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50mm "normal" lens with digital SLR?

 
 
Chris Brown
Guest
Posts: n/a
 
      06-19-2004
In article <0k0Bc.70978$eu.6254@attbi_s02>,
Tom <(E-Mail Removed)> wrote:
>
>So far all the advice you have been given is flawed.
>
>The 50mm lens does NOT somehow magically become a 80mm lens when you stick
>it on a 1.6 crop factor camera. Neither is it a "pseudo-equivalent" as you
>state above.
>
>The reason portrait shooters like the short (80 to 105mm or so) teles is
>because the short tele has the effect of slightly flattening the image. It
>reduces the "Big Nose" syndrome where body parts (like the nose in a
>headshot) nearest the lens are exaggerated in size because of the
>perspective of the lens.
>
>A 50mm lens gives EXACTLY the same perspective on a 35mm camera, a
>medium-format 6x6, a 4x5 press camera, an 8x10 view camera or a digital SLR.
>EXACTLY THE SAME.


Every time this comes up, someone mentions this "perspective" nonsense.
Perspective is simply the way distant objects appear smaller than nearby
objects, and depends on where you stand. The focal length of the lens you're
looking through has absolutely nothing to do with it - there's no way it
can. If you stand somewhere and look at two identical balls, at different
distances, such that the further ball appears to be half the size of the
nearer one, it will still look half the size with no camera, when looking
through a camera with a 28mm lens attached, when looking through a camera
with a 35mm lens attached, when looking through a camera with a 50mm lens
attached, ad nauseum.

The reason people's noses look too big when their portraits are taken on
35mm cameras with 50mm lenses is because in order to fill the frame, the
photographer has to stand too close to the subject. You can try this for
yourself with a willing volunteer, and no camera at all. Simply move your
head closer and closer to their face, and notice how their nose starts to
dominate the field of view as you get closer.

When taking a portrait of someone with a 50mm lens on a DSLR with a 24mm
sensor, you have to stand further back to fill the frame. In fact, you have
to stand in the same place you'd stand were you using a 35mm camera with an
80mm lens on. As a result, 50mm lenses make great portrait lenses on these
cameras.

Conversely, if you try taking a portrait of someone using a 6*6 medium
format camera with an 80mm lens, and fill the frame, their nose will look
bulbous, even though you're using an 80mm lens, because it has a wider angle
of view on these cameras. By the same token, you can take someones portrait
with a Coolpix 4500, and they won't look like they have a big nose, even
though at maximum zoom, its lens only goes to 32mm.
 
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Joseph Meehan
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Posts: n/a
 
      06-19-2004
Kakadu wrote:
> The real new about the 1.6 magnification factor with DSLRs is that it
> is not actually a magnification factor at all. It is a *clip* factor.
> The lens resolves exactly the same as if it were on film except the
> area of the frame capture is smaller. Sort of like using 110 roll
> film in a 35mm camera.
>
> There are many side effects to this reduction of capture area.
> Probably the most usable is the fact that lens makers plagued with
> image fall-off at the corners can now sell their barely usable 35mm
> lenses as "made for digital" and achieve better results.
>
> Another side effect is the reduced capture size effectively clips the
> image so that a "normal" 50 mm lens will display the area of a 70mm
> telephoto lens but it will not be a telephoto picture, just one
> clipped down to capture a smaller area of the film/frame.


You mean like a 135mm lens is not a telephoto because if it were on a
4x5 camera it would be a normal lens?

You did make a very good point about the fact that lenses designed for
full frame 35mm used on digitals with less than full frame sensor area are
using the sweet spot of the lens so often the results are better than
expected for a given lens. Many people miss this.

A normal lens is usually described at the diagonal measurement of the
image area. That works out to something less than 50mm, close to 47mm as I
recall. Most digital sensors are smaller than 35mm film so they use the
"factor" to adjust.

As for the original question, I suggest that "normal" is whatever you
want it to be. I don't like "normal" lenses. In 35 mm terms I like
something a little longer like 75-80 and something wider like 24-35. But
that is just what I like to work with. There is nothing magic about any of
those numbers. Use what you like, not what I like or what is considered
"normal."

