Lens multipliers for Canon lenses

cmyk · Jan 4, 2005

Now I am totally confuzzled about lens multipliers. For a 20D it is in round numbers '2'...so for a 20mm lens, it would be the equivalent of a 40mm lens on a 'traditional' film camera.

Went to the local dealer to see what they had (looking to purchase, leaning heavily towards the 20D at the moment). They said for an EF-S digital lens, it is what is marked--so the 20mm lens is 20mm, and no multiplier is necessary.

So...for an EF-S lens, do I need to to the conversion or not???????

hands thrown up in frustration

Side note--they offer internet uploading for printing, and so I asked him about being able to get their color profile...he said that is useless (in not so many words), and that they are all balanced by the person at the shop. Only those 'other' mail order shops let you do that. Heh. So much for supporting a local shop (even though they are a national type chain).

irm · Jan 4, 2005

cmyk said:
Now I am totally confuzzled about lens multipliers. For a 20D it
is in round numbers '2'...so for a 20mm lens, it would be the
equivalent of a 40mm lens on a 'traditional' film camera.

Went to the local dealer to see what they had (looking to purchase,
leaning heavily towards the 20D at the moment). They said for an
EF-S digital lens, it is what is marked--so the 20mm lens is 20mm,
and no multiplier is necessary.

So...for an EF-S lens, do I need to to the conversion or not???????

hands thrown up in frustration

Side note--they offer internet uploading for printing, and so I
asked him about being able to get their color profile...he said
that is useless (in not so many words), and that they are all
balanced by the person at the shop. Only those 'other' mail order
shops let you do that. Heh. So much for supporting a local shop
(even though they are a national type chain).

For a 10D/20D/300D it is 1.6. For a 1D/1DmkII it is 1.3

An EF-S lens is designed to fit a 20D/300D only and doesn't require a multiplier to work out its equivalent FOV.

Now having said that, have you done any searches of this forum or the 300D or the D30/D60/10D/20D forums?
I would also recommend you have a read of the terminknowledgy page.
--
my 2 exposed flashcubes worth.

Ian the pbase supporter.
http://pbase.com/ianm_au
An amateur with dreams of being a good to excellent photographer.

john cornicello · Jan 4, 2005

Focal Length is Focal Length. A lens has a set focal legth. Changing camera bodies (with different size sensors) will not affect the focal length of the lens.

On a 20D the sensor is smaller than a 35mm film frame (or the sensor on a 1Ds). So the field of view is different. Multiply the focal length of the lens by 1.6 to get an idea of what the field of view will look like compared to a full-size sensor.

EF-S lenses are no different. You have to multiply the focal length by 1.6.

If you have an EF-S lens set to 10mm it will give the view of a 16mm lens.

If the EF-S lens is set to 20mm it will give the view of a 32mm lens.

John

cmyk said:
Now I am totally confuzzled about lens multipliers. For a 20D it
is in round numbers '2'...so for a 20mm lens, it would be the
equivalent of a 40mm lens on a 'traditional' film camera.

Went to the local dealer to see what they had (looking to purchase,
leaning heavily towards the 20D at the moment). They said for an
EF-S digital lens, it is what is marked--so the 20mm lens is 20mm,
and no multiplier is necessary.

So...for an EF-S lens, do I need to to the conversion or not???????

hands thrown up in frustration

Side note--they offer internet uploading for printing, and so I
asked him about being able to get their color profile...he said
that is useless (in not so many words), and that they are all
balanced by the person at the shop. Only those 'other' mail order
shops let you do that. Heh. So much for supporting a local shop
(even though they are a national type chain).

irm · Jan 4, 2005

cmyk said:
Now I am totally confuzzled about lens multipliers. For a 20D it
is in round numbers '2'...so for a 20mm lens, it would be the
equivalent of a 40mm lens on a 'traditional' film camera.

