What's the point of EF-S lenses?

Eric Sorensen · Aug 19, 2004

Frank Weston said:
I'm encouraged that Canon is introducing more EF-S lenses ...

You must not have a 10D, which is not EF-S compatable.

--
Eric.
N8BTL

'Charlie don't surf.'

Sheld · Aug 19, 2004

Even the 28-135, which is the FF equivalent of the 17-85, is telecentric. That's because the SLR lens box is about 35mm or so between the mount and the sensor/film plane. I think any SLR lens wider than 35mm has to be at least a little bit telecentric, or reverse telephoto, in design.

Shel

Michael Schaefer said:
p5freak said:

neorf said:

Can anyone tell me the point of EF-S lenses? Are they technically
different/better or what? If so, what makes them different/better?

I don't see why canon would make lenses that only work on 2 of
their cameras.

Thanks,

Phil

Click to expand...

--
Stupid is as stupid does - Forrest Gump

Click to expand...

Michael Schaefer · Aug 19, 2004

Sheld said:
Even the 28-135, which is the FF equivalent of the 17-85, is
telecentric. That's because the SLR lens box is about 35mm or so
between the mount and the sensor/film plane. I think any SLR lens
wider than 35mm has to be at least a little bit telecentric, or
reverse telephoto, in design.

A retrofocal design is needed for any lens having a focal length of 42 mm or less. This, however, does not mean that the lens has a telecentric design (and the 28-135 hasn´t). A telecentric design (faced to the sensor) means that the position of the exit pupil is in infinite. Any zoom lens has a certain variability in the position of the exit pupil and, therefore, cannot be really 100% telecentric.

What we are talking about is a relative telecentric design. The four-thirds specs claim telecentricity of their lenses if the exit pupil features an at least sixfold distance from the sensor compared to the largest sensor diameter.

Frank Weston · Aug 19, 2004

Actually, I do. But, I'm considering the 20D if noise levels are comparable to the 10D.

Eric Sorensen said:
Frank Weston said:

I'm encouraged that Canon is introducing more EF-S lenses ...

Click to expand...

You must not have a 10D, which is not EF-S compatable.

--
Eric.
N8BTL

'Charlie don't surf.'

--
Frank Weston - http://www.weston.smugmug.com

JamesMD · Aug 19, 2004

neorf said:
Can anyone tell me the point of EF-S lenses? Are they technically
different/better or what? If so, what makes them different/better?

I don't see why canon would make lenses that only work on 2 of
their cameras.

Thanks,

Phil

JamesMD · Aug 19, 2004

for Canon's mid range dslr's. Something for every price level. Good Job Canon : )

ngap · Aug 19, 2004

Shan Zhu said:
characteristics of EF-S lenses into "1)" and "2)" which most
people do not.

I completely agree with your view of "1)".

But for "2)", I am pretty sure that it will also drastically reduce
the cost because it naturally reduces the focal length (for
wide angle lenses) without introducing the optical complication.

Think this way, it is euivalent to shrink a full frame camera with
an EF lens by 1.6 factor. This means you need to also reduce
the overall distance from the lens to the sensor.

Changing sensor size does not change focal length. A 18mm lens has to be the same distance away for any sensor size.

The reason given by Canon doesn't seem to fit with other brands.

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What's the point of EF-S lenses?

Eric Sorensen

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Sheld

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Michael Schaefer

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Frank Weston

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JamesMD

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