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ef-s vs. ef lens in 300d... confused...

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Anonymous
January 26, 2005 8:35:55 PM

Archived from groups: rec.photo.digital (More info?)

hello,

after seeing some posts here in this newsgroup, i am still confused...
my understanding is a 18-55mm ef-s lens working with a 300d will
provide the same result as i use a 28.8-88mm ef lens (if there's one)
with a film eos camera, right? so how about if i use a 18-55mm ef lens
(if there's any) in the 300d? will it have the same result of the
1.6x?

thanks!

More about : lens 300d confused

Anonymous
January 27, 2005 5:33:29 AM

Archived from groups: rec.photo.digital (More info?)

Correct. The 18-55 zoom on the 300D (dRebel) is roughly equiv. in field of
view to a 28-90mm zoom on 35mm film. To get the equiv field of view of a
lens on the 300D (or D60, 10D, 20D for that matter) multiply by 1.6. For
example, a 200mm lens on the 300D has the same field of view as a 320mm lens
in 35mm.
John

"Lun Mo Mo" <lunmomo@hotmail.com> wrote in message
news:5e863aa0.0501261735.261ceff3@posting.google.com...
> hello,
>
> after seeing some posts here in this newsgroup, i am still confused...
> my understanding is a 18-55mm ef-s lens working with a 300d will
> provide the same result as i use a 28.8-88mm ef lens (if there's one)
> with a film eos camera, right? so how about if i use a 18-55mm ef lens
> (if there's any) in the 300d? will it have the same result of the
> 1.6x?
>
> thanks!
Anonymous
January 27, 2005 5:33:30 AM

Archived from groups: rec.photo.digital (More info?)

"JohnR66" <nospam@att.net> wrote in message
news:ZpYJd.95404$w62.91037@bgtnsc05-news.ops.worldnet.att.net...
> Correct. The 18-55 zoom on the 300D (dRebel) is roughly equiv. in field of
> view to a 28-90mm zoom on 35mm film. To get the equiv field of view of a
> lens on the 300D (or D60, 10D, 20D for that matter) multiply by 1.6. For
> example, a 200mm lens on the 300D has the same field of view as a 320mm
> lens in 35mm.
> John
>

John, some clarification please:

I thought the EF-S lenses were engineered to take the 1.6 multiplier into
account and be true to their focal lengths? Yes? No?

To what, then, are "they" refering when you see references regarding a
"shorter rear element to sensor distance?" Isn't the rear element to sensor
distance what dictates the size of the image on the sensor? Isn't this why
they are not compatible with other EOS cameras becuase you'd get a "reverse
crop" and not fill the entire frame with an EF-S lens?

In 35mm parlance, is the 18-55mm EF-S viewing at 18-55mm or is it viewing at
28.8-88mm?

TIA,

Jay
Related resources
Anonymous
January 27, 2005 5:36:28 AM

Archived from groups: rec.photo.digital (More info?)

Jay Beckman wrote:

> 1) Take a picture with an 18-55mm EF-S on a 20D @ 55mm...
>
> Then...
>
> 2) Take a picture with an 18-55mm EF on an Elan @ 55mm...
>
> Do I get the same FOV in each picture?
>
> This is what I'm trying to wrap my brain around. If the EF-S lenses
are
> designed specifically for the sensor size in the 20D and the 300D,
then they
> are delivering a "Full Frame" image (albeit to a smaller target) and
there
> should be no "crop factor" right? The FOVs should be identical,
shouldn't
> they?

this is what i confused at first... after surfing the net and some
photography forums, i found out the only reason(s) ef-s exists is for
cheaper, lighter and smaller (for wide-angle lens). for what i
understand, if you use a 18-55mm ef-s on a 20d, your field of view is
28.8-88mm. but if you use a 18-55mm ef on a elan, your fov is still
18-55mm. and even you use 18-55mm ef (no "s") lens on a 20d, your field
of view is still the same as you use a 18-55mm ef-s on the same 20d
(that is, 28.8-88mm). i checked some prices, a ef lens which can do
14mm is a lot more expensive than the new ef-s 10-22mm... anyone please
correct me if i am wrong, i really know the "truth"... thanks! (btw, if
everything is correct in the above i just mentioned, why people buy a
darn expensive ef-s 10-22mm but not a sigma 8mm? wrt wide-angle fov...)
Anonymous
January 27, 2005 9:54:48 AM

Archived from groups: rec.photo.digital (More info?)