Went to the local dealer to see what they had (looking to purchase,
leaning heavily towards the 20D at the moment). They said for an
EF-S digital lens, it is what is marked--so the 20mm lens is 20mm,
and no multiplier is necessary.

So...for an EF-S lens, do I need to to the conversion or not???????

hands thrown up in frustration

Side note--they offer internet uploading for printing, and so I
asked him about being able to get their color profile...he said
that is useless (in not so many words), and that they are all
balanced by the person at the shop. Only those 'other' mail order
shops let you do that. Heh. So much for supporting a local shop
(even though they are a national type chain).

--
my 2 exposed flashcubes worth.

Ian the pbase supporter.
http://pbase.com/ianm_au
An amateur with dreams of being a good to excellent photographer.

RDKirk · Jan 4, 2005

Forget about "crop factors," forget about "magnification factors." Those are garbage jargon created by marketers to get 35mm camera users to go into DSLRs.

Here is how you should think about it, especially if you've never used 35mm before. This is the way people who have used several different formats have thought about it for decades.

First you have to know what the "normal" focal length is for your camera format. The "normal" focal length is the length that does not show wide angle exaggerated perspective or telephoto compressed perspecting. The "normal" focal length is the measure of the diagonal of the format. For your Canon 20D, that's 28mm. The normal focal length for the 20D is 28mm.

Everything longer than 28mm is a telephoto. Everything shorter than 28mm is a wide angle. If you want to magnify your image 2x, you get a lens that's 2x28mm. If you want to get a wide angle twice as wide as the normal focal length, you get a 14mm lens. But just remember that your normal lens is 28mm.

Now, if you want to relate to other formats, such as 35mm, you simply see how their various lenses differ from their normal lenses. The normal lens for a 6x6 medium format camera is 80mm. A 40mm lens is half of the normal focal length, which is equivalent in effect to a lens that's half of YOUR camera's normal focal length. Therefore, a 40mm lens on a Hasselblad is equivalent to a 14mm lens on a 20D.

A 150mm lens on a Hasselblad is nearly twice its normal focal length. That would be equivalent to a lens that twice the normal focal length on a 20D, which would be something in the range of 60mm. Easy.

The normal focal length for 35mm is 50mm (actually, it should be 43mm, but manufacturers settled on 50mm for quirky historical reasons). If you see a picture taken with a 35mm camera using a 100mm lens, you see that's twice the normal focal length for a 35mm camera (2x50mm), so you duplicate the effect with a lens that's twice the normal focal length of a 20D--again, something in the range of 60mm.

People who have used multiple formats for years have never fooled with silly things like "crop factors" and magnification factors. It just confuses things, especially new people.

--
RDKirk
'TANSTAAFL: The only unbreakable rule in photography.'

Just Looking · Jan 4, 2005

irm said:
irm said:

So...for an EF-S lens, do I need to to the conversion or not???????

Click to expand...

An EF-S lens is designed to fit a 20D/300D only and doesn't require
a multiplier to work out its equivalent FOV.

I know, you said below that you got it wrong. But, what's wrong about it?

The truth is, it's true of both EF-S lenses and all other lenses, too. You don't require a multiplier to work out the lens's equivalent Field of View.

Actually, what's wrong is the notion of "equivalent field of view". The lens has a different field of view on each camera, but that's an equivalent field of view?

Probably you meant to refer to the "35mm FOV-equivalent Focal Length". That's the focal length of a hypothetical lens that would give you the same field of view if used on a full-frame 35mm camera. To get that, of course, you multiply your camera's actual focal length by your camera's FLM or cropfactor.

It makes not one bit of difference what format the lens was designed for or what the mount is called.

j

Just Looking · Jan 4, 2005

RDKirk said:
Forget about "crop factors," forget about "magnification factors."
Those are garbage jargon created by marketers to get 35mm camera
users to go into DSLRs.

