Canon 350D + EF 28-105 lens = actually 45-160?

I have a Canon 350D with the standard bundled kit lens. I may get
another lens, like the Canon EF 28-105 F3.5-4.5 II USM. But I ran
across some confusing comments. I know that digital cameras have a
different size (smaller?) image sensor (than 35mm film) and that if you
mix and match lenses it changes things. "I did extensive research and
finally decided on the 28-105 canon. This equates to 45-160 which is
good walking around range." and "It is sad that canon has absolutely NO
cost effective lens equivalent of the ubiquitous 28-105 for a DSLR."

Are these comments (full quotes below) due to the smaller image sensor
on digital cameras?
Is the Canon EF 28-105 F3.5-4.5 (II) USM actually not a digital lens,
that is, it was designed originally for 35mm film cameras?
Is that why the guy says "28-105 equates to 45-160"? Does this imply
that the F3.5-4.5 should also be recalculated?
Is the kit lens a "digital lens" i.e. its focal length and aperture
numbers don't need any recalculation?
Are Canon and everyone planning to move the camera bodies to new 35mm
sized digital sensors, so they figure there's no reason to re-design
the lenses, in anticipation of that?
If I stick this lens on a 350D (= Rebel XT), do I end up "using just
the middle of the lens", and iisn't there some downside to that?

Steve

-----
Here are the 2 comments that got me scratching my head:

"First off I don't own an 18-55. I've been using the first and the
second iteration of this lens, the ones which came along with the 300D
and 350D. From all the photos I've shot with these lenses, they are
both worse than almost all other lenses I've used, except for
(possibly) the canon 28-90 kit lens which comes along with the film SLR
kits.

When I compare this lens with the canon 20-35 and 28-105, the 18-55 is
much worse wide open, and doesn't get any better even at f/8. I am
quite surprised at this performance, by f/8 most lenses are pretty darn
good, and the copy of the 28-105/3.5-4.5USM I have gives the 28-70L a
good run for the money at f/8 between 40-70mm.

It is sad that canon has absolutely NO cost effective lens equivalent
of the ubiquitous 28-105 for a DSLR. The 17-85IS is not something I'd
get, given that it's an EF-S lens, and at that price. The 18-55 is
something I'd not even consider. The alternatives are a very expensive
17-40L or an even more expensive 16-35L. Nikon has a very good 17-55
AF-S ED lens which does a great job.

Come on Canon, it's been years with 1.6x DSLR's, we don't have a single
decent mid range zoom. What are they thinking?

-- Vincent J M, May 26, 2005





"This is a great lens. I bought the digital rebel kit recently and soon
'outgrew' the efs 18-55 kit lens. It is particularly soft at large
apertures and makes it totally unsuitable for indoor handheld
photography. I decided to go for 35 mm lenses rather than 'digital'
format lenses as an upgrade to the kit lens. They are lower in price
(relatively) and you also only see the center of the lens where the
picture quality is the best. The Quantaray 28-200 (this is actualy a
tamron) was the first lens I considered. i returned it after just 2
photos. it was much worse than the kit lens. Then I did extensive
research and finally decided on the 28-105 canon. This equates to
45-160 which is good walking around range. Also fro outdoor wide angle
landscapes, the kit lens good enough stopped down. I got the lens today
from adorama and the indoor test photos are GREAT and show fine detail.
The shallow DOF in macro mode is also nice. The kit lens is no
comparison to this lens. I would highly recommend this to new
enthusiast dslr (like Drebel)users on a tight budget but also crave for
more from their digital rebel. All in all a wonderful lens. And did I
say the build quality is great too not to mention the ghostly silent
lightening fast focussing?

Steve wrote:
I have a Canon 350D with the standard bundled kit lens. I may get
another lens, like the Canon EF 28-105 F3.5-4.5 II USM. But I ran
across some confusing comments. I know that digital cameras have a
different size (smaller?) image sensor (than 35mm film) and that if
you mix and match lenses it changes things. "I did extensive research
and finally decided on the 28-105 canon. This equates to 45-160 which
is good walking around range." and "It is sad that canon has
absolutely NO cost effective lens equivalent of the ubiquitous 28-105
for a DSLR."