It is true that EFS lenses are designed to take the smaller sensor into
consideration ( the image projected is large enough only fo rthe smaller
sensor) ..but the focal length remains 18- 55mm. Beacuse the seosore is
smaller, the mirror can be made smaller, so the rear element can protrude
into the body, thus making the lens shorter ( which is why the EFS lense is
not compatable with te old 1.6, the 1.3 and full frame cameras)

one element which causes confusion is the FOV - what is really happening is
the image is being cropped, in the case of the 300d, to an image 5/8 the
size of a 35mm frame . The lense will behave exactly the same as if it were
projected on to a full frame wrt DOF and so on. The effect of the crop is
the same as viewing the subject thru a lense 1.6 the focal length (ie a
50mm has teh same FOV as an 80mm, but take a shot on film, and on the 300d
of a subject the same distance away at the same aperture and teh DOF will be
the same)

This is why DOF is so difficult to control on digicams, as lenses with short
focal lengths have a greater DOF at a given distance than longer lenses at
the same aperture at the same distance..


"Jay Beckman" <jnsbeckman@cox.net> wrote in message
news:MI%Jd.5884$av.4385@fed1read01...
> "JohnR66" <nospam@att.net> wrote in message
> news:ZpYJd.95404$w62.91037@bgtnsc05-news.ops.worldnet.att.net...
>> Correct. The 18-55 zoom on the 300D (dRebel) is roughly equiv. in field
>> of view to a 28-90mm zoom on 35mm film. To get the equiv field of view of
>> a lens on the 300D (or D60, 10D, 20D for that matter) multiply by 1.6.
>> For example, a 200mm lens on the 300D has the same field of view as a
>> 320mm lens in 35mm.
>> John
>>
>
> John, some clarification please:
>
> I thought the EF-S lenses were engineered to take the 1.6 multiplier into
> account and be true to their focal lengths? Yes? No?
>
> To what, then, are "they" refering when you see references regarding a
> "shorter rear element to sensor distance?" Isn't the rear element to
> sensor distance what dictates the size of the image on the sensor? Isn't
> this why they are not compatible with other EOS cameras becuase you'd get
> a "reverse crop" and not fill the entire frame with an EF-S lens?
>
> In 35mm parlance, is the 18-55mm EF-S viewing at 18-55mm or is it viewing
> at 28.8-88mm?
>
> TIA,
>
> Jay
>
Anonymous
January 27, 2005 9:54:49 AM

Archived from groups: rec.photo.digital (More info?)

"stanb" <soxy1@NOSPAMcyberone.com.au> wrote in message
news:41f89037@news.comindico.com.au...
> It is true that EFS lenses are designed to take the smaller sensor into
> consideration ( the image projected is large enough only fo rthe smaller
> sensor) ..but the focal length remains 18- 55mm. Beacuse the seosore is
> smaller, the mirror can be made smaller, so the rear element can protrude
> into the body, thus making the lens shorter ( which is why the EFS lense
> is not compatable with te old 1.6, the 1.3 and full frame cameras)
>
> one element which causes confusion is the FOV - what is really happening
> is the image is being cropped, in the case of the 300d, to an image 5/8
> the size of a 35mm frame . The lense will behave exactly the same as if it
> were projected on to a full frame wrt DOF and so on. The effect of the
> crop is the same as viewing the subject thru a lense 1.6 the focal length
> (ie a 50mm has teh same FOV as an 80mm, but take a shot on film, and on
> the 300d of a subject the same distance away at the same aperture and teh
> DOF will be the same)
>
> This is why DOF is so difficult to control on digicams, as lenses with
> short focal lengths have a greater DOF at a given distance than longer
> lenses at the same aperture at the same distance..
>
>

stanb,

I understand all that you are saying above, but (with respect) it doesn't
answer my original question (but, your points regarding DOF are worth
remembering, thanks)

I realize that if I take a picture with an 18-55mm EF @ 55mm on a 20D I get
the FOV equivalent of an 88mm lens. So, let's try this experiement:

1) Take a picture with an 18-55mm EF-S on a 20D @ 55mm...