That sure wasn't a big success, was it? I agree that "crop factor" is the worst possible name, because it seems to not apply in the case of a lens being used for the format it was designed for. Hence the orignal poster's confusion.

But the idea of knowing the factor and using it for comparisons is not without some value. I always thought FLM (focal length multiplier) made more sense. Its a factor that you multiply your focal length by to get a 35mm-FOV-equivalent Focal Length. Simple enough.

j

Just Looking · Jan 4, 2005

john cornicello said:
Focal Length is Focal Length. A lens has a set focal legth.
Changing camera bodies (with different size sensors) will not
affect the focal length of the lens.

On a 20D the sensor is smaller than a 35mm film frame (or the
sensor on a 1Ds). So the field of view is different. Multiply the
focal length of the lens by 1.6 to get an idea of what the field of
view will look like compared to a full-size sensor.

EF-S lenses are no different. You have to multiply the focal length
by 1.6.

If you have an EF-S lens set to 10mm it will give the view of a
16mm lens.

If the EF-S lens is set to 20mm it will give the view of a 32mm lens.

John, allow me to get ultra picky with you. I do this because informal speaking just propagates the confusion. If you can't state truth precisely, you can do more harm that good.

The only place you mentioned 35mm format above is in a comparison to 20D sensor, "smaller than a 35mm film frame." Yet almost everything else you said is meaningless unless it is carefully qualified as being with respect to the full-frame 35mm format.

"Multiply the focal length of the lens by 1.6 to get an idea of what the field of view will look like compared to a full-size sensor" makes no sense, mixing up comparisons of focal lengths, fields of view, and sensors. You meant to say "Multiply the focal length of the lens by 1.6 to find what focal length lens on a full-frame 35mm format camera would have the same field of view as your lens on your camera."

"EF-S lenses are no different. You have to multiply the focal length by 1.6" is false. It can be made true by saying "EF-S lenses are no different. You can multiply the focal length by 1.6 to find the 35mm FOV-equivalent focal length."

"If you have an EF-S lens set to 10mm it will give the view of a 16mm lens" is false. Make it true as "If you have an EF-S lens set to 10mm it will give you the same field of view as a 16mm lens on a full-frame 35mm camera."

Get it?

j

Just Looking · Jan 4, 2005

cmyk said:
Now I am totally confuzzled about lens multipliers.

From the various responses and my comments on them you by now might be aware why you or anyone are so confuzzled.

Here's the key to unconfuse you: the factor goes with the camera. All lenses are marked with their actual focal length. Lens type and brand don't matter.

j

cmyk · Jan 4, 2005

Thank You everyone!!...now it all makes sense... Effectively just a way to convert FOV on a particular camera to some 'standard' (in this case from a dSLR to a 35mm-filmSLR).

irm · Jan 4, 2005

I was apologising because I thought incorrectly that the S on an EFS lens indicated they were designed to provide a full FOV for the smaller chip size in the 300D and 20D with additional physical changes to the mount eg 10mm = 10mm FOV on a 300D not the FOV equivalent.

I will leave it at that.

--
my 2 exposed flashcubes worth.

Ian the pbase supporter.
http://pbase.com/ianm_au
An amateur with dreams of being a good to excellent photographer.

peteb · Jan 5, 2005

Since the person at this shop obviously doesn't know if it is Monday or Marble Arch.

cmyk said:
Now I am totally confuzzled about lens multipliers. For a 20D it
is in round numbers '2'...so for a 20mm lens, it would be the
equivalent of a 40mm lens on a 'traditional' film camera.

Went to the local dealer to see what they had (looking to purchase,
leaning heavily towards the 20D at the moment). They said for an
EF-S digital lens, it is what is marked--so the 20mm lens is 20mm,
and no multiplier is necessary.

All lenses are what they are marked as, so an EF-S lens marked as 20mm is 20mm. But so are EF lenses. The framing you'll get on either an EF or and EF-S lens marked the same focal length will be identical on a camera with the same sensor size though. EF-S lenses are not marked differently or relative to their 'crop' factor.

cmyk said:
So...for an EF-S lens, do I need to to the conversion or not???????

