 f1.2 NOCT.

--
David Dyer-Bennet, <(E-Mail Removed)>, <http://www.dd-b.net/dd-b/>
RKBA: <http://noguns-nomoney.com/> <http://www.dd-b.net/carry/>
Pics: <http://dd-b.lighthunters.net/> <http://www.dd-b.net/dd-b/SnapshotAlbum/>
Dragaera/Steven Brust: <http://dragaera.info/>
 
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Graeme Cogger
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Posts: n/a
 
      01-24-2005
In article <(E-Mail Removed)>,
http://www.velocityreviews.com/forums/(E-Mail Removed) says...
> On Mon, 24 Jan 2005 11:33:59 -0800, Bob Williams
> <(E-Mail Removed)> wrote:
> >
> >On all 35 mm film cameras the sensor size is FIXED at 24 x 36 mm.
> >So all 35 mm camera users know immediately and instinctively whether a
> >certain focal length lens is super wide angle, extreme telephoto or
> >something in between.
> >With Digicams the sensor size varies all over the place, from 24 x 35 mm
> >in the Canon D1s to 3.34 x 4.45 mm in the Canon A400.
> >So just telling you the focal length of your lens without also telling
> >you the sensor size, doesn't give you a clue whether the lens is wide
> >angle or tele when used with that particular camera. For instance, a
> >F.L. of 28 mm on a D1s is a wide angle lens. On a Canon A400 that same
> >focal length would be a strong telephoto.

>
> I hate to be pedantic on this point but the focal length of the lens
> doesn't change with the size of the sensor. The crop size of the image
> changes. There is no change in the focal length.
>
> " the cropped area created by the multiplier factor increases the
> perceived (practical) focal length of the lens."
>
> Rest of article here.
>
> http://www.lonestardigital.com/multipler.htm
>
>

To be pedantic right back at you
He didn't say that the focal length changed, just (correctly) that the
sensor size determines whether a certain focal length is
wide/normal/tele.
 
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C Wright
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      01-24-2005
On 1/24/05 1:33 PM, in article (E-Mail Removed), "Bob Williams"
<(E-Mail Removed)> wrote:

>
>


>> Why don't the manufacturers just tell us what a "normal" lens is for a
>> particular camera. If, for example, the manufacturers would tell us that a
>> 35mm lens is a normal lens for a particular digital camera we would know
>> that we would need shorter lenses than that if we expected to get
>> wide-angle. You would also know, of course, that anything longer than that
>> would be moving toward telephoto.
>>

>
> On all 35 mm film cameras the sensor size is FIXED at 24 x 36 mm.
> So all 35 mm camera users know immediately and instinctively whether a
> certain focal length lens is super wide angle, extreme telephoto or
> something in between.
> With Digicams the sensor size varies all over the place, from 24 x 35 mm
> in the Canon D1s to 3.34 x 4.45 mm in the Canon A400.
> So just telling you the focal length of your lens without also telling
> you the sensor size, doesn't give you a clue whether the lens is wide
> angle or tele when used with that particular camera. For instance, a
> F.L. of 28 mm on a D1s is a wide angle lens. On a Canon A400 that same
> focal length would be a strong telephoto.
> Bob Williams
>

You apparently missed the point suggesting that manufacturers tell us what a
"normal" lens is for a given camera - that then would be the starting point
for determining whether a lens was wide-angle or telephoto for that
particular camera.
At the same I would agree with you and not for a second suggest that sensor
size not be included in the specs. That would be important information for
any knowledgeable buyer. It is just that I see new comers struggling with
lens equivalencies!
Chuck

 
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