Then...

2) Take a picture with an 18-55mm EF on an Elan @ 55mm...

Do I get the same FOV in each picture?

This is what I'm trying to wrap my brain around. If the EF-S lenses are
designed specifically for the sensor size in the 20D and the 300D, then they
are delivering a "Full Frame" image (albeit to a smaller target) and there
should be no "crop factor" right? The FOVs should be identical, shouldn't
they?

Or, am I not understanding what the results should be as they relate to the
"shorter rear element to sensor distance" claims?

Thanks for your time and interest here...

Jay
Anonymous
January 27, 2005 10:44:56 AM

Archived from groups: rec.photo.digital (More info?)

"Jay Beckman" <jnsbeckman@cox.net> wrote in message
news:MI%Jd.5884$av.4385@fed1read01...
> "JohnR66" <nospam@att.net> wrote in message
> news:ZpYJd.95404$w62.91037@bgtnsc05-news.ops.worldnet.att.net...
> > Correct. The 18-55 zoom on the 300D (dRebel) is roughly equiv. in field
of
> > view to a 28-90mm zoom on 35mm film. To get the equiv field of view of a
> > lens on the 300D (or D60, 10D, 20D for that matter) multiply by 1.6. For
> > example, a 200mm lens on the 300D has the same field of view as a 320mm
> > lens in 35mm.
> > John
> >
>
> John, some clarification please:
>
> I thought the EF-S lenses were engineered to take the 1.6 multiplier into
> account and be true to their focal lengths? Yes? No?
>
> To what, then, are "they" refering when you see references regarding a
> "shorter rear element to sensor distance?" Isn't the rear element to
sensor
> distance what dictates the size of the image on the sensor? Isn't this
why
> they are not compatible with other EOS cameras becuase you'd get a
"reverse
> crop" and not fill the entire frame with an EF-S lens?
>
> In 35mm parlance, is the 18-55mm EF-S viewing at 18-55mm or is it viewing
at
> 28.8-88mm?
>
> TIA,
>
> Jay
>
The focal length is a fixed physical property of a lens. the 18mm on the
18-55mm zoom is 18mm no matter what camera it is on (if it were possible).
Imagine 5mm sensor used with the lens. The angle of view would be so narrow,
it would appear to be a telephoto lens because it is using only the vary
small central area of the image. Note the focal length numbers of compact
digital cameras.

The rear element distance from the sensor simply eases lens design of wide
angle lenses. If you ever wondered why some range finder cameras had such
small wide angle lenses, it is because they don't have to use a retro focus
lens design as 35mm SLR lenses of focal lengths 35mm and less. The SLRs have
to have the retrofocus design because the swinging mirror would hit the rear
of the lens if it projected back into the camera. IIRC, the retrofocus
design is a wide angle lens mated to a telephoto design which allows the
rear of the lens to be further from the image plane.
bg
Anonymous
January 27, 2005 10:44:56 AM

Archived from groups: rec.photo.digital (More info?)