Yup, sorry.

cmyk said:
hands thrown up in frustration

Side note--they offer internet uploading for printing, and so I
asked him about being able to get their color profile...he said
that is useless (in not so many words), and that they are all
balanced by the person at the shop. Only those 'other' mail order
shops let you do that. Heh. So much for supporting a local shop
(even though they are a national type chain).

As I said above, you go to the time of colour matching your shots, then some twerp in the back room adjusts the slider according to what colour he or she 'thinks' your curtains should be.... Run, don't walk away...

--
http://public.fotki.com/wibble/public_display/

RDKirk · Jan 5, 2005

Just Looking wrote:
ster's confusion.

Just Looking said:
But the idea of knowing the factor and using it for comparisons is
not without some value. I always thought FLM (focal length
multiplier) made more sense. Its a factor that you multiply your
focal length by to get a 35mm-FOV-equivalent Focal Length. Simple
enough.

The problem there is in making 24x36mm an absolute base format. As has not been the case in 50 years, we will have people deeply involved in photography who may never use the 24x36mm format.

So what do they care about what the 35mm equivalent is? The more basic (and easier) skill is to equate any format with any other format. It wouldn't make much sense for a person who used a Canon 20D and an Olympus E-1 to compare his lenses by converting both to 24x36mm format. It makes much more sense to understand the differences from the normal focal lengths of each format he actually uses.

--
RDKirk
'TANSTAAFL: The only unbreakable rule in photography.'

BlueEyesPhoto · Jan 5, 2005

EF-S lenses are designed to NOT have a multiplier effect. They are set back into the camera body further, thus why is only works on certain cameras.

john cornicello said:
On a 20D the sensor is smaller than a 35mm film frame (or the
sensor on a 1Ds). So the field of view is different. Multiply the
focal length of the lens by 1.6 to get an idea of what the field of
view will look like compared to a full-size sensor.

EF-S lenses are no different. You have to multiply the focal length
by 1.6.

If you have an EF-S lens set to 10mm it will give the view of a
16mm lens.

If the EF-S lens is set to 20mm it will give the view of a 32mm lens.

John

cmyk said:

Now I am totally confuzzled about lens multipliers. For a 20D it
is in round numbers '2'...so for a 20mm lens, it would be the
equivalent of a 40mm lens on a 'traditional' film camera.

Went to the local dealer to see what they had (looking to purchase,
leaning heavily towards the 20D at the moment). They said for an
EF-S digital lens, it is what is marked--so the 20mm lens is 20mm,
and no multiplier is necessary.

So...for an EF-S lens, do I need to to the conversion or not???????

hands thrown up in frustration

Side note--they offer internet uploading for printing, and so I
asked him about being able to get their color profile...he said
that is useless (in not so many words), and that they are all
balanced by the person at the shop. Only those 'other' mail order
shops let you do that. Heh. So much for supporting a local shop
(even though they are a national type chain).

Click to expand...

--
http://www.pbase.com/blueeyesphoto/

BlueEyesPhoto · Jan 5, 2005

That "so-called" jargon is actually the best way to describe it.

You're trying to say that a Canon 70-200 mm IS lens is different based on the camera . . . yeah, sure.

A 35 mm formatted lens will be a 35 mm formatted lens whether or not it's a 35mm film plane or a 28mm digital sensor. Saying to think of it as anything different is a little odd, to say the least.

They used to call it "magnification factor" because a 100mm lens on a 10D would give you the same FOV as a 160mm lens on a 1V. This worked for a while to help "ease" photographers into digital because they could understand that. A lot of people, liked that your lens was more "powerful" now. And even now, a lot of photographers love that little "perk."