Good Luck

>
> Kakadu,
> A Photographers paradise.
> -----------------------------
> "john" <(E-Mail Removed)> wrote in message
> news:eG%Ac.810896$oR5.193432@pd7tw3no...
>> Hi folks,
>>
>> When I was in junior high photography class, we learned about how
>> 50mm lenses were considered to be "normal" (ie. not wide-angle or
>> telephoto). 50mm was recommended for high quality shots where you
>> could zoom-with-your-feet.
>>
>> With my film SLRs, I always used my 50mm when zooming or wide-angle
>> wasn't necessary, and I was very happy.
>>
>> Now that I've moved to digital SLR, the one lens that I have that
>> isn't compatible with my digital camera is the 50mm lens (too old).
>> I've found a good 50mm F1.8 for a very good price (less than $100).
>> But the question I have is...
>>
>> With the digital magnification factor, a 50mm lens is
>> pseudo-equivilent to a 75mm. Soooo, is it still a "normal" lens
>> anymore? Is there any real benefit to buying this lens?
>>
>> Thanks in advance!
>> J


--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math



 
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Frank
Guest
Posts: n/a
 
      06-19-2004
On Sat, 19 Jun 2004 19:18:20 GMT, "Tom"
<(E-Mail Removed)> wrote:

>
>
>So far all the advice you have been given is flawed.
>
>The 50mm lens does NOT somehow magically become a 80mm lens when you stick
>it on a 1.6 crop factor camera. Neither is it a "pseudo-equivalent" as you
>state above.
>
>The reason portrait shooters like the short (80 to 105mm or so) teles is
>because the short tele has the effect of slightly flattening the image. It
>reduces the "Big Nose" syndrome where body parts (like the nose in a
>headshot) nearest the lens are exaggerated in size because of the
>perspective of the lens.
>
>A 50mm lens gives EXACTLY the same perspective on a 35mm camera, a
>medium-format 6x6, a 4x5 press camera, an 8x10 view camera or a digital SLR.
>EXACTLY THE SAME.
>
>The multiplication factor in digital SLRs is merely a crop factor, NOT a
>lens focal length transmutation device.
>
>Tom
>

I wonder if all this is applicable. The real thing that affects the
"perspective" in a photograph is the shooting distance, not the focal
length of the lens. A 35 mm and a 150 mm lens, if shot from the same
distance will display the same perpective (relative size of objects in
the image.) They will not, however show the same image area. The real
reason for using a short tele for portraits is to fill the frame for a
head shot from a longer distance than you would use with a shorter
lens, thus getting a more pleasing perspective. Thus it seems to me
that a 50 mm (75 mm equivalent) when used at a distance to fill the
frame with a head shot would be at the same distance as a 75 mm framed
identically on a film camera and would see the same perpective.
 
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leo
Guest
Posts: n/a
 
      06-19-2004
"john" <(E-Mail Removed)> wrote in message
news:eG%Ac.810896$oR5.193432@pd7tw3no...
> Hi folks,
>
> When I was in junior high photography class, we learned about how 50mm
> lenses were considered to be "normal" (ie. not wide-angle or telephoto).
> 50mm was recommended for high quality shots where you could
> zoom-with-your-feet.
>
> With my film SLRs, I always used my 50mm when zooming or wide-angle wasn't
> necessary, and I was very happy.
>
> Now that I've moved to digital SLR, the one lens that I have that isn't
> compatible with my digital camera is the 50mm lens (too old). I've found a
> good 50mm F1.8 for a very good price (less than $100). But the question I
> have is...
>
> With the digital magnification factor, a 50mm lens is pseudo-equivilent to

a
> 75mm. Soooo, is it still a "normal" lens anymore? Is there any real

benefit
> to buying this lens?
>
> Thanks in advance!
> J



I like using 50mm f/1.4 on Digital Rebel alot if there were no special
requirement. Get the f/1.8 when your budget is tight. It's too cheap to pass
up.


 
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Nick C
Guest
Posts: n/a
 
      06-20-2004

"Helge Olsen" <(E-Mail Removed)> wrote in message
news:40d4aa58$(E-Mail Removed)...
>
> "Kakadu" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
> > The real new about the 1.6 magnification factor with DSLRs is that it is

> not
> > actually a magnification factor at all. It is a *clip* factor. The lens
> > resolves exactly the same as if it were on film except the area of the

> frame
> > capture is smaller. Sort of like using 110 roll film in a 35mm camera.
> >
> > There are many side effects to this reduction of capture area. Probably

> the
> > most usable is the fact that lens makers plagued with image fall-off at

> the
> > corners can now sell their barely usable 35mm lenses as "made for

digital"
> > and achieve better results.
> >
> > Another side effect is the reduced capture size effectively clips the

> image
> > so that a "normal" 50 mm lens will display the area of a 70mm telephoto

> lens
> > but it will not be a telephoto picture, just one clipped down to capture

a
> > smaller area of the film/frame.
> >
> > Kakadu,
> > A Photographers paradise.
> > -----------------------------

>
> THANK YOU! Finally a person who got the point! Kudos!
>
> /Helge



Perhaps not.