"Jay Beckman" <jnsbeckman@cox.net> wrote in message
news:MI%Jd.5884$av.4385@fed1read01...
> "JohnR66" <nospam@att.net> wrote in message
> news:ZpYJd.95404$w62.91037@bgtnsc05-news.ops.worldnet.att.net...
> > Correct. The 18-55 zoom on the 300D (dRebel) is roughly equiv. in field
of
> > view to a 28-90mm zoom on 35mm film. To get the equiv field of view of a
> > lens on the 300D (or D60, 10D, 20D for that matter) multiply by 1.6. For
> > example, a 200mm lens on the 300D has the same field of view as a 320mm
> > lens in 35mm.
> > John
> >
>
> John, some clarification please:
>
> I thought the EF-S lenses were engineered to take the 1.6 multiplier into
> account and be true to their focal lengths? Yes? No?
>
> To what, then, are "they" refering when you see references regarding a
> "shorter rear element to sensor distance?" Isn't the rear element to
sensor
> distance what dictates the size of the image on the sensor? Isn't this
why
> they are not compatible with other EOS cameras becuase you'd get a
"reverse
> crop" and not fill the entire frame with an EF-S lens?
>
> In 35mm parlance, is the 18-55mm EF-S viewing at 18-55mm or is it viewing
at
> 28.8-88mm?
>
> TIA,
>
> Jay
>
The focal length is a fixed physical property of a lens. the 18mm on the
18-55mm zoom is 18mm no matter what camera it is on (if it were possible).
Imagine 5mm sensor used with the lens. The angle of view would be so narrow,
it would appear to be a telephoto lens because it is using only the vary
small central area of the image. Note the focal length numbers of compact
digital cameras.

The rear element distance from the sensor simply eases lens design of wide
angle lenses. If you ever wondered why some range finder cameras had such
small wide angle lenses, it is because they don't have to use a retro focus
lens design as 35mm SLR lenses of focal lengths 35mm and less. The SLRs have
to have the retrofocus design because the swinging mirror would hit the rear
of the lens if it projected back into the camera. IIRC, the retrofocus
design is a wide angle lens mated to a telephoto design which allows the
rear of the lens to be further from the image plane.
bg
Anonymous
January 27, 2005 1:40:57 PM

Archived from groups: rec.photo.digital (More info?)

"Jay Beckman" <jnsbeckman@cox.net> wrote in message
news:GI0Kd.7101$av.5580@fed1read01...
> "stanb" <soxy1@NOSPAMcyberone.com.au> wrote in message
> news:41f89037@news.comindico.com.au...
> I understand all that you are saying above, but (with respect) it doesn't
> answer my original question (but, your points regarding DOF are worth
> remembering, thanks)
>
> I realize that if I take a picture with an 18-55mm EF @ 55mm on a 20D I
> get the FOV equivalent of an 88mm lens. So, let's try this experiement:
>
> 1) Take a picture with an 18-55mm EF-S on a 20D @ 55mm...
>
> Then...
>
> 2) Take a picture with an 18-55mm EF on an Elan @ 55mm...
>
> Do I get the same FOV in each picture?

no - the 20d's image will be the centre of the elan's ( imagine a rectangle
22 * 33 with a similar proportioned rectangle 15 * 22 in its centre... ) ie
the same as if you cropped the 35mm frame down
>
> This is what I'm trying to wrap my brain around. If the EF-S lenses are
> designed specifically for the sensor size in the 20D and the 300D, then
> they are delivering a "Full Frame" image (albeit to a smaller target) and
> there should be no "crop factor" right? The FOVs should be identical,
> shouldn't they?

no - the crop factor is dependant on teh sensor size, not the image circle
projected from the lense.. the smaller sensors mean that the diameter of the
optics can be made smaller - the length is a real world measurement ( ie a
50 mm lense is a 500 lense whether is on a didgican, a slr or a 6*7 medium
format camera!)


> Or, am I not understanding what the results should be as they relate to
> the "shorter rear element to sensor distance" claims?
>
> Thanks for your time and interest here...
>
> Jay

the shorter rear element to sensor distance means that teh rearmost elemnt
of the lense protrudes into the camera body - which is why you cant use EF-S
lenses on anything but a 300d/20d - on any other camera, the mirro could hit
the lense. Canon have done this to reduce the overall length of the lense
when fitted to the camera ( and generally make it smaller)
>
Anonymous
January 27, 2005 1:40:58 PM

Archived from groups: rec.photo.digital (More info?)