But alas, you get people who get upset at being fooled . . . because really, you weren't magnifying anything. Instead, you were taking a larger image and cropping it. My God, we have a CROP FACTOR. Take a picture, any ol' picture will do my friend. Now, take this picture and assume it was shot with a 35mm film plane. Now, assuming your picture was an 8x10, crop it down to a 4x5. Just find something and crop down. Now, once you have your 4x5 crop, enlarge it to an 8x10.

Now you got two 8x10's, right? One looks "zoomed in" or "magnified." Why you ask? Because you cropped it, duh. That's what a 28mm digital sensor does when you attach a 35mm formatted lens onto it. Instead of recording the entire possible image provided by the lens, you're only recording the 4x5 crop and blowing it up to an 8x10. See where we're going with this . . . ?

Now, an EF-S lens, which is a 28mm formatted lens (catching up yet?) is designed to cast it's image over a 29mm diagonal plane, thus no cropping. However, if you were to stick this lens on a 35mm film plane (which isn't possible btw) you would wind up with an 8x10 print with only a 4x5 image on that sheet. You would just have a giant black frame . . .

Essnetially, the moved the lens further back in the camera, so NEVER attach an EF-S lens to a EF only mount, you'll damage your mirror.

RDKirk said:
Forget about "crop factors," forget about "magnification factors."
Those are garbage jargon created by marketers to get 35mm camera
users to go into DSLRs.

Here is how you should think about it, especially if you've never
used 35mm before. This is the way people who have used several
different formats have thought about it for decades.

First you have to know what the "normal" focal length is for your
camera format. The "normal" focal length is the length that does
not show wide angle exaggerated perspective or telephoto compressed
perspecting. The "normal" focal length is the measure of the
diagonal of the format. For your Canon 20D, that's 28mm. The
normal focal length for the 20D is 28mm.

Everything longer than 28mm is a telephoto. Everything shorter
than 28mm is a wide angle. If you want to magnify your image 2x,
you get a lens that's 2x28mm. If you want to get a wide angle
twice as wide as the normal focal length, you get a 14mm lens. But
just remember that your normal lens is 28mm.

Now, if you want to relate to other formats, such as 35mm, you
simply see how their various lenses differ from their normal
lenses. The normal lens for a 6x6 medium format camera is 80mm. A
40mm lens is half of the normal focal length, which is equivalent
in effect to a lens that's half of YOUR camera's normal focal
length. Therefore, a 40mm lens on a Hasselblad is equivalent to a
14mm lens on a 20D.

A 150mm lens on a Hasselblad is nearly twice its normal focal
length. That would be equivalent to a lens that twice the normal
focal length on a 20D, which would be something in the range of
60mm. Easy.

The normal focal length for 35mm is 50mm (actually, it should be
43mm, but manufacturers settled on 50mm for quirky historical
reasons). If you see a picture taken with a 35mm camera using a
100mm lens, you see that's twice the normal focal length for a 35mm
camera (2x50mm), so you duplicate the effect with a lens that's
twice the normal focal length of a 20D--again, something in the
range of 60mm.

People who have used multiple formats for years have never fooled
with silly things like "crop factors" and magnification factors.
It just confuses things, especially new people.

--
RDKirk
'TANSTAAFL: The only unbreakable rule in photography.'

--
http://www.pbase.com/blueeyesphoto/

Ron Parr · Jan 5, 2005

BlueEyesPhoto said:
EF-S lenses are designed to NOT have a multiplier effect. They are
set back into the camera body further, thus why is only works on
certain cameras.

No. The focal length marked on the lens in the true focal length.

If you want to compare to your 35mm film experience field of view you need to multiply the true focal length by 1.6.

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/

peteb · Jan 5, 2005

RDKirk said:
RDKirk said:

But the idea of knowing the factor and using it for comparisons is
not without some value. I always thought FLM (focal length
multiplier) made more sense. Its a factor that you multiply your
focal length by to get a 35mm-FOV-equivalent Focal Length. Simple
enough.