A lens may serve a duel purpose. It is what it is on a dSLR and on a SLR.
The lens is not the determining factor in photo capture size, In a dSLR it's
the size of the sensing element that's used. To say a picture is "cropped"
because it's sensing element is smaller in size as compare to 35mm film is,
IMO, wrong and misleading.

To support my contention, one only need physically move from one position to
another to obtain the same image prospective when using a given lens on a
dSLR as opposed to a SLR. For example: A 50mm lens on a SLR has a diagonal
view of about 46 degrees. The same lens placed on a 10D would be converted
to 80mm having a diagonal view of about 30 degrees. To obtain the diagonal
view of 46 degrees, one need only to physically move. It would be closer to
the truth to refer to different image sizes obtained from a fixed photo
position when using a dSLR as lens-sensor focal length multipliers. Reason
being, the size of the sensor, in effect, 'resembles' using a given size
teleconverter, without the loss of f-stops and using the best part of a
lens, which is about 10mm from the lens center. If one were to accept the
terminology that a given lens on a dSLR crops an image then one have to
accept that all lenses, regardless of what type camera they may be used on,
crops images because of changes in angles of view associated with different
focal lenght lenses. Nope, I don't think it would be proper to accept that
contention.

A lens which may perform poorly on a SLR may be a wonder on a dSLR that has
a sensor (hopefully with large pixel sizes and thin boarders) which has a
1.5x or 1.6x effect on a given lens. That's the way I see the differences,
ymmv.

nick

>
>



 
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Phil Wheeler
Guest
Posts: n/a
 
      06-20-2004


Nick C wrote:

>
> A lens may serve a duel purpose.


Only if it is one of those really heavy white ones

Phil

 
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Nick C
Guest
Posts: n/a
 
      06-20-2004

"Phil Wheeler" <(E-Mail Removed)> wrote in message
news:HH4Bc.29614$(E-Mail Removed)...
>
>
> Nick C wrote:
>
> >
> > A lens may serve a duel purpose.

>
> Only if it is one of those really heavy white ones
>
> Phil
>


LOL

I forgot to mention, Canon considers the sensor size in a dSLR as a lens
multiplier and not a given lens as being an image cropper.

In the spec section of the EOS 10D (for example), Canon clearly states:

"Focal length conversion factor: Equivalent to approx. 1.6x indicated focal
length compared to 35mm format." If Canon recognizes and refers to the
sensor size (22.7 x15.1mm) as being a lens multiplier, why should I object.
A 50mm lens on a 10D gives the same diametrical angle of view as an 80mm
would give on a 35mm SLR.

BTW, on the spec. sheet for the EOS-1D Mark II (which has my interest),
Canon words it a little differently.

"35mm-equivalent focal length is approx. 1.3 times the marked focal length."
In my math book that means the 28.7x19.1 sensor has a 1.3 multiplying effect
on a lens designed for the 35mm format being used on the Mark II. Kool.

Sure makes one wonder if folks understand the meaning of "Focal length
conversion factor." Not in any of Canon's literature that I have, which
includes Canon's published book "EF Lens Work III, The Eyes of EOS" can one
find where Canon refers to various 35mm lens effects upon a dSLR as
"cropped" images.

nick





 
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leo
Guest
Posts: n/a
 
      06-20-2004
"Nick C" <(E-Mail Removed)> wrote in message
news:3B5Bc.59384$Hg2.8030@attbi_s04...
>
> "Phil Wheeler" <(E-Mail Removed)> wrote in message
> news:HH4Bc.29614$(E-Mail Removed)...
> >
> >
> > Nick C wrote:
> >
> > >
> > > A lens may serve a duel purpose.

> >
> > Only if it is one of those really heavy white ones
> >
> > Phil
> >

>
> LOL
>
> I forgot to mention, Canon considers the sensor size in a dSLR as a lens
> multiplier and not a given lens as being an image cropper.
>
> In the spec section of the EOS 10D (for example), Canon clearly states:
>
> "Focal length conversion factor: Equivalent to approx. 1.6x indicated

focal
> length compared to 35mm format." If Canon recognizes and refers to the
> sensor size (22.7 x15.1mm) as being a lens multiplier, why should I

object.
> A 50mm lens on a 10D gives the same diametrical angle of view as an 80mm
> would give on a 35mm SLR.
>
> BTW, on the spec. sheet for the EOS-1D Mark II (which has my interest),
> Canon words it a little differently.
>
> "35mm-equivalent focal length is approx. 1.3 times the marked focal

length."
> In my math book that means the 28.7x19.1 sensor has a 1.3 multiplying

effect
> on a lens designed for the 35mm format being used on the Mark II. Kool.
>
> Sure makes one wonder if folks understand the meaning of "Focal length
> conversion factor." Not in any of Canon's literature that I have, which
> includes Canon's published book "EF Lens Work III, The Eyes of EOS" can

one
> find where Canon refers to various 35mm lens effects upon a dSLR as
> "cropped" images.
>
> nick