The "digital" lenses do not need to be recalculated as they are specked
out at their true focal length, not their equivalent full frame size. Just
to be sure, you should compare the angular width not the focal length. Also
keep in mind that Canon uses several different sizes sensors not just two.


Are these comments (full quotes below) due to the smaller image sensor
on digital cameras?
Is the Canon EF 28-105 F3.5-4.5 (II) USM actually not a digital lens,
that is, it was designed originally for 35mm film cameras?
Is that why the guy says "28-105 equates to 45-160"? Does this imply
that the F3.5-4.5 should also be recalculated?
Is the kit lens a "digital lens" i.e. its focal length and aperture
numbers don't need any recalculation?
Are Canon and everyone planning to move the camera bodies to new 35mm
sized digital sensors, so they figure there's no reason to re-design
the lenses, in anticipation of that?
If I stick this lens on a 350D (= Rebel XT), do I end up "using just
the middle of the lens", and iisn't there some downside to that?

Steve

-----
Here are the 2 comments that got me scratching my head:

"First off I don't own an 18-55. I've been using the first and the
second iteration of this lens, the ones which came along with the 300D
and 350D. From all the photos I've shot with these lenses, they are
both worse than almost all other lenses I've used, except for
(possibly) the canon 28-90 kit lens which comes along with the film
SLR kits.

When I compare this lens with the canon 20-35 and 28-105, the 18-55 is
much worse wide open, and doesn't get any better even at f/8. I am
quite surprised at this performance, by f/8 most lenses are pretty
darn good, and the copy of the 28-105/3.5-4.5USM I have gives the
28-70L a good run for the money at f/8 between 40-70mm.

It is sad that canon has absolutely NO cost effective lens equivalent
of the ubiquitous 28-105 for a DSLR. The 17-85IS is not something I'd
get, given that it's an EF-S lens, and at that price. The 18-55 is
something I'd not even consider. The alternatives are a very expensive
17-40L or an even more expensive 16-35L. Nikon has a very good 17-55
AF-S ED lens which does a great job.

Come on Canon, it's been years with 1.6x DSLR's, we don't have a
single decent mid range zoom. What are they thinking?

-- Vincent J M, May 26, 2005





"This is a great lens. I bought the digital rebel kit recently and
soon 'outgrew' the efs 18-55 kit lens. It is particularly soft at
large apertures and makes it totally unsuitable for indoor handheld
photography. I decided to go for 35 mm lenses rather than 'digital'
format lenses as an upgrade to the kit lens. They are lower in price
(relatively) and you also only see the center of the lens where the
picture quality is the best. The Quantaray 28-200 (this is actualy a
tamron) was the first lens I considered. i returned it after just 2
photos. it was much worse than the kit lens. Then I did extensive
research and finally decided on the 28-105 canon. This equates to
45-160 which is good walking around range. Also fro outdoor wide angle
landscapes, the kit lens good enough stopped down. I got the lens
today from adorama and the indoor test photos are GREAT and show fine
detail. The shallow DOF in macro mode is also nice. The kit lens is no
comparison to this lens. I would highly recommend this to new
enthusiast dslr (like Drebel)users on a tight budget but also crave
for more from their digital rebel. All in all a wonderful lens. And
did I say the build quality is great too not to mention the ghostly
silent lightening fast focussing?

--
Joseph Meehan

Dia duit

"Steve" wrote in message
ups.com...
I have a Canon 350D with the standard bundled kit lens. I may get
another lens, like the Canon EF 28-105 F3.5-4.5 II USM. But I ran
across some confusing comments. I know that digital cameras have a
different size (smaller?) image sensor (than 35mm film)
Snipped.

Hi.

The specified Focal Lengths for lenses are accurate, whatever size of Film
or Sensor they are going to be used with.

A 18 mm lens is a 18 mm lens always and can not be anything except a 18 mm
lens.

When that lens is used on a DSLR it is a moderate Wide Angle. When it is
used on a 35mm Film or a "Full Frame Digital" Camera it is an Extreme Wide
Angle. If it could be fitted to a Med. Format Camera it would be a Fisheye.
(Assuming it could cover that big frame).

