Wide Angle lense for newbie (20D)

Wilt wrote in post #7660497
I agree with your post, except for the urban legend in red!

A 'normal' lens by convention is (about) the diagonal measure of the frame. 135 film format, being 24x36mm has a diagonal of 42mm, but the convention of 'about 50mm' was adopted decades ago, and we see 135 film cameras with 40-58mm normal lenses as delivered from the factories, between the 60's and 90's.

The 'like a human eye' is totally bogus. An ophthamologist will confirm that the acuity for the human eye is in a VERY NARROW cone of vision. The peripheral vision is very wide, yet it is horrible for detail, and mostly good for detection of motion (so that nature protects you from predatory animals surprising you!) The only reason you think you have a wide, sharp field of vision is that your eye constantly MOVES and your brain constantly INTEGRATES all of it into a single scene!

But I'm not addressing ophthamologists nor referring to the eye in ioslation, I am referring to the human eye as most of us experience it, i.e., normal visual perception from within the context of the entire human visual system including muscles and nerves and brain and human being.

JackProton wrote in post #7668058
But I'm not addressing ophthamologists nor referring to the eye in ioslation, I am referring to the human eye as most of us experience it, i.e., normal visual perception from within the context of the entire human visual system including muscles and nerves and brain and human being.

But even by that standard, the 'like the human eye' is bogus! The 50mm normal lens on 135 format sees horizontally less than 40 degrees (and 30mm on APS-C sees 41 degrees horizontally ) . The human eye can easily move side to side to encompass a sharp FOV over 100 degrees wide!

Wilt wrote in post #7668351
But even by that standard, the 'like the human eye' is bogus! The 50mm normal lens on 135 format sees horizontally less than 40 degrees (and 30mm on APS-C sees 41 degrees horizontally ) . The human eye can easily move side to side to encompass a sharp FOV over 100 degrees wide!

Even still, the scene you perceive looking through the viewfinder and then looking with your naked eyes will appear to match more closely somewhere around the focal length of a normal lens.

Wilt wrote in post #7659202
To help guide your FL selection, here are conventional well established (for many decades) terms for different 'wide' FL, and the the APS-C focal length needed, and the FF/135 formal focal length needed...

special wide (fisheye): available? APS-C, 8-12mm FF/film
ultra wide: 10-11mm APS-C, 16-17mm FF/film
super wide: 12mm APS-C, 20mm FF/film
very wide: 15mm APS-C, 24mm FF/film
wide: 18mm APS-C, 28mm FF/film
moderate wide: 22mm APS-C, 35mm FF/film

...and as a frame of reference,
normal: 25-35 mm APS-C 40-58mm FF/film

A few slight corrections...
Fisheye (Circular): APS-C? 4.5mm-8mm, FF/Film? 6.5mm (adapted Nikkor) - 8mm
Fisheye (Rectangular): APS-C? 10mm-17mm, FF/Film? 15mm-16mm
UltraWide: APS-C? 10mm-16mm, FF/Film? 12mm-24mm
Wide: APS-C? 16mm-18mm, FF/Film? 24mm-28mm

past that... its normal range from 29mm - 75mm on FF/Film
and 19mm - 50mm for APS-C.

the "classic" normal lenses are 35mm and 50mm (55mm, and 58mm also) for film/FF. For APS-C the closest equivalents to those normal primes = 24mm and 30mm.

But all your mini-classifications are not exactly correct ... there aren't that many "sub" categories last I remember. And in either case each category is defined by a range. And in some (such as UWA on film/FF) new technology has expanded those ranges... as in the case of the Sigma 12-24mm EX DG HSM which came out in 2003 - it redefined how you look at UWA.. 12mm is something new to that arena in a rectilinear lens.

nureality wrote in post #7669259
A few slight corrections......But all your mini-classifications are not exactly correct ... there aren't that many "sub" categories last I remember. And in either case each category is defined by a range. And in some (such as UWA on film/FF) new technology has expanded those ranges... as in the case of the Sigma 12-24mm EX DG HSM which came out in 2003 - it redefined how you look at UWA.. 12mm is something new to that arena in a rectilinear lens.

I won't get into a debate, because it is pointless, as the definitions of what number equates to what description are continuously evolving! For example. 28mm was once called 'super wide', but as technology progressed, that FL became a very ordinary 'wide' lens and 24mm became the new 'super wide'. Then 24mm later became 'very wide' and 20mm was the new 'super wide'. When the term 'ultra' replaced the word 'super' is debatable. The terminology I used are in conformity with established 'lens handbooks' such as those published by Olympus in the mid-1980's.

Similarly, 35mm was commonly called 'moderate wide', but many photographers were accustomed to using this FL as their usual lens, ergo it was effectively their 'normal', even though the classic definition of that term is the diagonal measure of the frame. The diversity of what manufacturers provided with a 135 format body led to the 'pancake normal' 40mm up thru about 58mm as the standard lens sold with the body.

Honestly, if you are just starting out with a 20D, I don't think you can do better than the relatively new combination of the Canon EF-S 18-55 IS and the EF-S 55-250 IS and then the EF 50 f/1.8.

The reason is simple: you can get all three lenses for, what, $500USD? And you both cover a wide range in focal length and also have a lens that can handle lower light situations. What's not to love?

I'm not dissing the 17-40 by any means, but it's a lens that belongs to a class of lenses that, IMO, should be bought into after some experience and thought. Many people would get much more by upgrading to the EF-S 17-55 f/2.8 IS, one of the truly amazing lenses made for crop cameras, than the 17-40. For newcomers, I shamelessly advocate the best for crop bodies, both in the budget categories and then the "best of the best", and the 17-55 is right there.

Thank you for all the responses. I currently have: canon 28-135mm IS, canon 18-55mm, and 75-300mm

I would highly recommend the 18-55mm IS kit lens. It stacks up favorably with the six-times pricier 17-40mm f/4L: http://www.the-digital-picture.com …omp=0&FLIComp=1​&APIComp=0