"stanb" <soxy1@NOSPAMcyberone.com.au> wrote in message
news:41f8c538@news.comindico.com.au...
>
> "Jay Beckman" <jnsbeckman@cox.net> wrote in message
> news:GI0Kd.7101$av.5580@fed1read01...
>> "stanb" <soxy1@NOSPAMcyberone.com.au> wrote in message
>> news:41f89037@news.comindico.com.au...
>> I understand all that you are saying above, but (with respect) it doesn't
>> answer my original question (but, your points regarding DOF are worth
>> remembering, thanks)
>>
>> I realize that if I take a picture with an 18-55mm EF @ 55mm on a 20D I
>> get the FOV equivalent of an 88mm lens. So, let's try this experiement:
>>
>> 1) Take a picture with an 18-55mm EF-S on a 20D @ 55mm...
>>
>> Then...
>>
>> 2) Take a picture with an 18-55mm EF on an Elan @ 55mm...
>>
>> Do I get the same FOV in each picture?
>
> no - the 20d's image will be the centre of the elan's ( imagine a
> rectangle 22 * 33 with a similar proportioned rectangle 15 * 22 in its
> centre... ) ie the same as if you cropped the 35mm frame down
>>
>> This is what I'm trying to wrap my brain around. If the EF-S lenses are
>> designed specifically for the sensor size in the 20D and the 300D, then
>> they are delivering a "Full Frame" image (albeit to a smaller target) and
>> there should be no "crop factor" right? The FOVs should be identical,
>> shouldn't they?
>
> no - the crop factor is dependant on teh sensor size, not the image circle
> projected from the lense.. the smaller sensors mean that the diameter of
> the optics can be made smaller - the length is a real world measurement
> ( ie a 50 mm lense is a 500 lense whether is on a didgican, a slr or a 6*7
> medium format camera!)
>
>
>> Or, am I not understanding what the results should be as they relate to
>> the "shorter rear element to sensor distance" claims?
>>
>> Thanks for your time and interest here...
>>
>> Jay
>
> the shorter rear element to sensor distance means that teh rearmost
> elemnt of the lense protrudes into the camera body - which is why you cant
> use EF-S lenses on anything but a 300d/20d - on any other camera, the
> mirro could hit the lense. Canon have done this to reduce the overall
> length of the lense when fitted to the camera ( and generally make it
> smaller)
>>
>

Ok, I think I've got it now.

Doesn't matter if it's EF-S or EF ... you're still affected by the 1.6x crop
factor.

I guess that explains why a 10mm (in the EF-S 10-22mm zoom) doesn't become a
fish eye lens because it's giving you the FOV of a 16mm lens.

Thanks for the info

Jay
Anonymous
January 27, 2005 6:20:41 PM

Archived from groups: rec.photo.digital (More info?)

"Jay Beckman" <jnsbeckman@cox.net> wrote in message
news:tI8Kd.11071$av.2749@fed1read01...
>
> Ok, I think I've got it now.
>
> Doesn't matter if it's EF-S or EF ... you're still affected by the 1.6x
> crop factor.
>
> I guess that explains why a 10mm (in the EF-S 10-22mm zoom) doesn't become
> a fish eye lens because it's giving you the FOV of a 16mm lens.
>
> Thanks for the info
>
> Jay
>
Yep, a 10mm lens is still a 10mm lens, whether it's mounted on a digital
camera, 35mm film camera, medium format or a large format camera. It's the
measurement of the focal length of the lens. That's all.

--
Skip Middleton
http://www.shadowcatcherimagery.com
January 27, 2005 9:11:49 PM

Archived from groups: rec.photo.digital (More info?)

"stanb" <soxy1@NOSPAMcyberone.com.au> wrote in message
news:41f89037@news.comindico.com.au...
> It is true that EFS lenses are -------------

>-------------------------------------------------as lenses with short
> focal lengths have a greater DOF at a given distance than longer lenses at
> the same aperture at the same distance..
>
>
> "Jay Beckman" <jnsbeckman@cox.net> wrote in message
> news:MI%Jd.5884$av.4385@fed1read01...
>> "JohnR66" <nospam@att.net> wrote in message
>> news:ZpYJd.95404$w62.91037@bgtnsc05-news.ops.worldnet.att.net...
>>> Correct. The 18-55 zoom on the 300D (dRebel) is roughly equiv. in field
>>> of view to a 28-90mm zoom on 35mm film. To get the equiv field of view
>>> of a lens on the 300D (or D60, 10D, 20D for that matter) multiply by
>>> 1.6. For example, a 200mm lens on the 300D has the same field of view as
>>> a 320mm lens in 35mm.
>>> John
>>>

John is very correct in what he is saying.