The only thing that varies is the Frame Size of the Camera, and that has an
effect on the amount of the subject which will be included in the image, at
any given Camera / Subject distance.

Hence the use of the Phrase "Crop Factor", and its associated "Multiplier"

Roy G

I'm confused. What do you mean "lenses do not need to be recalculated"?
Focal length is focal length, but unless the camera has full-frame
sensor (Canon 30D), you have to recalculate, because almost all of us
think in terms of 35mm (film frame) dimensions. A 21mm lens is almost
an extreme wide angle on a 35mm, but it's equivalent to 33mm on, say, a
350D, and a 42mm on an Olympus. And the 35mm standard is handy, because
we all know what sort of lens we're talking about.
Doubletruck

Hmmm... so is it accurate to say that,

35mm film camera bodies have a 35mm "sensor" (i.e. the film)
DSLR's have 25mm sensors (?) (some newer ones have 35mm sensors?)
The "crop factor" "multiplier" is 1.6.

e.g. if I bought a 28mm F3.5 "prime" lens, it would give me just that
on a 35mm film body.
but if I fit it to my 350D DSLR, it would actually crop rather a lot of
the image,
and behave as though it were a 45mm lens on a body with a 35mm sensor.
In other words, the outer edges would go outside the sensor edges,
resulting in cropping.
And by extension, in that situation, I'm only using the inner parts of
the lens glass.
It seems to me that this would mean I'm losing some light then, and as
such there
should also be a "multiplier" for a change to the effective F stop??
Or is it merely that I'm just carrying around extra glass and weight,
compared to
a lens that was designed to focus straight onto a DSLR 25mm sensor?
Should I then get an adapter (adding another lens, and more weight) to
get around this?
And... the stock kit lens... its also quoted in the same old 35mm
metrics and subject
to cropping alike?

I see that the 30D, and I suppose the 20D, have a "22.5 x 15.0 mm CMOS
sensor"

Let me put it another way. My wife says that a 90mm prime lens is the
bees knees for portrait photography. So if we had a 20D, we'd get a
85mm prime lens and enjoy great boket.

But since we have a 350D, the 50mm lens, after the multiplier or
cropping effect, is about 80mm. So is this the right equivalent lens to
use for portraits?

You can see my confusion, what I'm trying to understand is the actual
differences between using an 85mm prime on a 20D with its big CMOS 35mm
equivalent image sensor, and on a DSLR. I can see that I can get the
equivalent angles, but is there any loss in F stop or depth of field?
It seems to me that of course if I put an 85mm prime on a DSLR I'd only
use the center of the lens, get a lot of cropping, and pay for and
carry around extra glass that never projects onto the sensor. That in
effect I'd have a 136mm lens.

I put a 50mm prime on a 350D, do I have a 100% equivalent situation to
an 85mm prime on the 20D?

"Steve" wrote in message
oups.com...
Hmmm... so is it accurate to say that,

35mm film camera bodies have a 35mm "sensor" (i.e. the film)
DSLR's have 25mm sensors (?) (some newer ones have 35mm sensors?)
The "crop factor" "multiplier" is 1.6.

e.g. if I bought a 28mm F3.5 "prime" lens, it would give me just that
on a 35mm film body.
but if I fit it to my 350D DSLR, it would actually crop rather a lot of
the image,
and behave as though it were a 45mm lens on a body with a 35mm sensor.
In other words, the outer edges would go outside the sensor edges,
resulting in cropping.
And by extension, in that situation, I'm only using the inner parts of
the lens glass.
It seems to me that this would mean I'm losing some light then, and as
such there
should also be a "multiplier" for a change to the effective F stop??
Or is it merely that I'm just carrying around extra glass and weight,
compared to
a lens that was designed to focus straight onto a DSLR 25mm sensor?
Should I then get an adapter (adding another lens, and more weight) to
get around this?
And... the stock kit lens... its also quoted in the same old 35mm
metrics and subject
to cropping alike?

Hi.

You are correct, only part of the image gathered by the lens will fall on
the sensor.

