Canon says: more EF-S lenses

Started Oct 6, 2004 | Discussions thread
bds231
Regular MemberPosts: 404
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Re: Canon says: more EF-S lenses
In reply to ChuckH, Oct 7, 2004

I think you're confusing the physics of photography with the reality we've been forced into with our 1.6x dSLRs.

Remember that originally, the size of the 35mm film frame was arbitrarily chosen.

(As the anecdote goes: "One day Thomas Edison (I think it was him) and Eastman Kodak were sitting around playing with a lightbulb (or doing some other such inane thing...). Edison said, 'So how big do you want that new film stuff to be?' Kodak considered for a moment, held his thumb and forefinger about 35mm apart, and said 'Something like this.' And 35mm film was born).

Therefore, a 28mm lens is not intrinsically a wide angle lens. In fact, if you put such a lens on a tiny sensor, like that found in an ultra-compact digicam, it's a telephoto lens. And a quality wideangle lens on such a sensor, which might have a focal length of around 7mm, wouldn't necessarily have significant distortion.

We only think of 28mm as a wideangle lens because, on the 35mm film frame, it draws a wide angle of light onto the film. It does so because its focal length (28mm) is significantly less than the diagonal of the 35mm film frame ( 43mm). And that relationship is also why it produces distortion.

You're right, a 28mm lens is almost exactly 'normal' on a 1.6x sensor (that is, it provides an angle of view similar to what the human eye sees, etc.). But if you made a 28mm lens that was designed to cast an image circle only as large as the 1.6x sensor itself (22.7mm x 15.1mm), there's no fundamental reason it should show any more distortion than a conventional 43mm lens on a full frame camera.

Ben

ChuckH wrote:

bka1 wrote:

i agree with you...people keep making the assumption that full
frame is coming to the masses andd yet lens development and camera
development keep suggesting otherwise. perhaps people need to
re-orient their thinking. i've never heard a medium format person
complaining about not being able to use a 50mm lens for a normal
perspective, they understand that for them (6 x4.5 that is) the
35mm camera equivalent to a 50mm lens for thier camera is an 80mm
lens. when i talk about a normal perspective lens with my 10d/20d i
think interms of a 35mm lens as oppose to the 50mm lens that is
regarded as the normal lens for film slr.

The problem is that wide angle lenses introduce a fair bit of
perspective distortion. So, in order to duplicate the perspective
of a normal lens with the 1.6 crop factor, one has to settle for a
fair bit of distortion. Such is not the case for a medium format
photographer using an 80mm lens to achieve the same perspective.

That, in my opinion, is the biggest drawback to an increased
emphasis on smaller sensors and EF-S lenses. Wide angle lenses are
the most difficult to design and still end up producing the most
distortion. As a result, in our attempts to achieve a normal
perspective, we find ourselves paying more for lenses that don't
perform nearly as well. Consider the fact that Canon's 50mm f/1.8
lens is by far the cheapest in the lineup and yet is optically
excellent whereas the 28mm lens that produces a roughly equivalent
perspective on a 1.6X crop factor camera costs many times the price
and yields a far more distorted image.
--
Chuck

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