Click to expand...

The problem there is in making 24x36mm an absolute base format.
As has not been the case in 50 years, we will have people deeply
involved in photography who may never use the 24x36mm format.

But they are all already familiar with 35mm equivalence. The P&S cameras all quote to the 35mm equivalent first, then their real 8-50mm or whatever they are. In an ideal world you are correct, however the world isn't ideal and people want to be able to use a quick and dirty comparison. The world that doesn't deal in 35mm equivalence is, frankly, very small and historically highly professional and/or serious amatuers, not today's Joe Public.

RDKirk said:
So what do they care about what the 35mm equivalent is? The more
basic (and easier) skill is to equate any format with any other
format. It wouldn't make much sense for a person who used a Canon
20D and an Olympus E-1 to compare his lenses by converting both to
24x36mm format. It makes much more sense to understand the
differences from the normal focal lengths of each format he
actually uses.

--
RDKirk
'TANSTAAFL: The only unbreakable rule in photography.'

--
http://public.fotki.com/wibble/public_display/

peteb · Jan 5, 2005

But they still frame on the 20D/300D as if they were 1.6x the focal length of a 35mm frame lens used on a 35mm format. Using a 10-22mm lens on 20D/300D from the same (viewing) position as a 1Ds with a 16-35mm lens yields the same frame (give or take), with the exception that the 1Ds shot has less DOF at the same aperture.

BlueEyesPhoto said:
john cornicello said:

On a 20D the sensor is smaller than a 35mm film frame (or the
sensor on a 1Ds). So the field of view is different. Multiply the
focal length of the lens by 1.6 to get an idea of what the field of
view will look like compared to a full-size sensor.

EF-S lenses are no different. You have to multiply the focal length
by 1.6.

If you have an EF-S lens set to 10mm it will give the view of a
16mm lens.

If the EF-S lens is set to 20mm it will give the view of a 32mm lens.

John

cmyk said:

Now I am totally confuzzled about lens multipliers. For a 20D it
is in round numbers '2'...so for a 20mm lens, it would be the
equivalent of a 40mm lens on a 'traditional' film camera.

Went to the local dealer to see what they had (looking to purchase,
leaning heavily towards the 20D at the moment). They said for an
EF-S digital lens, it is what is marked--so the 20mm lens is 20mm,
and no multiplier is necessary.

So...for an EF-S lens, do I need to to the conversion or not???????

hands thrown up in frustration

Side note--they offer internet uploading for printing, and so I
asked him about being able to get their color profile...he said
that is useless (in not so many words), and that they are all
balanced by the person at the shop. Only those 'other' mail order
shops let you do that. Heh. So much for supporting a local shop
(even though they are a national type chain).

Click to expand...

Click to expand...

--
http://www.pbase.com/blueeyesphoto/

--
http://public.fotki.com/wibble/public_display/

BlueEyesPhoto · Jan 5, 2005

Um, a EF-S lens will give you the field of view marked on the lens . . . which would be the same field of view if you were using that same length lens on a 35mm format camera . . . The EF-S (which are SPECIAL lenses) give you the equvilant of a 35mm film plane experience because there is no cropping. . .

Film experience?

Ron Parr said:
BlueEyesPhoto said:

EF-S lenses are designed to NOT have a multiplier effect. They are
set back into the camera body further, thus why is only works on
certain cameras.

Click to expand...

No. The focal length marked on the lens in the true focal length.

If you want to compare to your 35mm film experience field of view
you need to multiply the true focal length by 1.6.

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/

--
http://www.pbase.com/blueeyesphoto/

Ron Parr · Jan 5, 2005

EF-S is a mount. The specification permits a shorter backfocus distance, but doesn't require it.

A 24mm EF-S lens and a 24mm EF lens will both behave exactly the same way - excpet that an EF-S lens MIGHT vignette if used on a 24x36 mm capture medium.

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/

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