The size of the sensor determines the so called "Multiplier", which is
really only of use to people who still think in terms of the sort of image
produced by various focal length lenses on 35mm cameras.

All parts of the lens surface contribute to producing all parts of the
image, but very generally speaking the central part of most images has the
better quality.

The maximum F number for any lens is determined by a calculation which does
not involve the sensor size. Therefore it does not change, and the amount
of light falling on the sensor is still determined by the specified F
number.

Lenses for 35mm cameras tend to be bulkier and heavier than the same Focal
Length lenses designed for Digitals.

No, do not think about lens adaptors, just learn what sort of image a
particular Focal length of lens will produce on a Digital.

No, the Kit lens is not quoted in "Old 35mm Metrics" it is quoted in its
actual focal length. The Focal Length of a lens is not dependant on the
Sensor size, it only depends on the physical construction of the lens.

A "17 to 55mm" Zoom lens is a "17 to 55mm" Zoom lens no matter what camera,
or none, it is mounted on.

Roy G

"Steve" wrote in message
oups.com...
Let me put it another way. My wife says that a 90mm prime lens is the
bees knees for portrait photography. So if we had a 20D, we'd get a
85mm prime lens and enjoy great boket.

But since we have a 350D, the 50mm lens, after the multiplier or
cropping effect, is about 80mm. So is this the right equivalent lens to
use for portraits?

You can see my confusion, what I'm trying to understand is the actual
differences between using an 85mm prime on a 20D with its big CMOS 35mm
equivalent image sensor, and on a DSLR. I can see that I can get the
equivalent angles, but is there any loss in F stop or depth of field?
It seems to me that of course if I put an 85mm prime on a DSLR I'd only
use the center of the lens, get a lot of cropping, and pay for and
carry around extra glass that never projects onto the sensor. That in
effect I'd have a 136mm lens.

I put a 50mm prime on a 350D, do I have a 100% equivalent situation to
an 85mm prime on the 20D?

Hi again.

You really are getting your knickers in a right twist about this.

Roughly speaking a 50mm on a DSLR will give a similar image as a 80mm on a
35mm Camera.

The 20D is a DSLR and has a similar sensor size to the Rebels. Crop factor
of 1.6. I know that and I am a long time Nikon user. (Nikons have a crop
factor of 1.5)

The F numbers on the lenses apply irrespective of the Sensor or Film size.

The advantage of the bulkier and heavier 35mm lenses, is that they will work
on Full Frame cameras, but the smaller lighter lenses designed for Digital
won't.

Roy G

"Steve" wrote in message
oups.com...
Let me put it another way. My wife says that a 90mm prime lens is the
bees knees for portrait photography. So if we had a 20D, we'd get a
85mm prime lens and enjoy great boket.

But since we have a 350D, the 50mm lens, after the multiplier or
cropping effect, is about 80mm. So is this the right equivalent lens to
use for portraits?

You can see my confusion, what I'm trying to understand is the actual
differences between using an 85mm prime on a 20D with its big CMOS 35mm
equivalent image sensor, and on a DSLR. I can see that I can get the
equivalent angles, but is there any loss in F stop or depth of field?
It seems to me that of course if I put an 85mm prime on a DSLR I'd only
use the center of the lens, get a lot of cropping, and pay for and
carry around extra glass that never projects onto the sensor. That in
effect I'd have a 136mm lens.

I put a 50mm prime on a 350D, do I have a 100% equivalent situation to
an 85mm prime on the 20D?

Ok, you have one problem here, the 20D has the same size sensor as the 350D.
It's the 5D and 1Ds mkII that have 35mm sized sensors. In that context, you
would get the same composition, standing the same distance from your
subject, on an image with a 50mm on a 350D or 20D that you would, roughly,
with an 85mm lens on a 5D. Actually it would be the same as an 80mm lens,
but, hey, who's picky? BUT! You run into other problems, like distortion
if you're too close to your subject, since it really is a 50mm lens, not an
80mm.
BTW, the new 30D has the same sensor as the 20D, too.
--
Skip Middleton
http://www.shadowcatcherimagery.com