The whole thing about focal length is pointless unless it's reference to,
let's say, 35mm frame. It's more acurate to state the angle of view. SO,
it's a cropping fractor nevertheless. Try find a reasonable price ULTRA WIDE
angle lens and you'd know the pain. I can simulate telephoto by cropping!
What I mean is if they settle with 1.5x/1.6x crop factor, I'd rather use the
4/3 format, at least the lens would be smaller & lighter.


 
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David J. Littleboy
Guest
Posts: n/a
 
      06-20-2004

"Kakadu" <(E-Mail Removed)> wrote:
>
> Another side effect is the reduced capture size effectively clips the

image
> so that a "normal" 50 mm lens will display the area of a 70mm telephoto

lens
> but it will not be a telephoto picture, just one clipped down to capture a
> smaller area of the film/frame.


It _will_ be a telephoto picture.

This is because the relative sizes of objects in the image is due to the
relative distances from the camera. You get the "telephoto effect" by
standing back from your subject (thus changing the relative distances
between things in the image) and using either a longer lens or more
magnification when printing.

Basic reality check: A 110mm lens on my 645 camera takes images
indistinguishable (other than resolution and DOF) from either a 75mm lens on
a 35mm camera or a 16mm or so lens on a consumer digital. Short
telephoto/portrait lens effect. Why would a dSLR somehow differ?

What all this means is that if you take the same picture from the same place
with a 75mm or 80mm lens on a 35mm camera, and a 50mm lens on a dSLR, and
print them at the same size, there will be a _slight_ difference in depth of
field (about the same as 1/2 and f stop), but otherwise the images will be
identical.

So a 50mm lens on a 1.5x/1.6x dSLR is, exactly and only, a portrait/short
telephoto lens.

David J. Littleboy
Tokyo, Japan



 
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Phil Wheeler
Guest
Posts: n/a
 
      06-20-2004
Perhaps Canon, which does seem to try to simplify their manuals a bit,
does not want to confuse their customers with the concept of "cropping
factor". But in designing the EF-S mount, they clearly understand what
is going on -- thankfully.

Phil at dpreview

http://www.dpreview.com/learn/?/Glos...tiplier_01.htm

likes the term "focal length multiplier".

But a rose by any other name is a rose.

So call it what you want.

Nick C wrote:
> "Phil Wheeler" <(E-Mail Removed)> wrote in message
> news:HH4Bc.29614$(E-Mail Removed)...
>
>>
>>Nick C wrote:
>>
>>
>>>A lens may serve a duel purpose.

>>
>>Only if it is one of those really heavy white ones
>>
>>Phil
>>

>
>
> LOL
>
> I forgot to mention, Canon considers the sensor size in a dSLR as a lens
> multiplier and not a given lens as being an image cropper.
>
> In the spec section of the EOS 10D (for example), Canon clearly states:
>
> "Focal length conversion factor: Equivalent to approx. 1.6x indicated focal
> length compared to 35mm format." If Canon recognizes and refers to the
> sensor size (22.7 x15.1mm) as being a lens multiplier, why should I object.
> A 50mm lens on a 10D gives the same diametrical angle of view as an 80mm
> would give on a 35mm SLR.
>
> BTW, on the spec. sheet for the EOS-1D Mark II (which has my interest),
> Canon words it a little differently.
>
> "35mm-equivalent focal length is approx. 1.3 times the marked focal length."
> In my math book that means the 28.7x19.1 sensor has a 1.3 multiplying effect
> on a lens designed for the 35mm format being used on the Mark II. Kool.
>
> Sure makes one wonder if folks understand the meaning of "Focal length
> conversion factor." Not in any of Canon's literature that I have, which
> includes Canon's published book "EF Lens Work III, The Eyes of EOS" can one
> find where Canon refers to various 35mm lens effects upon a dSLR as
> "cropped" images.
>
> nick
>
>
>
>
>


 
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