All of this confusion is because of the use of that "multiplier". It is
only used by the Camera Manufacturers to give 35mm users an idea of what
sort of View they would get when using any particular Focal Length of Lens
on a Digital Camera. It does not have any other use or meaning, it is only
used for descriptive purposes. It varies from Camera to Camera depending on
the size of the Sensor.

To simplify things let us just talk about the 18mm end of the Zoom.
>>
>>
>> I thought the EF-S lenses were engineered to take the 1.6 multiplier into
>> account and be true to their focal lengths? Yes? No?

Yes - they are true to their Focal Length of 18mm. Which makes them a
Moderate Wide Angle on Digital. They would be Wide Angle on 35mm.
They will give a view when used on a Digital, roughly equivalent to using a
28mm ( wide angle) on a 35mm camera. (Multiplier being applied for
descriptive purposes only)
They are designed for use on Digital Cameras, with the smaller Sensors,
which is where the engineering comes in.
They are still, and always will be 18mm lenses.

>> To what, then, are "they" refering when you see references regarding a
>> "shorter rear element to sensor distance?" Isn't the rear element to
>> sensor distance what dictates the size of the image on the sensor?

No. The distance from the rear element to the Sensor is only a feature of
the design of that particular Lens. It has no effect on light transmission,
or angle of view or anything much. The only thing that does is the Focal
Length, and that is still 18mm.

>> Isn't this why they are not compatible with other EOS cameras becuase
>> you'd get a "reverse crop" and not fill the entire frame with an EF-S
>> lens?

Yes. Because it is designed for a small Digital Sensor, you would only see
a Circular Image in the Viewfinder of a 35mm, and the Lens would hit the
Mirror. BUT, and it is an enomous BUT - The illuminated part of the
viwfinder would show the subject at exactly the same size as it would be
shown by any other 18mm Lens. You just would not be able to see those parts
of the Subject outside the Circle of Light.

>>
>> In 35mm parlance, is the 18-55mm EF-S viewing at 18-55mm or is it viewing
>> at 28.8-88mm?
>>
In 35mm parlance the Efs ACTUALLY IS an 18-55mm Zoom, and is viewing, just
like any other 18-55mm Zoom, except that because of its design it is not
usable on a 35mm Camera, ( unless you can lock up the mirror and are willing
to accept the circular image). In Digital Camera Parlance, the Efs is an
18-55mm Zoom, and is viewing, just like any other 18-55mm Zoom, except that
because it is designed for Digital, it may give a better quality result than
one designed for 35mm.

To let you imagine what that view would be like, assuming you were a 35mm
user who had never looked through a Digital Camera, Canon suggest that it
would give the same sort of view as a 27-82mm on 35mm. That is what the
"Multiplier" is for, and it is only so that 35mm users can imagine what sort
of view they might get, if they changed to a Digital Camera and fitted that
Lens onto it.

Roy
Anonymous
January 29, 2005 2:03:50 PM

Archived from groups: rec.photo.digital (More info?)

>
> This is why DOF is so difficult to control on digicams, as lenses with
> short focal lengths have a greater DOF at a given distance than longer
> lenses at the same aperture at the same distance..
>
>

This is not strictly true as you should scale the diameter of the circle of
confusion for the same level of sharpness, i.e. COF should be c/1.6 for a
1.6X crop factor and a full frame 35mm COF of c.

So the DOF in this case is not exactly the same.

Doing the maths the DOF range (non macro distances) is

H X S H X S
------ to -------
H + S H - S

where H is the hyperfocal distance and S is the focused subject distance.


H=(F X F) / (f X c), F is the focal length of the lens and f is the fstop.

For full frame 35mm a common value of c is 0.03mm but some tables use
F/1000.

So for a sensor crop factor of 1.6 use c=0.03/1.6.

Same sort of thing applies to macro shots but the equations are different.

Sorry for the nerd mode....


Lester
!